Assembly of Thiosubstituted Benzoxazoles via Copper-Catalyzed Coupling of Thiols with 5-Iodotriazoles Serving as Diazo Surrogates.

An efficient cascade approach to thiosubstituted benzoxazoles has been developed. The transformation starts with in situ generation of a diazo compound via annulation-triggered electrocyclic opening of the 1,2,3-triazole ring. The subsequent Cu-catalyzed trapping of diazo intermediates by various thiols affords the desired heterocycles in generally good yields of up to 91%. The protocol features very good functional group tolerance and is applicable to substrates with different electronic properties.