Review on Asymmetric Transformations with Chiral Phase-Transfer Catalysts

Abstract

This review focuses onasymmetric transformations with Chiral Phase-Transfer Catalysts and its application. Phase-transfer catalysis is practical methodology for organic synthesis. It is possible to achieve highly enantio selective transformations under phase-transfer conditions for a variety of ─C─C─ ─C─O─ and ─C─N─ bond-forming reactions. The asymmetric transformations using modified cinchona alkaloids, chiral spiro ammonium salts and crown ether are among the primary source of effective chiral phase-transfer catalyst, which allows access to enantiomerically pure unnatural amino acids and synthetically useful adducts containing quaternary stereogenic centers. The advantage of this method is its simple experimental procedure, large chiral pool, mild reaction condition, inexpensive, environmentally benign reagent and use of simple and inexpensive reactants. Nowadays, it appears to be the most important synthetic method used in various fields of organic chemistry, and also found widespread industrial applications. This review summarizes the synthesis application, enantio selective transformation of some selected reaction, biological activities and catalytic activities of Phase-transfer catalysis and especial emphasis is given for organo catalysis. In asymmetric organo catalyst, it is possible to obtain chiral organic products in high enantio enriched form by steric hindrance approach method. The advantage of organic molecules as chiral catalysts complements the traditional organo-metallic and biological approaches to asymmetric catalysis.