Carbon monoxide as a building block in organic synthesis. Part V. Involvement of palladium-hydride species in carbonylation reactions of monoterpenes. X-ray crystal structure of 4

Article abstract of DOI:10.1016/0022-328X(94)87106-X

A palladium precursor and SnCl2 as cocatalyst were used under 4 MPa of carbon monoxide for the catalytic alkoxycarbonylation of several monoterpenes into C11 esters.The active catalyst involves a palladium-hydride species whose formation was investigated.In the case of the model substrate 3-phenylpropene, the source of the hydrido ligand was determined to be the alkene itself.Allylic hydrogen abstraction seems to be a general way to produce the active hydridopalladium species since monoterpenes having labile allylic hydrogens were converted under exceptional mild conditions.An X-ray crystal structure analysis was carried out on <(Ph3PCH2CH=CHPh)4(PdCl6)(SnCl6)>. Key words: Palladium; X-ray structure; Terpenes; Carbonylation; Hydroesterification