Solvent-free synthesis of 2-amino-5-aryloxymenthyl-1,3,4-thiadiazoles and their coumarin or benzofuran bis-heterocyclic derivatives

摘要

2-amino-5-aryloxymethyl-1,3,4-thiadiazoles were synthesized rapidly by a microwave-accelerated solvent- free procedure in high yield via the condensation of thiosemicarbazide with aryloxyacetic acids using poly(ethylene glycol)-supported dichlorophosphate as a dehydration reagent. The solvent- free N-acylation of 2-amino-5-aryloxymethyl-1,3,4-thiadiazoles with coumarin-3-carboxylic acid chloride or benzofuran-2-carboxylic acid chloride efficiently afforded corresponding bis-heterocyclic derivatives, 2-(coumarin-3-carboxamido)-5-aryloxymethyl-1,3,4-thiadiazoles, and 2-( benzofuran-2-carboxamido)-5-aryloxymethyl-1,3,4-thiadiazoles. The strategy has advantages of no organic solvent pollution, an elevated reaction rate, an improved yield, and a simple work-up procedure.