Regioselective Intramolecular Arylthiolations by Ligand Free Cu and Pd Catalyzed Reaction

Abstract

2-Fluoro and 2-chloro aryl thioureas, which are usually inert toward heteroarylation forms intramolecular C–S linkage by Cu(I) and Pd(II) catalyst. A regioselective intramolecular C–S bond formation is observed during the formation of 2-aminobenzothiazoles from 2-halothioureas using both these transition metal catalysts. While Cu prefers a dehalogenative path, Pd favors predominantly C–H activation strategy during the formation of 2-aminobenzothiazoles. In the absence of 2-halo (−F, −Cl) groups, Pd favors C–H activation, while Cu is unproductive. However, identical selectivities were observed both for Cu- and Pd-catalyzed reactions for 2-bromo and 2-iodo aryl thioureas.