Chiral lithium(I) binaphtholate salts for the enantioselective direct Mannich-type reaction with a change of syn/anti and absolute stereochemistry

Abstract

A highly diastereo- and enantioselective direct Mannich-type reaction of aldimines with 1,3-dicarbonyl compounds using Li(I) BINOLate salts as effective Lewis acid-Brønsted base catalysts has been developed. Li(I) BINOLate salts offered high catalytic activity toward 1,3-dicarbonyl compounds such as diketone, ketoester, ketothioester, ketoamide, and ketolactone. The reactions proceeded at -78 degrees C within 1-2 h in the presence of 1-10 mol % catalyst, which showed a catalytic activity (turnover frequency = 284 h(-1)) quite unlike those of other previous catalysts. Anti products were selectively obtained from acyclic ketoesters without epimerization at an alpha-tertiary-carbon center, and these are valuable since previous catalysts often gave syn/anti mixtures or the stereochemistry has not yet been determined.