Studies with enamines: Reactivity of N,N‐dimethyl‐N‐[(E)‐2‐(4‐nitrophenyl)‐1‐ethenyl]amine towards nitrilimine and aromatic diazonium salts

Abstract magnified image In the presence of triethylamine, cycloaddition reaction of enamine 1 with hydrazonoyl halides 2 followed by dimethylamine elimination was achieved, yielding the corresponding 1,3,4‐trisubstituted pyrazoles 4. Coupling of enamine 1 with aromatic diazonium salts afforded 2‐(arylhydrazono)‐2‐(4‐nitrophenyl)acetaldehyde 9 in good yield. Refluxing the phenyl hydrazone 9a with chloroacetone in ethanol in the presence of triethylamine afforded 1,3,5‐trisubstituted pyrazole 12a, formed via intermediate 11a. Reaction of 9a with hydroxylamine hydrochloride in ethanol in the presence of anhydrous sodium acetate yielded oxime 13a which was irradiated in a microwave oven in the presence of acetic acid to afford a mixture of 15a and 16a.