Recent development and application of chiral phase-transfer catalysts

A review on the asymmetric reactions with various types of chiral quaternary ammonium salts which is used as the phase-transfer catalysts is presented which shows off the variations of the molecular designs and synthetic applications. The topics discussed include the alkylation, the Michael addition, the aldol reaction, Mannich reaction, Darzens reaction, the Neber rearrangement, epoxidation, aziridination, dihydroxylation, fluorination, and the Strecker reaction. Chiral phase-transfer catalysts maybe developed with the reliance on the molecular design of both the natural product-derived and purely synthetic chiral quaternary ammonium salts. This development provides new synthetic opportunities by expanding the applicability of this catalysis in modern organic synthesis.