Chiral Lithium(I) Binaphtholate Salts for the Enantioselective Direct Mannich-Type Reaction with a Change of Syni/Anti and Absolute Stereochemistry

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-Bronsted 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-3 degrees-carbon center, and these are valuable since previous catalysts often gave syn/anti Mixtures or the stereochemistry has not yet been determined.