Visible-Light Photocatalyzed Oxidative Coupling of Benzylamines with Nucleophiles: Synthesis of 2-Aryl benzothiazoles and α,β-Unsaturated esters

Abstract

The oxidation of amines is considered as one of the important way for producing key synthetic intermediates such as aldehydes, ketones, imines, oximes, amides, nitriles and nitro compounds using suitable reaction conditions. Recently, the utilization of light as an energy source in organic synthesis have gained significant interest and has delivered the key development to the visible-light photoredox catalysis. Herein, we have developed the oxidation of benzylamine derivatives using rose bengal as a photocatalyst under visible-light irradiation followed by trapping with nucleophiles like 2-aminothiophenol and dimethylmalonate for the construction of 2-aryl benzothiazoles and α,β -unsaturated esters. The proof of concept has been established by synthesizing five benzothiazole derivatives and five α,β -unsaturated esters. The key features of this method are metal-free, no external oxidants such as peroxide and ambient reaction temperature.