Diastereoselective and Enantioselective Rh(I)-Catalyzed Additions of Arylboronic Acids to N-tert-Butanesulfinyl and N-Diphenylphosphinoyl Aldimines

Two new Rh(I)-catalyzed methods for the synthesis of chiral alpha-branched amines via addition of arylboronic acids to N-tert-butanesulfinyl and N-diphenylphosphinoyl imines have been developed. The syntheses are more functional group tolerant than alternative methods utilizing Grignard or organolithium reagents, and the imine activating groups used are easily removed. These methods are both high-yielding (70-97% yield) and very selective (>93:7 dr and 88-94% ee). Significantly, the N-tert-butanesulfinyl imine method works for aliphatic imines with enolizable protons. In addition, a one-pot procedure for the synthesis of N-tert-butanesulfinyl protected alpha-branched amines from aldehydes has been developed.