N′-diphenylthiourea, triethylamine, and primary alkyl halides is described. Microwave-assisted heating and a catalytic amount of 4-(dimethylamino)pyridine (DMAP) further improved the yields. Both aromatic and aliphatic carboxylic acids were converted to the corresponding thioesters, and many functionalgroups were compatible with this reaction. Several possible reaction intermediates were investigated, and the