Spirobutyrolactone derived from 1-phenyl-3-methyl-2-pyrazolin-5-one

X-ray diffraction and NMR spectral examination have shown that 1-phenyl-3-methyl-2-pyrazolin-5-one reacts with methyl acrylate in methanol to give spiro[(1-phenyl-3-methyl-2-pyrazolin-5-one)-4,5-butyrolactone]. The conformation has been shown to be the same in the crystal and in solution, the pyrazoline ring has been found to be nonplanar, the reasons for the acoplanarity established, stabilizing and destabilizing interactions studied, and the orientation of the phenyl substituent relative to the pyrazolin-5-one ring determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 909–913, July, 1988.