Synthesis of Carboxylic Acids by Palladium‐Catalyzed Hydroxycarbonylation

Abstract

The synthesis of carboxylic acids is of fundamental importance in the chemical industry and the corresponding products find numerous applications for polymers, cosmetics, pharmaceuticals, agrochemicals, and other manufactured chemicals. Although hydroxycarbonylations of olefins have been known for more than 60 years, currently known catalyst systems for this transformation do not fulfill industrial requirements, for example, stability. Presented herein for the first time is an aqueous‐phase protocol that allows conversion of various olefins, including sterically hindered and demanding tetra‐, tri‐, and 1,1‐disubstituted systems, as well as terminal alkenes, into the corresponding carboxylic acids in excellent yields. The outstanding stability of the catalyst system (26 recycling runs in 32 days without measurable loss of activity), is showcased in the preparation of an industrially relevant fatty acid. Key‐to‐success is the use of a built‐in‐base ligand under acidic aqueous conditions. This catalytic system is expected to provide a basis for new cost‐competitive processes for the industrial production of carboxylic acids.

In silico investigation of ligand-regulated palladium-catalysed formic acid dehydrative decomposition under acidic conditions

“…(path E and F) Comparing the energy profiles of four paths (path A, C, E and F) together in Scheme 2, we can see that although the reaction process of dehydrogenation has fewer elementary steps than dehydration, the PTSA-mediated dehydration of HCOOH catalysed by Pd-py t bpx is obviously more favourable than the corresponding dehydrogenation, owing to the much lower apparent activation energy of path A than E. Such advantage is unaffected under the PTSA-free reaction conditions, since the dehydrogenation of 2a-py t bpx should be accomplished by HCOOH instead of PTSA (via TS4b-py t bpx instead of TS4a-py t bpx), which rationalizes the stable chemoselectivity to CO by Pd-py t bpx under the PTSA-absent conditions. In sharp contrast to the observed remarkable stability of Pd-py t bpx catalyst, 25,33,34 the catalyst of Pd-d t bpx is always prone to decompose in either the absence or the presence of PTSA under heating conditions, which leads to the formation of Pd nanoparticles (i.e., Pd black). 34,35 Such distinction on stability is more obvious under the water-contained acidic conditions.…”

Selectively Upgrading Lignin Derivatives to Carboxylates through Electrochemical Oxidative C(OH)−C Bond Cleavage by a Mn‐Doped Cobalt Oxyhydroxide Catalyst

“…Carboxylic acids represent an important class of compounds in the fine and bulk chemical industry with wideapplications as food preservatives,p harmaceuticals,a nd building blocks of polymers. [1] Most of these commodities are currently produced from fossil-derived hydrocarbons via tandem oxidation (Scheme 1a). Alternatively,l ignin, am ain constituent of biomass,offers asustainable source to alleviate the petroleum depleting and associated environmental issues.…”

Reaction Mechanism of Pd‐Catalyzed “CO‐Free” Carbonylation Reaction Uncovered by In Situ Spectroscopy: The Formyl Mechanism

“…These surrogate molecules are easier to handle on a small scale than a comparable synthesis gas (a mixture of CO and H 2 ) feedstock thus enabling a decentralized chemical industry. It comes as no surprise that this type of carbonylation has been used to synthesize a wide variety of organics ranging from industrially relevant carboxylic acids [7] to pharmaceutical products [6] . Often, “CO‐free” carbonylations are catalyzed by phosphine complexes of late transition metals (i.e., Pd, Rh, Ru or Ir) [4]…”