Metal-Free Synthesis of 2-Substituted (N, O, C) Benzothiazoles via an Intramolecular C-S Bond Formation

Enguang Feng, He Huang, Yu Zhou, Deju Ye, Hualiang Jiang, and Hong Liu

An efficient, economical, and convenient method was developed for the preparation of 2-substituted (N, O,
C) benzothiazoles from N′-substituted-N-(2-halophenyl)thioureas, O′-substituted-N-(2-halophenyl) carbamothioates,
or N-(2-halophenyl) thioamides via a base-promoted cyclization in dioxane without any transition
metal. A one-pot variant combining the synthesis of the thiourea and the cyclization was also demonstrated.
High yields were obtained, and a variety of functional groups were tolerated under these conditions. Transitionmetal-
free, mild reactive conditions, wide application scope, and shorter reaction times make this method
superior to the reported methods for the synthesis of 2-substituted benzothiazoles and suitable for combinatorial
format.