SYNTHESIS OF ISOTHIAZOLES - TRANSFORMATION OF ISOXAZOLES INTO ISOTHIAZOLES

A method has been devised whereby a substituted isoxazole (I) can be efficiently converted to an isothiazole (III) with a similar substitution pattern. The isoxazole ring is opened by reduction with Raney nickel, and the resulting enamino ketone (II) is treated with phosphorus pentasulfide and chloranil to give the corresponding isothiazole derivative. Thus, by taking advantage of the relatively numerous and reliable routes available for the preparation of variously substituted isoxazoles, it is now possible to obtain readily many isothiazole derivatives which were previously available only with great difficulty. © 1969.