Heterogeneous photocatalytic synthesis of sulfenamides with carbon doped potassium poly(heptazine imide) through effective electron delocalization

Abstract

Sulfur–heteroatom bonds, such as S–N bonds, are valuable motifs in pharmaceuticals and agrochemicals, but the creation of new green synthetic methods to construct these compounds via rational design of catalysts remains challenging. Hence, we report an environmentally benign photocatalytic S–N coupling reaction between thiols and amines over carbon-doped potassium poly(heptazine imide), resulting in the synthesis of sulfenamides. Encouragingly, after optimizing the C-doping content of potassium poly(heptazine imide), we can achieve high sulfenamide conversion rates of 92% (10 W white LED, 24 h) and 86% (real sunlight irradiation in summer, 5 h). Moreover, the present catalyst possesses good substrate tolerance for the photocatalytic S–N coupling of thiols and amine derivatives, great recyclability, and a gram-scale synthesis was also possible. We provide good evidence that the carbon-doping of potassium poly(heptazine imide) can extend its optical absorption range to near-infrared light while inhibiting the intrinsic radiative recombination of photoexcited electron–hole pairs and facilitating the single electron transfer process owing to its delocalized electron density. Overall, boosting the photosynthetic sulfenamide activity by introducing delocalized electrons is demonstrated, and this could be applied more widely in heterogeneous photocatalysis in organic synthesis.