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).
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