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

In the presence of triethylamine, cycloaddition reaction of enarnine 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.