Synthesis of spiro[3H-indole-3,2′-tetrahydro-1,3-thiazine]-2,4′(1H)-diones

The title compounds have been prepared by the cyclocondensation of 3-mercaptopropanoic acid with isat-in-3-imines. The 1-benzyl derivatives have been synthesized by simultaneously reacting 1-benzylisatin, substituted anilines and 3-mercaptopropanoic acid. Mannich condensation of the spiro thiazanones with secondary amines gave the corresponding 1-aminomethyl derivatives.