One‐pot tandem synthesis and spontaneous product separation of N‐heterocycles based on bifunctional small‐molecule photocatalyst

Abstract

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 propose an efficient approach for the one‐pot tandem synthesis of quinazolines, quinazolinones and benzothiadiazine 1,1‐dioxides from alcohols and amines utilizing a bifunctional bipyridiniun photocatalyst with redox and Lewis acid sites with 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.