Decatungstate-photocatalyzed hydroacylation of azobenzenes with aldehydes to access N,N'-diarylhydrazides

Abstract

A photocatalytic hydroacylation of azobenzenes with aldehydes has been developed. With tetrabutylammonium decatungstate (TBADT) as the photocatalyst, a wide range of azobenzenes and aldehydes reacted smoothly under visible light irradiation, affording various N,N'-diarylhydrazides in generally high yields. Mechanistic studies indicate that TBADT-mediated hydrogen atom transfer (HAT) photocatalysis enables the reaction. This work uses abundant and cheap aldehydes as the acyl radical sources and has advantages including readily available acylation agents, no use of any additives and bases, no waste generation, excellent controllability, broad scope, and 100% atom economy. It provides a mild, efficient, and sustainable route to synthesizing N,N'-diarylhydrazides.