New Methodologies for Organocatalytic C-C Bond Formations

Synthesis of enantiomerically pure molecules has become a significant area of research in organic synthesis in recent years. For a few decades, asymmetric synthesis mainly relied on the use of metal based catalysts which provided synthetic chemists with powerful tools to perform asymmetric oxidations, reductions, cycloadditions, conjugate additions, and -bond activation reactions. The importance of enantioselective metal catalysis has been recognized by awarding the 2001 Nobel Prize in Chemistry to William S. Knowles. Ryoji Noyori and K. Barry Sharpless for their landmark works in this field. In recent years metal-free chiral organic molecules have emerged as alternative catalysts in organic synthesis. In 1912, Bredig reported that cinchona alkaloids were used as catalysts in a cyanohydrin synthesis8 with low enantioselectivities. Later, in 1960 Pracejus reported an asymmetric ketene methanolysis catalyzed by optically active alkaloids. Hajos and Wiechert11discovered that the enantioselective aldol reactions could be catalyzed by the simple amino acid proline to yield the desired aldol which is widely used as a precursor in natural product synthesis…