Reactions of the activated, rigid, alfa-diazometine group of 1,2,5-thiadiazoles 1,1 dioxide

CARAM, JA; OSCAR ENRIQUE PIRO; CASTELLANO, EE; MIRIFICO, MARÍA; VASINI, ENRIQUE

Journal of Physical Organic Chemistry

Wiley InterScience

Año: 2006 vol. 19 p. 229 - 237

The reactions of n-butylamine (BuNH2), 2-aminoethanol (H2N(CH2)2OH), diethylamine (Et2NH), and phenylhydrazine (PhN2H3) with 3,4-diphenyl-(1a) and phenanthro[9,10-c]-1,2,5-thiadiazole 1,1-dioxide (1b) were studied by cyclic voltammetry (CV) and 1H- and 13C-NMR in aprotic solvent solution. The course of the reactions depended on the substrate-nucleophile combination: Et2NH added to 1a or 1b, forming the corresponding thiadiazolines in an equilibrium monoaddition reaction. The equilibrium constants were evaluated and compared. With primary amines and PhN2H3, the nucleophile added to both C=N double bonds of 1a and displaced the sulfamide moiety. In the case of the reaction of 1a with PhN2H3, the intermediate monoaddition thiadiazoline, 3-(2-phenylhydrazino)-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide, was also isolated. BuNH2 and H2N(CH2)2OH reacted with 1a to give alpha-bis-imines, while 1a with PhN2H3 gave the alpha-bis-hydrazone. The configurations of benzil bis(ethanolimine) and benzilosazone were determined by single crystal x-ray diffraction analysis as Z,Z. BuNH2 and PhN2H3 reduced 1b to the corresponding thiadiazoline compound 1bH2.