Mechanistic features of isomerizing alkoxycarbonylation of methyl oleate.

The weakly coordinated triflate complex [(P∧P)Pd(OTf)]+(OTf)− (1) (P∧ P = 1,3-bis(di-tert-butylphosphino) propane) is a suitable reactive precursor for mechanistic studies of the isomerizing alkoxcarbonylation of methyl oleate. Addition of CH3OH or CD3OD to 1 forms the hydride species [(P∧P)PdH(CH3OH)]+(OTf)− (2-CH3OH) or the deuteride [(P∧P)PdD(CD3OD)]+(OTf)− (2DCD3OD), respectively. Further reaction with pyridine cleanly affords the stable and isolable hydride [(P∧P)PdH- (pyridine)]+(OTf)− (2-pyr). This complex yields the hydride fragment free of methanol by abstraction of pyridine with BF3·OEt2, and thus provides an entry to mechanistic observations including intermediates reactive toward methanol. Exposure of methyl oleate (100 equiv) to 2D-CD3OD resulted in rapid isomerization to the thermodynamic isomer distribution, 94.3% of internal olefins, 5.5% of α,β-unsaturated ester and