Bifunctionalized Ionic Liquid Catalyze The Oxidation Of Aromatic Compounds

Oxidation is an important reaction in organic chemistry. However, in the laboratory, oxidation is usually carried out by using hazardous, toxic, and corrosive oxidant (permanganate, chromate, or periodate etc.) with serious environmental hazards with respect to the handling, transportation and storage. Amongst oxidants, hydrogen peroxide is a valuable oxidant since water is the only effluent of the process. The oxidation halogenation and oxidation of alcohols are two kinds of oxidation reactions which are widely studied.Oxidation halogenation using safe and cheap halogen reagents in the presence of H2O2allows complete utilization of halogen atoms and therefore the atom economy is much higher compared to the traditional halogenation. In addtion, the clean oxidation of alcohols to aldehydes/ketones using hydrogen peroxide as the oxidant is also of great significance. In this work, five kinds of functionalized ionic liquids (ILs). including the sulfoacid-functionalized IL of [Psmim]2SO4, the metallated-functionalized ILs of [Bmim]2TiF6, and [Bmim]2Na3PMo10V2O40,and the bifunctionalized ILs of [Psmim]2TiF6and [Psmim]2H3PMo10V2040, have been synthesized and characterized. These sysnthzied functionalized ILs were applied as the catslysts for1) the oxidative halogenation using hydrogen peroxide and halide acids/salts, and2) the oxidation of alcohols using hydrogen peroxide, with the comibantion of the room temperature IL of [Bmim]BF4as the reaction medium.As for the oxidative halogenation using hydrogen peroxide and halide acids/salts, it was found that the bifunctionalized IL of [Psmim]2TiF6exhibited the best catalytic performance, in which the synergetic catalytic effect coming from the two incorporated functionalities of SO3H and TiF62-were embodied in this method. When halide salts were used as the halogenation source.[Psmim]2TiF6could catalyze oxidative halogenation of various organics under mild conditions and the reaction rate was in the ranking of NaBr>> NaCl> K.I. The presence of proton acids could guaranteed the recyc lability of[Psmim]2TiF6 When halogen acids were used as the halogenation source,1equivalent of the halogen acid to the organic substrate could result in the complete oxidative halogenations, indicating almost100%halogen atom utilization. The catalyst of [Psmim]2TiF6could be recycled for8runs without activity loss with [Bmim]BF4.As for the oxidation of alcohols using hydrogen peroxide, the bifunctionalized IL of [Psmim]2H3PMo10V2O40could catalyze oxidation of various alcohols to aldehydes (or ketones) with high selectivity. The synergetic catalytic effect coming from the two incorporated functionalities of SO3H and [H3PMo10V2O40]2-were still embodied in this system. However, the recyc lability of [Psmim]2H3PMo10V2O40was unavailable in the oxidation of alcohols. The31P NMR and FT-IR spectroscopy analyses indicated that the destruction of the Keggin structure of [H3PMo10V2O40]2-anion led to the deactivation.