Recent Developments in Asymmetric Phase-Transfer Reactions

Phase‐transfer catalysis has been recognized as a powerful method for establishing practical protocols for organic synthesis, because it offers several advantages, such as operational simplicity, mild reaction conditions, suitability for large‐scale synthesis, and the environmentally benign nature of the reaction system. Since the pioneering studies on highly enantioselective alkylations promoted by chiral phase‐transfer catalysts, this research field has served as an attractive area for the pursuit of “green” sustainable chemistry. A wide variety of asymmetric transformations catalyzed by chiral onium salts and crown ethers have been developed for the synthesis of valuable organic compounds in the past several decades, especially in recent years. Work in process: The variations in the synthetic applications of phase‐transfer reactions between 2006 and the middle of 2012 have been summarized to show the recent progress made in this field. The reactions have been applied to the synthesis of biologically active natural products and the large‐scale preparation of drugs. The conceptually new catalyst design, reaction system, and reaction mode are also described.