Cobalt-catalyzed Deoxygenation Of ?-Oxoacetophenone And Dehydroboration Of Aryl Olefin

Metal-boryl complexes are highly efficient catalyst species that can be inserted with unsaturated bonds and then undergo a variety of catalytic conversions.The metal-boryl complexes can also react with the C=O bond to achieve the borylation or diboration of aldehydes and ketones.Although the metal-boryl complexes show good reactivity in the reaction with carbonyl compounds,the catalytic system(Cu-B)and the type of reaction(borylation and diboration)are limited.Therefore,I hope to develop new conversion methods for metal-boryl complexes and carbonyl compounds by screening different metals and ligands.The research in this article mainly includes the following two aspects:(1)Study on cobalt-catalyzed deoxyboration of ?-oxoacetophenone.This article discusses the development of a new cobalt-boryl catalytic system with good chemical selectivity,promoted by bis(Imino)pyridine(PDI)ligands,and successfully achieved the C-O bond cleavage of ?-oxoacetophenone to obtain ketones and phenols.The method can be applied to cut the C-O bond of lignin ?-O-4 model ketone,and has important value for lignin degradation.This method uses classic PDI ligands and inexpensive cobalt salts.The functional groups are well tolerated,and the reaction can be successfully scaled up to the gram level.It can also be applied to the depolymerization of ?-O-4 ketone polymers.In addition,the kinetic experiments carried out in this paper determine the possible rate-determining step of the reaction,and based on this,the possible mechanism is proposed,which are all related to the results of DFT calculations.(2)Study on cobalt-catalyzed dehydroboration of aryl olefin.Based on the previous work,this paper uses the developed diphenylphosphine-diphenylamine-oxazoline(PAO)ligand to achieve the cobalt-catalyzed stereoselective dehydroboronation of aryl olefins,and then synthetically valuable alkenyl borates are obtained.The advantages of this reaction include that it does not require an external hydrogenation acceptor and it has high stereoselectivity(E/Z > 20:1).Besides,the gram-level reaction is successfully carried out,and the amount of catalyst can be reduced to 1%.The reaction mechanism is preliminarily determined by the results of deuterium labeling experiment.