Vinylcyclopropanes 2-cyclohexenone ring

Iron pentacarbony 1/irradiation 2-Cyclohexenone ring from cyclic vinylcyclopropanes... 

Vinylcyclopropanes can react with pentacarbonyliron to give two different types of addition products i) (diene)tricarbonyliron 7r-complexes as the result of ring opening, hydrogen shift, and complexation ii) cyclohexenones by photoinduced carbonyl insertions across the vinyl-cyclopropane system. 

In addition to the a-substituted VCP derivatives, more substrates with different substitution patterns were also proved suitable for the [5-Tl] reaction (Scheme 17.20). For example, 1-substituted vinylcyclopropanes (78), 2-substituted vinylcyclopropanes (80), and bicyclic compound (82 and 84) can aU react well, delivering functional cyclo-hexenones in moderate to good yields (in some cases, only nonconjugated cyclohexenones were obtained under both conditions). Interestingly, the reaction seems highly sensitive to the ring size of the substrates and the substitution patterns of the double bond, because 86,87, and 88 cannot be used as substrates for the [5-1-1] cycloaddition. 

Cyclopropane rings. Synthesis of (diene)Fe(CO)3 complexes, and of cyclohexenones, lactones, ketones, or sulfones, can follow from the opening of vinylcyclopropanes with Fe(CO)s under either thermal or photochemical conditions. Reactions of the vinylcyclopropane (15) with Fe(CO>5 under thermal conditions resulted in ring opening with concomitant hydrogen shift to form the diene complex (16) (eq 7) 2.63,64... 

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