Studies in Asymmetric Epoxidation of Chalcone Using Quaternary Salts and Nonionic Surfactants Based on 6-Amino-6-deoxy-glucose as Chiral Phase Transfer Catalysts

Lalit Sharma,Saroj Saroj,Subhash Chander Sharma

doi:10.1155/2011/873253

Abstract

Quaternary salts and nonionic surfactants based on 6-amino-6-deoxy-glucose were explored as chiral phase transfer catalysts for the asymmetric epoxidation of chalcone. Quaternary salts used in the present study, were void of any branched chain or long hydrocarbon chain, whereas the sugar based nonionic surfactants have a long hexadecyl moiety as tail. It was observed that quaternary salts showed no activity as phase transfer catalysts but sugar based nonionic surfactants acted as chiral phase transfer catalysts. It was also revealed that hydrophilicity of the surfactant favors more yield whereas stereochemistry governs enantioselectivity. (6,6'-Hexadecylimino) bis(6-deoxy-1,2-O-isopropylidene-α-D-glucofuranose) was found to be the most suitable chiral phase transfer catalyst, resulting asymmetric epoxidation of chalcone with 90% yield and 16.5% enantiomeric excess (ee).

Highlights

Sharpless paved the way for much of today’s catalytic asymmetric syntheses1, the use of phase-transfer catalysts in asymmetric synthesis was described2-6 in the mid-1970s
The present study describes the use of quaternary salts of some 6-amino-6-deoxy-D-glucose derivatives and glucose based nonionic surfactants for the asymmetric epoxidation of chalcone
Preliminary studies were focused on the investigation of the asymmetric epoxidation of chalcone [1] with catalytic amount (0.5 mM) of sugar quaternary salts [3,4,5] of 6-amino-6

Summary

Introduction

Sharpless paved the way for much of today’s catalytic asymmetric syntheses1, the use of phase-transfer catalysts in asymmetric synthesis was described2-6 in the mid-1970s. Some new methods for asymmetric enone epoxidation have been reported10-15, but the possibility of using sugar based quaternary salts and nonionic surfactants as chiral phase transfer catalysts has not been systematically explored or generalized. The present study describes the use of quaternary salts of some 6-amino-6-deoxy-D-glucose derivatives and glucose based nonionic surfactants for the asymmetric epoxidation of chalcone.

Results

Conclusion