Regioselective Reactions of Pyridine-2-sulfenyl Bromide with Vinyl and Allyl Ethers

Abstract— Annulation reactions of pyridine-2-sulfenyl bromide with vinyl and allyl ethers proceeded regioselectively, but with opposite regiochemistry. Reactions with vinyl ethers led to 3-organyloxy-2,3-dihydro[1,3]thiazolo[3,2-a]pyridin-4-ium bromides (91–99% yields), while allyl ethers gave 2-substituted derivatives of 2,3-dihydro[1,3]thiazolo[3,2-a]pyridin-4-ium (90–98% yields). Tricyclic condensed compounds were synthesized by reactions of pyridine-2-sulfenyl bromide with cyclic ethers (2,3-dihydrofuran, 3,4-dihydro-2H-pyran and 2,5-dihydrofuran).