Abstract
A facile one-pot two-stage photochemical synthesis of aromatic azoxy compounds and imines has been developed by coupling the selective reduction of nitroaromatic compounds with the selective oxidation of amines in an aqueous solution. In the first stage (light illumination, Ar atmosphere), the light excited nitroaromatic molecule abstract H from amine to form ArNO2H and amine radical, which then form nitrosoaromatic, hydroxylamine and imine compounds. Water acts as a green solvent for the dispersion of the reactants and facilitates the formation of nitrosoaromatic and hydroxylamine intermediate compounds. In the second stage (no light, air atmosphere), the condensation of nitrosoaromatic and hydroxylamine compounds yields aromatic azoxy product with the aid of molecular oxygen in air. This photochemical synthesis achieved both high conversion and high product selectivity (>99%) at room temperature.
Highlights
The selective reduction of nitroaromatic compounds to azo/azoxy compounds and the selective oxidation of amines to imines are two important types of reactions
Given the light absorption of nitroaromatic compounds in the near-UV and the H-donating ability of amines[17], it is possible that an amine can act as the reducing agent for the selective reduction of a nitroaromatic compound and itself is oxidized to its corresponding imine
Three main products from NB were detected with gas chromatography mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC) analysis, including nitrosobenzene (NSB), phenyl-hydroxylamine (PHA) and azoxybenzene (AOB)
Summary
The selective reduction of nitroaromatic compounds to azo/azoxy compounds and the selective oxidation of amines to imines are two important types of reactions. The direct oxidation of amines using molecular oxygen under light irradiation has drawn a lot of attention lately, with metal oxides such as TiNb2O711 and Nb2O512 or metal free photocatalyst such as carbazolic conjugated microporous polymer[13] exhibiting good catalytic activity for the oxidation reaction. Given the light absorption of nitroaromatic compounds in the near-UV and the H-donating ability of amines[17], it is possible that an amine can act as the reducing agent for the selective reduction of a nitroaromatic compound and itself is oxidized to its corresponding imine If it works, both the reactants convert to valuable products without the need of a catalyst using a one-pot reaction. The reaction was conducted in a green solvent - water
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
