Mechanism Study On The Two Types Of C-X(X=C,O) Coupling Reactions Synergistic Catalyzed By Heterbimetallic Catalysts

Heterbimetallic catalysis plays an indispensable role in many important organic reactions.These catalysts exhibit unique properties due to the interactions between two different metal centers,and the binuclear effects provide more possibilities to improve the activity,selectivity and stability of catalysts.Ketones are one of the ideal chemical intermediates with high reactivity and relative stability,they are widely used in organic synthesis,natural products,drug synthesis and other fields.Therefore,developing the practical and simple synthesis methods of ketones is of great significance to promote their wide application.In this paper,two typical reactions of synthesis of ketones catalyzed by heteronuclear bimetallic catalysts were studied by density functional theory（DFT）functionals,at PBEPBE-D3/def2-TZVP//PBEPBE-D3/def2-SVP level.One is the Suzuki-Miyaura coupling reaction of aryl boron esters with alkyl halides catalyzed by[Cu-Mn]bimetallic catalysts to synthesize aryl ketones.The other is the[Au-Pd]bimetallic catalysts catalyzed synthesis of oxazolones from N-alkynyl carbamates.The details are as follows:1.The reaction mechanism of aryl ketones synthesis from arylboron esters and haloalkanes catalyzed by[Cu-Mn]bimetallic catalysts.The calculation results show that the whole reaction consists of two cycles:one is the arylboryl esters（Ar-Bneop）transforming to alkoxyboryl esters（RO-Bneop）and aryl copper（LCu-Ar）catalyzed by[Cu]catalyst,and the other is the halogenated alkyl carbonylation catalyzed by[Mn]catalyst,in which RCH₂（CO）Mn（CO）₅is generated through Heck-Breslow cycle.Finally,the C-C coupling between the intermediates of LCu-Ar and RCH₂（CO）Mn（CO）₅,which are obtained from the above two cycles,are occurred to get the product aryl ketones.The carbonylation process catalyzed by Na[Mn（CO）₅]catalyst belongs to the S_N2 mechanism,wheras the carbonylation catalyzed by Mn₂（CO）₁₀belongs to the single electron transfer mechanism.The whole catalytic reaction is an exothermic process,and the C-C coupling process is the rate-determining step of the reaction.In addition to the[Mn（CO）₅]^-,other carbonyl anions with medium or low nucleophilicity also have good reactivity and can synergistically catalyze this reaction with copper catalysts.2.The reaction mechanism of oxazolone synthesis from carbamate catalyzed by[Au-Pd]bimetallic catalysts.The calculation results show that the reaction begins from the cycloaddition reaction of N-alkynylcarbamate catalyzed by[Au]catalyst.After the formation of the intermediate with a five-membered ring structure,the catalytic cycle of[Pd（0）]starts.The[Pd（0）]catalytic cycle consists of three steps:oxidative addition,transmetallation and reductive elimination.The reductive elimination is the rate-determining step of the whole reaction.Both[Pd（0）]catalyst and anion bridge are indispensable in the transmetalation process.In the Au Cl（PMe₃）/Ag OTf-Pd（0）catalyzed system,Cl^-rather than OTf^-plays a bridging role.The cheaper metal compounds,Cu Cl（PMe₃）and Ag Cl（PMe₃）,can replace Au Cl（PMe₃）to catalyze the reaction with[Pd（0）]catalyst.Our works elucidate the detailed mechanisms of the synthesis of ketones catalyzed by[Cu-Mn]and[Au-Pd]bimetallic catalysts,the roles of two metal centers in the catalytic process are clarified.The resluts of provide theoretical explanations for the experimental results and give guidances for the screening of the cheaper and more efficient catalysts.