Dual Silane-Promoted Palladium Catalysis: Synthesis of Phenols from Carbon Dioxide and 1,4-Enynes

A palladium-catalyzed reductive carbonylative benzannulation of 1,4-enynes with carbon dioxide (CO2) as carbonyl source has been developed for the first time, offering an efficient approach to a wide range of multi-substituted phenols in high yields. The success of this transformation hinges on a synergistic dual silane reduction system: one silane acts as a reductant for the conversion of CO2 to CO, while the other serves as a hydrogen source to generate Pd-H species. This method is operationally simple, exhibits broad substrate scope, and can be applied to the late-stage modification of complex pharmaceutical molecules as well as the synthesis of bioactive compounds such as thymol.