The enantiomerically pure tertiary carbinamines are among the most important synthesis targets in modern organic synthesis. One of the direct synthesis methods would be the asymmetric nucleophilic addition to ketimines. However, general asymmetric catalytic reactions of such are still challenging because of the intrinsic problems with ketimines: 1) the low reactivity of ketimines; 2) the difficulty to differentiate the two-enantio faces of ketimines. In this context, we describe here the enantioselective nucleophilic addition of silicon-based nucleophiles to simple ketimines. The reactions were catalyzed by a new class of helical-chiral pyridine N-oxide catalysts developed in our lab. The effects of key reaction parameters (i.e. solvent and temperature) on the yield and selectivity of this reaction have been carefully studied. And a stereochemical model for the reaction has been proposed based on the sense of enantioselection observed and the structure of the catalysts.  These reactions provide a direct route to optically active amine derivatives possessing a-tetrasubstituted carbon stereocenters with good enantioselectivity.

Helical-Chiral pyridine N-oxides catalyzed nucleophilic addition reactions to ketimines

247th National Meeting (2014)

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