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‐butyloxycarbony)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)‐11H‐pyrazoles(6). Subsequent reaction of the pyrazole 6 (R¹ = R² = 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 N²‐nitrogen and then loss of a nitroxyl (HNO) species to furnish the N‐nitroso product 7.