Applicability of Semiconductor Photocatalysts in Photoredox Reactions: Highlighting the Performance of Polymeric Carbon Nitrides in Radical Three-Component Couplings

A set of five polymeric carbon nitrides (pCNs) made from diverse low-molecular precursors was compared with metal chalcogenide and pnictogenide semiconductors for their effectiveness in visible light-induced organic radical reactions. The productivity of the heterogenous photocatalysts in the decarboxylative Giese addition of N-phenylglycine with cyclopentenone was studied at different irradiation wavelengths ranging from 380 to 450 nm, as well as in the deaminative radical donor–acceptor–donor (DAD) three-component coupling of N-benzyl pyridinium salts with N-methylmaleimide and 1,1-diarylethylenes. The heterogenous photocatalytic radical three-component reactions were achieved in high diastereoselectivities and with high yields if the electronic and steric properties of the reactants were matched with the appropriate heterogeneous photocatalyst.