Construction Of Catalytic Systems Based On TEMPO And Non-noble Metals( Fe,Cu) And Their Catalytic Performances On The Aerobic Oxidation Of Alcohols

The oxidation of alcohols to the corresponding aldehydes and ketones is one of the most important reactions in organic chemistry, and the systems based on stable nitroxyl radical 2,2,6,6-tetramethylpiperidine-1-oxyl（TEMPO） in combination with metals as co-catalysts are among the most efficient ones.In this paper, three precursor quaternary ammonium with a TEMPO moiety（[Quaternium-TEMPO]+Brˉ） were firstly synthesized from three kinds of tertiary amines, and then three novel deep eutectic solvent supported TEMPO（DES-TEMPO） were prepared by mixing [Quaternium-TEMPO]+Brˉ with urea in different molar ratios. The structures of [Quaternium-TEMPO]+Brˉ and intermediates were characterized by NMR and HR-MS（ESI）. An efficient catalytic system for the oxidation of alcohols with molecular oxygen as terminal oxidant has been developed from DES-TEMPO and Fe（NO₃）₃·9H2O under mild and solvent-free conditions. The reactions were optimized with benzyl alcohol as a model substrate. The types of metal salts, every component loading and reaction temperature were investigated respectively. The final optimized conditions were: DES-TEMPO 1.25 mol%,Fe（NO₃）₃·9H2O 3 mol%,reaction temperature 60 ℃. In addition, this system was also applied to the oxidation of various alcohols including aromatic, aliphatic, heterocyclic, etc. and good results were received. The DES could be recovered easily and recycled up to five times in the oxidation of benzyl alcohol without significant loss of catalytic activity.A novel benzoxazine with a imidazole moiety ligand（L） was synthesized by a Mannich condensation reaction from 2,4-di-tert-butyl phenol, histamine hydrochloride and formaldehyde. The structure of this ligand was characterized by NMR and HR-MS（ESI）. An efficient catalytic system based on this ligand for the oxidation of alcohols has been developed combined with Cu（OTf） and TEMPO. The reactions were also optimized with benzyl alcohol as a model substrate. Different copper metal salts, different solvents, every component loading and reaction temperature were investigated respectively. The final optimized conditions were: Cu（OTf） 5 mol%, L 4 mol%, TEMPO 5 mol%, dichloromethane 1ml, reaction temperature 25 ℃. This system was applied to the oxidation of various alcohols and the results indicated that it not only showed good performances on primary alcohols including aromatic, allyl and some heterocyclic, but also has certain catalytic activity with good to excellent selectivity for secondary alcohols.