Title of Invention	A PROCESS FOR THE PREPARATION OF DIPHENYLACETYLENES EXHIBITING CHIRAL NEMATIC PHASE
Abstract	In this invention we have provided with an alternative process for the preparation of technologically important chiral unsymmetrical dimeric liquid crystalline compounds avoiding the use of commercially available chiral moieties those are generally expensive. We have explored the possibility using the naturally occurring optically active compounds such as steroids that are coupled with various phenyl acetylenes in the presence of organic solvent or their mixtures and a coupling catalyst at a temperature in the range of 40 °C to 120 °C in an inert atmosphere.

Title of Invention

A PROCESS FOR THE PREPARATION OF DIPHENYLACETYLENES EXHIBITING CHIRAL NEMATIC PHASE

Abstract

In this invention we have provided with an alternative process for the preparation of technologically important chiral unsymmetrical dimeric liquid crystalline compounds avoiding the use of commercially available chiral moieties those are generally expensive. We have explored the possibility using the naturally occurring optically active compounds such as steroids that are coupled with various phenyl acetylenes in the presence of organic solvent or their mixtures and a coupling catalyst at a temperature in the range of 40 °C to 120 °C in an inert atmosphere.

Full Text	This invention relates to novel unsymmetrical dimeric liquid crystals and a process for their preparation. The novel cholesterol-based liquid crystalline (LC) unsymmetrical dimers exhibit chiral nematic (N) mesophase. The chiral nematic (also referred to as cholesteric phase) exists over a temperature range of 60-80°C in convenient operating temperature limits. The compounds of the present invention can be used in many applications like thermal sensors, reflective displays, toys and decorative materials etc. Liquid crystal is an intermediate state between that of a solid and a liquid. Transition to this state is brought about either by thermal processes (thermotropic liquid crystals) or by the influence of solvents (lyotropic liquid crystals). The compounds discussed here are thermotropic liquid crystals. These are broadly classified into (1) those composed of rod-shaped molecules (called "calamitic" liquid crystals) (2) those composed of disc-shaped molecules (called "discotic" liquid crystals). The simplest thermotropic liquid crystalline phase is known as the nematic phase. It is a fluid phase consisting of an orientationally ordered arrangement of molecules, but no long range transalational order, as shown in figure 1. The preferred orientation of the molecules is referred to as director (n). Figure 1: Schematic representation of the molecular arrangement in the nematic (N) phase. The first thermotropic liquid crystalline phase observed by Reinitzer was in a compound called cholesteryl benzoate of the formula la shown below [F. Reinitzer, Montatsh Chem., 9, 421, (1888)]. This exhibits a chiral nematic phase (N) which is nothing but a nematic phase consisting of chiral or optically active molecules. Historically the N* phase was generally known as cholesteric phase because the first materials exhibiting this phase were cholesterol derivatives. However, in the present-day scenario, there are many different types of chiral materials other than cholesterol derivatives, which exhibit N* phase [A. I. Galatina, N. S. Novikova, L. G. Derkach, N. L. Kramarenko, O. M. Tsyguleva and V. F. Kuzin, Mol Cryst. Liq. Cryst, 140,11, (1986)]. Due to the presence of chiral molecules the structure of the N* phase acquires a spontaneous helical twist about an axis normal to the preferred orientation of the molecules shown in figure 2. The twist may be either right-handed or left-handed depending on the molecular conformation and has a specific, temperature-dependent pitch. The helical structure has the ability to selectively reflect light of wavelength proportional to that of the helical pitch length. If the pitch length is of the order of wavelength of visible light then colors are selectively reflected. The pitch and hence the color of the reflected light are temperature-dependant. This phenomenon has been employed in one of the first commercial applications of liquid crystals namely, thermal sensors. The cholesteric liquid crystal temperature sensors are used in a wide variety of applications like for example fever thermometers, monitoring devices for the packaging of chilled food and battery testers etc. They are also used in "stress" and "mood" sensors, and color changing jewelry, clothing, decorative wall coverings and tiles. These sensors can also be used in medical thermography, in which application of a color sensitive device to a part of the body produces a visual image of the temperature variations of the skin, thus providing a tool for the diagnosis of circulation problems and cancerous growths. Other applications include the use of these devices in the electronics industry wherein they are used to detect the local heating due to poor electrical connections on circuit boards. Cholesteric liquid crystals are also used in reflective type of displays, for example in what has been referred to as electronic paper. 'Because cholesteric liquid crystals selectively reflect one circular polarization, films made from the materials can replace the linear dichroic polariser. A lot of research work is going on in order to develop cholesteric wide-band polarisers with good transmission and extinction properties. Generally, the cholesteric thermal sensors are built using a mixture of different chiral nematic compounds so that the device can be operated over wide temperature range. There are not many single component cholesteric compounds available, which have a wide temperature range N* mesophase with convenient operating temperature limits as well as temperature dependence of color in the visible range. Since the discovery of cholesteryl benzoate of the formula (la) over 100 years ago, more than 3000 cholesterol derivatives (as a single component) have been reported. To the best of our knowledge most of the derivatives stabilize N* mesophase but at elevated temperatures. On the other hand the compounds of the formulae 2 to 8 listed below are some of the single component materials reported earlier which have shown N* phase at lower temperatures. These chiral molecules contain either a 2-methylbutyl or a 2-octyloxy tail as a chiral part which is responsible in inducing molecular chirality and to have N* mesophase. Limits of N* temperature range from; 26.5 to 95.5 " C Temperature range: 69.5 °C Phase sequence: K 26.0 N* 95.5 BP 96.0 I [L. K. M. Chan, G. W. Gray, D. Lacey and K. J. Toyne MoLCryst.Liq.Cryst.l5SB, 209, (1988)] Limits of N* temperature range from: -11.0 to 45.0 ° C Temperature range: 56 °C Phase sequence: K [P. Balkwill, D. Bishop, A. Pearson and I. Sage Mol.Cryst.Liq.Cryst.123, 1, (1985) ] /-si i Limits of N* temperature range from: 6.0 to 72.0 ° C Temperature range: 66 °C Phase sequence: K Limits of N* temperature range from: -2.0 to 48.0 ° C Temperature range: 50.0 ° Phase sequence: K -2.0 N* 48.0 I S. M. Kelly, Liq.Cryst.5, 171, (1981) Limits of N* temperature range from: -42.0 to 40.0 °C Temperature range: 82.0 °C Phase sequence: K - 42.0 N* 40.0 I [S. M. Kelly, Liq.Cryst.5, 171, (1981)] Limits of N* temperature range from: -104.0 to -13.5 °C Temperature range: 117.0 °C Phase sequence: K 16.5 (S -104.0) NM3.5 I [BDH product information 1986] Limits of N* temperature range from: -69.0 to 7.0 °C Temperature range: 38.0°C Phase sequence: K 9.0 (S - 69.0 N* -7.0) I [BDH product information 1986] The chiral moieties that are mentioned above are commercially available but expensive due to the enantioselective synthesis, which involves the usage of a chiral reagent, catalyst and solvent in synthetic process. Some time it is difficult to obtain a chiral compound with high enantiomeric (99%) excess although the synthetic process is stereocontrolled. The above mentioned chiral and similar moieties are very important in making chiral liquid crystals those serve as a media in many device applications such as thermal sensors, reflective displays etc. On the other hand cholesterol having the formula (A) shown below is a well-known natural product found in all body tissues, spinal cord and in animal fats or oils. Cholesterol frequently appears as an important building block in many molecular assemblies such as liquid crystals (LCs), organic gels and monolayers. Its versatility originates from its unique structural characteristics not found in other molecules. Its structure is rigid possessing 8-chiral centers giving rise to a total of 256 stereoisomers. Quite interestingly only one stereoisomer of the formula (A) is naturally available. It is a commercially available inexpensive natural product. It is well known that cholesterol on derivatization to its ester, namely cholesteryl ester show liquid crystalline properties. The low-molar-mass [less than 1000 molecular weight (MW)] liquid crystals (LCs) usually consist of a mesogenic rigid core (monomer) while high-molar-mass (MW> 10,000) liquid crystals contain many repeating mesogenic rigid cores (polymer) separated by central spacers. Over the years both monomeric liquid crystals (MLCs) and polymeric liquid crystals (PLCs) has been the subject of many investigations and consequently are well-studied systems. Their liquid crystalline behavior is quite well understood and they are either serving or potential materials in many applications. During the last two decades there is another class of low-molar-mass liquid crystals that has emerged out as yet another new, challenging and interesting area in liquid crystals. These systems consist of "n" number (n = 2 to 8) of mesogenic segments separated by (n-1) spacers and are called oligomeric liquid crystals (OLCs). These systems are now gaining importance in material sciences for the following reasons. (1) They are regarded as model compounds for the synthesis of liquid crystalline polymers. (2) They help in understanding the behavior of liquid crystalline polymers. (3) They can be synthesized and characterized easily and systematically. (4) They are the bridging structures between monomeric and polymeric liquid crystals. (5) Most importantly, these non-conventional LCs can exhibit properties usually associated with polymers, while still retaining the fluidity and viscosity of a low molar mass LC. Further, if the OLC is monodisperse it will lead to rather well defined properties unlike in polymers. Of all the oligomeric molecular architectures known to support liquid crystalline behavior, the dimers composed of either identical (symmetrical) or non-identical (unsymmetrical) mesogenic segments connected by a central spacer-such as a polymethylene or a oligo(oxyethylene) or a oligosiloxyl group are particularly attractive due to their unique thermal behavior [For a recent review on dimers see: C.T. Imrie and G.R. Luckhurst., 1998, Handbook of Liquid Crystals, Vol 2B, edited by. D.Demus, J.Goodby, G.W.Gray, H.W.Spiess and V.Vill, p.801 (Wiley-VCH, Weinheim, 1998)]. Further, there are remarkable differences in the behavior of symmetrical and unsymmetrical dimers. There have been reports on chiral unsymmetrical dimers consisting of the cholesteryl ester unit as a chiral segment. The non-chiral segment containing one of the following moieties; a Setoffs base, azo, stilbene [(a) J.-I. Jin, H. S. Kim, J.-W. Shin, B. Y. Chung and B. W. Jo., Bull Korea, Chem. Soc, 11, 209 (1990); (b) F. Hardouin, M. F. Achard, J.-I. Jin, J-W. Shin and Y.-K. Yun., 1 Phys.II Fr., 4, 627, (1994); (c) F. Hardouin, M. F. Achard, J.-I. Jin, Y.-K. Yun., and S.J.Chung, E. Phys. J., Bl, 47, (1998); (d) S.-W. Cha, , J.-I. Jin, M. Laguerre, M. F. Achard and F. Hardouin, Liq. CrysL, 26, 1325, (1999)], [C.V.Yelamaggad, A.Srikrishna, D. S. Shankar Rao and S.Krishna Prasad, Liq. CrysL 26, 1547, (1999)] tolan [C.V.Yelamaggad., Mol. CrysL Liq. Cryst ., 326, 149, (1999)]. or a biphenyl unit. [(a)A.T.M. Marcelis, A.Koudijs and EJ.R. Sudholter, Liq. Cryst, 18, 843, (1995) and (b) V. Surendranath, Mol. Qyst.Liq.Qyst.,332,135,(1999)]. A polymethylene unit serves as a spacer between the two segments. These investigations reveal that such compounds exhibit a variety of interesting mesophases. In one of our recent investigation on these compounds, the combination of the cholesteryl ester segment with a tolan (diphenylacetylene) unit, the unsymmetrical dimer of the formula (9) was found to stabilize N* phase over wide temperature range (~ 130°C), the transition temperature being: Heating cycle, K 111.5 °C N* 203.3 °C I; Cooling cycle, I 201.9 °C N* 64.11 °C K. [C.V.Yelamaggad., Mol. CrysL Liq. Cryst.,326, 149,(1999)]. It may be possible that the N* mesophase can be stabilized over a useful working temperature range by the structural variation over the dimer 9 that can be achieved by developing a process for their preparation. Based on the literature reports for the low melting and high clearing temperatures it appears that, the substitution with either a 2,3,4-trialkoxy or a 3,4,5-trialkoxy tails on tolan (diphenylacetylene) mesogenic segment of the dimer 9 would serve the purpose. Keeping these points in view, we initiated the research program to provide an alternative process for the preparation of chiral unsymmetrical dimeric liquid crystalline compounds avoiding the use of commercially available chiral moieties those are generally expensive. With this objective we explored the possibilities of using naturally occurring products such as cholesterol, menthol etc. as chiral moieties. In the present invention we use cholesterol as a chiral entity to prepare chiral liquid crystalline dimers. In the present invention the new compounds of the general formula DG-1 and their position isomers of the general formula DG-1P are prepared starting from (i) cholesteryl 6-(substituted phenoxy)hexanoates of the formula SM-1 and (ii) 2,3,4 or 3,4,5-/r/-n-alkoxyphenylacetylene of the formula SM-2 or their positional isomers of the formula SM-2P where: n = 1 to 20 numbers of carbon atoms X = CI, Br, F, N02 and CN etc. Rb R2 and R3 = Alkyl chains having carbon atoms 1 to 20 numbers where: n = 1 to 20 numbers of carbon atoms X - H, CI, Br, F, N02 and CN etc. Y = CI, Br and I WI1C1C. R1? R2 and R3 = Alkyl chains having carbon atoms 1 to 20 numbers The starting compounds of the general formulae SM-1, SM-2 and SM-2P have been reported by us in our under mentioned publications, (a) C.V.Yelamaggad., Mol. Cryst. Liq. Cryst ., 326, 149, (1999), (b) C.V.Yelamaggad, U.S. Hiremath, D.S.Shankar Rao and S. Krishna Prasad, Chem. Comm., (2000), 57] [C.V. Yelamaggad, S. Anitha Nagamani, U. S. Hiremath, D. S. Shankar Rao and S. Krishna Prasad (Communicated)]. These compounds can be prepared by the process described in the above publications. For example the compounds of the formula SM-1 can be prepared by reacting cholesteryl bromoalkanoates of the formula SM-CBr with 2,4-disubstituted phenol of the formula Ph-OH under mild basic (K2CO3) reaction condition in refluxing acetone as shown below. The compounds of the formula SM-2 can be prepared starting from l,2,3-//7-n-alkoxybenzene of the formula SM-2a as shown below. The trialkoxy compound of the formula SM-2a, upon iodination furnishes trialkoxy iodo compound of the formula SM-2b that on condensation with 2-methyl-3-butyn-2-ol yields protected alkyne of the formula SM-2c. This on treating with base (potassium hydroxide) gives 2,3,4-tri-alkoxyphenylacetylene of the formula SM-2. where: Rb R2 and R3 = Alkyl chains having carbon atoms 1 to 20 numbers The compounds of the formula SM-2P can be prepared by firstly nitrating trialkoxy compound of the formula SM-2a with nitrating reagent to get nitro compound of the formula SM-2Pb which on catalytic hydrogenation furnishes amine of the formula SM-2Pc. The amine on diazotization followed by treatment with potassium iodide gives the iodo compound of the formula SM-2Pd that on coupling witn metnyio-ouiyn-z-ui yields protected alkyne of the formula SM-2Pe. The protected alkyne upon refluxing with potassium hydroxide in toluene yields the alkyne of the formula SM-2P. As the cholesteryl 6-(substituted phenoxy)hexanoates of the general formula SM-1 , compounds of the formula 16 or 17 may be used. As the phenylacetylenes of the general formula SM-2 compounds of the formula 18,19, 20 and 21 and their positional isomers of the general formula SM-2P for example compound of the formula 22 may be used. Accordingly, the present invention provides a process for the preparation of novel unsymmetrical dimers having the general formula DG-1 and their positional isomers DG-1P which comprises coupling of cholesterol derivatives of the formula SM-1 with an appropriate 2,3,4- or 3,4,5-//7-n-alkoxyphenylacetylene of the formula SM-2 or SM-2P in the presence of organic solvent or their mixtures and a coupling catalyst at a temperature in the range of 40°C to 120°C in an inert atmosphere. According to an embodiment of the present invention the organic solvent such as diethylamine, trimethylamine, dipropylamine, diisopropylamine, ether, tetrahydrofuran and the like or their mixture is used. According to another embodiment of the present invention coupling catalyst such as palladium(II) acetate monohydrate, palladium(II)chloride, bis(triphenylphosp-hine)palladium-(II)chloride,tetrakis(triphenylphospine)palladium(0), bis(tiphenylphos-phine)dicarbonylnickle are used. According to yet another embodiment of the present invention th^ catalyst contains copper salts such as copper(II)acetate monohydrate or copper(I)iodide, According to still another embodiment of the present invention the catalyst contains triphenylphosphine According to further embodiment of the present invention the coupling is effected by heating the reaction mixture at a temperature in the range of 60°C to 100°C. According to another embodiment of the present invention the inert atmosphere is maintained by using a moisture free nitrogen or argon gas. By employing the process of the present invention the unsymrnetrical dimers of the formulae 10, 11, 12, 13,14 and 15 have been prepared The novel unsymmetrical dimers of the formulae DG-1 and DG-1P, particularly the compounds of the formulae 12 and 14 prepared by the process of the present invention exhibit N* mesophase over a wide temperature range. The N* phase exists from -27.7 °C to +75.2 °C and -19.TC to +55.6°C for the compounds of the formulae 12 and 14 respectively. This large temperature range is an essential requirement for the compound to be a suitable material for practical applications, especially in thermal sensing devices. Besides, these dimers are stable to moisture and heat. They are nonvolatile in nature and have a long life. Thus satisfying most of the conditions required for practical applications in thermal sensing devices. Additionally, the compounds are medium-molar-mass liquid crystal representing the intermediate structure of monomeric and polymeric liquid crystals and such liquid crystals may find a suitable position in practical applications. The invention is described in more detail in the Examples given below which are provided only to illustrate the invention and therefore should not be construed to limit the scope of the invention. Example 1: Process for the preparation of Cholesteryl 6-{4-[4-(2,3,4-/r/-n-butyloxy)phenylethynyl]phenoxy}hexanoate of the formula (10): A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-/r/-n-butyloxyphenylacetylene of the formula (18) (0.29g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%). triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 75°C under argon atmosphere for 16 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04. Evaporation of solvent furnished a thick gummy mass, which then solidifies as an off-white solid material that was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid compound. Yield 0.58gm (91%). The physical characteristics of the resulting compounu of the formula 10 are: Rf=0.5l (10% EtOAc-hexanes); IR (Neat): Ymax 2933, 2869, 1733, 1606 and 1511cm'1; lHNMR (200MHz, CDC13): 7.42 (d, J=8.76Hz, 2H, Ar), 7.13 (d, .7=8.62, 1H, Ar), 6.84 (d, J=8.78, 2H, Ar), 6.60 (d, J=8.72, 1H, Ar), 5.38 (brd, J-4.05, 1H, Olefmic), 4.60 (m, 1H, -CH-O-CO-), 4.16 (t, .7=6.3, 2H, -OCH2-), 3.97 (m, 6H, 3x -OCH2-), 2.31 (m, 4H, 2 x allylic methylene), 2.01-0.84 (m, 53H, 3xCH3-, 19x-CH2-, 6x-CH-), 1.01 (s, 3H, -CH3), 0.91 (d, .7=4.1, -CH3), 0.86 (d, J=6.56, 6H, 2xCH3-,) and 0.67 (s, 3H, -CH3); FAB Mass: 893.8 [M+l]+ (C59 H88 06). Thermal behavior (Phase sequence): Heating cycle, K 65.0 ° C N* 104.7 ° C I; Cooling cycle, I 103.7 ° C N* Example 2: Process for the preparation of Cholesteryl 6- {4-[4-(2,3,4-frv-n-butyloxy)phenylethynyl]phenoxy} hexanoate of the formula (10): A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-fr/-n-butyloxyphenylacetylene of the formula (18) (0.29g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.02Smmol, 4%), triphenylphosphine (37mg, O.Hmmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), diisopropylamine (10ml) and dry tetrahydrolliran was heated at 50 ° C under argon atmosphere for 48 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04. Evaporation of solvent furnished a thick gummy mass, which then solidifies as an off-white solid material that was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid compound. Yield 0.57gm (90%). The physical characteristics of the resulting compound of the formula 10 are as mentioned in example 1 Example 3: Process for the preparation of Cholesteryl 6-{4-[4-(2,3,4-//v'-n-hexyloxy)phenylethynyl]phenoxy}hexanoate of the formula (11): A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-frv-n-hexyloxyphenylacetylene of the formula (19) (0.3 9g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 75°C under argon atmosphere for 20 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCl3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04. Evaporation of solvent furnished a thick gummy mass, which then solidifies was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid. Yield 0.54gm (78%). The physical characteristics of the resulting compound of the formula 11 are Rf =0.54 (10% EtOAc-hexanes).; IR (Neat): ymax 2933, 2868, 1733, 1606 and 1511cm'1; lHNMR (200MHz, CDC13): 7.42 (d, 7=8.74Hz, 2H, Ar), 7.13 (d, 7=8.62, 1H, Ar), 6.83 (d, 7=8.78, 2H, Ar), 6.60 (d, 7=8.72, 1H, Ar), 5.36 (brd, 7=4.05, 1H, Olefinic), 4.62 (m, 1H, -CH-0-CO-), 4.14 (t, 7-6.42, 2H, -OCH2-), 3.97 (t, 7=6.5, 6H, 3x -OCH2-), 2.31 (m, 4H, 2 * allylic methylene), 2.01-0.84 (m, 65H, 3> Example 4: Process for the preparation of Cholesteryl 6-{4-[4-(2,3,4-/r/-n-hexyloxy)phenylethynyl]phenoxy}hexanoate of the formula (11): A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the tormtila (10) (U.Sg, 0.71 mtnol), 2,3,4-/r/-n-hexyloxyphenylacetylene of the formula (19) (0.39g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 60 °C under nitrogen atmosphere for 30 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCb (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04. Evaporation of solvent furnished a thick gummy mass, which then solidifies was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid. Yield 0.6gm (86%). The physical characteristics of the resulting compound of the formula 11 are as mentioned in example 3 Example 5: Process for the preparation of Cholesteryl 6-{4-[4-(2,3,4-/r/-n-octyloxy)phenylethynyl]phenoxy}hexanoate of the formula (12): A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-//7-n-octyloxyphenylacetylene of the formula (20) (0.45g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, O.I2mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofiiran was heated at 75°C under argon atmosphere for 16 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow thick gummy mass obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH4. Evaporation of solvent furnished a thick gummy mass, which was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a thick colored gummy mass. Yield 0.65gm (86%). The physical characteristics of the resulting compound of the formula 12 are: Rf-0.3% (10% EtOAc-hexanes).; IR (Neat): ymax 2929, 2856, 2362, 1732, 1606 and 1511cm'1; 1HNMR (500MHz, CDCI3): 7.42 (d, J=8.5Hz, 2H, Ar), 7.13 (d, J=8.55, 1H, Ar), 6.83 (d, > 8.45, 2H, Ar), 6.6 (d, 7=8.75, 1H, Ar), 5.37 (brd, J=4.05, 1H, Olefinic), 4.62 (m, 1H, -CH-O-CO-), 4.15 (t, J=6.4Hz, 2H, lx -OCH2-), 3.97 (brs, 6H, 3x -OCH2-), 2.32 (m, 4H, 2 x allylic methylene), 2.02-0.84 (m, 86H, 6xCH3-, 31x-CH2-, 6-CH-), 1.02 (s, 3H, -CH3), and 0.67 (s, 3H, -CH3); FAB Mass: 1060.8 [M]+ (C71 Hn2 06). Thermal behavior (Phase sequence): Heating cycle, Tg -25.45 °C N 75.16 °C I; Cooling cycle, I 74.34 ° C N* -27.67 °CTg Example 6: Process for the preparation of Cholesteryl 6-{4-[4-(2,3,4-/r/-n-dodecyloxy)phenylethynyl]phenoxy}hexanoate of the formula (13): A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-/rz-n-dodecyloxyphenylacetylene of the formula (21) (0.604g, 0.92mmol), bis(triphenylphosphine)palla-dium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 75°C under argon atmosphere for 16 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04-Evaporation of solvent furnished a thick gummy mass, which then solidifies was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white of the solid. Yield 0.68gm (80 %). The physical characteristics of the resulting compound formula 13 are Rf -0.55 (10% EtOAc-hexanes).; IR (Neat); Ymax 2919, 2850, 1732, 1606 and 1512cm"1; 1HNMR (400MHz, CDCb): 7.42 (d, 7=8.84Hz, 2H, Ar), 7.12 (d, 7=8.64, 1H, Ar), 6.83 (d, 7=8.SS, 2H, Ar), 6.59 (d, 7=8.72, 1H, Ar), 5.37 (brd, 7=4.05, 1H, Olefinic), 4.62 (m, 1H, -CH-O-CO-), 4.14 (t, 7=6.52, 2H, -OCH2-), 3.95 (t, 7=6.5, 6H, 3* -OCH2-), 2.31 (ITL 4H, 2 * allyllicmethylene), 2.02-0.84 (m, 110H, 6x-CH3, 43x-CH2-, 6x-CH-), 1.02 (s, 3H, -CH3), and 0.67 (s, 3H, -CH3); FAB Mass: 1229.1 [M+l]+ (C83 Hi36 06) Thermal behavior (Phase sequence): Heating cycle, K 40.3 ° C N* 75.4 ° C I; Cooling cycle, I 74.6 ° C W Example 7: Process for the preparation of Cholesteryl 6-{4-[4-(2,3,4-//v-n-octyloxy)phenyIethynyl]-2-nitrophenoxy}-hexanoate of the formula (14): A mixture of cholesteryl 6-(4-bromo-2-nitrophenoxy)hexanoate of the formula (17) (0.49g, 0.71 mmol), 2,3,4-f/v-n-octyIoxyphenyIacetylene of the formula (20) (0.45g, 0.92mmol), bis(triphenylphosphine)- palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran (THF) was heated at 75°C under argon atmosphere for 16hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale dull-yellow gummy mass obtained was dissolved in CHCl3(20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2SC>4. Evaporation of solvent furnished a thick dull-yellow gummy mass, which was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a thick yellow gummy mass. Yield 0.58gm (74%). The physical characteristics of the resulting compound of the formula 14: Rf =032 (10% EtOAc %); IR (Neat): ymax 2928, 2855, 2362, 2213,1731, 1616 and 1536cm-1; 1HNMR (500MHz, CDC13): 7.94 (s, 1H, Ar), 7.61 (d, J=8.7, 1H, Ar), 7.14 (d, ./= 8.5, 1H, Ar), 7.01 (d, J=8.S0,1H, Ar), 6.62 (d, .7=8.60, 1H, Ar), 5.37 (brd, .7=4.08, 1H, Olefinic), 4.61 (m, 1H, -CH-0-CO-), 4.15 (m, 4H, 2x -OCH2-), 3.98 (brs, 4H, 2x -OCH2-), 2.32 (m, 4H, 2 * allylic methylene), 2.01-0.85 (m, 86H, 6xCH3-, 31x-CH2-, 6x-CH-), 1.02 (s, 3H, -CH3), and 0.68 (s, 3H, -CH3); 13CNMR (125 MHz, CDC13) : 173.68, 155.30, 155.22, 152.46, 142.46, 140.39, 137.27, 128.97, 128.39, 123.30, 117.04, 115.00, 110.6, 108.93, 89.62, 87.59, 75.07, 74.56, 74.50, 70.14, 69.50, 57.39, 56.82, 50.72, 43.00, 40.42, 40.21, 38.83, 37.68, 37.29, 36.87, 35.16, 32.55, 31.18, 30.99, 30.39, 30.20, 30.04, 29.96, 29.30, 28.92, 28.70, 2S.49, 26.95, 26.78, 26.07, 25.28, 24.97, 24.52, 23.51, 23.35, 23.25, 21.72, 20.01, 19.40, 14.78 and 12.54; FAB Mass: 1106.3 [M+lf (C71 Hm N08).Thermal behavior (Phase sequence): Heating cycle, Tg -19.12 ° C N* 55.6 ° C 1; Cooling cycle, I 52.7 °CN* -19.54 °C Tg . Example 8: Process for the preparation of Cholesteryl 6- {4-[4-(3,4,5-/r/-n-butyloxy)phenylethynyl]phenoxy} hexanoate of the formula (15): A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 3,4,5-/n'-n-butyloxyphenylacetylene of the formula (22) (0.29g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12rrimbl, 16.8%), diisopropylamine (5ml), triethylamine (5ml), dry tetrahydrofuran and ether was heated at 45°C under argon atmosphere for 70 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCb (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2SC>4. Evaporation of solvent furnished an off-white solid material, which was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid compound. Yield 0.55gm (87%). The physical characteristics of the resulting compound of the formula 15 are: Rf=0.5\ (10% EtOAc-hexanes) ; IR (Neat): ymax 2936, 2869, 2361, 1732, 1605 and 1571cm"1; 1HNMR (500MHz, CDCI3): 7.42 (d, J=8.84Hz, 2H, Ar), 6.84 (d, J=8.55, 2H, Ar), 6.71 (s, 2H, Ar), 5.37 (brd, J=4.05, 1H, Olefinic), 4.60 (m, 1H, -CH-O-CO-), 3.97 (m, 8H, 4x -OCH2-), 2.31 (m, 4H, 2 x allylicmethylene), 2.01-0.84 (m, 53FT,-3xCH3-, 19x-CH2-, 6X-CH-), 0.91 (d, 7=6.52, -CH3), 1.01 (s, 3H, -CH3), 0.87 (d, 7=1.84, 3H, -CH3), 0.85 (d, 7=1.84, 3H, -CH3) and 0.67 (s, 3H, -CH3); FAB Mass: 893.9 [M+l]' (C59 H8g Oe). Thermal behavior (Phase sequence): Heating cycle, K 91.0 °C I; Cooling cycle I 47.0 °C Soft solid Example 9: Process for the preparation of Cholesteryl 6-{4-[4-(3,4,5-//*/-n-butyloxy)phenylethynyl]phenoxy}hexanoate of the formula (15): A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 3,4,5-/rz-n-butyloxyphenylacetylene of the formula (22) (0.29g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 75°C under argon atmosphere for 16 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCI(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04-Evaporation of solvent furnished an off-white solid material, which was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid compound. Yield 0.57gm (90%). The physical characteristics of the resulting compound of the formula 15 are as mentioned in example 7 The advantage of the present invention. • Employment of naturally occurring cholesterol as a chiral entity • Preparation of the novel compounds in reasonably good ( 74 to 91 %) yields We claim i. Novel unsymmetrical dimers having the general formula DG-1 and their positional isomers of the formula DG-1P. 2. Novel compound of the formula 10 3. Novel compound of the formula 11 8. A process for the preparation of novel unsymmetrical dimers having the general formula DG-1 and their positional isomers DG-1P as defined in claim 1 which comprises of coupling of cholesterol derivatives of the formula SM-1 with an appropriate 2,3,4- or 3,4,5-/r/-n-alkoxyphenylacetylene of the formula SM-2 and SM-2P in the presence of organic solvents or their mixtures and a coupling catalyst at a temperature in the range of 40°C to 120°C in an inert atmosphere. 9. A process as claimed in claim 8 wherein the organic solvent such as diethylamine, trimethylamine, dipropylamine, diisopropylamine, ether, tetrahydrofuran and the like or their mixture is used. 10. A process as claimed in claims 8 and 9 wherein coupling catalyst such as palladium (Il)acetate monohydrate, palladium(II)chloride, bis(triphenylphosphine)palladium-(Il)chloride, tetrakis(triphenylphospine)palladium(0), bis(tiphenylphosphine)dicar-bonylnickle like are used. 11. A process as claimed in claim 10 wherein the catalyst contains copper salts such as copper(II)acetate monohydrate or copper(I)iodide 12. A process as claimed in claim 10 wherein the catalyst contains triphenylphosphine 13. A process as claimed in claims 8 to 12 wherein the coupling is effected by heating the reaction mixture at a temperature in the range of 40°C to 120°C. 14. A process as claimed in claims 8 to 13 wherein the reaction is effected under inert atmosphere. 15. A process as claimed in claim 14 wherein the inert atmosphere is maintained by using a moisture free nitrogen or argon gas. 16. Novel unsymmetrical dimers having the general formula DG-1 and their positional isomers of the general formula DG-1P as defined in claim 1 substantially as herein described with reference to the Examples. 17. A process for the preparation of Novel unsymmetrical dimers having the general formula DG-1 and their positional isomers of the general formula DG-1P as defined in claim 1 substantially as herein described with reference to the Examples.

Full Text

This invention relates to novel unsymmetrical dimeric liquid crystals and a process for their preparation. The novel cholesterol-based liquid crystalline (LC) unsymmetrical dimers exhibit chiral nematic (N*) mesophase. The chiral nematic (also referred to as cholesteric phase) exists over a temperature range of 60-80°C in convenient operating temperature limits. The compounds of the present invention can be used in many applications like thermal sensors, reflective displays, toys and decorative materials etc.
Liquid crystal is an intermediate state between that of a solid and a liquid. Transition to this state is brought about either by thermal processes (thermotropic liquid crystals) or by the influence of solvents (lyotropic liquid crystals). The compounds discussed here are thermotropic liquid crystals. These are broadly classified into (1) those composed of rod-shaped molecules (called "calamitic" liquid crystals) (2) those composed of disc-shaped molecules (called "discotic" liquid crystals). The simplest thermotropic liquid crystalline phase is known as the nematic phase. It is a fluid phase consisting of an orientationally ordered arrangement of molecules, but no long range transalational order, as shown in figure 1. The preferred orientation of the molecules is referred to as director (n).

Figure 1: Schematic representation of the molecular arrangement in the nematic (N) phase.
The first thermotropic liquid crystalline phase observed by Reinitzer was in a compound called cholesteryl benzoate of the formula la shown below [F. Reinitzer, Montatsh Chem., 9, 421, (1888)]. This exhibits a chiral nematic phase (N*) which is nothing but a nematic phase consisting of chiral or optically active molecules.

Historically the N* phase was generally known as cholesteric phase because the first materials exhibiting this phase were cholesterol derivatives. However, in the present-day scenario, there are many different types of chiral materials other than cholesterol derivatives, which exhibit N* phase [A. I. Galatina, N. S. Novikova, L. G. Derkach, N. L. Kramarenko, O. M. Tsyguleva and V. F. Kuzin, Mol Cryst. Liq. Cryst, 140,11, (1986)]. Due to the presence of chiral molecules the structure of the N* phase acquires a spontaneous helical twist about an axis normal to the preferred orientation of the molecules shown in figure 2. The twist may be either right-handed or left-handed depending on the molecular conformation and has a specific, temperature-dependent pitch.

The helical structure has the ability to selectively reflect light of wavelength proportional to that of the helical pitch length. If the pitch length is of the order of wavelength of visible light then colors are selectively reflected. The pitch and hence the color of the reflected light are temperature-dependant. This phenomenon has been employed in one of the first commercial applications of liquid crystals namely, thermal sensors.
The cholesteric liquid crystal temperature sensors are used in a wide variety of applications like for example fever thermometers, monitoring devices for the packaging of chilled food and battery testers etc. They are also used in "stress" and "mood" sensors,

and color changing jewelry, clothing, decorative wall coverings and tiles. These sensors can also be used in medical thermography, in which application of a color sensitive device to a part of the body produces a visual image of the temperature variations of the skin, thus providing a tool for the diagnosis of circulation problems and cancerous growths. Other applications include the use of these devices in the electronics industry wherein they are used to detect the local heating due to poor electrical connections on circuit boards. Cholesteric liquid crystals are also used in reflective type of displays, for example in what has been referred to as electronic paper. 'Because cholesteric liquid crystals selectively reflect one circular polarization, films made from the materials can replace the linear dichroic polariser. A lot of research work is going on in order to develop cholesteric wide-band polarisers with good transmission and extinction properties.
Generally, the cholesteric thermal sensors are built using a mixture of different chiral nematic compounds so that the device can be operated over wide temperature range. There are not many single component cholesteric compounds available, which have a wide temperature range N* mesophase with convenient operating temperature limits as well as temperature dependence of color in the visible range.
Since the discovery of cholesteryl benzoate of the formula (la) over 100 years ago, more than 3000 cholesterol derivatives (as a single component) have been reported. To the best of our knowledge most of the derivatives stabilize N* mesophase but at elevated temperatures. On the other hand the compounds of the formulae 2 to 8 listed below are some of the single component materials reported earlier which have shown N* phase at lower temperatures. These chiral molecules contain either a 2-methylbutyl or a 2-octyloxy tail as a chiral part which is responsible in inducing molecular chirality and to have N* mesophase.

Limits of N* temperature range from; 26.5 to 95.5 " C
Temperature range: 69.5 °C
Phase sequence: K 26.0 N* 95.5 BP 96.0 I
[L. K. M. Chan, G. W. Gray, D. Lacey and K. J. Toyne
MoLCryst.Liq.Cryst.l5SB, 209, (1988)]

Limits of N* temperature range from: -11.0 to 45.0 ° C
Temperature range: 56 °C
Phase sequence: K [P. Balkwill, D. Bishop, A. Pearson and I. Sage
Mol.Cryst.Liq.Cryst.123, 1, (1985) ] /-si i
Limits of N* temperature range from: 6.0 to 72.0 ° C Temperature range: 66 °C Phase sequence: K

Limits of N* temperature range from: -2.0 to 48.0 ° C
Temperature range: 50.0 °
Phase sequence: K -2.0 N* 48.0 I
S. M. Kelly, Liq.Cryst.5, 171, (1981)

Limits of N* temperature range from: -42.0 to 40.0 °C Temperature range: 82.0 °C Phase sequence: K - 42.0 N* 40.0 I [S. M. Kelly, Liq.Cryst.5, 171, (1981)]

Limits of N* temperature range from: -104.0 to -13.5 °C
Temperature range: 117.0 °C
Phase sequence: K 16.5 (S -104.0) NM3.5 I
[BDH product information 1986]

Limits of N* temperature range from: -69.0 to 7.0 °C Temperature range: 38.0°C Phase sequence: K 9.0 (S - 69.0 N* -7.0) I [BDH product information 1986]

The chiral moieties that are mentioned above are commercially available but expensive due to the enantioselective synthesis, which involves the usage of a chiral reagent, catalyst and solvent in synthetic process. Some time it is difficult to obtain a chiral compound with high enantiomeric (99%) excess although the synthetic process is stereocontrolled. The above mentioned chiral and similar moieties are very important in making chiral liquid crystals those serve as a media in many device applications such as thermal sensors, reflective displays etc.
On the other hand cholesterol having the formula (A) shown below is a well-known natural product found in all body tissues, spinal cord and in animal fats or oils. Cholesterol frequently appears as an important building block in many molecular assemblies such as liquid crystals (LCs), organic gels and monolayers. Its versatility originates from its unique structural characteristics not found in other molecules. Its structure is rigid possessing 8-chiral centers giving rise to a total of 256 stereoisomers. Quite interestingly only one stereoisomer of the formula (A) is naturally available. It is a commercially available inexpensive natural product. It is well known that cholesterol on derivatization to its ester, namely cholesteryl ester show liquid crystalline properties.

The low-molar-mass [less than 1000 molecular weight (MW)] liquid crystals (LCs) usually consist of a mesogenic rigid core (monomer) while high-molar-mass (MW> 10,000) liquid crystals contain many repeating mesogenic rigid cores (polymer) separated by central spacers. Over the years both monomeric liquid crystals (MLCs) and polymeric liquid crystals (PLCs) has been the subject of many investigations and consequently are well-studied systems. Their liquid crystalline behavior is quite well

understood and they are either serving or potential materials in many applications. During the last two decades there is another class of low-molar-mass liquid crystals that has emerged out as yet another new, challenging and interesting area in liquid crystals. These systems consist of "n" number (n = 2 to 8) of mesogenic segments separated by (n-1) spacers and are called oligomeric liquid crystals (OLCs). These systems are now gaining importance in material sciences for the following reasons. (1) They are regarded as model compounds for the synthesis of liquid crystalline polymers. (2) They help in understanding the behavior of liquid crystalline polymers. (3) They can be synthesized and characterized easily and systematically. (4) They are the bridging structures between monomeric and polymeric liquid crystals. (5) Most importantly, these non-conventional LCs can exhibit properties usually associated with polymers, while still retaining the fluidity and viscosity of a low molar mass LC. Further, if the OLC is monodisperse it will lead to rather well defined properties unlike in polymers.
Of all the oligomeric molecular architectures known to support liquid crystalline behavior, the dimers composed of either identical (symmetrical) or non-identical (unsymmetrical) mesogenic segments connected by a central spacer-such as a polymethylene or a oligo(oxyethylene) or a oligosiloxyl group are particularly attractive due to their unique thermal behavior [For a recent review on dimers see: C.T. Imrie and G.R. Luckhurst., 1998, Handbook of Liquid Crystals, Vol 2B, edited by. D.Demus, J.Goodby, G.W.Gray, H.W.Spiess and V.Vill, p.801 (Wiley-VCH, Weinheim, 1998)]. Further, there are remarkable differences in the behavior of symmetrical and unsymmetrical dimers.
There have been reports on chiral unsymmetrical dimers consisting of the cholesteryl ester unit as a chiral segment. The non-chiral segment containing one of the following moieties; a Setoffs base, azo, stilbene [(a) J.-I. Jin, H. S. Kim, J.-W. Shin, B. Y. Chung and B. W. Jo., Bull Korea, Chem. Soc, 11, 209 (1990); (b) F. Hardouin, M. F. Achard, J.-I. Jin, J-W. Shin and Y.-K. Yun., 1 Phys.II Fr., 4, 627, (1994); (c) F. Hardouin, M. F. Achard, J.-I. Jin, Y.-K. Yun., and S.J.Chung, E. Phys. J., Bl, 47, (1998); (d) S.-W. Cha, , J.-I. Jin, M. Laguerre, M. F. Achard and F. Hardouin, Liq.

CrysL, 26, 1325, (1999)], [C.V.Yelamaggad, A.Srikrishna, D. S. Shankar Rao and S.Krishna Prasad, Liq. CrysL 26, 1547, (1999)] tolan [C.V.Yelamaggad., Mol. CrysL Liq. Cryst ., 326, 149, (1999)]. or a biphenyl unit. [(a)A.T.M. Marcelis, A.Koudijs and EJ.R. Sudholter, Liq. Cryst, 18, 843, (1995) and (b) V. Surendranath, Mol. Qyst.Liq.Qyst.,332,135,(1999)]. A polymethylene unit serves as a spacer between the two segments. These investigations reveal that such compounds exhibit a variety of interesting mesophases. In one of our recent investigation on these compounds, the combination of the cholesteryl ester segment with a tolan (diphenylacetylene) unit, the unsymmetrical dimer of the formula (9) was found to stabilize N* phase over wide temperature range (~ 130°C), the transition temperature being: Heating cycle, K 111.5 °C N* 203.3 °C I; Cooling cycle, I 201.9 °C N* 64.11 °C K. [C.V.Yelamaggad., Mol. CrysL Liq. Cryst.,326, 149,(1999)].

It may be possible that the N* mesophase can be stabilized over a useful working temperature range by the structural variation over the dimer 9 that can be achieved by developing a process for their preparation. Based on the literature reports for the low melting and high clearing temperatures it appears that, the substitution with either a 2,3,4-trialkoxy or a 3,4,5-trialkoxy tails on tolan (diphenylacetylene) mesogenic segment of the dimer 9 would serve the purpose.
Keeping these points in view, we initiated the research program to provide an alternative process for the preparation of chiral unsymmetrical dimeric liquid crystalline compounds avoiding the use of commercially available chiral moieties those are generally expensive. With this objective we explored the possibilities of using naturally

occurring products such as cholesterol, menthol etc. as chiral moieties. In the present invention we use cholesterol as a chiral entity to prepare chiral liquid crystalline dimers.
In the present invention the new compounds of the general formula DG-1 and their position isomers of the general formula DG-1P are prepared starting from (i) cholesteryl 6-(substituted phenoxy)hexanoates of the formula SM-1 and (ii) 2,3,4 or 3,4,5-/r/-n-alkoxyphenylacetylene of the formula SM-2 or their positional isomers of the formula SM-2P

where:
n = 1 to 20 numbers of carbon atoms
X = CI, Br, F, N02 and CN etc.
Rb R2 and R3 = Alkyl chains having carbon atoms 1 to 20 numbers

where:
n = 1 to 20 numbers of carbon atoms X - H, CI, Br, F, N02 and CN etc. Y = CI, Br and I

WI1C1C.
R1? R2 and R3 = Alkyl chains having carbon atoms 1 to 20 numbers
The starting compounds of the general formulae SM-1, SM-2 and SM-2P have been reported by us in our under mentioned publications, (a) C.V.Yelamaggad., Mol. Cryst. Liq. Cryst ., 326, 149, (1999), (b) C.V.Yelamaggad, U.S. Hiremath, D.S.Shankar Rao and S. Krishna Prasad, Chem. Comm., (2000), 57] [C.V. Yelamaggad, S. Anitha Nagamani, U. S. Hiremath, D. S. Shankar Rao and S. Krishna Prasad (Communicated)]. These compounds can be prepared by the process described in the above publications.
For example the compounds of the formula SM-1 can be prepared by reacting cholesteryl bromoalkanoates of the formula SM-CBr with 2,4-disubstituted phenol of the formula Ph-OH under mild basic (K2CO3) reaction condition in refluxing acetone as shown below.

The compounds of the formula SM-2 can be prepared starting from l,2,3-//7-n-alkoxybenzene of the formula SM-2a as shown below. The trialkoxy compound of the formula SM-2a, upon iodination furnishes trialkoxy iodo compound of the formula SM-2b that on condensation with 2-methyl-3-butyn-2-ol yields protected alkyne of the formula SM-2c. This on treating with base (potassium hydroxide) gives 2,3,4-tri-alkoxyphenylacetylene of the formula SM-2.

where:
Rb R2 and R3 = Alkyl chains having carbon atoms 1 to 20 numbers
The compounds of the formula SM-2P can be prepared by firstly nitrating trialkoxy compound of the formula SM-2a with nitrating reagent to get nitro compound of the formula SM-2Pb which on catalytic hydrogenation furnishes amine of the formula SM-2Pc. The amine on diazotization followed by treatment with potassium iodide gives

the iodo compound of the formula SM-2Pd that on coupling witn metnyio-ouiyn-z-ui yields protected alkyne of the formula SM-2Pe. The protected alkyne upon refluxing with potassium hydroxide in toluene yields the alkyne of the formula SM-2P.

As the cholesteryl 6-(substituted phenoxy)hexanoates of the general formula SM-1 , compounds of the formula 16 or 17 may be used. As the phenylacetylenes of the general formula SM-2 compounds of the formula 18,19, 20 and 21 and their positional isomers of the general formula SM-2P for example compound of the formula 22 may be used.

Accordingly, the present invention provides a process for the preparation of novel unsymmetrical dimers having the general formula DG-1 and their positional isomers DG-1P which comprises coupling of cholesterol derivatives of the formula SM-1 with an appropriate 2,3,4- or 3,4,5-//7-n-alkoxyphenylacetylene of the formula SM-2 or SM-2P in the presence of organic solvent or their mixtures and a coupling catalyst at a temperature in the range of 40°C to 120°C in an inert atmosphere.
According to an embodiment of the present invention the organic solvent such as diethylamine, trimethylamine, dipropylamine, diisopropylamine, ether, tetrahydrofuran and the like or their mixture is used.
According to another embodiment of the present invention coupling catalyst such as palladium(II) acetate monohydrate, palladium(II)chloride, bis(triphenylphosp-hine)palladium-(II)chloride,tetrakis(triphenylphospine)palladium(0), bis(tiphenylphos-phine)dicarbonylnickle are used.

According to yet another embodiment of the present invention th^ catalyst contains copper salts such as copper(II)acetate monohydrate or copper(I)iodide,
According to still another embodiment of the present invention the catalyst contains triphenylphosphine
According to further embodiment of the present invention the coupling is effected by heating the reaction mixture at a temperature in the range of 60°C to 100°C.
According to another embodiment of the present invention the inert atmosphere is maintained by using a moisture free nitrogen or argon gas.
By employing the process of the present invention the unsymrnetrical dimers of the formulae 10, 11, 12, 13,14 and 15 have been prepared

The novel unsymmetrical dimers of the formulae DG-1 and DG-1P, particularly the compounds of the formulae 12 and 14 prepared by the process of the present invention exhibit N* mesophase over a wide temperature range. The N* phase exists from -27.7 °C to +75.2 °C and -19.TC to +55.6°C for the compounds of the formulae 12 and 14 respectively. This large temperature range is an essential requirement for the compound to be a suitable material for practical applications, especially in thermal sensing devices. Besides, these dimers are stable to moisture and heat. They are nonvolatile in nature and have a long life. Thus satisfying most of the conditions required for practical applications in thermal sensing devices. Additionally, the compounds are medium-molar-mass liquid crystal representing the intermediate structure of monomeric and polymeric liquid crystals and such liquid crystals may find a suitable position in practical applications.

The invention is described in more detail in the Examples given below which are provided only to illustrate the invention and therefore should not be construed to limit the scope of the invention.
Example 1: Process for the preparation of
Cholesteryl 6-{4-[4-(2,3,4-/r/-n-butyloxy)phenylethynyl]phenoxy}hexanoate of the formula (10):

A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-/r/-n-butyloxyphenylacetylene of the formula (18) (0.29g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%). triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 75°C under argon atmosphere for 16 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04. Evaporation of solvent furnished a thick gummy mass, which then solidifies as an off-white solid material that was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid

compound. Yield 0.58gm (91%). The physical characteristics of the resulting compounu of the formula 10 are: Rf=0.5l (10% EtOAc-hexanes); IR (Neat): Ymax 2933, 2869, 1733, 1606 and 1511cm'1; lHNMR (200MHz, CDC13): 7.42 (d, J=8.76Hz, 2H, Ar), 7.13 (d, .7=8.62, 1H, Ar), 6.84 (d, J=8.78, 2H, Ar), 6.60 (d, J=8.72, 1H, Ar), 5.38 (brd, J-4.05, 1H, Olefmic), 4.60 (m, 1H, -CH-O-CO-), 4.16 (t, .7=6.3, 2H, -OCH2-), 3.97 (m, 6H, 3x -OCH2-), 2.31 (m, 4H, 2 x allylic methylene), 2.01-0.84 (m, 53H, 3xCH3-, 19x-CH2-, 6x-CH-), 1.01 (s, 3H, -CH3), 0.91 (d, .7=4.1, -CH3), 0.86 (d, J=6.56, 6H, 2xCH3-,) and 0.67 (s, 3H, -CH3); FAB Mass: 893.8 [M+l]+ (C59 H88 06). Thermal behavior (Phase sequence): Heating cycle, K 65.0 ° C N* 104.7 ° C I; Cooling cycle, I 103.7 ° C N* Example 2: Process for the preparation of
Cholesteryl 6- {4-[4-(2,3,4-frv-n-butyloxy)phenylethynyl]phenoxy} hexanoate of the formula (10):

A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-fr/-n-butyloxyphenylacetylene of the formula (18) (0.29g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.02Smmol, 4%), triphenylphosphine (37mg, O.Hmmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), diisopropylamine (10ml) and dry tetrahydrolliran was heated at 50 ° C under argon

atmosphere for 48 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04. Evaporation of solvent furnished a thick gummy mass, which then solidifies as an off-white solid material that was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid compound. Yield 0.57gm (90%). The physical characteristics of the resulting compound of the formula 10 are as mentioned in example 1
Example 3: Process for the preparation of
Cholesteryl 6-{4-[4-(2,3,4-//v'-n-hexyloxy)phenylethynyl]phenoxy}hexanoate of the formula (11):

A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-frv-n-hexyloxyphenylacetylene of the formula (19) (0.3 9g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 75°C under argon atmosphere for 20 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate

was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCl3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04. Evaporation of solvent furnished a thick gummy mass, which then solidifies was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid. Yield 0.54gm (78%). The physical characteristics of the resulting compound of the formula 11 are Rf =0.54 (10% EtOAc-hexanes).; IR (Neat): ymax 2933, 2868, 1733, 1606 and 1511cm'1; lHNMR (200MHz, CDC13): 7.42 (d, 7=8.74Hz, 2H, Ar), 7.13 (d, 7=8.62, 1H, Ar), 6.83 (d, 7=8.78, 2H, Ar), 6.60 (d, 7=8.72, 1H, Ar), 5.36 (brd, 7=4.05, 1H, Olefinic), 4.62 (m, 1H, -CH-0-CO-), 4.14 (t, 7-6.42, 2H, -OCH2-), 3.97 (t, 7=6.5, 6H, 3x -OCH2-), 2.31 (m, 4H, 2 * allylic methylene), 2.01-0.84 (m, 65H, 3> Example 4: Process for the preparation of
Cholesteryl 6-{4-[4-(2,3,4-/r/-n-hexyloxy)phenylethynyl]phenoxy}hexanoate of the formula (11):

A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the tormtila (10) (U.Sg, 0.71 mtnol), 2,3,4-/r/-n-hexyloxyphenylacetylene of the formula (19) (0.39g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 60 °C under nitrogen atmosphere for 30 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCb (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04. Evaporation of solvent furnished a thick gummy mass, which then solidifies was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid. Yield 0.6gm (86%). The physical characteristics of the resulting compound of the formula 11 are as mentioned in example 3
Example 5: Process for the preparation of
Cholesteryl 6-{4-[4-(2,3,4-/r/-n-octyloxy)phenylethynyl]phenoxy}hexanoate of the formula (12):

A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-//7-n-octyloxyphenylacetylene of the formula (20) (0.45g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, O.I2mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofiiran was heated at 75°C under argon atmosphere for 16 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow thick gummy mass obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH4. Evaporation of solvent furnished a thick gummy mass, which was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a thick colored gummy mass. Yield 0.65gm (86%). The physical characteristics of the resulting compound of the formula 12 are: Rf-0.3% (10% EtOAc-hexanes).; IR (Neat): ymax 2929, 2856, 2362, 1732, 1606 and 1511cm'1; 1HNMR (500MHz, CDCI3): 7.42 (d, J=8.5Hz, 2H, Ar), 7.13 (d, J=8.55, 1H, Ar), 6.83 (d, > 8.45, 2H, Ar), 6.6 (d, 7=8.75, 1H, Ar), 5.37 (brd, J=4.05, 1H, Olefinic), 4.62 (m, 1H, -CH-O-CO-), 4.15 (t, J=6.4Hz, 2H, lx -OCH2-), 3.97 (brs, 6H, 3x -OCH2-), 2.32 (m, 4H, 2 x allylic methylene), 2.02-0.84 (m, 86H, 6xCH3-, 31x-CH2-, 6*-CH-), 1.02 (s, 3H, -CH3), and 0.67 (s, 3H, -CH3); FAB Mass: 1060.8 [M]+ (C71 Hn2 06). Thermal behavior (Phase sequence): Heating cycle, Tg -25.45 °C N* 75.16 °C I; Cooling cycle, I 74.34 ° C N* -27.67 °CTg
Example 6: Process for the preparation of
Cholesteryl 6-{4-[4-(2,3,4-/r/-n-dodecyloxy)phenylethynyl]phenoxy}hexanoate of the formula (13):

A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 2,3,4-/rz-n-dodecyloxyphenylacetylene of the formula (21) (0.604g, 0.92mmol), bis(triphenylphosphine)palla-dium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 75°C under argon atmosphere for 16 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04-Evaporation of solvent furnished a thick gummy mass, which then solidifies was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white of the solid. Yield 0.68gm (80 %). The physical characteristics of the resulting compound formula 13 are Rf -0.55 (10% EtOAc-hexanes).; IR (Neat); Ymax 2919, 2850, 1732, 1606 and 1512cm"1; 1HNMR (400MHz, CDCb): 7.42 (d, 7=8.84Hz, 2H, Ar), 7.12 (d, 7=8.64, 1H, Ar), 6.83 (d, 7=8.SS, 2H, Ar), 6.59 (d, 7=8.72, 1H, Ar), 5.37 (brd, 7=4.05, 1H, Olefinic), 4.62 (m, 1H, -CH-O-CO-), 4.14 (t, 7=6.52, 2H, -OCH2-), 3.95 (t, 7=6.5, 6H, 3* -OCH2-), 2.31 (ITL 4H, 2 * allyllicmethylene), 2.02-0.84 (m, 110H, 6x-CH3, 43x-CH2-, 6x-CH-), 1.02 (s, 3H, -CH3), and 0.67 (s, 3H, -CH3); FAB Mass: 1229.1 [M+l]+ (C83 Hi36 06) Thermal behavior (Phase sequence): Heating cycle, K 40.3 ° C N* 75.4 ° C I; Cooling cycle, I 74.6 ° C W
Example 7: Process for the preparation of
Cholesteryl 6-{4-[4-(2,3,4-//v-n-octyloxy)phenyIethynyl]-2-nitrophenoxy}-hexanoate of the formula (14):

A mixture of cholesteryl 6-(4-bromo-2-nitrophenoxy)hexanoate of the formula (17) (0.49g, 0.71 mmol), 2,3,4-f/v-n-octyIoxyphenyIacetylene of the formula (20) (0.45g, 0.92mmol), bis(triphenylphosphine)- palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran (THF) was heated at 75°C under argon atmosphere for 16hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale dull-yellow gummy mass obtained was dissolved in CHCl3(20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2SC>4. Evaporation of solvent furnished a thick dull-yellow gummy mass, which was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a thick yellow gummy mass. Yield 0.58gm (74%). The physical characteristics of the resulting compound of the formula 14: Rf =032 (10% EtOAc %); IR (Neat): ymax 2928, 2855, 2362, 2213,1731, 1616 and 1536cm-1; 1HNMR (500MHz, CDC13): 7.94 (s, 1H, Ar), 7.61 (d, J=8.7, 1H, Ar), 7.14 (d,

./= 8.5, 1H, Ar), 7.01 (d, J=8.S0,1H, Ar), 6.62 (d, .7=8.60, 1H, Ar), 5.37 (brd, .7=4.08, 1H, Olefinic), 4.61 (m, 1H, -CH-0-CO-), 4.15 (m, 4H, 2x -OCH2-), 3.98 (brs, 4H, 2x -OCH2-), 2.32 (m, 4H, 2 * allylic methylene), 2.01-0.85 (m, 86H, 6xCH3-, 31x-CH2-, 6x-CH-), 1.02 (s, 3H, -CH3), and 0.68 (s, 3H, -CH3); 13CNMR (125 MHz, CDC13) : 173.68, 155.30, 155.22, 152.46, 142.46, 140.39, 137.27, 128.97, 128.39, 123.30, 117.04, 115.00, 110.6, 108.93, 89.62, 87.59, 75.07, 74.56, 74.50, 70.14, 69.50, 57.39, 56.82, 50.72, 43.00, 40.42, 40.21, 38.83, 37.68, 37.29, 36.87, 35.16, 32.55, 31.18, 30.99, 30.39, 30.20, 30.04, 29.96, 29.30, 28.92, 28.70, 2S.49, 26.95, 26.78, 26.07, 25.28, 24.97, 24.52, 23.51, 23.35, 23.25, 21.72, 20.01, 19.40, 14.78 and 12.54; FAB Mass: 1106.3 [M+lf (C71 Hm N08).Thermal behavior (Phase sequence): Heating cycle, Tg -19.12 ° C N* 55.6 ° C 1; Cooling cycle, I 52.7 °CN* -19.54 °C Tg .
Example 8: Process for the preparation of
Cholesteryl 6- {4-[4-(3,4,5-/r/-n-butyloxy)phenylethynyl]phenoxy} hexanoate of the formula (15):

A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 3,4,5-/n'-n-butyloxyphenylacetylene of the formula (22) (0.29g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%),

triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12rrimbl, 16.8%), diisopropylamine (5ml), triethylamine (5ml), dry tetrahydrofuran and ether was heated at 45°C under argon atmosphere for 70 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCb (20ml) and the resultant solution was washed with a 0.1M HCl(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2SC>4. Evaporation of solvent furnished an off-white solid material, which was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid compound. Yield 0.55gm (87%). The physical characteristics of the resulting compound of the formula 15 are: Rf=0.5\ (10% EtOAc-hexanes) ; IR (Neat): ymax 2936, 2869, 2361, 1732, 1605 and 1571cm"1; 1HNMR (500MHz, CDCI3): 7.42 (d, J=8.84Hz, 2H, Ar), 6.84 (d, J=8.55, 2H, Ar), 6.71 (s, 2H, Ar), 5.37 (brd, J=4.05, 1H, Olefinic), 4.60 (m, 1H, -CH-O-CO-), 3.97 (m, 8H, 4x -OCH2-), 2.31 (m, 4H, 2 x allylicmethylene), 2.01-0.84 (m, 53FT,-3xCH3-, 19x-CH2-, 6X-CH-), 0.91 (d, 7=6.52, -CH3), 1.01 (s, 3H, -CH3), 0.87 (d, 7=1.84, 3H, -CH3), 0.85 (d, 7=1.84, 3H, -CH3) and 0.67 (s, 3H, -CH3); FAB Mass: 893.9 [M+l]' (C59 H8g Oe). Thermal behavior (Phase sequence): Heating cycle, K 91.0 °C I; Cooling cycle I 47.0 °C Soft solid
Example 9: Process for the preparation of
Cholesteryl 6-{4-[4-(3,4,5-//*/-n-butyloxy)phenylethynyl]phenoxy}hexanoate of the formula (15):

A mixture of cholesteryl 6-(4-iodophenoxy)hexanoate of the formula (16) (0.5g, 0.71 mmol), 3,4,5-/rz-n-butyloxyphenylacetylene of the formula (22) (0.29g, 0.92mmol), bis(triphenylphosphine)palladium (II) chloride (20mg, 0.028mmol, 4%), triphenylphosphine (37mg, 0.14mmol, 20%), copper(I)iodide (23mg, 0.12mmol, 16.8%), triethylamine (10ml) and dry tetrahydrofuran was heated at 75°C under argon atmosphere for 16 hrs. The reaction mixture was filtered through celite bed when hot. The filtrate was evaporated under vaccum and the pale yellow solid obtained was dissolved in CHCI3 (20ml) and the resultant solution was washed with a 0.1M HCI(aq)(10x2ml), 5% solution of NaOH(aq) (10x2ml), water (10x2), brine and then was dried over anhyd. Na2S04-Evaporation of solvent furnished an off-white solid material, which was purified by column chromatography using alumina (neutral). Elution with a mixture of 10% EtOAc-hexanes furnished a white solid compound. Yield 0.57gm (90%). The physical characteristics of the resulting compound of the formula 15 are as mentioned in example 7
The advantage of the present invention.
• Employment of naturally occurring cholesterol as a chiral entity
• Preparation of the novel compounds in reasonably good ( 74 to 91 %) yields

We claim
i. Novel unsymmetrical dimers having the general formula DG-1 and their positional isomers of the formula DG-1P.

2. Novel compound of the formula 10

3. Novel compound of the formula 11

8. A process for the preparation of novel unsymmetrical dimers having the general formula DG-1 and their positional isomers DG-1P as defined in claim 1 which comprises of coupling of cholesterol derivatives of the formula SM-1 with an appropriate 2,3,4- or 3,4,5-/r/-n-alkoxyphenylacetylene of the formula SM-2 and SM-2P in the presence of organic solvents or their mixtures and a coupling catalyst at a temperature in the range of 40°C to 120°C in an inert atmosphere.

9. A process as claimed in claim 8 wherein the organic solvent such as diethylamine, trimethylamine, dipropylamine, diisopropylamine, ether, tetrahydrofuran and the like or their mixture is used.
10. A process as claimed in claims 8 and 9 wherein coupling catalyst such as palladium (Il)acetate monohydrate, palladium(II)chloride, bis(triphenylphosphine)palladium-(Il)chloride, tetrakis(triphenylphospine)palladium(0), bis(tiphenylphosphine)dicar-bonylnickle like are used.
11. A process as claimed in claim 10 wherein the catalyst contains copper salts such as copper(II)acetate monohydrate or copper(I)iodide
12. A process as claimed in claim 10 wherein the catalyst contains triphenylphosphine
13. A process as claimed in claims 8 to 12 wherein the coupling is effected by heating the reaction mixture at a temperature in the range of 40°C to 120°C.
14. A process as claimed in claims 8 to 13 wherein the reaction is effected under inert atmosphere.

15. A process as claimed in claim 14 wherein the inert atmosphere is maintained by using
a moisture free nitrogen or argon gas.
16. Novel unsymmetrical dimers having the general formula DG-1 and their positional isomers of the general formula DG-1P as defined in claim 1 substantially as herein described with reference to the Examples.
17. A process for the preparation of Novel unsymmetrical dimers having the general formula DG-1 and their positional isomers of the general formula DG-1P as defined in claim 1 substantially as herein described with reference to the Examples.

Documents:

148-mas-2001-abstract.pdf

148-mas-2001-claims duplicate.pdf

148-mas-2001-claims original.pdf

148-mas-2001-correspondance others .pdf

148-mas-2001-correspondance po.pdf

148-mas-2001-description complete duplicate.pdf

148-mas-2001-description complete original.pdf

148-mas-2001-form 1.pdf

148-mas-2001-form 19.pdf

« Previous Patent

Next Patent »

Patent Number

206286

Indian Patent Application Number

148/MAS/2001

PG Journal Number

26/2007

Publication Date

29-Jun-2007

Grant Date

23-Apr-2007

Date of Filing

19-Feb-2001

Name of Patentee

CENTRE FOR LIQUID CRYSTAL RESEARCH

Applicant Address

P.O.BOX NO.1329, JALAHALLI, BANGALORE-560013.

Inventors:

#	Inventor's Name	Inventor's Address
1	CHANNABASAVESHWAR VEERAPPA YELAMAGGAD	CENTRE FOR LIQUID CRYSTAL RESEARCH P.O.BOX NO.1329, JALAHALLI, BANGALORE-560013.
2	UMA SIDDHALINGAYYA HIREMATH	CENTRE FOR LIQUID CRYSTAL RESEARCH P.O.BOX NO.1329,JALAHALLI,BANGALORE-560013
3	GEETHA GOPINATHAN NAIR	CENTRE FOR LIQUID CRYSTAL RESEARCH P.O.BOX NO.1329,JALAHALLI,BANGALORE-560 013,
4	SHANKAR NARAYAN ANITHA NAGAMANI	CENTRE FOR LIQUID CRYSTAL RESEARCH P.O.BOX NO.1329,JALAHALLI,BANGALORE-560 013,

PCT International Classification Number

C 0 9K 19

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA