Construction And Application Of Non-transition Metal-catalyzed Aerobic Oxidation Systems

Oxidation reaction is a fundamental transformation in organic synthesis,the selective oxidation is the most important and challenging research issue.Traditional oxidation methods have some shortcomings in safety and environment friendly aspects.Molecular oxygen has attracted great attention due to its remarkable advantages,such as abundant,inexpensive and clean.There is no doubt that molecular oxygen as oxidant for oxidation reaction was the best alternative from both economical and environmental considerations.The development of proper catalysts and catalytic systems for selective oxidation reaction is still a research hotspot by chemists.Recent years,the stable nitroxyl radicals（TEMPO、AZADOs、ABNO）and DDQ have been widely used to catalyze the selective oxidation reaction.According to the literatures and our previous research,several non-transition metal-catalyzed aerobic oxidation systems were developed and applied into selective oxidation reactions.The ABNO/TBN/KPF₆/O₂ catalytic system was developed for aerobic oxidation of secondary alcohols in water.In this catalytic system,ABNO was catalyst,TBN was co-catalyst,KPF₆ was salts additive,oxygen was terminal oxidant and water was the green reaction solvent.Cyclohexanol was selected as a model substrate to identify the optimal reaction conditions.The salts,nitroxyl radicals,the amount of ABNO,oxygen pressures,reaction temperatures,the amount of TBN and KPF₆ were screened.Under the optimal reaction conditions,cyclohexanone could be obtained in 1.5 h with 96% yield as determined by GC using an internal standard method.In addition,a number of secondary unactivated and activated alcohols were examined,numerous ketones could be obtained conveniently in the medium of water.The ABNO/KOH/O₂ catalytic system was developed for aerobic oxidative synthesis of 2-substituted 4H-3,1-benzoxazines and quinazolines.In this catalytic system,ABNO was catalyst,KOH was the most important base,oxygen was the terminal oxidant.The reaction between 2-aminobenzyl alcohol and benzaldehyde was chosen as the model reaction.The KOH,oxygen,nitroxyl radicals,base and solvents were screened.Under the optimal reaction conditions,the two kinds of heterocycles were obtained in 72-97% isolated yields.In addition,the role of KOH was invesigated.The results showed that KOH accelerates the regeneration of ABNO from ABNOH.A new type of 2-azaadamantane-N-oxyl was prepared.The synthetic route of this compound was started with 1,3-dihydroxyadamantane,through ring-opening,aldol reaction,the protect of hydroxyl,oximation reaction,reduction of oxime,ring closure,deiodination,deprotection and oxidation of amino to produce 4-（2-hydroxylphenyl）methyl-1-methyl-2-azaadamantane-N-oxyl.The DDQ/TBN/AcOH/O₂ catalytic system was developed for aerobic oxidation of diarylmethanes sp³ C-H Bonds.Under the optimal reaction conditions,a number of diarylmethanes can be converted to corresponding diarylketones directly in good to excellent yields.In the part of the possible reaction mechanism,the function of AcOH was investigated and the role of H₂O was discussed through isotope trace experiment.It was found that CDC reaction was occurred between diarylmethane and AcOH,then the CDC product transformed into diarylketone in the help of H₂O.