Synergistic Catalysis-Enabled Thia-Aza-Prins Cyclization with DMSO and Disulfides: Entry to Sulfenylated 1,3-Oxazinanes and Oxazolidines.

A novel synergistically catalyzed thia-aza-Prins cyclization of alkenylamines with disulfides is reported, rendering the first synthesis of sulfenylated 1,3-oxazinanes and oxazolidines in good to high yields. Importantly, DMSO serves simultaneously as a reaction medium and a surrogate for formaldehyde. Mechanistic studies provide evidence that actions of CuBr2 and in situ formed sulfinic acids as a Lewis acid and Brønsted acid catalyst, respectively, synergistically catalyze these cyclization processes.