Chelation-Controlled Addition of Organozincs to α‑Chloro Aldimines

Nucleophilic additions to α-chiral α-halo carbonyl derivatives are well-known to generate Cornforth–Evans products via a nonchelation pathway. What was unprecedented before this report is C–X bonds reversing the diastereoselectivity through coordination to metals during C–C bond-forming reactions (chelation control). Herein we describe chelation control involving C–X bonds in highly diastereoselective additions of organozinc reagents to a variety of α-chloro aldimines. The unique ability of alkylzinc halide Lewis acids to coordinate to the Cl, N, and O of α-chloro sulfonyl imine substrates is supported by computational studies.