Nucleophilic additions to alpha-chiral alpha-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 alpha-chloro aldimines. The unique ability of alkylzinc halide Lewis acids to coordinate to the Cl, N, and O of alpha-chloro sulfonyl imine substrates is supported by computational studies.