Synthesis of New 1-[4-Methane(amino)sulfonylphenyl)]-5-[4-(aminophenyl)]-3-trifluoromethyl-1H-pyrazoles

A regiospecific cyclization-dehydration reaction of a 1-[4-(N-alkyl-N-(tert-butyloxycarbonyl)amino)phenyl]-4,4,4-trifluorobutane-1,3 -done with a 4-aminosulfonyl-, or 4-methylsulfonyl-, phenylhydrazine hydrochloride in refluxing ethanol proceeded with simultaneous loss of the N-tert-butyloxycarbonyl protecting group to afford a group of 1-(4-methanesulfonylphenyl or 4-aminosulfonylphenyl)-5-[4-(N-alkylaminophenyl)]-3-(trifluoromethyl)-1H-pyrazoles (6). Subsequent reaction of the pyrazole 6 (R-1 = R-2 = Me) with nitric oxide (40 psi) proceeded via a N-methylamino-N-diazen-1-ium-1,2-diolate intermediate that undergoes protonation of the more basic diazen-1-ium-1,2-diolate N-2-nitrogen and then loss of a nitroxyl (HNO) species to furnish the N-nitroso product 7.