Title of Invention

"A PROCESS FOR THE PREPARATION OF MONOSUBSTITUTED CYCLOALKANONES"

Abstract

A process for the preparation of monosubstituted cycloalka-nones by reacting cycloalkanone with 4-amino benzaldehyde in the presence of an alcoholic solution of alkali metal hydrox-ide in an inert atmosphere stirring the reaction mixture for a period ranging from 120 to 130 hours, neutralising the result-ant reaction mixture with a mineral acid, dissolving the reaction product in an organic chlorinated solvent, washing the extract with water, drying the extract over a suitable drying agent at ambient temperature for 12 to 16 hours, con-centrating the extract, and separating mono substituted cycle alkanone by column chromatography methods using eluent mix-ture .

Full Text

This a invention relates to a process for the preparation of monosubstituted cycloalkanones. More particularly it relates to the preparation of 2-(4-amino benzylidene) cycloalkanones having the general formula 1 given in the drawing accompanying this specification wherein R = nil, -CH2-, -CH(CH3)- These compounds form precursors that are useful for the preparation of mesogens for non-linear optical applications. The precursors prepared by the process of this invention are based on mono substituted cyclohexanones/ cyclopentanones. The precursors prepared by the process of this invention can be further reacted under suitable reaction conditions to prepare new mesogens useful for the synthesis of new side chain liquid crystalline polymers. The new side chain liquid crystalline polymers prepared are 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 properties. 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 of non-linear optical applications are inorganic salts such as potassium dideuterium phosphate, lithium niobate, potassium titanyl phosphate etc. Organic materials offer the advantage of high density packing and specific arrangement of molecules in the crystalline state. While the organic materials offer superior properties in comparison with inorganic materials, practical utilization poses several problems. In addition, the development of organic materials which offer superior non-linear optical properties have been hindered because of the low threshold limits of these materials on exposure to strong radiations such as laser beam. Amongst the various approaches towards development of materials for non-linear optical applications such as crystal growth, growth in confined structures, monolayer assemblies such as the Langmuir-Bludget films and poled polymer systems. The precursors prepared by the process of this invention can be used in the preparation of side chain liquid crystalline polymers for poled polymer systems. The advantages offered by the poled polymer systems are greater flexibility in the selection of mesogenic and polymeric structures and ease of fabrication of devices. The side chain liquid crystalline polymer synthesised using the mesogen as per the process of this invention could be used in poled polymer systems. Poling of polymers is done by subjecting the polymer usually in the form of a film to an external electric field at an elevated temperature followed by cooling to ambient temperature before the 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 applica-tions, it must satisfy primary optical property requirements. The primary optical property is characterised by the material having substantial transparency to light of desired frequency. The main object of the present invention is therefore to provide a process for the preparation of substituted benzyli-dene cycloalkanones. The substituted benzylidene cycloalkanones, namely 2-(4-amino benzylidene) cycloalkanones are reportedly synthesised for the first time by the inventors of the present invention and hence there are no earlier methods known for the prepara-tion of these compounds. The precursors prepared by the process of this invention can be further reacted under suitable reaction conditions to prepare new mesogens useful for the synthesis of side chain liquid crystalline polymers. The side chain liquid crystalline polymer prepared is useful for non-linear optical applica¬tions . Accordingly, the present invention provides a process for the preparation of monosubstituted cycloalkanones of formula 1 of the drawing accompanying the specification wherein R=nil,-CH2, -CH(CH3)- which comprises : (i) reacting cycloalkanone with 4-amino benzaldehyde in the presence of an alcoholic solution of alkali metal hydroxide in an inert atmosphere stirring the reaction mixture for a period ranging from 120 to 130 hours, (ii) neutralising the resultant reaction mixture with a mineral acid, (iii) dissolving the reaction product in an organic chlorinat¬ed solvent, (iv) washing the extract with water, (v) drying the extract over a suitable drying agent at ambi¬ent temperature for 12 to 16 hours, (vi) concentrating the extract, and separating mono substi¬tuted cycle alkanone by column chromatography methods using eluent mixture. In an embodiment of the present invention, the gas used for inert atmosphere is selected from nitrogen or argon. In yet another another feature of the invention, the cy-cloalkanone used is selected from cyclohexanone, cyclopenta-none, 4-methyl cyclohexanone. In yet another feature of the invention, the alcohol used to prepare the solution of alkali metal hydroxide is selected from methanol, ethanol. In yet another feature of the invention, the alkali metal hydroxide used is selected from sodium hydroxide, potassium hydroxide. In yet another embodiment of the invention, the mineral acid used for neutralising the reaction is selected from hydro¬chloric acid, nitric acid, sulphuric acid. In yet another embodiment of the invention, the chlorinated solvent used may be such as dichloromethane, chloroform, carbon tetrachloride, dichloroethanes. In yet another embodiment of the invention, the drying agent may be such as sodium sulphate, magnesium sulphate, phosphorous pentoxide. In yet another embodiment of the invention, the eluent used to separate the product may be in the ratio of 10 : 90 to 16 : 84 mixture of acetone and petroleum ether. In a feature of the invention, the product is separated by column chromatography using a neutral alumina column. 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 0.49 gram of cyclohexanone and 0.18 gram of 4-amino benzaldehyde were mixed with 20 ml of 3 weight % methanolic potassium hydroxide solution in an inert atmosphere of nitrogen. The resulting solution was stirred for 5 days at a temperature of 50°C. The reaction was then cooled to ambient temperature and neutralised with 10 % hydrochloric acid to a pH of 7.5. Methanol was removed under reduced pressure. The product was dissolved in dichloromethane and washed with water. The organic phase was dried over anhydrous sodium sulphate and concentrated under reduced pressure followed by column chromatography on neutralalumina using 13 % (V/V) mixture of acetone in petroleum ether to get pure 2-(4-amino benzylidene)cyclohexanone. The yield obtained was 0.195 gram. Example 2 0.32 gram of cyclohexanone and 0.12 gram of 4-amino benzaldehyde were mixed with 12 ml of 3 weight % ethanolic potassium hydroxide solution in an inert atmonphoro of: argon. The resulting solution was stirred for 130 hours at a temperature of 45°C. The reaction was then cooled to ambient temperature and neutralised with 10 % sulphuric acid to a pH of 7.5. Ethanol was removed under reduced pressure. The product was dissolved in dichloroethane and washed with water. The organic phase was dried over anhydrous magnesium sulphate and concentrated under reduced pressure followed by column chromatography on neutral alumina using 13 % (V/V) mixture of acetone in petroleum ether to get pure 2- (4-amino benzylidene)cyclohexanone. The yield obtained was 0.13 gram. Example 3 0.75 gram of cyclohexanone and 0.26 gram of 4-amino benzaldehyde were mixed with 35 ml of 3 weight % methanolic sodium hydroxide solution in an inert atmosphere of nitrogen. The resulting solution was stirred for 125 hours at a temperature of 55°C. The reaction was then cooled to ambient temperature and neutralised with 10 % sulphuric acid to a pH of 7.5. Methanol was removed under reduced pressure. The product was dissolved in carbon tetrachloride and washed with water. The organic phase was dried over anhydrous magnesium sulphate and concentrated under reduced pressure followed by column chromatography on neutral alumina using 13 % (V/V) mixture of acetone in petroleum ether to get pure 2-(4-amino benzylidene)cyclohexanone. The yield obtained was 0.30 gram. Example 4 0.42 gram of cyclopentanone and 0.18 gram of 4-amino benzaldehyde were mixed with 20 ml of 3 weight % ethanolic sodium hydroxide solution in an inert atmosphere of nitrogen. The resulting solution was stirred for 120 hours at a temperature of 50°C. The reaction was then cooled to ambient temperature and neutralised with 10 % nitric acid to a pH of 7.5. Ethanol was removed under reduced pressure. The product was dissolved in carbon tetrachloride and washed with water. The organic phase was dried over anhydrous magnesium sulphate and concentrated under reduced pressure followed by column chromatography on neutral alumina using 13 % (V/V) mixture of acetone in petroleum ether to get pure 2-(4-amino benzylidene)cyclopentanone. The yield obtained was 0.21 gram. Example 5 0.28 gram of cyclopentanone and 0.12 gram of 4-amino benzaldehyde were mixed with 14 ml of 3 weight % ethanolic potassium hydroxide solution in an inert atmosphere of argon. The resulting solution was stirred for 130 hours at a temperature of 45°C. The reaction was then cooled to ambient temperature and neutralised with 10 % sulphuric acid to a pH of 7.5. Ethanol was removed under reduced pressure. The product was dissolved in dichloroethane and washed with water. The organic phase was dried over anhydrous magnesium sulphate and concentrated under reduced pressure followed by column chromatography on neutral alumina using 13 % (V/V) mixture of acetone in petroleum ether to get pure 2-(4-amino benzylidene)cyclopentanone. The yield obtained was 0.14 gram. Example 6 0.63- gram of cyclopentanone and 0.26 gram of 4-amino benzaldehyde were mixed with 35 ml of 3 weight % methanolic sodium hydroxide solution in an inert atmosphere of nitrogen. The resulting solution was stirred for 125 hours at a temperature of 55°C. The reaction was then cooled to ambient temperature and neutralised with 10 % hydrochloric acid to a pH of 7.5. Methanol was removed under reduced pressure. The product was dissolved in dichloromethane and washed with water. The organic phase was dried over anhydrous magnesium sulphate and concentrated under reduced pressure followed by column chromatography on neutral alumina using 13 % (V/V) mixture of acetone in petroleum ether to get pure 2-(4-amino benzylidene)cyclopentanone. The yield obtained was 0.32 gram. Example 7 0.56 gram of 4-methyl cyclohexanone and 0.18 gram of 4-amino benzaldehyde were mixed with 20 ml of 3 weight % methanolic potassium hydroxide solution in an inert atmosphere of nitrogen. The resulting solution was stirred for 120 hours at a temperature of 50°C. The reaction was then cooled to ambient temperature and neutralised with 10 % hydrochloric acid to a pH of 7.5. Methanol was removed under reduced pressure. The product was dissolved in dichloromethane and washed with water. The organic phase was dried over anhydrous sodium sulphate and concentrated under reduced pressure followed by column chromatography on neutral alumina using 13 % (V/V) mixture of acetone in petroleum ether to get pure 2-(4-amino benzylidene)-4-methyl cyclohexanone. The yield obtained was 0.19 gram. Example 8 0.38 gram of 4-methyl cyclohexanone and 0.12 gram of 4-amino benzaldehyde were mixed with 15 ml of 3 weight % ethanolic potassium hydroxide solution in an inert atmosphere of argon. The resulting solution was stirred for 130 hours at a temperature of 45°C. The reaction was then cooled to ambient temperature and neutralised with 10 % hydrochloric acid to a pH of 7.5. Ethanol was removed under reduced pressure. The product was dissolved in dichloroethane and washed with water. The organic phase was dried over anhydrous magnesium sulphate and concentrated under reduced pressure followed by column chromatography on neutral alumina using 13 % (V/V) mixture of acetone in petroleum ether to get pure 2-(4-amino benzylidene)-4-methyl cyclohexanone. The yield obtained was 0.13 gram. Example 9 0.95 gram of 4-methyl cyclohexanone and 0.26 gram of 4-amino benzaldehyde were mixed with 35 ml of 3 weight % methanolic sodium hydroxide solution in an inert atmosphere of nitrogen. The resulting solution was stirred for 125 hours at a temperature of 55°C. The reaction was then cooled to ambient temperature and neutralised with 10 % sulphuric acid to a pH of 7.5. Methanol was removed under reduced pressure. The product was dissolved in carbon tetrachloride and washed with water. The organic phase was dried over anhydrous magnesium sulphate and concentrated under reduced pressure followed by column chromatography on neutral alumina using 13 % (V/V) mixture of acetone in petroleum ether to get pure 2-(4-amino benzylidene)-4-methyl cyclohexanone. The yield obtained was 0.30 gram. The advantages of the present invention are : 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, .pa We claim : 1. A process for the preparation of monosubstituted cycloal- kanones of formula 1 of the drawing accompanying the specifi¬ cation wherein R=nil,-CH2, -CH(CH3)- which comprises : (i) reacting cycloalkanone with 4-amino benzaldehyde in the presence of an alcoholic solution of alkali metal hydroxide in an inert atmosphere stirring the reaction mixture for a period ranging from 120 to 130 hours, (ii) neutralising the resultant reaction mixture with a mineral acid, (iii) dissolving the reaction product in an organic chlorinat¬ed solvent, (iv) washing the extract with water, (v) drying the extract over a suitable drying agent at ambi¬ent temperature for 12 to 16 hours, (vi) concentrating the extract, and separating mono substi¬tuted cycle alkanone by column chromatography methods using eluent mixture. 2. A process as claimed in claim 1, wherein, the gas used for inert atmosphere is nitrogen or argon. 3. A process as claimed in claims 1 and 2, wherein, the cycloalkanone used is cyclohexanone, cyclopentanone, 4-methyl cyclohexanone. 4. A process as claimed in claims 1 to 3, wherein, the alco¬ hol used to prepare the solution of alkali metal alkoxide is methanol, ethanol. 5. A process as claimed in claims 1 to 4, wherein, the alkali metal hydroxide used is sodium hydroxide, potassium hydroxide. 6. A process as claimed in claims 1 to 5, wherein, the mineral acid used for neutralising the reaction is hydrochloric acid, nitric acid, sulphuric acid. 7. A process as claimed in claims 1 to 6, wherein, the chlo- rinated organic solvent used is dichloromethane, chloroform, carbon tetrachloride, dichloroethanes. 8. A process as claimed in claims 1 to 7, wherein, the drying agent used is sodium sulphate, magnesium sulphate, phosphorous pentoxide. 9. A process as claimed in claims 1 to 8, wherein, the eluent mixture used for separation of the compound is a mix- ture of acetone and petroleum ether in a ratio of ranging from 10:90 to 16:84. 10. A process for the preparation of monosubstituted cycloal- kanones substantially as described hereinbefore with reference to the examples.

Documents:

3348-del-1997-abstract.pdf

3348-del-1997-claims.pdf

3348-del-1997-correspondence-others.pdf

3348-del-1997-correspondence-po.pdf

3348-del-1997-description (complete).pdf

3348-del-1997-drawings.pdf

3348-del-1997-form-1.pdf

3348-del-1997-form-2.pdf

3348-del-1997-form-3.pdf

3348-del-1997-form-6.pdf

3348-del-1997-gpa.pdf

3348-del-1997-petition-138.pdf