Novel bipyrazole and pyrazolopyridazinone derivatives via regioselective cycloaddition reaction of nitrilimines to enaminone: Synthesis and structural elucidation

Abstract

Listen

Translate article

1-(3,5-Dimethyl-1-(4-nitrophenyl)-1H-pyrazol-4-yl)-3-(dimethylamino)prop‑2-en-1-one 2 was prepared by refluxing of 1-(3,5-dimethyl-1-(4-nitrophenyl)-1H-pyrazol-4-yl)ethan-1-one 1 with dimethylformamide dimethyl acetal (DMF-DMA). Heating of enaminone 2 with hydrazonoyl halides 3a–h or C-alkoxy carbonylhydrazonoyl chlorides 3i-p in chloroform in the presence of triethylamine afforded novel bipyrazole derivatives 4a–h or 9i-p. The structures of compounds 9i-p were confirmed chemically via their conversion to pyrazolopyridazinones 11i-m upon the reaction with hydrazine hydrate in refluxing ethanol. Moreover, the structures of the novel bipyrazoles and pyrazolopyridazinones were confirmed via spectral data and elemental analyses, in addition to single-crystal X-ray diffraction.