Regioselective Synthesis of New [1,3]Thiazolo- and [1,3]Selenazolo[3,2-a]pyridinium Derivatives

The reactions of pyridine-2-sulfenyl and pyridine-2-selenenyl halides with heteroatomic vinyl compounds were used as a basis for the development of effective regioselective methods for the synthesis of new fused 3- and 2-functionally substituted 2,3-dihydro[1,3]thiazolo- and 2,3-dihydro[1,3]selenazolo[3,2-a]pyridin-4-ium derivatives. Unlike the reactions with vinyl ethers, vinyl sulfide, and vinylamide, leading to 3-substituted derivatives, the annulation with vinylsilane gives another regioisomer: 2-silyl derivatives.