Preparation of first examples of RFCCIF4 molecules. A study of the fluorination of selected 1-iodoalk-1-ynes with xenon difluoride/boron trifluoride

First examples of alk-1-yn-1-yliodine(V) molecules, CF3CCIF4 and C6F13CCIF4, were prepared by fluorination of the corresponding 1-iodoperfluoroalk-1-ynes with XeF2 in 1,1,1,3,3-pentafluorobutane (PFB) in the presence of BF3. The reaction of 1-iodo-2-(4-heptafluorotolyl)ethyne, 4-CF3C6F4CCI, with XeF2 (1.5 equiv) and BF3 resulted in a mixture of 4-CF3C6F4CCIF2 (main product), 4-CF3C6F4CCIF4, and trans-(4-CF3C6F4)CFCFI, whereas under the action of 3 equiv of XeF2/BF3 a complex mixture of polyfluoroorganics and IF5 resulted. Non-fluorinated C4H9CCI reacted with XeF2/BF3 preferentially under fluorine addition across the triple bond and gave mainly C4H9CF2CF2I. The differing reactivity of CnF2n+1CCI and C4H9CCI is in accordance with the experimentally proved different reactivity of the triple bond in C6F13CCH and C4H9CCH toward XeF2/BF3 in PFB. Compound C6F13CCH was inert whereas C4H9CCH was converted into C4H9CF2CF2H (main product) under the same conditions.

A synthetic methodology to obtain perfluoroalk-1-yn-1-yliodine tetrafluorides is reported for the first time. Activation of XeF2 by an excess of BF3 is necessary for the successful fluorine addition to iodine. No addition proceeded to the CC triple bond in RFCCI compounds (RF = perfluoroalkyl).Figure optionsDownload as PowerPoint slideHighlights
► The synthesis of perfluoroalk-1-yn-1-yliodine tetrafluorides is realized for the first time.
► The combination XeF2/BF3/CF3CH2CF2CH3 allows the addition of fluorine to iodine in perfluoroalk-1-yn-1-yl iodides.
► In case of 4-CF3C6F4CCI only mixtures of 4-CF3C6F4CCIF2 and 4-CF3C6F4CCIF4 were obtained.
► Non-fluorinated C4H9CCI reacts preferentially at the triple bond and forms mainly C4H9CF2CF2I.