Reaction of the isomers of Feist's ester (dimethylmethylenecyclopropane-2,3-dicarboxylate) with diiron enneacarbonyl

Abstract

The reaction of diiron enneacarbonyl with the isomers of Feist's ester leads first to the formation of the corresponding iron tetracarbonyl olefin complexes, and then predominantly to the cleavage of the strained sp 2 sp 3 bond of the three-membered ring. This cleavage is followed by a stereospecific series of reactions leading eventually to diene—iron tricarbonyl complexes of dimethyl cis- and trans-1,3-butadiene-1,2-dicarboxylate. A minor pathway involves cleavage of the sp 3 sp 3 ring bond, and leads to the diiron species (IV). Photochemically, the iron complexes follow rather different pathways, the cis isomer giving products paralleling the thermal products, while the trans isomer gives a new product tentatively assigned an acyl (π-allyl) structure.