Primary Amine Containing Bifunctional Catalysts for Asymmetric Aldol and Mannich Reactions
- The synthesis of enantiomerically pure compounds is one of the major areas of organic chemistry, with emphasis on the elaboration of commodity chemicals into advanced high value enantiopure building blocks. Organocatalysis, when small chiral organic molecules catalyze product formation, is a relatively new field, which has grown explosively and become a main focus of research. In the past 5 years chiral primary amine derivatives, usually based on naturally occurring cinchonine alkaloids, have been successfully shown for asymmetric aldol, Michael, and Mannich reactions. The results have been impressive but substrate classes remain untested or are still challenging. To overcome these limitations, modular catalyst designs based on new template will be required. To address this problem, we have designed two types of catalysts: 1) primary-tertiary diamine (picolylamines) and 2) assembled based catalysts. Our chiral primary-tertiary diamine catalyst is good for aldol reactions, while the self-assembled catalyst was found to be superior for asymmetric Mannich reactions. Both of these catalyst categories operative via in situ chiral enamine, enolate equivalents, which then trap electrophiles to give the desired products.