摘要:
Iron carbonyls have been found to promote the cyclocarbonylation of 1,6-enynes to give cyclopentenones in good yield. The reaction is essentially the same as the intramolecular Pauson-Khand reaction. The best results were obtained using allyl propargyl ethers as substrates. Isomerization of the alkene moiety competes with cyclization in some cases, leading to reduced yields. Stereoselectivity comparable with that obtained in the Pauson-Khand reaction was observed during the cyclization of alkoxy-substituted enynes; this stereoselectivity appears to be kinetic rather than thermodynamic.