SYNTHESIS OF BENZOFURAN-5,6-DICARBONITRILES ANNELATED WITH PYRAZOLE CYCLE

Abstract

The principal method for the preparation of substituted 4-formyl-1H-pyrazoles was the treatment of hydrazones of different structure with Vilsmeier-Haack reagent. However, for the heterocyclic benzofuran system this reaction is rarely used. Synthetic methods for preparation of novel substituted 3-(4-fomyl-1H-pyrazole-3-yl)-2-methylbenzofuran-5,6-dicarbonitriles and 2-(1H-pyrazole-4-yl)-benzofuran-5,6-dicarbonitriles were developed by modification of 2,3-disubstituted benzofuran-5,6-dicarbonitriles via Vilsmeier-Haack reaction. New substituted 3-(4-fomyl-1H-pyrazole-3-yl)-2-methylbenzofuran-5,6-dicarbonitriles were obtained by reacting 3-acetyl-2-methyl-1-benzofuran-5,6-dicarbonitrile with hydrochloric substituted phenylhydrazines followed by treatment with the Vilsmeier reagent formed hydrazones. A new method for the synthesis of 3-substituted 2-(1H-pyrazol-4-yl)-benzofuran-5,6-dicarbonitriles was based on condensation of aminovinylbenzofuranes with hydrazine hydrate in refluxing acetic acid. The structure of synthesized compounds was determined by data of the IR and NMR spectroscopy, including two-dimensional correlation 1H-1H spectroscopy, and mass spectrometry. The signals of cyano and formyl groups were characteristic in IR spectra; the signals of phthalonitrile protons and proton of aldehyde group - in 1H NMR spectra for 3-(4-formyl-1H-pyrazole)-2-methyl-1-benzofuran-5,6-dicarbonitriles. Also, structure of synthesized 4-formylpyrazoles is confirmed by their reaction with hydrazine hydrate to give corresponding hydrazones. The signals of NH-pronon of pyrazole ring, cyano and carbonyl groups were characteristic in IR spectra; signal broadened singlet of NH-proton of pyrazole ring, which determined to prototropic ring tautomerism of pyrazole ring, and singlets of phthalonitrile protons - in 1H NMR spectra for 3-substituted 2-(1H-pyrazol-4-yl)-benzofuran-5,6-dicarbonitriles. Development of methods for the synthesis of new 4-formylpyrazoles is an important task because the compounds exhibit various pharmacological properties: antimicrobial, anti-inflammatory, antituberculosis, antitumoral, antiparasitic, and antiviral.Forcitation:Chirkova Zh.V., Filimonov S.I., Abramov I.G. Synthesis of benzofuran-5,6-dicarbonitriles annelated with pyrazole cycle. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 45-51.