Zinc-Mediated syn-Selective Crotylation of N-Unsubstituted Imines

The first example of a zinc-mediated diastereoselective crotylation of N-unsubstititued imines is described. The use of Et3B as an additive was of crucial importance to achieve high yield and diastereoselectivity. Notably, a high level of syn-selectivity was observed. A mechanism involving an open transition state is suggested to explain this unique selectivity.