REACTIONS OF TETRAFLUOROETHENE OLIGOMERS. PART XII. CYCLOADDITION REACTIONS OF 3,3,4,4,4-PENTAFLUORO-2-PENTAFLUOROETHYL-2-TRIFLUOROMETHYLDIAZOBUTANE. A NOVEL SYNTHESIS OF PYRAZOLES

Article abstract of DOI:10.1016/S0022-1139(00)82868-7

The title diazoalkane (1) reacts smoothly with a variety of electron deficient alkenes to give, unexpectedly, the corresponding pyrazole derivatives.Thus, reaction with methyl or ethyl propenoate affords the methyl and ethyl esters of pyrazole-3-carboxylic acid (2) and (3).Reaction with diethyl maleate yields 3,4-bis-(ethoxycarbonyl)pyrazole (4), and dimethyl maleate gives the corresponding dimethyl ester (5).Treatment of (1) with propenonitrile afforded 3-cyanopyrazole (6), and with propenoic acid the corresponding pyrazole-3-carboxylic acid (7) was obtained.In all of these reactions two side products were isolated, namely perfluoro-(3-methylpent-2-ene) (8) and 3H-3-trifluoromethyldecafluoropentane (9).A mechanistic rationale for these unusual and potentially useful reactions is given.