ASYMMETRIC-SYNTHESIS USING CHIRAL BASES

Studies have been made to design chiral bidentate lithium amides and c hiral tetradentate amines, and to explore the use of these chiral base s for enantioselective formation and reactions of lithium enolates. Ch iral bidentate lithium amides having a chiral amide nitrogen made by v irtue of chelation were successfully applied to the enantioselective d eprotonation reaction of prochiral cyclic ketones, the kinetic resolut ion of racemic cyclohexanone derivatives by deprotonation, and the reg ioselective deprotonation of optically active 3-keto steroids. Structu res of some of these chiral bidentate lithium amides in the solid stat e and in solution were elucidated by X-ray and NMR spectroscopic analy ses. By the use of chiral tetradentate amines, enantioselective reacti ons of lithium enolates with electrophiles, such as alkylation, proton ation, and Michael addition, proceeded successfully. Examples of catal ytic enantioselective deprotonation, alkylation, and protonation by th e present strategy are also presented and discussed.