Stoichiometric and Catalytic Cross Dimerization between Conjugated Dienes and Conjugated Carbonyls by a Ruthenium(0) Complex: Straightforward Access to Unsaturated Carbonyl Compounds by an Oxidative Coupling Mechanism

A series of stoichiometric and catalytic cross dimerizations between conjugated dienes and conjugated carbonyls are studied. The reaction of Ru(η4-cisoid-1,3-butadiene)(η4-1,5-COD)(NCMe) (2a) with methyl acrylate gives a Ru(0) complex, Ru[methyl η4-cisoid-(2E,4E)-hepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3aa) in 97% yield. Similar treatments of 2a with a series of tert-butyl acrylate, methyl crotonate, 3-buten-2-one, and N,N-dimethylacrylamide produce similar analogues of 3ac. When (E)-1,3-pentadiene complex 2d is employed in the reaction with methyl acrylate, the branched coupling product Ru[methyl η4-cisoid-(2E,4E)-4-methylhepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3da-b) is dominantly obtained in 65% yield along with the linear product in 19% yield. In the case of the (E)-2,5-dimethylhexa-1,3-diene complex 2e, the corresponding branch product is exclusively obtained in 86% yield. The catalytic cross dimerizations between conjugated dienes and conjugated carbonyls are established by 2. The origin of the presen...