Fluorovinyl halides

Synthesis of a-fluoro-ot, -unsaturated ketones via palladium-catalyzed crosscoupling reaction of 1-fluorovinyl halides (79) with organostannanes (80)... 

C. Chen, K. Wilcoxen, C.Q. Fluang, N. Strack, J.R. McCarthy, New methods for the synthesis of fluoro olefins via the palladium catalyzed cross-coupling reaction of 1-fluorovinyl halides with organoboranes and organostannanes, J. Fluor. Chem. 101 (2000) 285-290. 

Preparation of a fluorovinylzinc reagent by direct metallation of a fluorovinyl halide preparation of 1,2,2-trifluoroethenylzinc bromide4,5... 

With the ready availability of 2-fluoro-allylic halides and a-fluoroacrylic acid derivatives, incorporation of a pendant fluorovinyl unit is easier than ever. The utility of these products is markedly enhanced by the reactivity of the fluorovinyl unit in olefin metathesis reactions. Some success has been found in cyclization reactions as shown below [83] (Scheme 36). 

Attempts to prepare a (/ -fiuorovinyl)iodonium salt from l-decynyl(phenyl)iodonium tetrafluoroborate by the procedures employed for / -chloro- and (/ -bromovinyl)iodonium halides have been unsuccessful103. Admixture of the decynyliodonium salt and lithium fluoride in acetic acid ultimately (2 days, rt) leads to l-acetoxy-2-decanone103. (Z )-(/ -Fluoro-jS-perfluoroalkylvinyl)iodonium triflates, on the other hand, can be made by the treatment of (1H, li/-perfluoroalkyl)phenyliodonium triflates with sodium hydride (equation 178)136. Apart from 2-fluoro-l-hexadecenyl(phenyl)iodonium chloride (synthesis not described)104, these are the only reported examples of (/ -fluorovinyl)iodonium salts. 

Another principal method is the fluorovinylation of suitable precursors by transition metal-catalyzed carbon-carbon coupling reactions [13]. Activated fluorovinyl species can be conveniently generated in situ from commonly used hydrofluorocarbons, for example HFC-134a [14] (Scheme 2.192). Fluorinated vinyl zinc halides are often used for the coupling reactions, but other activated species, for example stannanes [15] or boronates [16], have also been applied successfully. 

Mann et al. showed that various acetophenones can be synthesized by carbonylative coupling of aryl triflates with SnMe4 [65]. Under mild conditions using the catalyst system Pd(OAc)2/dppp, good yields (70-94 %) were obtained (Scheme 4.32). In 2002 Mido and colleagues reported the palladium-catalyzed carbonylative coupling of tributyl(l-fluorovinyl)stannane with aryl halides and aryl triflates [66]. In the presence of a catalytic amount of palladium catalyst and CsF in DMF, aryl 1-fluorovinyl ketones were formed in good yields. 

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