Reactions of tetrafluoroethene oligomers Part XII [1] cycloaddition reactions of 3,3,4,4,4-pentafluoro-2-pentafluoroethyl-2-trifluoromethyldiazobutane. A novel synthesis of pyrazoles

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Abstract

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 perfluoro-(3-methylpent-2-ene) (8) and 3H-3-trifluoromethyldecafluoropentane (9). A mechanistic rationale for these unusual and potentially useful reactions is given.

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