AN UNEXPECTED ISOMERIZATION OF N-ARYL-3-AMINO-4-NITROISOTHIAZOL-5(2H)-IMINES TO 2-(BENZOTHIAZOL-2-YL)-2-NITROETHENE-1,1-DIAMINES

The syntheses of several N-aryl-3-amino-4-nitroisothiazol-5(2H)-imines 12 from 3,3-diamino-2-nitrothioacrylamides 11 are reported (Scheme 3) . In polar solvents, a spontaneous isomerization of some of the prepar ed isothiazol-5(2H)-imines 12 yielded benzothiazoles 13 (Scheme 4). In the case of 2-alkyl-substituted derivatives of type 12, the isomeriza tion occurred only at higher temperatures. Electronic influences of di fferent substituents on the rate of the isomerization were studied, an d a polar reaction mechanism is proposed in Scheme 6. The structures o f 12e and 13e were established by X-ray crystallography. Conformationa l analyses of -nitro-N-phenyl-3-(pyrrolidin-1-yl)thioacrylaminde (111) by NMR and X-ray methods were performed with the aim of explaining th e distinct behavior of this amide towards Br, or diethyl azodicarboxyl ate.