An improved one-pot synthesis of 1,5-benzothiazepinone derivatives is described. 2-Aminobenzenethiols are conveniently converted into 2,3-dihydro-1,5-benzothiazepin-4(5H)-ones by reaction with ß-propiol-actone or ß-butyrolactone in anhydrous pyridine followed by treatment with acetic anhydride. Some substituent effects are noted.