Photocatalytic organic transformations: Simultaneous oxidation of aromatic alcohols and reduction of nitroarenes on CdLa2S4 in one reaction system

Abstract

Photocatalytic selective organic transformations (SOTs) with sunlight offer a “green” route for synthesis of fine chemicals. In this work, a bare ternary chalcogenide CdLa2S4 photocatalyst was fabricated to couple the selective oxidation (SO) of aromatic alcohols to aldehydes and selective reduction (SR) of nitroarenes to anilines in one reaction system. The photocatalyst showed a high stability and a good generality for the conversions due to the well–matched band structure and the high separation efficiency of photoinduced electrons (e–) and holes (h+). For p–substituted aromatic alcohols, the selectivities to the corresponding aldehydes are as high as ca. 90%. The electro–donating substituent in the para position benefits the SO reactions, which are triggered by h+ via a successive deprotonation; while for p–substituted nitroarenes, the SR to the corresponding anilines is vulnerable to the electro–withdrawing groups and the steric hindrance of the substituent and the selectivities to anilines are substantially lower than that of the SO conversions. H+ deprotonated in the SO of aromatic alcohols is indispensable for the SR of nitroarenes as they are achieved by a H+–coupled six e– reduction process, which leads to the low conversion efficiencies. The half conversions not only be coupled by the photoinduced e– and h+, but also collaborate with each other through H+. Our results clearly demonstrate the emerging concept of a coupled reaction system for sunlight–driven synthesis of fine chemicals and reveal the underlying mechanism.