Synthesis and structure of new 3-pyrazolinylcoumarins and 3-pyrazolinyl-2-quinolones

The reactions of substituted 3-cinnamoyl-4-hydroxycoumarins and 3-cinnamoyl-4-hydroxy-2-quinolones with different phenylhydrazines gave 3-hetaryl-1H-4,5-dihydropyrazoles. The product structures were studied by 1H NMR spectroscopy and mass spectrometry. 4-Hydroxy-3-pyrazo-linylcoumarins exist in DMSO as two tautomers (4-enol and chromane-2,4-dione), while 4-hydroxy-3-pyrazolinyl-2-quinolones exist only in the enol form.