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-butylphos-phino-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.

Fatty Acids and their Derivatives as Renewable Platform Molecules for the Chemical Industry

“…Themechanism of the isomerizing alkoxycarbonylation of unsaturated fatty compounds was studied in detail, including computational studies. [78][79][80] Mecking et al fully analyzed the products of the methoxycarbonylation of 2b with the welldefined precatalyst [(dtbpx)Pd(OTf) 2 ], [81] and found the formation of the linear a,w-diester with as electivity of 90.6 %, besides all possible branched diesters in minor amounts. [82] Thed iester was obtained in high purity by simple recrystallization from methanol.…”

Efficient Palladium‐Catalyzed Carbonylation of 1,3‐Dienes: Selective Synthesis of Adipates and Other Aliphatic Diesters

“…In general, the polarity and protic nature of the solvent can influence the formation of the active hydride species and each of the individual elementary steps in the two catalytic cycles as well as the isomerization reactions [16b,c] . As an example, Gabriele and co‐workers discovered that, for Pd‐catalyzed oxidative dicarbonylation of alkynes, a large excess of water as co‐solvent promoted the formation of maleic acid with unprecedented catalytic efficiencies [17] .…”

Computational modelling of Pd-catalysed alkoxycarbonylation of alkenes and alkynes

“…At the PBE0-D3/def2-TZVP/COSMO level of theory, Jameel et al suggested a higher linear selectivity for Pd-catalysed methoxycarbonylation of methyl 10-undecenoate with the DTBPX ligand system. 104 Again the authors report an overall barrier relative to the reactant complex (affording B18.9 kcal mol À1 ). However, when applying the energy span model, 89,90 it turns out that the Pd-acyl complex should be taken as the MARI; increasing the overall barrier to B40.0 kcal mol À1 (see Scheme S2 in the ESI ‡ for more details).…”