Nucleophilic Reactions of N-Unsubstituted Sulfoximines with Activated Acetylenes, Olefins, and Diphenylcyclopropenone

A study of the stereochemical course of the nucleophilic addition of N-unsubstituted sulfoximines 1a-e to dimethyl acetylenedicarboxylate showed that Z-adducts were formed as the major products in methanol whereas E-adducts were predominantly or almost exclusively obtained in DMSO. The reactions of dimethylsulfoximine (1a) with ethyl propiolate and acetylacetylene were complicated by the concomitant isomerization of the adducts under the reaction conditions used. The reaction of 1a with trans-1, 2-dibenzoylethylene gave a normal 1 : 1 adduct, while that with tetracyanoethylene gave an addition-elimination product, N-(1, 2, 2-tricyanovinyl) dimethylsulfoximine. Heating 1a with diphenylcyclopropenone in refluxing toluene gave N-(3-amino-2, 3-diphenylpropenoyl)-dimethylsulfoximine. The mechanisms of these reactions are discussed.