Protonated DBU as catalyst for cascade addition–cyclization of 2-alkynylaniline and carbon disulfide

Protonated 1,8-diazabicyclo[5,4,0]undec-7-ene as catalyst for cascade addition/cyclization of 2-alkynylaniline and carbon disulfide has been described. This process provides a convenient route for synthesis of a variety of benzo[d][1,3]thiazine-2(4H)-thiones in high yields with high regio- and stereoselectivity at room temperature without metal.