One‐pot Tandem Synthesis and Spontaneous Product Separation of N‐heterocycles based on Bifunctional Small‐molecule Photocatalyst

Homogeneous and heterogeneous reactions wherein the resulting products remain dissolved in solvents generally require complicated separation and purification process, despite the advantage of heterogeneous systems allowing retrieval of catalysts. Herein, we have developed an efficient approach for the one‐pot tandem synthesis of quinazolines, quinazolinones and benzothiadiazine 1,1‐dioxides from alcohols and amines utilizing a bifunctional bipyridinium photocatalyst with redox and Lewis acid sites using air as an oxidant. Through solvent‐modulation strategy, the photocatalytic system exhibits high performance and enables most products to separate spontaneously. Consequently, the homogeneous catalyst can be reused by direct centrifugation isolation of the products. Notably, the method is also applicable to the less active substrates, such as heterocyclic alcohols and aliphatic alcohols, and thus provides an efficient and environmentally friendly photocatalytic route with spontaneous separation of N‐heterocycles to reduce production costs and meet the needs of atomic economy and green chemistry. The first reusable homogeneous system with spontaneous product separation for transforming alcohols and amines into N‐heterocycles through solvent‐modulated one‐pot tandem reactions has been developed by utilizing the bifunctional small‐molecule photocatalyst with redox and Lewis acid sites, which demonstrates excellent substrate compatibility and holds significant promise for industrial‐scale production.