| Abstract: | The thermal reactions of 1-aryl-1-cyclopropylethylenes and 1,1-dicyclopropylethylene with pentacarbonyliron are investigated. Reactions of the former substrates yield 2-aryl-1,3-pentadiene-tricarbonyliron complexes via cyclopropane ring opening, hydrogen migration and coordination to iron. Reaction with the latter substrate gives 2-cyclopropyl-1,3-pentadienetricarbonyliron in similar fashion, and, in addition, 3-(1′-propenyl)-cyclohex-2-enone tricarbonyliron derived from the opening of the second ring coupled with carbon monoxide insertion. The cyclopropane ring serves as a two π-electron donor in these reactions, and the vinylcyclopropane system emerges as a novel source of four π-electrons which are available to coordination in direct analogy to reactions of formal diene systems with iron carbonyls. |
