Palladium-Catalyzed Hydroxycarbonylation of Pentenoic Acids. Computational and Experimental Studies on the Catalytic Selectivity

Abstract

The palladium-catalyzed conversion of (bio)pentenoic acid isomers (PEAs) occurs with high activity and selectivity to adipic acid (ADA) in the presence of the diphosphine ligand L 2 = 1,2-bis[(di-tert-butyl)phosphinomethyl]benzene (DTBPX) and an acid cocatalyst. Using density functional theory (DFT) calculations, we show that the active catalyst ([L 2 Pd II -H] + ) isomerizes the PEAs to their equilibrium mixture, from which selective carbonylation and hydrolysis results in the ADA product. Hydrolysis is the rate-limiting and also selectivity-determining step, consisting of two parts, hydration and "product release". After the separation of ADA from Pd(0), the product is in a hydrate form. The conversion of this Pd(0) species to the active catalyst occurs quickly with an acid cocatalyst. This conclusion is also supported by the experimental finding that a moderate acidity increases the overall reaction rate. The bulky P substituents in the DTBPX ligand largely prevent chelation of the pending COOH moiety of PEAs, thus allowing the same high regioselectivity as is obtainable with unfunctionalized long-chain alkenes. We also modeled the CO insertion into the chelate complexes and confirmed an increase of more than 50 kJ mol −1 in the barrier for their conversion.

Direct and Selective Synthesis of Adipic and Other Dicarboxylic Acids by Palladium‐Catalyzed Carbonylation of Allylic Alcohols

“…Other commonly used bisphosphine ligands, such as DPPP L4, DPPB L5 and BINAP L6, did not exhibit any catalytic activity. Interestingly, when testing 1,2-bis[(di-tert-butyl)phosphino-methyl]benzene (L7, d t bpx), [10] which is used by Lucite International to produce methyl methacrylate and was also employed by Drent for carbonylation of 1,3-butadiene, [11] the major product is still 5 a; however, in addition 17 % of C6-diacids are achieved with high selectivity (95 %) for linear adipic acid. Unfortunately, using ligands L8 and L9 in which the di-tert-butylphosphine units are replaced with more stable di-phenylphosphine or diadamantyl units did not give better results.…”

Sustainable Routes for the Synthesis of Renewable Adipic Acid from Biomass Derivatives

“…[100] Recently, Zhao and co-workers proposed another novel two-step process for the synthesis of AA from GVL. [6] Firstly, GVL was distilled over ZSM-5 catalyst to obtain a mixture of PEAs with a yield of 96 %. [101] Then, in the presence of CO and water, the mixture of PEAs were transformed into AA using a Pd diphosphine catalyst by a tandem isomerization-hydroxycarbonylation reaction in the homogeneous media with an overall yield of 48 % (Scheme 11a).…”

“…[1b] Furthermore, another serious drawback of this pathway is producing approximately 10 % of annual global emissions of the greenhouse gas N 2 O. [6] Although several new catalytic systems have been reported, the feedstock still relies on nonrenewable petroleum-derived benzene. [7] Therefore, it remains urgent to design and develop renewable resources for the synthesis of AA to replace the traditional fossil resources.…”

Cooperative Use of Brønsted Acids and Metal Catalysts in Tandem Isomerization Reactions of Olefins

“…Even the most stable conjugated alkene can undergo this transformation. Notably, pentenoic acids can be obtained from biomass via γ‐valerolactone . It was demonstrated that by using the above described ALPHA‐process catalyst in the methoxycarbonylation of pentenoic acid, the corresponding dimethyl adipate ( 14 ) was obtained with 97 % selectivity and full conversion of the substrate .…”