Fluorophosphoniums as Lewis acids in organometallic catalysis: application to the carbonylation of ß-lactones.

We describe the synthesis and characterisation of four organic Lewis acids based on fluorophosphoniums, with tetracarbonyl cobaltate as the counter-anion: [R3PF]+[Co(CO)4]- (with R = o-Tol, Cy, iPr, and tBu). Their catalytic activity was investigated for the carbonylation of ß-lactones to succinic anhydrides. In the presence of [tBu3PF]+[Co(CO)4]- IV (3 mol%), 90% of succinic anhydride was afforded from ß-propiolactone after 16 h at 80 °C, at a very mild pressure of 2 bar of carbon monoxide. Our study sets the first example of the use of a main-group cation as a Lewis acidic partner in the cobalt-catalyzed carbonylation of ß-lactones.

Coupling Electrocatalytic CO2 Reduction with Thermocatalysis Enables the Formation of a Lactone Monomer.

Carbonylation reactions that generate high-value chemical feedstocks are integral to the formation of many industrially significant compounds. However, these processes require the use of CO, which is invariably derived from fossil-fuel-reforming reactions. CO may also be generated through the electroreduction of CO2 , but the coupling of these two processes is yet to be considered. Merging electrocatalytic reduction of CO2 to CO with thermocatalytic use of CO would expand the range of the chemicals produced from CO2 . This work describes the development of a system coupling a high-pressure CO2 electrolytic cell containing a bimetallic ZnAg catalyst at the cathode for production of CO with a reactor with a Faradaic efficiency of >90 % where high pressure CO is used for carbonylating propylene oxide into ß-butyrolactone by thermal catalysis, the latter step having a reaction yield above 80 %. Although the production of monomers and polymers from CO2 is currently limited to organic carbonates, this strategy opens up the access to lactones from CO2 , for the formation of polyesters.