Photocatalytic Dehydroformylation of Benzyl Alcohols to Arenes

Abstract

In the last decades, a plethora of C–C bond forming reactions have been developed, while less attention has been paid to the design of strategies involving C–C bond cleavage. We report a photocatalytic dehydroformylation sequence for the conversion of benzyl alcohols to arenes in a one‐pot two‐step process. Herein, the initial dehydrogenation of benzyl alcohols to the corresponding benzaldehydes is combined with an additional decarbonylation step yielding unfunctionalized arenes. As a result, a broad range of benzyl alcohols can be easily degraded in short times under mild photocatalytic conditions. The conducted mechanistic studies indicate that our cooperative hydrogen atom transfer (HAT)‐cobalt system proceeds through the formation of α‐alkoxy‐ and acyl‐radicals as key intermediates, involving concomitant syngas (CO + H2) generation.

Recent advances of decatungstate photocatalyst in HAT process

“…König et al 62 developed a photocatalytic process for the successive dehydroformylation of benzyl alcohols to arenes (Scheme 20). TBADT serves as a photoexcitable HAT agent, while cobaloxime pyridine chloride (COPC) acts as a co-catalyst to form a cooperative photocatalytic system that generates concomitant syngas (CO + H 2 ).…”

“…TBADT serves as a photoexcitable HAT agent, while cobaloxime pyridine chloride (COPC) acts as a co-catalyst to form a cooperative photocatalytic system that generates concomitant syngas (CO + H 2 ). They proposed a plausible mechanism (Scheme 21) 62 to explain how benzyl alcohols are dehydroformylated. A stepwise radical mechanism which proceeds through photoinduced C–H activation could be involved in this transformation.…”