Experimental And Theoretical Study On Organoboron-involved Photooxidation And Cyclization Reactions

In recent years,organic chemical transformations involving organoboron have gained more and more attention and research.In traditional organic transformations,with the development of the field of photocatalysis,visible light-induced catalysis has become increasingly prominent in the field of synthesis.At present,it has become the symbol of mild conditions and green environment.People are developing newer photocatalysts day and night,which makes them more versatile,more powerful and compatible with more reaction systems.In the context of the thriving photocatalysis,photooxidation has also become the focus of attention.Photooxidation,as its name implies,is an oxidation reaction promoted by photochemical means.Nowadays,under the guidance of the tenet of green chemistry,people are constantly looking for more environmentally friendly and cheaper synthetic methods.For oxidation reactions,from the point of view of atomic economy,it is the most ideal method to directly use oxygen as the oxidant to develop oxygenated compounds.Therefore,the development of new methods for visible light-induced aerobic oxidation is the top priority in the current green synthesis field.The main research contents of this thesis are divided into the following four parts:(1)In this chapter,we report a method for metal-free photocatalytic aerobic oxidation using tetrabutylammonium tribromide(TBATB)as catalyst.This reaction can realize the photocatalytic deboronation of boronate esters to the corresponding aldehydes and ketones under mild conditions.Using a catalytic amount of TBATB as the photocatalyst,oxygen as the oxidant,and tetrahydrofuran(THF)as the solvent,under irradiation with a 10 W 455 nm blue LED light source for 16 h at room temperature,the selective oxidation of C-B bonds can be very simply achieved with moderate to corresponding aromatic aldehydes and ketones were obtained in excellent yields.(2)Based on the work of the previous chapter,this chapter uses density functional theory(DFT)to perform theoretical calculations for the photocatalytic deboronation oxidation reaction based on tetrabutylammonium tribromide(TBATB),by deriving the potential energy surface energy of the reaction,trying to elucidate the reaction mechanism and discuss the chemical selectivity and feasibility of this reaction.Then,under the guidance of the theoretical calculation results,a mechanism experiment is carried out to prove the accuracy of the potential energy surface,and the final results show that the theoretical calculation is consistent with the experimental results.(3)The work of this chapter is that our research group and the research group of Professor Li Pengfei of Xi’an Jiaotong University are invited to cooperate to carry out theoretical calculation on the original research of "Catalysis with Diboron(4)/Pyridine: Application to the Broad-Scope [3 + 2] Cycloaddition of Cyclopropanes and Alkenes" to explore the mechanism.On the basis of the original experimental results,following the principle of combining theory and practice,and applying density functional theory(DFT),we tried to explore the reaction mechanism,and discussed the reaction kinetics and chemical selectivity.(4)This work aims to develop a light/nickel dual catalysis for the decarboxylation cross-oxidative coupling reaction of benzoylformic acid and halobenzene.As a photocatalytic oxidation reaction,the photocatalyst used in this method is a new low-cost four-coordinate boron-based photocatalyst(PC)previously developed by our research group.In the presence of nickel(II)dibromide glycol dimethyl etherate complex(Ni Br2·dme)and its ligand 4,4’-di-tert-butyl-2,2’-bipyridine(dtbbpy),cesium carbonate as the base and N,N-dimethylformamide(DMA)as the solvent under 10 W 455 nm blue LED light source for 22 h in air atmosphere,the corresponding compounds can be obtained in moderate to good yields ester compounds.This work strives to be environmentally friendly and cheap,and does not rely on toxic organic dyes or expensive noble metal complex photocatalysts,which provides a new idea for the development of new photocatalytic oxidative coupling reactions.