Microwave-assisted synthesis of novel 2,4-dihydro-5-[4-(trifluoromethyl) phenyl]-3h-1,2,4-triazol-3-ones and potentiometric determination of their pKa in nonaqueous solvents

Abstract

The novel 4-amino- or 4-aryl-substituted 2,4-dihydro-5-[(4-trifluoromethyl) phenyl]-3H-1,2,4-triazol-3-ones 3a-3g were synthesized by reaction of N-(ethoxycarbonyl)-4-(trifluoromethyl)benzenehydrazonic acid ethyl ester (2) and primary amines or hydrazine by microwave irradiation. Compounds 3a-3g were potentiometrically titrated with tetrabutylammonium hydroxide (Bu 4NOH) in four nonaqueous solvents, i.e., iPrOH, tBuOH, MeCN, and N,N-dimethylformamide (DMF). Also half-neutralization potential values and the corresponding pKa values were determined in all cases. © 2010 Verlag Helvetica Chimica Acta AG, Zürich, Switzerland.