Machanistic Insight Into Aerobic Alcohol Oxidation Mediated By Cu-based Catalytic System

The oxidation of alcohols to aldehydes or ketones is one of the most important reactions in the organic synthesis and chemical industry.The products have a wild application,such as Organic intermediates,fine chemicals.In order to meet the requirements of environment and economy,people are looking for the green and efficient oxidation method instead of the traditional oxidation.It is one of today's chemistry and bionic frontier subject which to synthesis of small molecular compound that has the natural properties of efficiency and high selectivity of enzyme catalysis.A variety of Cu catalytic system have been synthesized,it is very effective for the oxidation of primary alcohols.Thus,investigating the catalytic reaction mechanism for the Cu catalytic system will not only provide the useful insights,but also provide an important basis for designing new high efficient catalysts.In this work,based on density function theory,we calculate the reactant,intermediate state,transition state and product.we consider the alcohol oxidation mechanism of two copper catalyst systems.1.The catalytic mechanism for the oxidation of primary alcohols catalyzed by CuII/bipy/TEMPO/DBU?NMI?catalytic system.we proposed two possible reaction paths?path A,path B?.The calculations indicate that the hydrogen atom transfer within the substrate oxidation part is the rate-determining step for both catalysts,but,DBU as the base,the hydrogen atom transfers to OH;NMI as the base,the hydrogen atom transfers to TEMPO,in agreement with the experimental observation.In?bipy?CuII-TEMPO catalytic system,the overall activation barrier for DBU base is preferred over the NMI base.This is consistent with the experimental result that NMI base is less efficient compared with DBU base.In addition,it is evaluated that the importance of the anion ?OTf,the calculations indicate that the anion ?OTf can help the base abstraction the hydrogen atom.2.The catalytic mechanism for the oxidation of primary alcohol and secondary alcohol catalyzed by CuBr/tert-butyldiaziridinone.In this catalytic system,two possible structures are proposed about the active center is [CuL]Br,[Cu?II?-·L?]Br? or[Cu?III?-L^2-]Br?.The calculations indiate that the valence state of Cu is +2,there is a single electron distribute in the ligand L.Two possible mechanisms?path A and path B?are proposed,but path B cannot be accomplished.Path A consist of two parts,namely,proton transfer and hydrogen atom abstraction.The calculations indicate that proton transfer part is the rate-determing step.In the reaction mechanism,the ratio of L ligand and substrate is1:1,which is agreement with the experimental observation.