Synthesis and Study of New N-Substituted Pyrazolines with 2,5-Dimethylfuryl and p-Halophenyl Fragments

Abstract The paper presents the results of a study of an efficient approach to the synthesis of new functionally substituted chalcone and pyrazoline derivatives based on 3-acetyl-2,5-dimethylfuran. The starting chalcones were obtained by aldol-crotonic condensation of 3-acetyl-2,5-dimethylfuran with p-chloro- and p-bromobenzaldehyde. It was found that the reaction of the synthesized 3-(4-halophenyl)-1-(2,5-dimethylfuran-3-yl)prop-2-en-1-ones with hydrazine hydrate and phenylhydrazine in pyridine and ethanol leads to the formation of new 2-pyrazoline derivatives. To obtain N-substituted pyrazolines, the reaction of chalcones with hydrazine hydrate was carried out in ethanol in the presence of formic and acetic acids, which made it possible to selectively modify the pyrazoline core. As a result, a series of new 1-phenyl-, 1-formyl-, and 1-acetyl-substituted 2-pyrazolines containing furyl and chloro-, bromo-substituted phenyl rings in the molecule were synthesized in high yields. The structure and composition of the obtained α,β-unsaturated ketones and 2-pyrazoline derivatives were confirmed by IR, 1H and 13C NMR spectroscopy methods. The obtained results indicate the promise of the developed synthetic approach to the preparation of functionally substituted pyrazolines of interest for further study of biological activity, and also open up opportunities for the targeted synthesis of fused heterocyclic compounds.