Cobalt‐Catalyzed Reduction of Propargyl Alcohols for the Synthesis of 1,3‐Diarylallenes under N,N‐Ligand and Hydride‐free Conditions

Allenes are a class of important organic compounds, and their synthesis has always been of great interest. In this article, we have developed a cobalt‐catalyzed photoredox strategy, providing an alternative and efficient approach for the synthesis of 1,3‐diarylallenes from propargyl alcohols. The reaction utilized organic amines as a hydrogen source to avoid the use of conventional hydride additives, and does not require the addition of extra ligands to activate the cobalt catalyst, achieving a mild reaction condition. As a result, the reaction was able to synthesize the desired 1,3‐diarylallene compounds with good yields and functional group compatibility.