A rapid and efficient route to benzazole heterocycles.

This protocol describes a rapid, high-yielding, microwave-mediated route that affords benzazole heterocycles in high crude purity and represents a significant advancement toward an environmentally friendly reaction. The reaction of aryl isothiocyanates with o-nucleophilic anilines produces thiourea intermediates that, in the presence of a carbodiimide-functionalized resin, cyclize to benzazoles with the safe removal of one equivalent of hydrogen sulfide. This procedure takes ∼ 8.5 h to complete: 1-3 h for setup, 4.5 h for benzazole formation and 2 h for workup and purification.