engleski

CLASSICAL AND MICROWAVE-ASSISTED SYNTHESIS AND SPECTROSCOPIC ANALYSIS OF SOME PYRAZOLE DERIVATIVES

In continuation of our studies in the field of N- containing heterocycles1, 2 we decided to examine cyclizations of hydrazines with polyketones. Some of these well-known methods have been recently performed by microwaves irradiation (MW)3. Here we report on acid catalyzed reactions of triketone (1, Ar = p-tolyl) with Ar?NHNH2 (Ar? = phenyl, p- nitrophenyl) in ethanol in comparison with the transformations achieved by MW technique without solvent. By heating of an ethanolic solution of 1 with p-nitrophenylhydrazine pyrazol-hydrazone 2 accompanied with addition intermediate were obtained. Under the similar conditions phenylhydrazine hydrochloride gave 3, 4 and several unidentified byproducts. The short MW irradiation of the same reaction mixture without solvent resulted in formation of 3. The structures of the obtained compounds were determined by 1D and 2D homo- and heteronuclear NMR techniques.

pyrazole derivatives; spectroscopic analysis; microwave-assisted synthesis

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