Catalytic enantioselective addition to imines.

Abstract

Chiral nitrogen-containing compounds are widely distributed in nature and include many biologically important molecules (Chart 1). In these compounds, the nitrogen-containing units are known to play important roles for their bioactivities. For the synthesis of these chiral nitrogen-containing building blocks, use of imines as electrophiles is the most promising and convenient route.1 While many approaches using chiral imines or chiral nucleophiles have been reported,1 these diastereoselective reactions have some disadvantages. First, the procedures to introduce chiral auxiliaries to substrates and to remove them after the diastereoselective reactions are often tedious. Second, more than stoichiometric amounts of chiral sources are needed to obtain chiral compounds according to these reactions. On the other hand, catalytic enantioselective reactions provide the most efficient methods for the synthesis of chiral compounds,2 because large quantities of chiral compounds are expected to be prepared using small amounts of chiral sources. While much progress has been made recently in catalytic enantioselective reactions of aldehydes and ketones such as aldol,3 allylation,4 Diels-Alder,5 cyanation reactions,6 reduction,1b,2b etc., progress in catalytic enantioselective reactions of imines is rather slow. There are some difficulties in performing catalytic enantioselective reactions of imines. For example, in the cases of chiral Lewis acid promoted asymmetric Shū Kobayashi was born in 1959 in Tokyo, Japan. He studied chemistry at the University of Tokyo and received his Ph.D. in 1988 (Professor T. Mukaiyama). After spending 11 years at Science University of Tokyo (SUT), he moved to Graduate School of Pharmaceutical Sciences, University of Tokyo, in 1998. His research interests include development of new synthetic methods, development of novel catalysts (especially chiral catalysts), organic synthesis in water, solid-phase organic synthesis, total synthesis of biologically interesting compounds, and organometallic chemistry. He received the first Springer Award in Organometallic Chemistry in 1997.