Chemo-, site-selective reduction of nitroarenes under blue-light, catalyst-free conditions

The tandem reaction of photoinduced double hydrogen-atom transfer and deoxygenative transborylation for chemo- and site-selective reduction of nitroarenes into aryl amines under catalyst-free, room temperature conditions was disclosed in excellent yields. In this reaction, isopropanol ((PrOH)-Pr-i) was used as hydrogen donor and tetrahydroxydiboron [B-2(OH)(4)] as deoxygenative reagent with green, cheap, and commercially available credentials. In particular, a wide range of reducible functional groups such as halogen (-Cl, -Br and even -I), alkenyl, alkynyl, aldehyde, ketone, carboxyl, and cyano are all tolerated. Moreover, the reaction preferentially reduces the nitro group at the electron-deficient site over another nitro group in the same molecule. A detailed mechanistic investigation in combination of experiments and theoretical calculations gave a reasonable explanation for the reaction pathway. (C) 2021 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

A new tandem reaction involving photoinduced double hydrogen-atom transfer and deoxygenative transborylation has been developed for the chemo- and site-selective reduction of nitroarenes. The reaction proceeds under catalyst-free, room temperature conditions, and shows excellent yields. The use of isopropanol as a hydrogen donor and tetrahydroxydiboron as a deoxygenative reagent makes this method convenient and cost-effective. The reaction can tolerate a wide range of reducible functional groups and selectively reduces the nitro group at the electron-deficient site.