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.