Photolysis of CO2 Carbamate for Hydrocarboxylation Reactions.

The conversion of carbon dioxide into value-added products has emerged as an alternative method to achieve net-zero emissions. While technologies that transform CO2 into fuels and chemical feedstocks have made great strides, the direct use of CO2 as a C1 synthon for the formation of new carbon-carbon bonds remains a critical challenge. Herein, we present a new catalytic CO2 activation mode for hydrocarboxylation reactions. Key to this methodology is the formation of a CO2 carbamate with a phenothiazine catalyst, which sets the required trigonal geometry for the release of CO2•- via photolysis upon absorption of visible light. The polarity-reversed CO2•- is employed in the hydrocarboxylation reactions of alkenes and heterocycles. This protocol is distinguished by its mild reaction conditions, wide substrate scope and broad applicability, even in the context of pharmaceutical cores. Our chemistry can also be utilized for the synthesis of carbon-13 labeled spirolactones using 13CO2. Mechanistic experiments support the photolysis of the CO2 carbamate as the main productive pathway under our optimized reaction conditions.