Synthesis, thermal transformations, and mass spectrometric fragmentation of 4,4'-[1,2-bis(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethane-1,2-diyl]-bis(5-methyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one)

Quinoxaline reacted with 3-methyl-1-phenylpyrazol-5-one at room temperature in the presence of triethylamine in DMSO solution, to form 4,4'-[1,2-bis(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-ethane-1,2-diyl]bis(5-methyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one). Heating of the obtained crystalline product at 240-250°C temperature led to the known 4-[(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)methylidene]-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one. The mass spectral fragmentation of the obtained compounds was characterized.