1,1′-Binaphthyldiamine-Based Lewis Bases as Readily Available and Efficient Organocatalysts for the Reduction of N-Aryl and N-Alkyl Ketimines

The development of simple, low-cost, efficient, and sustainable routes to enantiomerically pure amines is a topic of extraordinary interest, specially in view of future industrial applications. In this context, we wish to report a chemical and stereochemical efficient synthesis of chiral amines through the Lewis base activated trichlorosilane reduction of ketimines. An organocatalyst, easily prepared in a single step through the condensation of picolinic acid and commercially available 1,1'-binaphthyldiamine, is the key element of this metal-free methodology, that allowed the synthesis of chiral secondary and primary amines in high yields and stereoselectivity. Noteworthy, such catalysts are able to promote the reduction of N-alkyl ketimines, often in quantitative yield and up to 87% enantioselectivity; it is worth mentioning that for such transformations only one other organocatalytic system has been reported so far. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)