Synthesis of Fluoroalkyl Methyl Thioethers by Formal Addition of Methanesulfenyl Fluoride to Alkenes

Article abstract of DOI:10.1021/jo00028a056

The electrophilic anti-1,2-addition of the elements of methanesulfenyl fluoride to carbon-carbon double bonds by a one-pot reaction of dimethyl(methylthio)sulfonium tetrafluoroborate and triethylamine trishydrofluoride with various types of alkenes is used for the synthesis of β-fluoroalkyl methyl thioethers.This reaction is stereospecific: starting from cis-cycloalkenes (1) trans-1-fluoro-2-(methylthio)cycloalkanes (2) are formed, while trans-cyclododecene (3) gives the cis product 4 everytime in good yields.With unsymmetrical alkenes these reactions proceed regioselectively to produce Markovnikov-oriented fluoro thioethers.With 2,6-norbornadiene (26) exclusive exo attack on one double bond and subsequent transannular participation of the second ?-bond gives rise to two isomeric 3,5-disubstituted nortricyclanes, 28 and 29, while starting from the medium-sized cis,cis-1,5-cyclooctadiene (10) no transannular ?-participation is observed: the trans-1,2-addition product to one of the double bonds in 11 is isolated.In contrast, in the reaction of the monoepoxide 30 of this diene in addition to the simple 1,2-adduct 31 a transannular oxygen participation occurs producing three oxa bicyclic compounds 32-34.The oxidation of 1-fluoro-2-(methylthio)cyclooctane (2a) by sodium periodate yields the expected mixture of two diastereomeric 1-fluoro-2-(methylsulfinyl)cyclooctanes (36) which on pyrolysis give 3-fluorocyclooctene (37).