Eco-efficient, regioselective and rapid access to 4,5-disubstituted 1,2,3-thiadiazoles via [3 + 2] cycloaddition of α-enolicdithioesters with tosyl azide under solvent-free conditions

Abstract

An efficient, sustainable, and regioselective one-pot synthesis of hitherto unreported 4-aroyl/hetaroyl/alkanoyl-5-alkyl/allyl/benzylsulfanyl-1,2,3- thiadiazoles has been achieved by [3 + 2] cycloaddition of α- enolicdithioesters with tosyl azide through cascade 1-2 (S-N) and 3-4 (C-N) bond connections involving Wolff-type heterocyclization. Optimally, the reactions are very fast and completed within 2-15 minutes, when a mixture of α-enolicdithioester and tosyl azide was stirred at 0°C in the presence of Et3N under solvent-free conditions. Furthermore, no co-catalyst or activator is necessary. The eco-compatibility, mild conditions, excellent yields, easy purification, and avoidance of expensive/toxic reagents are advantages of this protocol to access this medicinally privileged substructure. © 2013 The Royal Society of Chemistry.