Title of Invention

"A PROCESS FOR THE SEPARATION OF UNSYMMETRICALLY DISTRIBUTED CYCLOALKANONES"

Abstract

This invention provides a process for the preparation of unsymmetrically disubstituted cycloalkanones . The compounds prepared by the process of this invention are useful for the preparation of mesogens that would find applications in the synthesis of side chain liquid crystalline polymers. Said process comprises reacting 2-(aryl-l-hydroxy methylene) cycloalkanones in the presence of a catalyst and a dry organic solvent a period up to 60 minutes, refluxing the reaction mixture for a period 14 hours , getting the desired unsymmetrically disubstituted cycloalkanones by column chromatographic separation.

Full Text

This invention relates to a process for the preparation of unsymmetrically disubstituted cycloalkanones. In particular this invention describes a process for the preparation of unsymmetrically disubstituted 2,6 -cyclohexanones/2,5 -disubstituted cyclopentanones; the substituents being 4-hydroxy benzylidene on one position and 4-cyano/nitro benzylidene on the other. More particularly it relates to the preparation of 2-(4-hydroxy benzylidene)-6-(4-cyano/nitro benzylidene)cyclohexanones, 2-{4-hydroxy benzylidene)-6 - (40cyano/nitro benzylidene)4 -methylcyclohexanones and 2-(4-hydroxy benzylidene)-5- (4-cyano/nitro benzylidene)cyclopentanones having general formula 1 given in the drawing accompanying this specification wherein R = nil, -CH2-, -CH(CH3)-; X = cyano and nitro. The compounds prepared by the process of this invention are useful for the preparation of mesogens that would find applications in the synthesis of side chain liquid crystalline polymers. The compounds prepared by the process of this invention namely 2-(4-hydroxy benzylidene)-5 or 6-(4-cyano/nitro benzylidene) cycloalkanones are new. Hitherto there are no known process of making unsymmetrically disubstituted cycloalkanones and symmetrically disubstituted cycloalkanones are obtained. The mesogens prepared by the process of this invention are based on 2 - (aryl-1-methylene) cycloalkanones of formula 2 wherein R = nil, -CH2-, -CH(CH3)-; X = cyano and nitro. In our copending application number NF 183/96, we have described and claimed a process for the preparation of 2 -(aryl-1-hydroxy methylene) cyclcalkanones. Yesogens prepared as per the process of this invention are compounds which form part of the polymeric structure in liquid crystalline polymers. If the mesogens form part of the backbone of the polymers, then the polymers are known as main chain liquid crystalline polymers and if it is in the form of pendant groups along the backbone of the polymers, then the polymers are referred to as side chain liquid crystalline polymers. The mesogens prepared as per the process of this invention are therefore useful for the synthesis of side chain liquid crystalline polymers that could be used for non-linear optical applications. The mesogens prepared by the process of this invention, can be further hooked throucgh the hydroxy group using polymethylene . polyoxymethylene/polyoxyethylene spacers to a polymer backbone. The polymer backbone chosen could be from acrylic, methacrylic, scyreneic, epichlorohydrin, maleimide, 2,2-bis(chloromethyl) crimethyleneoxy, vinyl alcohol, vinyl chloride to prepare side chain liquid crystalline polymers. The side chain liquid crystalline polymers prepared are useful for non-linear optical applications. Alternately, the mesogen could hooked through the hydroxy group using polymethylene/polyoxymethylene/polyoxyethylene spacer to vinyl monomer selected from acrylic, methacrylic, styreneic, epichlorohydrin, maleimide, 2,2-bis(chloromethyl) oxitane and such like. The monomer can then be subsequently polymerised to prepare side chain liquid crystalline polymer useful for non¬linear optical applications. The need for newer materials for use in non-linear optical application is strongly felt by researchers. The need is desired by those involved in the developmental efforts for optical signaling manipulation, parallel optical image processing systems in the wake of developments in the area of fibre optics. The material development is directed towards materials with non¬linear optical properties. It is known that response factor to radiation is linear so long as intensity of radiation is weak. However, in the presence of intense source such as the laser, non-linear effects are detectable. Materials with large non-linear optical coefficients are desired for applications in the areas of electro-optical switching, higher data storage devices and the like. The other characteristic feature of these materials is fast response times required for processing desired device structures. Properties that are critical for materials to qualify for non¬linear optical applications include transparency, thermal, photochemical and chemical stability, dielectric constant etc. Both inorganic and organic salts exhibit non-linear optical properties. Materials that have been extensively used in the area applied external field is removed. During this process the dipolar species in the polymer film would reorient and a net alignment is retained in the film. For a polymer to be useful for non-linear optical applications, it must satisfy primary optical property requirements. The primary optical property is characterized by the material having substantially transparency to light of desired frequency. The main object of the present invention is to provide a process for the preparation of unsymmetrically disubstituted cycloalkanones. Disubstituted mesogens with extended conjugation with electron donor group at one end and electron acceptor group at the other end are useful in the preparation of side chain liquid polymers for non-linear optical applications. Accordingly, the present invention provides a process for the preparation of unsymmetrically disubstituted cycloalkanones which comprises ; reacting 2-(aryl-1-hydroxy methylene) cycloalkanones of formula 2 of the drawing accompanying this specification , in the presence of a catalyst and a dry organic solvent respectively such as herein described, under inert atmosphere, stirring the mixture initially at ambient temperature for a period up to 60 minutes, refluxing the reaction mixture for a period 14 hours, removing the organic solvent under reduced pressure, dissolving the obtained residue in an organic solvent as defined herein , washing with water, followed by brine solution, drying the organic layer over a drying agent, concentrating under reduced pressure and separating the compound by column chromatography using a silica gel column and suitable eluent solvent system as described herein followed by re crystallization to get desired unsymmetrically disubstituted cycloalkanones of formula 1 of the drawing accompanying this specification. In on embodiment of the present invention, 2 - (aryl - 1 - hydroxy methylene) cycloalkanone may selected from 2 - (4-cyano/nitro phenyl - 1 hydroxy methylene) cyclohexanone, 2 - (4-cyano/nitro phenyl -1- hydroxy methylene) cyclopentanone, 4 - methyl -2-(4-cyano/nitro phenyl-1-hydroxy methylene) cyclohexanone. According to another feature of the invention, the inert atmosphere may be maintained by using nitrogen or argon. According to yet another feature of the invention, the catalyst used may be such as boron trifluoride etherate, titanium tetrachloride,, anhydrous aluminium chloride. In yet another feature of the invention, the reflux time of the reaction may preferably be 8 hours. According to yet another feature of the invention, the dry organic solvent used may be such as acetonitrile, methanol, ethanol, isopropanol, chloroform, dichloroethane, dichloromethane. According to yet another feature of the invention, the solvent used for purification of the compound by column chromatography may be such as chloroform, carbon tetrachloride, dichloroethane, dichloromethane. silica gel column and suitable eluent solvent system, followed by recrystallisation to get crystals of unsymmetrically disubstitut-ed cycloalkanones of formula 1 of the drawing accompanying this specification. In one embodiment of the present invention, 2-(aryl -1-hydroxy methylene) cycloalkanone may selected from 2-(4-cyano/nitro phenyl-l-hydroxy methylene) cyclohexanone, 2-(4-cyano/nitro phenyl-1-hydroxy methylene) cyclopentanone, 4-methyl-2-( 4-cyano/nitro phenyl-l-hydroxy methylene) cyclohexanone. According to another feature of the invention, the inert atmosphere may be maintained by using nitrogen or argon. According to yet another feature of the invention, the catalyst used may be such as boron trifluoride etherate, titanium tetrachloride, anhydrous aluminium chloride. In yet another feature of the invention, the reflux time of the reaction may preferably be 8 hours. According to yet another feature of the invention, the dry organic solvent used may be such as acetonitrile, methanol, ethanol, isopropanol, chloroform, dichloroethane, dichloromethane. According to yet another feature of the invention, the solvent used for purification of the compound by column chromatography may be such as chloroform, carbon tetrachloride, dichloroethane, dichloromethane. According to yet another feature of the invention, the drying agent used may be such as sodium sulphace, magnesium sulphate, phosphorous pentoxide and calcium chloride. The invention is described with reference to the examples given below which are illustrative in nature and should not be construed to limit the scope of this invention. Example 1 (a) The 1-trimethyl silyloxy-1-cyclohexene is prepared by the known process and is described first. 32.6 gram of 1-trimethyl silyl chloride and 60.6 gram of triethylamine in 100 ml dry dimethyl formamide and 24.5 gram of cyclohexanone were stirred together in an inert atmosphere. The reaction mixture was refluxed for 6 hours under inert atmosphere. The reaction was then cooled to ambient temperature and diluted with 200 ml of pentane, washed with 300 ml of cold aqueous sodium bicarbonate. The organic layer was then washed with cold 1.5 N hydrochloric acid. The resulting organic layer was dried over anhydrous sodium sulphate and concentrated under reduced pressure and distilled under vacuum to get 32 gram of colourless 1-trimethyl silyloxy-1-cyclohexene. 1.36 gram of 1-trimethyl silyloxy-1-cyciohexene was mixed with 0.95 gram of 4-cyano benzaldehyde and 0.24 gram of sulphated zirconia in 40 ml of dichloromethane. A nitrogen atmosphere was maintained. The reactants were stirred a: a tenperature of 35°C for 40 hours. The reaction mass was filtered to recover the solid catalyst. The filtrate was washed with distilled water, dried over sodium sulphate and the solvent was removed under reduced pressure. The resultant mass was then chromatographed through a silica gel column using a petroleum ether : ace:one mixture (5:1 V/V) as the eiuent to get the pure 2- (4-cyano phenyl-1-hydroxy methylene) cyclohexanone. The yield obtained was 1.4 gram. Example 1 (b) 0.68 gram of 1-trimethyl silyloxy-1-cyclohexene was mixed with 0.54 gram of 4-nitro benzaldehyde and 0.12 gram of sulphated zirconia in 20 ml of dichloromethane. A nitrogen atmosphere was maintained. The reactants were stirred at a temperature of 35°C for 48 hours. The reaction mass was filtered to recover the solid catalyst. The filtrate was washed with distilled water, dried over sodium sulphate and the solvent was removed under reduced pressure. The resultant mass was then chromatographed through a silica gel column using a petroleum ether : acetone mixture (5:1 V/V) as the eluent to get the pure 2- (4-nitro phenyl-1-hydroxy methylene) cyclohexanone. The yield obtained was 0.76 gram. Example 1 0.S2 gram of 2- 4-cyano phenyl-1-hydroxy methylene) cyclohexanone prepared as described in example la and 0.55 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.05 gram of boron trifluoride etherace in 20 ml dry methanol was added and the resulting mixture was stirred at ambient temperature for 40 minutes. The reaction mixture was then refiuxed for S. hours. The reaction mixture was then cooled to ambient temperature and methanol distilled off under reduced pressure. The residue was dissolved in chloroform, washed with water, brine solution and dried over sodium sulphate. The solvent chloroform was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2-(4-hydroxy benzylidene)-6-(4-cyano benzylidene) cyclohexanone. The product was recrystallised in chloroform. The yield obtained was 1.15 gram. Example 2 1.35 gram of 2-(4-cyano phenyl-1-hydroxy methylene) cyclohexanone prepared as described in example la and 0.85 gram of 4-hydroxy benzaldehyde were mixed under argon atmosphere. To this mixture 0.08 gram of titanium tetrachloride in 30 ml dry acetonitrile was added and the resulting mixture was stirred at ambient temperature for 60 minutes. The reaction mixture was then refluxed for 10 hours. The reaction mixture was then cooled to ambient temperature and acetonitrile distilled off under reduced pressure. The residue was dissolved in dichloromethane, washed with water, brine solution and dried over sodium sulphate. The solvent dichloromethane was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2-(4-hydroxy benzylidene)-6 -(4 -cyano benzylidene) cyclohexanone. The product was recrystallised in dichloromethane. The yield obtained was 1.75 gram. Example 3 1.85 gram of 2-(4-cyano phenyl-1-hydroxy methylene) cyclohexanone prepared as described in example la and 1.15 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.10 gram of anhydrous aluminium chloride in 40 ml dry dichloroethane was added and the resulting mixture was stirred at ambient temperature for 30 minutes. The reaction mixture was then refluxed for 12 hours. The reaction mixture was then cooled to ambient temperature and dichloroethane distilled off under reduced pressure. The residue was dissolved in dichloroethane, washed with water, brine solution and dried over sodium sulphate. The solvent dichloroethane was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2-(4-hydroxy benzylidene) -6 -(4-cyano benzylidene) cyclohexanone. The product was recrystallised in dichloroethane. The yield obtained was 2.35 gram. Example 4 1.00 gram of 2-(4-nitro phenyl-1-hydroxy methylene) cyclohexanone prepared as described in example lb and 0.55 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.05 gram of boron trifluoride etherate in 20 ml dry methanol was added and the resulting mixture was stirred at ambient temperature for 40 minutes. The reaction mixture was then refluxed for 8 hours. The reaction mixture was then cooled to ambient temperature and methanol distilled off under reduced pressure. The residue was dissolved in chloroform, washed with water, brine solution and dried over sodium sulphate. The solvent chloroform was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2-(4-hydroxy benzylidene)-6-(4-nitro benzylidene) cyclohexanone. The yield obtained was 1.22 gram. Example 5 1.5 gram of 2-(4-nitro phenyl-1-hydroxy methylene) cyclohexanone prepared as described in example lb and 0.75 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.08 gram of titanium tetrachloride 30 ml dry ethanol was added and the resulting mixture was stirred at ambient temperature for 50 minutes. The reaction mixture was then refluxed for 10 hours. The reaction mixture was then cooled to ambient temperature and ethanol distilled off under reduced pressure. The residue was dissolved in chloroform, washed with water, brine solution and dried over sodium sulphate. The solvent chloroform was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2- (4-hydroxy benzylidene)-6-(4-nitro benzylidene) cyclohexanone. The yield obtained was 1.80 gram. Example 6 0.75 gram of 2-(4-nitro phenyl-1-hydroxy methylene) cyclohexanone prepared as described in example lb and 0.85 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere . To this mixture 0.75 gram of anhydrous aluminium chloride in 2 0 ml dry dichloromethane was added and the resulting mixture was stirred an ambient temperature for 60 minutes. The reaction mixture was then refluxed for 12 hours. The reaction mixture was then cooled to ambient temperature and dichloromethane distilled off under reduced pressure. The residue was dissolved in dichloromethane, washed with water, brine solution and dried over magnesium sulphate. The solvent dichloromethane was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2- 4-hydroxy benzylidene)-6-(4-nitro benzylidene) cyclohexanone. The yield obtained was 1.65 gram. Example 7 (a) The 1-trimethyl silyloxy-1-cyclopentene is prepared by the known process and is described first. 32.6 gram of 1-trimethyl silyl chloride and 60.6 gram of triethylamine in 100 ml dry dimethyl fcrmamide and 21.0 gram of cyclopentanone were stirred together in an inert atmosphere. The reaction mixture was refluxed for 7 hours under inert atmosphere. The reaction was then cooled to ambient temperature and diluted with 200 ml of pentane, washed wich 300 ml of cold aqueous sodium bicarbonate. The organic layer was then washed with cold 1.5 N hydrochloric acid. The resulting organic layer was dried over anhydrous sodium sulphate and concentrated under reduced pressure and distilled under vacuum to get 18 grarr. of colourless 1-trimethyl silyloxy-1-cyclopentene. 1.26 grarr. of 1-trimethyl silyloxy-1-cyclopentene was mixed with 0.94 grarr. of 4-cyano benzaldehyde and 0.24 gram of sulphated zirconia in 40 ml of dichloromethane. A nitrogen atmosphere was maintained. The reactants were stirred at a temperature of 4 0°C for 48 hours. The reaction mass was filtered to recover the solid catalyst. The filtrate was washed with distilled water, dried over anhydrous sodium sulphate and the solvent was removed under reduced pressure. The resultant mass was then chromatographed through a silica gel column using a petroleum ether : acetone mixture {5:1 V/V) as the eluent to get the pure 2-(4-cyano phenyl-1-hydroxy methylene) cyclopentanone. The yield obtained was 1.34 gram. Example 7 (b) 0.46 gram of 1-trimethyl silyloxy-1-cyclopentene was mixed with 0.54 gram of 4-nitro benzaldehyde and 0.12 gram of sulphated zirconia in 20 ml of dichloromethane. A nitrogen atmosphere was maintained. The reactants were stirred at a temperature of 40°C for 40 hours. The reaction mass was filtered to recover the solid catalyst. The filtrate was washed with distilled water, dried over anhydrous sodium sulphate and the solvent was removed under reduced pressure. The resultant mass was then chromatographed through a silica gel column using a petroleum ether : acetone mixture {5:1 V/V) as the eluent to get the pure 2-(4-nitro phenyl-1-hydroxy methylene) cyclopentanone. The yield obtained was 1.3 4 gram. Example 7 C.55 gram of 2- (4-cyano phenyl-1- hydroxy methylene) cyclopentanone prepared as described in example 7a and 0.55 gram of 4-hydroxy benzaldehyde were mixed under argon atmosphere. To this mixture 0.05 gram of boron trifluoride etherate in 20 ml dry methanol was added and the resulting mixture was stirred at ambient temperature for 40 minuses. The reaction mixture was then refluxed for 8 hours. The reaction mixture was then cooled to ambient temperature and methanol distilled off under reduced pressure. The residue was dissolved in chloroform, washed with water, brine solution and dried over sodium sulphate. The solvent chloroform was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : peroleum ether as the eluent to get 2-(4-hydroxy benzylidene)-5-(4-cyano benzylidene) cyclopentanone. The product was recrystallised in chloroform. The yield obtained was 1.0 gram. Examp1e 8 1.26 gram of 2-(4-cyano phenyl-1-hydroxy methylene) cyclopentanone prepared as described in example 7a and 0.85 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.08 gram of titanium tetrachloride in 30 ml dry iscpropanol was added and the resulting mixture was stirred at ambient temperature for 50 minutes. The reaction mixture was then refluxed for 10 hours. The reaction mixture was then cooled to ambient temperature and isoprcpar.ol distilled off under reduced pressure. The residue was dissolved in chloroform, washed with water, brine solution and dried over magnesium sulphate. The solvent chloroform was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2-(4-hydroxy benzylidene)-5- (4-cyano benzylidene) cyclopentanone. The product was recrystallised in chloroform. The yield obtained was 1.45 gram. Example 9 0.62 gram of 2-(4-cyano phenyl-1-hydroxy methylene) cyclopentanone prepared as described in example 7a and 0.43 gram cf 4-hydroxy benzaldehyde were mixed under argon atmosphere. To this mixture 0.04 gram of anhydrous aluminium trichloride in 20 ml dry dichloromethane was added and the resulting mixture was stirred at ambient temperature for 45 minutes. The reaction mixture was then refluxed for 14 hours. The reaction mixture was then cooled to ambient temperature and dichloromethane distilled off under reduced pressure;. The residue was dissolved in dichloromethane, washed with water, brine solution and dried over magnesium sulphate. The solvent dichloromethane was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum, ether as the eluent to get 2-(4-hydroxy benzylidene)-5-(4 -cyano benzylidene) cyclopentanone. The product was recrystallised in dichloromethane. The yield obtained was 0.75 gram. Example 10 C. .55 gram of 2- (4-nitro phenyl-1-hydroxy methylene) cyclopentanone prepared as described in example 7b and 0.55 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.05 gram of boron trifluoride etherate in 20 ml dry methanol was added and the resulting mixture was stirred at ambient temperature for 40 minutes. The reaction mixture was then refluxed for 8 hours. The reaction mixture was then cooled to ambient temperature and methanol distilled off under reduced pressure. The residue was dissolved in chloroform, washed with water, brine solution and dried over sodium sulphate. The solvent chloroform was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2-(4-hydroxy benzylidene)-5-(4-nitro benzylidene) cyclopentanone. The yield obtained was 1.15 gram. Example 11 1.23 gram of 2- (4-nitro phenyl-1-hydroxy methylene) cyclopentanone prepared as described in example 7b and 0.85 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.08 gram of titanium tetrachloride in 30 ml dry isopropanol was added and the resulting mixture was stirred at ambient temperature for 50 minutes. The reaction mixture was then refluxed for 10 hours. The reaction mixture was then cooled to ambient temperature and isopropanol distilled off under reduced pressure. The residue was dissolved in chloroform, washed with water, brine solution and dried over magnesium sulphate. The solvent chloroform was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2-(4-hydroxy benzylidene)-5-(4-nitro benzylidene) cyclopentanone. The product was recrystallised in chloroform. The yield obtained was 1.80 gram. Example 12 0.95 gram of 2-(4-nitro phenyl-1-hydroxy methylene) cyclopentanone prepared as described in example 7b and 0 . 54 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.04 gram of anhydrous aluminium trichloride in 2 0 ml dry dichloromethane was added and the resulting mixture was stirred at ambient temperature for 45 minutes. The reaction mixture was then refluxed for 14 hours. The reaction mixture was then cooled to ambient temperature and dichloromethane distilled cff under reduced pressure. The residue was dissolved in dichloromethane, washed with water, brine solution and dried over magnesium sulphate. The solvent dichloromethane was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get 2-(4-hydroxy benzylidene)-5-(4-nitro benzylidene) cyclopentanone. The yield obtained was 1.15 gram. Example 13 (a) The 4-methyl-1-trimethyl silyloxy-1-cyclohexene is prepared by the known process. 32.6 gram of 1-trimethyl silyl chloride and 60.6 gram of triethylamine in 100 ml dry dimethyl formamide and 23.0 gram of 4-methyl cyclohexanone v/ere stirred together in an inert atmosphere. The reaction mixture was refiuxed for 5 hours under inert atmosphere. The reaction was then cooled to ambient temperature and diluted with 200 ml of pentane, washed with 300 ml of cold aqueous sodium bicarbonate. The organic layer was then washed with cold 1.5 N hydrochloric acid. The resulting organic layer was dried over anhydrous sodium sulphate and concentrated under reduced pressure and distilled under vacuum to get 32 gram of colourless 4-methyl-l-trimethyl silyloxy-1-cyclohexene. 1.40 gram of 4-methyl-1-trimethyl silyloxy-1-cyclohexene was mixed with 0.94 gram of 4-cyano benzaldehyde and 0.24 gram of sulphated zirconia in 40 ml of dichloromethane. A nitrogen atmosphere was maintained. The reactants were stirred at a temperature of 50°C for 36 hours. The reaction mixture was filtered to recover the solid catalyst. The filtrate was washed with distilled water, dried over anhydrous sodium sulphate and the solvent was removed under reduced pressure. The resultant mass was then chromatographed through a silica gel column using a petroleum ether : acetone mixture (5:1 V/V) as the eluent to get the pure 2- (4-cyano phenyl- 1 - hydroxy methylene)-4-methyl cyclohexanone. The yield obtained was 1.56 gram. Example 13 (b) 0.72 gram of 4-methyl-1-trimethyl silyloxy-1-cyclohexene was mixed with 0.55 gram of 4-nitro benzaldehyde and 0.12 gram of suiphated zirconia in 3 0 ml of dichloromethane. A nitrogen atmosphere was maintained. The reactants were stirred at a temperature of 4 0°C for 48 hours. The reaction mass was filtered to recover the solid catalyst. The filtrate was washed with disrilled water, dried over anhydrous magnesium sulphate and the solvent was removed under reduced pressure. The resultant mass was then chromatographed through a silica gel column using a petroleum ether : acetone mixture (5:1 V/V) as the eluent to get the pure 2-(4-nitro phenyl-1-hydroxy methylene)-4-methyl cyclohexanone. The yield obtained was 0.79 gram. Example 13 0.98 gram of 2-(4-cyano phenyl-1-hydroxy methylene)-4-methyl cyclohexanone prepared as described in example 13a and 0.55 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To ihis mixture 0.05 gram of boron trifluoride etherate in 20 ml dry methanol was added and the resulting mixture was stirred at ambient temperature for 40 minutes. The reaction mixture was then refluxed for 8 hours. The reaction mixture was then cooled to ambient temperature and methanol distilled off under reduced pressure. The residue was dissolved in chloroform, washed with water, brine solution and dried over sodium sulphate. The solvent chloroform was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as the eluent to get. 2-(4-hydroxy benzylidene)-6-(4-cyano benzylidene)-4-methyl cyclohexanone. The product was recrystallised in chloroform. The yield obtained was 1.20 gram. Example 14 1.47 gram of 2-(4-cyano phenyl-1-hydroxy methylene)-4-methyl cyclohexanone prepared as described in example 13a and 1.25 gram of 4-hydroxy benzaldehyde were mixed under argon atmosphere. To this mixture 0.08 gram of titanium tetrachloride in 30 ml dry acetonitrile was added and the resulting mixture was stirred at ambient temperature for 60 minutes. The reaction mixture was then refluxed for 10 hours. The reaction mixture was then cooled to ambient temperature and acetonitriie distilled off under reduced pressure. The residue was dissolved in dichloromethane, washed with water, brine solution and dried over sodium sulphate. The solvent dichloromethane was removed under reduced pressure and the material was column chromtatographed on silica gel using 10 % V/V acetone : petroleum ether as an eluent to get 2-(4-hydroxy benzylidene)-6-(4-cyano benzylidene)-4-methyl cyclohexanone. The product was recrystallised in dichloromethane. The yield obtained was 1.80 gram. Example 15 1.95 gram of 2-(4-cyano phenyl-1-hydroxy methylene)-4-methyl cyclohexanone prepared as described in example 13a and 1.10 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.10 gram of anhydrous aluminium chloride in 40 ml dry dichloroethane was added and the resulting mixture was stirred at ambient temperature for 30 minutes. The reaction mixture was then refluxed for 12 hours. The reaction mixture was then cooled to ambient temperature and dichloroethane distilled off under reduced pressure. The residue was dissolved in dichloroethane, washed with water, brine solution and dried over sodium sulphate. The solvent dichloroethane was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as an eluent to get 2-(4-hydroxy benzylidene) -6 - (4-cyano benzylidene) -4-methyl cyclohexanone. The product was recrystallised in dichloroethane. The yield obtained was 2.40 gram. Example 16 1.10 gram of 2- (4-nitro phenyl-1- hydroxy methylene) -4-methyl cyclohexanone prepared as described in example 13b and 0.55 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.05 gram of boron trifluoride etherate in 20 ml dry methanol was added and the resulting mixture was stirred at ambient temperature for 40 minutes. The reaction mixture was then refluxed for 8 hours. The reaction mixture was then cooled to ambient temperature and methanol distilled off under reduced pressure. The residue was dissolved in chloroform, washed with water, brine solution and dried over sodium sulphate. The solvent chloroform was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as an eluent to get 2-(4-hydroxy benzylidene)-6-(4-nitro benzylidene)-4-methyl cyclohexanone. The yield obtained was 1.27 gram. Example 17 1.65 gram of 2- (4-nitro phenyl-1 - hydroxy methylene)-4-methyl cyclohexanone prepared as described in example 13b and 0.85 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.08 gram of titanium tetrachloride in 3 0 ml dry acetonitrile was added and the resulting mixture was stirred at ambient temperature for 60 minutes. The reaction mixture was then refluxed for 10 hours. The reaction mixture was then cooled to ambient temperature and acetonitrile distilled off under reduced pressure. The residue was dissolved in dichloromethane, washed with water, brine solution and dried over sodium sulphate. The solvent dichloromethane was removed under reduced pressure and the material was column chronatographed on silica gel using 10 % V/V acetone : petroleum ether as an eluent to get 2-(4-hydroxy benzylidene)-5-(4-nitro benzylidene)-4-methyl cyclohexanone. The yield obtained was 1.87 gram. Example 18 1.95 gram of 2-(4-nitro phenyl-1-hydroxy methylene)-4-methyl cyclohexanone prepared as described in example 13b and 1.10 gram of 4-hydroxy benzaldehyde were mixed under nitrogen atmosphere. To this mixture 0.10 gram of anhydrous aluminium chloride in 40 ml dry dichloroethane was added and the resulting mixture was stirred at ambient temperature for 30 minutes. The reaction mixture was then refluxed for 12 hours. The reaction mixture was then cooled to ambient temperature and dichloroethane distilled off under reduced pressure. The residue was dissolved in dichloroethane, washed with water, brine solution and dried over sodium sulphate. The solvent dichloroethane was removed under reduced pressure and the material was column chromatographed on silica gel using 10 % V/V acetone : petroleum ether as an eluent to get 2-(4-hydroxy benzylidene)-6-(4-nitro benzylidene)-4-methyl cyclohexanone. The product was recrystallised in dichloroethane. The yield obtained was 2.40 gram. Advantages : 1. The product obtained as per the process of this invention meets the stringent purity requirements for use as a mesogen in the synthesis of side chain liquid crystalline polymers for non-linear optical applications. 2 . The process is amenable to scale up to meet the requirements which are usually small. We Claim: 1. A process for the preparation of unsymmetrically disubstituted cycloalkanones which comprises ; reacting 2-(aryl-1-hydroxy methylene) cycloalkanones of formula 2 of the drawing accompanying this specification , in the presence of a catalyst and a dry organic solvent such as herein described, under inert atmosphere, stirring the mixture initially at ambient temperature for a period up to 60 minutes, refluxing the reaction mixture for a period 14 hours, removing the organic solvent under reduced pressure, dissolving the obtained residue in an organic solvent as defined above, washing with water, followed by brine solution, drying the organic layer over a drying agent, concentrating under reduced pressure and separating the compound by column chromatography using a silica gel column and suitable eluent solvent system as described herein followed by re crystallization to get desired unsymmetrically disubstituted cycloalkanones of formula 1 of the drawing accompanying this specification. 2. A process as claimed in claim 1 wherein, the 2-(aryl-1-hydroxy methylene) cycloalkanone is selected from 2-(4-cyano/nitro phenyl-1-hydroxy methylene) cyclohexanone, 2-(4-cyano/nydro phenyl-1-hydroxy methylene) cyclopentanone, 2-(4-cyano/nitro phenyl-1-hydroxy methylene) 4-methyl cyclohexanone. 3. A process as claimed in claims 1 and 2 wherein, the inert atmosphere may be maintained by using nitrogen or argon. 4. A process as claimed in claims 1 to 3 wherein, the catalyst used is such as boron trifluoride etherate, titanium tetrachloride, anhydrous aluminium chloride. 5. A process as claimed in claims 1 to 4 wherein, the dry organic solvent used is such as acetonitrile, methanol, ethanol, isopropanol, chloroform, dichloroethane, dichloromethane. 6. A process as claimed in claims 1 to 5 wherein, the solvent used for purification of compound by column chromatography is such as chloroform, carbon tetrachloride, dichloroethane, dichloromethane. 7. A process as claimed in claims 1 to 6 wherein, the drying agent used is such as from sodium sulphate, magnesium sulphate, phosphorous pentoxide and calcium chloride. 8. A process for the preparation of unsymmetrically disubstituted cycloalkanones substantially as herein described with reference to the examples.

Documents:

426-del-1997-abstract.pdf

426-del-1997-claims.pdf

426-del-1997-complete specifiction (grantded).pdf

426-del-1997-correspondence-others.pdf

426-del-1997-correspondence-po.pdf

426-del-1997-description (complete).pdf

426-del-1997-drawings.pdf

426-del-1997-form-1.pdf

426-del-1997-form-19.pdf

426-del-1997-form-2.pdf

426-del-1997-form-3.pdf