Organic-inorganic hybrid chiral sorbent and process for the preparation thereof

Abstract

The present invention provides an organic-inorganic hybrid chiral sorbent for chiral resolution of various racemic compounds viz. racemic mandelic acid, 2-phenyl propionic acid, diethyl tartrate, 2,2′-dihydroxy-1,1′-binaphthalene (BINOL) and cyano chromene oxide with excellent chiral separation (enantiomeric excess, 99%) in case of mandelic acid under medium pressure column chromatography. These optically pure enantiomers find applications as intermediates in pharmaceutical industries.

1 . An organic-inorganic hybrid chiral sorbent comprising amino alcohol covalently bonded to the surface of mesoporous silica material. 
     
     
         2 . A product according to  claim 1 , wherein the amino alcohol used is amino propyl alcohol. 
     
     
         3 . A product according to  claim 1 , wherein the porous silica material used is having porosity in the range of 37 to 100 Å and is selected from the group consisting of MCM-41, SBA-15 and MCF-48. 
     
     
         4 . A product according to  claim 1 , wherein the product obtained is represented by the group of following chiral sorbents: (S)-aminopropyl alcohol@silica-41, (R)-aminopropyl alcohol@silica-41, (S)-aminopropyl alcohol@silica-15, (R)-aminopropyl alcohol@silica-15, (S)-aminopropyl alcohol@silica-F, (R)-aminopropyl alcohol@silica-F, (S)—N-methyl aminopropyl alcohol@silica-41, (R)—N-methyl aminopropyl alcohol@silica-41, (S)—N,N′dimethyl aminopropyl alcohol@silica-41, (S)—N,N′dimethyl aminopropyl alcohol@silica-15 and (S)—N-methyl aminopropyl alcohol@silica-15 
     
     
         5 . A product according to  claim 1 , wherein the chiral sorbent is useful for the separation of racemic mixture of compound selected from the group consisting of mandelic acid, 2-phenyl propionic acid, diethyl tartrate, 2,2′-dihydroxy-1,1′-binaphthalene (BINOL) and cyano chromene oxide. 
     
     
         6 . A process for the preparation of an organic-inorganic hybrid chiral sorbent, the said process comprising the steps of:
 a) silylating the chiral epoxide with a silylating agent in an organic solvent with a molar ratio of chiral epoxide to silylating agent of about 1:1 in the presence of an inorganic base in the range of 1:1 to 1:2.5,   b) refluxing, the above said reaction mixture obtained in step (a) under an inert atmosphere for a period of 8 to 16 hours, followed by filtration to obtain the resultant filtrate,   c) refluxing, the above said filterate obtained in step (b) with mesoporous silica, under inert atmosphere for a period of about 35 to 55 hours, followed by filtration and washing of the resultant solid product with toluene by known methods,   d) reacting the resultant washed product obtained in step (c) with aniline or substituted aniline in toluene, under reflux, under an inert atmosphere for a period of 8 to 16 hours, followed by filtration and washing off the resultant product with toluene and extracting the desired chiral sorbent in a solution mixture of toluene and isopropanol by known methods to obtain the desired product of organic-inorganic hybrid chiral sorbent.   
     
     
         7 . A process according to  claim 6 , wherein the chiral epoxide used in step(a) is selected from the group consisting of propene oxide, 1-chloro-2,3-epoxypropane, 1-fluoro-2,3-epoxypropane, 1-bromo-2,3-epoxypropane, 1-methyl-2,3-epoxypropane, 1-methoxy-2,3-epoxypropane and 1-nitro-2,3-epoxypropane. 
     
     
         8 . A process according to  claim 6 , wherein the silylating agent used in step(a) is selected from the group consisting of chloropropyl triethoxysilane, chloropropyltrimethoxy, nitropropyltriethoxysilane, aminopropyltriethoxysilane and aminopropyltrimethoxysilane. 
     
     
         9 . A process according to  claim 6 , wherein the inorganic base used in step (a) is selected from the group consisting of sodium carbonate, potassium carbonate, rubidium carbonate and cesium carbonate. 
     
     
         10 . A process according to  claim 6 , wherein the organic solvent used in step(a) is selected from the group consisting of ethanol, methanol, isopropanol, acetone, acetonitrile, toluene, tetrahydrofuran, dichloroethane and dichloromethane. 
     
     
         11 . A process according to  claim 6 , wherein the mesoporous silica used in step (c) is selected from the group consisting of MCM-41, SBA-15 and MCF-48. 
     
     
         12 . A process according to  claim 6 , wherein the inert atmosphere used is provided by using inert gas selected from nitrogen, argon and helium. 
     
     
         13 . A process according to  claim 6 , wherein the molar amount of aniline or substituted aniline with respect to chiral epoxide is in the range of 1:1 to 1:2. 
     
     
         14 . A process according to  claim 6 , wherein the substituted aniline used is selected from the group consisting of nitroaniline, chloroaniline, methoxyaniline and methylaniline. 
     
     
         15 . A process according to  claim 6 , wherein the amount of mesoporous silica used is in the range of 0.8 to 12 g/mmol of chiral epoxide. 
     
     
         16 . A process according to  claim 6 , wherein the chiral sorbent obtained in step(d) is represented by the group of following sorbents: mandelic acid, 2-phenyl propionic acid, diethyl tartrate, 2,2′-dihydroxy-1,1′-binaphthalene (BINOL) and cyano chromene oxide. 
     
     
         17 . A process according to  claim 6 , wherein the chiral sorbent obtained is useful for the separation of racemic mixtures of compound selected from the group consisting of mandelic acid, 2-phenyl propionic acid, diethyl tartrate, 2,2′-dihydroxy-1,1′-binaphthalene (BINOL) and cyano chromene oxide. 
     
     
         18 . A process according to  claim 17 , wherein the enantiomeric excess of racemates obtained is in the range of 30 to 99%. 
     
     
         19 . A process according to  claim 18 , wherein the maximum enantiomeric excess obtained for mandelic acid with aminopropylalcohol@silica sorbent is about 99%.