Isomerisation de dienes-1,5 fonctionnalises par le fer pentacarbonyle

Article abstract of DOI:10.1016/0022-328X(89)88097-0

A series of various, functionnalized 4-vinylcyclohexene derivatives, substituted with electron-withdrawing or -donating groups on the exocyclic double bond, have been isomerized by pentacarbonyliron, under thermodynamic control with heating, into a mixture of conjugated cyclohexadiene tricarbonyliron complexes, of which the 2-substituted derivative is the predominant.When ferrous chloride is used as the co-catalyst, the isomerisation proceeds under kinetic control to give the 1-substituted cyclohexadienetricarbonyliron complex as the major derivative.Reaction mechanisms, have been proposed for these isomerisation processes, which provide a new selective route to such derivatives.The formation of η⁴-1,4-cyclohexadienetricarbonyl complexes as intermediates has been excluded, and it is shown that the thermal isomerisation proceeds via η²-complexes that are formed by successive 1,3-hydrogen shifts.