Rh-Diene-Catalyzed Asymmetric Addition of Me₂Zn to N-Tosylimines

Significance

α-Chiral amines are important intermediates in the synthesis of drugs and other bioactive molecules. Their preparation by a catalytic enantioselective alkylation of imines is one of the simplest ways for their synthesis and, therefore, is a highly attractive process. Enantioselective addition of dimethylzinc to imines presents more difficulty, compared to the common reaction with diethylzinc, due to the lower reactivity of Me₂Zn. The authors, by a careful choice of the ligand, developed a simple protocol of Rh-catalyzed Me₂Zn addition to N-tosylimines giving excellent yields and enantioselectivities. The method is sufficiently general. This is also an interesting example in the relatively new field of enantioselective transition-metal catalysis, which uses chiral dienes as ligands.