Straightforward Approach to 5-Substituted 7 H -Imidazo[2,1-b ] [1,3]thiazines via Cyclization of 2-Alkynylthioimidazoles

Electrophile-initiated nucleophilic cyclization of 2-alkynylthiobenzimidazoles is a useful tool for synthesizing new heterocyclic systems. However, halogen-initiated cyclization demonstrates poor selectivity between electrophilic addition and substitution reactions using other imidazole analogues. In this research, several different coinage metal catalysts were employed to broaden the scope of 7H- imidazo[2,1-b][1,3]thiazines in atom-economic manner. Selective 6endo-dig pathway reactions were achieved in good to excellent yields using various 2-alkynylthioimidazoles with AuCl as the catalyst in DCE/DCM.

Automated summary

Electrophile-initiated nucleophilic cyclization of 2-alkynylthiobenzimidazoles is a useful tool for synthesizing new heterocyclic systems. However, halogen-initiated cyclization shows poor selectivity between electrophilic addition and substitution reactions using other imidazole analogues. In this research, different coinage metal catalysts were used to expand the scope of 7H-imidazo[2,1-b][1,3]thiazines in an atom-economic manner. Selective 6endo-dig pathway reactions were achieved in good to excellent yields using various 2-alkynylthioimidazoles with AuCl as the catalyst in DCE/DCM.