Ionic‐Liquid‐Assisted Metal‐Free Oxidative Coupling of Amines To Give Imines

Abstract

An oxidative coupling of amines to give imines in ionic liquids (ILs) under metal‐free aerobic conditions has been developed. The high efficiency achievable in ILs is mechanistically explained in terms of activation of the starting materials (benzylamine and molecular oxygen) by an initial electron transfer, promoted by the ionic nature of the solvent. Reactivity data of variously p‐substituted benzylamines show a general deactivating effect, which would imply a change in the rate‐determining step in the reaction mechanism.

ZnO/Ionic Liquid Catalyzed Biodiesel Production from Renewable and Waste Lipids as Feedstocks

“…Indeed, based on our previous findings [43], both the tetrahedral structure and the steric hindrance of alkyl chains of quaternary ammonium (or phosphonium) cations in TBAI, TBACl, TBPAc, etc., shields the positive charge on nitrogen (or phosphorous), leaving counteranion CH 3 O − poorly solvated especially in the oil phase, thus enhancing their nucleophilicity. This phenomenon is less evident in imidazolium and pyridinium analogs (BMIMCl, BDIMCl etc.)…”

Recent Advances in Aerobic Oxidation of Alcohols and Amines to Imines

“…Possible mechanism for the cross-coupling of amines in a biphasic system Ionic liquids (IL), for instance, tetra-butylammonium bromide (TBABr), also showed high efficiency toward amine oxidation. 82 Since the formation of hydrogen bond was determined by the capability of IL anion, AcO -, Cl -, and Br -promoted the reaction much better than BF 4 -and PF 6 -. Meanwhile, the water in the IL has a detrimental effect in terms of the competitive hydrogen bond with substrates.…”

Aerobic Oxidation of Benzylic Carbons Using a Guanidine Base

“…4,15 Alternatively, the peroxide intermediate can eliminate H 2 O 2 to produce an imine that can undergo hydrolysis and oxidation by O 2 or H 2 O 2 to generate 1b (route B). 10,32−34 The imine can also undergo further oxidation to afford a benzonitrile, which can be hydrolyzed to provide 1b (route C). To probe the working mechanism, 18 O-labeled H 2 O was added into a mixture containing benzyl amine, resulting in the formation of mixtures of 18 O- 1b and 16 O- 1b (Scheme 3, eq 1).…”