Access to functionalized 4-benzylidene-4H-benzo[d][1,3]thiazines via tandem addition-cyclization/cross-coupling reactions

Tandem addition-cyclization reactions of various 2-alkynylbenzenamines with CS2 lead to the formation of 2-mercapto-4-benzylidene-4H-benzo[d][1,3]thiazines under mild conditions. The reactions showed moderate to excellent yields and were highly regiospecific, and only the six-membered ring was generated via 6-exo-dig S-cyclization. The reaction can be transferred to highly functionalized 4-benzylidene-4H-benzo[d][1,3]thiazines via CuI-catalyzed crossing-coupling and reductive coupling reactions.