Difluoromaleic acid

Oxidation of perjliwro- 1,4-benzoquinone hy peroxyacetic acid gives comparatively good yields of 2,3-difluoromaleic acid [74] (equation 65). 

Oxidation of pentafluorophenol under the conditions descnbed in equation 65 leads to the formation of 2,3-difluoromaleic acid in a yield of 54% [74],... 

Catalytic hydrogenation of trarcs-a-fluorostilbene and of difluoromaleic acid does not give products expected from the addition of hydrogen across the double bonds. What are the products of catalytic hydrogenation of compounds D, and E, and F ... 

The compound D resulting from catalytic hydrogenation of trans-a-fluorostilbene is bibenzyl [5], and compounds E and F resulting from hydrogenation of difluoromaleic acid are fluorosuccinic acid and succinic acid, respectively [77]. Naturally similar hydrogenolyses of vinylic fluorine take place in the hydrogenation of difluorofumaric acid, fluoro-maleic and fluorofumaric acid, and many other unsaturated fluorides [77,72,73],... 

The treatment of tetrafluoro-o-benzoquinone with 40% peroxyacetic acid at 70-75 °C for 4.75 h degrades the quinone to difluoromaleic acid in 55% yield. The same acid is obtained in 59% yield under similar conditions from fluoranil (tetrafluoro-p-benzoquinone) [273]. 

Difluoromaleic acid has been obtained by oxidation (MeCOgH) of C(F OH and telated compounds (see p. 378). 

Halogenation. Halogens add directly to the double bond of maleic anhydride to give dihalo succinic acids. However, different procedures are used for dihalomaleic anhydride derivatives. Fluorinated substrates offer access to difluoromaleic anhydride [669-78-3] (64). 

Catalytic hydrogenation of substituted 2-fluoroprop-2-enoates over palladium at room temperature under atmospheric pressure results in saturation and only partial fluorine hydrogenolysis.100 The replacement of vinylic fluorines with hydrogen by catalytic hydrogenation proceeds more readily in fluoromaleic, fluorofumaric, difluoromaleic, and difluorofumaric acid 10.no It is assumed that fluorine hydrogenolysis occurs before saturation of the C = C bond. Yields of defluorinated products are strongly dependent on the catalyst used.110... 

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