Allylic derivatives double carbonylation

The above examples represent Jl-heteroaromatic annulation involving the reaction of allyl anions whose double bond is a part of the heterocyclic ring system (Scheme 1). The corresponding a-oxoketene dithioacetals (1,3-electrophilic component) were generally derived from nonheterocyclic carbonyl precursors. Alternatively the Jl-heteroaromatic annulation can also be employed to a-oxoketene dithioacetals derived from heterocyclic ketones (1,3-bielectrophile) and hetero/nonheteroallyl anions (1,3-binucleophile). These reactions are described below. 

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. 

The spectra fit the ester structure well, but not the more symmetrical diketone structure at all. There are three types of proton (cyclobuta-l,3-dione would have just one) with allylic coupling between one of the protons on the double bond and the CH2 group in the ring. The carbonyl group has the shift (185 p.p.m.) of an acid derivative (not that of a ketone which would be about 200 p.p.m.) and all four carbons are different. 

Asymmetric allylation of carbonyl substrates and their derivatives is currently of particular interest in the synthesis of a wide range of optically active compounds, owing to the easy derivatization of the carbon-carbon double bond to a desired functional group. The strategy for reaching this goal can be classified into three approaches ... 

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