The Reaction of Cobalt Hydrocarbonyl with Vinyl Ethers, Vinyl Esters and N-Vinyl Compounds, and Oxo Reaction of Them

Abstract

The substituent effects on the carbonylation reaction of cobalt hydrocarbonyl with polar olefins such as ethyl vinyl ether, vinyl acetate and N-vinyl compounds (N-vinylcarbazole, N-vinylindole, N-vinylpyrrole and N-vinylpyrrolidone) were studied. These olefins were carbonylated selectively on the α-carbon to give the branched-chain acyl complexes, though the α-carbon is more sterically hindered than the β-one. The branched-chain acyl complexes formed did not isomerize into the straight-chain one, though it is known that acylcobalt complexes easily undergo such a skeletal rearrangement. The branched-chain acyl complexes derived from ethyl vinyl ether, vinyl acetate, N-vinylindole and N-vinylpyrrole showed the great tendency to be reduced by cobalt hydrocarbonyl and to be transformed into the corresponding aldehydes.The oxo reactions of these olefins as well as phenyl vinyl ether were also studied with dicobalt octacarbonyl as the catalyst. The branched-chain aldehyde (and/or the corresponding alcohol) was produced with high selectivity from each olefin used. The effects of the reaction conditions (reaction temperature, partial pressure of carbon monoxide or hydrogen) on the distribution of the products (the straight or the branched-chain one) were very little. From these results, it was concluded that the distribution of the products in the oxo reaction of those olefins with electron-donative substituents such as alkoxy, acyloxy, and N-carbazolyl is mainly decided by the direction of the addition of cobalt hydrocarbonyl to the carbon-carbon double bond, and that the attack of cobalt occurs on the α-carbon from the substituent to give the products of the branched-chain structure.