Cycloaddition to aminomethylene derivatives of 1-phenyl-3-methylpyrazole-5-thione and 1-phenyl-3-methylpyrazole-5-selenone

Addition products — anhydrides of 1-phenyl-3-methyl-4-alkylamino-4,5,6-tetrahydrothio(seleno)pyrano-3, 2-pyrazole-5,6-dicarboxylic acids — were obtained by cycloaddition of maleic anhydride to aminomethylene derivatives of 1-phenyl-3-methylpyrazole-5-thione and 1-phenyl-3-methylpyrazole-5-selenone, while anhydrides of the corresponding dihydrothio(seleno)pyranopyrazoledicarboxylic acids were obtained by splitting out of an amine. The oxygen-containing analog does not undergo cycloaddition. An oxanol dye is formed from 1-phenyl-3-methyl-4-dimethylaminomethylene-5-pyrazolone, whereas the corresponding acyl derivative was isolated from the monomethyl derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 527–529, April, 1979.