Trifluoromethyl group decarboxylation reactions

A somewhat different approach is used for the preparation of the analogue that contains a trifluoromethyl group. The scheme involves first the conversion of ort/zo-trifluoromethyl aniline (27-1) to a quinolol. The compound is thus condensed with EMME and cyclized thermally (27-2). That intermediate is then saponified the resulting acid is decarboxylated and finally converted to the 4-chloroquinoline (27-3) by reaction with phosphorus oxychloride. The displacement of chlorine with methyl anthranilate (27-4) then affords the coupled intermediate (27-5). An ester interchange of that product with glycerol leads to the glyceryl ester. There is thus obtained the NSAID flocatfenine (27-6) [31]. 

An oxazole-alkene Diels-Alder reaction has also been used to synthesize a tri-fluoromethylated pyridine related to pyridoxol. 5-Ethoxy-4-(trifluoromethyl)-2-oxazolecarboxylic acid 41 decarboxylated and then reacted with acrylic acid to give the expected 3-hydroxy-2-(trifluoromethyl)pyridine-4-carboxylic acid 42 in 63% yield (Fig. 3.13)." The electron-withdrawing trifluoromethyl group of 41 strongly modulates its reactivity, however, and it does not react with ethyl acrylate or A-phenyl maleimide. 

Bis(trifluoromethyl)mercury is useful in the preparation of numerous CF3 derivatives, especially of group IV elements. It was first prepared in 1949 by irradiation of CF3I and Hg in the presence of Cd. Alternative routes include radiofrequency discharge methods, for example, reaction of CF3 radicals witli HgXz or elemental mercury. Preparative scale quantities are best obtained by decarboxylation of mercury trifluoroacetate in the presence of carbonate. ... 

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