Electrophilic acylation of fluoroolefines by unsaturated perfluoroacylfluorides

The Chemistry of Highly Fluorinated Carbocations

“…Recently it was found that stable acylium carbocations 55a − c can be generated by SbF 5 from acyl fluorides of α,β-unsaturated perfluorocarboxylic acids …”

“…In contrast to acyl fluorides of saturated perfluoro acids, the acyl fluorides of α,β-unsaturated acids are able to acylate fluoroolefins in the presence of SbF 5 . Reactions between acyl fluorides 56 and 57 and TFE proceed at 30−40 °C and atmospheric pressure, giving ketones 58 and 59 , respectively …”

“…Perfluorinated acyl fluorides are resistant to the action of strong Lewis acids and usually do not interact with them at 20−50 °C, but at higher temperatures they have a tendency to lose CO. , The generalized mechanism includes ionization of the acyl fluoride C−F bond to generate acylium cation 226 , which then readily loses CO. Perhaps the most effective catalyst is SbF 5 .

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“…85 This reaction has been reviewed. 36 However, more electron-deficient substrates, for example tetrafluoroethylene, do not interact with acyl fluorides in the presence of either SbF 5 86 or ACF 87 as catalyst. Furthermore, all attempts to observe saturated perfluoroacylium cations failed.…”

“…Recently it was found that stable acylium carbocations 55a-c can be generated by SbF 5 from acyl fluorides of R,β-unsaturated perfluorocarboxylic acids. 86 In contrast to acyl fluorides of saturated perfluoro acids, the acyl fluorides of R,β-unsaturated acids are able to acylate fluoroolefins in the presence of SbF 5 . Reactions between acyl fluorides 56 and 57 and TFE proceed at 30-40 °C and atmospheric pressure, giving ketones 58 and 59, respectively.…”