Mechanism and Control of the Palladium-Catalyzed Alkoxycarbonylation of Oleochemicals from Sustainable Sources

Abstract

The transformation of chemical production processes to a sustainable feedstock from renewable sources requires a careful assessment of current thermodynamic data, reaction mechanisms and kinetics. The Pd-catalyzed alkoxycarbonylation of the long chain olefin methyl 10-undecenoate (10-UME) from castor oil with methanol yields the building blocks for a renewable polyamide. The mechanism for the complex multi-step reaction cycle including active catalyst formation was elucidated. The experimental catalyst selectivity with 1,2-bis(di-tert-butylphosphino-methyl)benzene (1,2-DTBPMB) as a ligand towards the desired linear diester product can be reproduced and rationalized. The mechanisms of possible side reactions and well as catalyst inhibition by carbon monoxide were also investigated. Solvent effects have an influence on reaction equilibria and transition barriers. These were considered in polar (methanol) and nonpolar (dodecane) media using implicit or mixed cluster/continuum solvation models when explicit solvent coordination was critical.