Polyfluorinated 3-alkylthiophene

The introduction of a polyfluorinated chain is not so easy as that of an alkyl chain. Transition metal catalyzed cross-coupling of Grignard reagents and organozinc compounds are inefficient in the synthesis of polyfluorinated 3-alkylthiophene. The copper-catalyzed perfluoroalkylation results in the formation of 2-and 3-substituted thiophenes, which are difficult to separate from each other. The reaction of fluorinated alkylmagnesium iodide with 3-formylthiophene, follwed by reduction with lithium aluminum hydride, gave (22) in an overall yield of 40% [27]. 

Different strategies have been adopted to keep the oxidation potential of polyfluorinated 3-alkylthiophenes within acceptable limits. In the initial report on the subject, the effects of the length of an alkyl spacer inserted between the thiophene ring and the perfluoroalkyl moiety were analyzed, and the best results were ob-... 

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