DIRECT CONVERSION OF ALKENES INTO METHYL-SUBSTITUTED CYCLOPROPANES USING AN ORGANOIRON ETHYLIDENE TRANSFER REAGENT

Article abstract of DOI:10.1016/0022-328X(85)87371-X

(η⁵-C5H5)(CO)2FeCH(CH3)SPh (8) serves as a quite useful reagent for the transfer of ethylidene groups to alkenes to give methyl-substituted cyclopropanes in good yields.The reaction is accomplished by allowing 8 to react with an alkylating agent such as trimethyloxonium tetrafluoroborate or methyl fluorosulfonate in the presence of the alkene substrate.The active ethylidene transfer reagent is apparently a sulfonium salt which is too reactive to be isolated under normal conditions.In all csases, cyclopropanes are obtained stereospecifically with respect to the configuration of the starting alkenes, and with certain classes of substrates such as cis-disubstituted alkenes, the reaction also occurs with very high syn-stereoselectivity.