3-AMINO AND 3-ACYLAMINO-ISOTHIAZOLES

1,274,053. 3-Amino- or acylamino-isothiazoles. FARBENFABRIKEN BAYER A.G. 15 Sept., 1969 [17 Sept., 1968], No. 45340/69. Heading C2C. The invention comprises isothiazoles of the formula in which X represents hydrogen or an acyl group -COR1, where R1 is an optionally substituted aliphatic, aralkyl or aryl radical, R2 and R3 are hydrogen or optionally substituted aliphatic, aralkyl or aryl radicals or together form an optionally substituted, saturated or unsaturated, 5-7-membered fused ring, provided that R 2 and R 3 are not both hydrogen or one is hydrogen and the other is unsubstituted aryl and when R 2 and R 3 form a fused benzene ring, that ring is substituted, and a general process for preparing the above compound, including the known isothiazoles, wherein a compound of the formula is reacted with at least 2 molar equivalents of hydroxylamine at an elevated temperature in the presence of a water-miscible solvent and, if required, hydrolysing the resultant 3-acylaminoisothiazole to the amine. The hydroxylamine is preferably used in the form of a salt from which the free base is released in the reaction mixture by the addition of a base. Examples relate to the preparation of isothiazoles, benz[4,5]isothiazoles, tetrahydrobenz[4,5]isothiazoles and 5,6- dihydro-4H-cyclopenta-[d]isothiazoles in which the optional substituents are halogen, alkyl, alkoxy or nitro groups.