Formal [3 + 2] Annulation of β,β-Disubstituted Enesulfinamides with Vinyl Thianthrenium Salt: Asymmetric Construction of 3,3-Disubstituted 1-Pyrrolines

Five-membered endocyclic imines featuring a quaternary carbon stereocenter at the α position of the imino group can be stereoselectively synthesized through the formal [3 + 2] annulation of β,β-disubstituted enesulfinamides with vinyl thianthrenium salt. The deprotonated enesulfinamides undergo a nucleophilic addition to the vinyl sulfonium salt, which is followed by intramolecular cyclization, leading to the production of 3,3-disubstituted 1-pyrroline derivatives with high enantioselectivity. The stereochemistry of the resulting products is influenced by both the geometric configuration of the enesulfinamides and the absolute configuration of their sulfinyl group.