A Diverse Array of Catalytic Photoredox Reactions Based on Aluminum(III)‐Salen Complexes: Understanding the Enhancement of Catalytic Activity via Amine Association

Since aluminum is an earth‐abundant and environmentally benign main‐group metal, the development of aluminum‐complex‐based photoredox catalysts remains a significant issue. Herein, we report aluminum(III)‐salen complexes (Al‐salens) as versatile photoredox catalysts. The combination of an Al‐salen catalyst with an amine under visible‐light irradiation allowed the hydrodechlorinative transformations of aryl chlorides, the reductive coupling of carbonyl compounds, and the defluoroallylation of perfluoroalkylarenes. Mechanistic studies using transient absorption spectroscopy suggested that the Al‐salen complex associates with the amine via its vacant site to improve the reducing ability of its excited‐state. After electron transfer between the excited state of the Al‐salen/amine complex and an appropriate oxidant, the generated aminium radical cation is leveraged to achieve the oxidative transformations of amines, such as α‐arylation and α‐cyanation. The diversity of the catalytic photoredox reactions based on Al‐salen complexes is comparable to that of heavy‐precious‐metal‐based catalysts.