Carboxylic acid derivatives via catalytic carboxylation of unsaturated hydrocarbons: whether the nature of a reductant may determine the mechanism of CO₂incorporation?

Abstract

Application of CO2 as a renewable feedstock and C1 building block for production of commodity and fine chemicals is a highly challenging but obvious industry-relevant task. Of particular interest is the catalytic coupling of CO2 with inexpensive unsaturated hydrocarbons (olefins, dienes, styrenes, alkynes), providing direct access to carboxylic acids and their derivatives. Although not brand new for the scientific community, it is still a complete challenge, as no truly effective catalytic system has been reported to date. In this Perspective, we discuss the available experimental, theoretical and mechanistic data for such homogeneously catalyzed carboxylation processes. A special focus is placed on the understanding of the key elementary steps and of some thermodynamic and kinetic constraints.

Enantioselective Incorporation of CO2: Status and Potential

“…6,20,22,56 Here we give examples of diverse carboxylic acids formed in an enantioenriched manner from CO2.…”

“…A variety of comprehensive reviews on catalytic synthesis of organic molecules from CO2 have emerged in recent years, including metalbased and organic catalysis. 4,5,6,11,18,19,20,21,22,23,24,25,26,27,28 There are two catalytic approaches that have found widespread use for activation of the rather inert CO2 molecule (Scheme 1); both approaches involve incorporation of the entire CO2 molecule, which is our main focus here. In the first approach (Scheme 1a), C-CO2 bonds are primarily formed through insertion of CO2 into reactive metal-carbon bonds; in these reactions CO2 acts as an electrophile.…”

Ni- and Fe-catalyzed Carboxylation of Unsaturated Hydrocarbons with CO2

“…This is likely attributed to the intrinsic inertness of CO 2 , making the reaction energetically endergonic and kinetically disfavored [74]. Although this issue has been partially overcome with the activation of both counterparts in oxidative cyclization pathways mediated by selected metals (Ni, Fe, Co), the corresponding metallacycles are remarkably stable, hence preventing the implementation of a catalytic process.…”

“…Although a seemingly trivial transformation, there are a number of daunting challenges associated to this approach: (1) the direct transformation of ethylene and CO 2 into acrylic acid is endergonic by more than 20 kcal/mol, therefore making the reaction thermodynamically uphill [74];…”

Ni- and Fe-catalyzed Carboxylation of Unsaturated Hydrocarbons with CO2

“…Although a seemingly trivial transformation, there are a number of daunting challenges associated to this approach: 1) the direct transformation of ethylene and CO 2 into acrylic acid is endergonic by more than 20 kcal/mol, therefore making the reaction thermodynamically uphill [74]; 2) the activation barrier for β-hydride elimination step is energetically very costly (ca. 40 kcal/mol), resulting in a non-favorable kinetic profile [87] and 3) only a few number of ligands with specific features are able to efficiently promote the oxidative cyclization step en route to the key nickelalactone intermediates.…”