Heating of 3-(2-aminophenylthio)-2-methoxycarbonyl-4-methyl-2-penten-4-olide with triethylamine hydrochloride gave 3, 3-dimethyl-1H, 3H-furo[4, 3-b][1, 5]benzothiazepin-1-one. Some chemical modifications of the product including [2+2]cycloaddition and 1, 3-dipolar cycloaddition to the imino group in the product were performed.