Palladium-catalyzed intramolecular oxidative alkylation of 4-pentenyl beta-dicarbonyl compounds.

Reaction of 8-nonene-2,4-dione with a catalytic amount of [PdCl2(CH3CN)2] (2; 5 mol %) and a stoichiometric amount of CuCl2 (2.5 equiv) at room temperature for 3 h led to oxidative alkylation and formation of 2-acetyl-3-methyl-2-cyclohexenone in 80 % isolated yield. The oxidative alkylation of 4-pentenyl beta-diketones tolerated a number of terminal acyl groups and substitution at the C1 and C3 carbon atoms of the 4-pentenyl chain. Likewise, 4-pentenyl beta-keto esters that possessed geminal disubstitution at the C1, C2, or C3 carbon atom of the 4-pentenyl chain cyclized to form 2-carboalkoxy-2-cyclohexenones in moderate to good yield as the exclusive cyclized product. Deuterium-labeling experiments provided information regarding the mechanism of the palladium-catalyzed oxidative alkylation of 4-pentenyl beta-dicarbonyl compounds.

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Author Ross A. Widenhoefer Chemistry