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.