Transformation of Methyl Linoleate to its Conjugated Derivatives with Simple Pd(OAc)(2)/Lewis Acid Catalyst

摘要

With the rapid depletion of fossil resources, the exploitation of biomass to partly replace fossil resources as the source of carbon in the chemical industry constitutes a promising alternative for the near future. This work introduces catalytic transformation of vegetable oil, i.e., methyl linoleate, to its conjugated esters by a simple Pd(OAc)(2)/Sc(OTf)(3) catalyst, which has extensive applications in industry. It was found that adding non-redox metal ions like Sc(III) to a simple Pd(OAc)(2) catalyst can effectively improve its isomerization activity in toluene/t-BuOH solvent, whereas Pd(OAc)(2) alone is inactive. Preliminary mechanistic investigations together with previous studies suggested that the in situ-generated heterobimetallic Pd(II)/Sc(III) dimer serves as the key species for methyl linoleate isomerization, and the reaction proceeds by [1,3]-hydrogen shift mechanism involving a formal Pd(II)/Pd(IV) cycle.