Recent Advances in Aerobic Oxidative of C-H Bond by Molecular Oxygen Focus on Heterocycles

Aerobic oxidative cross-coupling represents one of the most straightforward and atom-economic methods for construction of C-C and C-X (X=N, O, S, or P) bonds using air as a sustainable external oxidant. The oxidative coupling of C-H bonds in heterocyclic compounds can effectively increase their molecular complexity by introducing new functional groups through C-H bond activation, or by formation of new heterocyclic structures through cascade construction of two or more sequential chemical bonds. This is very useful as it can increase the potential applications of these structures in natural products, pharmaceuticals, agricultural chemicals, and functional materials. This is a representative overview of recent progress since 2010 on green oxidative coupling reactions of C-H bond using O2 or air as internal oxidant focus on Heterocycles. It aims to provide a platform for expanding the scope and utility of air as green oxidant, together with a brief discussion on research into the mechanisms behind it.

One-pot multi-component process for the synthesis of 4-azaphenanthrene-3,10-dione, 1,8-dioxo-octahydroxanthene and tetrahydrobenzo[b]pyran derivatives catalyzed by the deep eutectic solvent choline chloride-oxalic acid

An effective method based on choline chloride (ChCl)-oxalic acid (Ox) deep eutectic solvent was proposed for the synthesis of 4-azaphenanthrene-3,10-dione, 1,8-dioxo-octahydroxanthene and tetrahydrobenzo[b]pyran derivatives. The eutectic mixture worked as both the solvent and acidic catalyst for conversion. The impacts of different variables, including the composition and volume of ChCl-Ox, and temperature, on reaction yield were studied for optimization. The crucial advantages of this process are simplicity of the experimental procedure, high yields, short reaction times, high recyclability, and the use of safe and inexpensive components.