Allylic derivatives intramolecular cyclization, carbonylative

Carbonyl couplings. Many variations of cross couplings are possible these include aldehydes with a-dicarbonyl compounds. Ketyl radicals derived from carbonyl compounds also add to alkenes such as acrylonitrile " or N-allyl moieties. Intramolecular cyclizations on terminal alkenes or allene species have also been exploited for synthetic purposes. 

Allyl methylcarbonate reacts with norbornene following a ruthenium-catalyzed carbonylative cyclization under carbon monoxide pressure to give cyclopentenone derivatives 12 (Scheme 4).32 Catalyst loading, amine and CO pressure have been optimized to give the cyclopentenone compound in 80% yield and a total control of the stereoselectivity (exo 100%). Aromatic or bidentate amines inhibit the reaction certainly by a too strong interaction with ruthenium. A plausible mechanism is proposed. Stereoselective CM-carboruthenation of norbornene with allyl-ruthenium complex 13 followed by carbon monoxide insertion generates an acylruthenium intermediate 15. Intramolecular carboruthenation and /3-hydride elimination of 16 afford the -olefin 17. Isomerization of the double bond under experimental conditions allows formation of the cyclopentenone derivative 12. 

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