A Facile Synthetic Approach to 3-Halo-4-substituted-l,5-dihydro-4H-1,2,4-triazoline-5-thiones Based on Retro-Michael Addition

A facile 3-step synthetic approach to 3-halo-4-substituted-l,5-dihydro-4H-1,2,4-triazolme-5-thiones （la--lk） from corresponding unhalogenated 8a---8i was developed based on the strategy of retro-Michael addition, with the key steps being regioselective S-alkylation of compounds 8a-8i with ethyl 3-iodopropionate（12c） and alkaline cleavage of the propionate protecting group via retro-Michael addition. The synthetic approach was characterized by simplicity of operation and wide substrate scope.