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RESEARCH PRODUCT

Perfluoroketene dithioacetals and perfluorodithiocarboxylic acid derivatives: Versatile tools for organofluorine synthesis

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Perfluoroketene dithioacetals are simple and versatile compounds that can be transformed into a large variety of trifluoromethyl derivatives, in particular aza- and thiaheterocycles, perhalodithiocrotonic esters, and fluorinated dithiol thiones. These unsaturated perfluorodithioesters and analogs give interesting polar cycloaddition reactions whose mechanism is strongly influenced by the fluorine substitution. This substitution plays an important role in the reactivity of saturated perfluorodithiocarboxylic acids as well. Except for the carbophilic addition of allyl Grignard reagents to perfluorocarboxamides, a domino thiophilic addition-fluoride elimination was the main reaction process. Interestingly, a three-step domino reaction occurs when pentafluorodithioesters are treated with allyl Grignard reagents, the third step being an effective σ[3,3] rearrangement, so that the overall reaction is a formal substitution of an allyl group for the α-fluorine atom. 2,2-Bis(allyl)-3,3,3-trifluorodithiopropanoates were prepared by performing this domino reaction twice, in a possible one-pot procedure. © 2007 Wiley Periodicals, Inc. 18:500–508, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20346