Photocatalytic Synthesis And Reaction Mechabism Of Benzimidazolone And Benzaldehyde

In recent years,photocatalytic technology has been widely studied in the fields of pollutant degradation,CO2 reduction,splitting water into hydrogen,etc.It has shown important scientific value and application prospect in environmental protection and energy production.With the development of research,photocatalysis,as a mild and green reaction synthesis method,is also unique in the field of organic synthesis.Benzimidazolidinone compounds are important intermediates of medicine,pigment and dyestuff.There are many problems in traditional reactions,such as harsh conditions,difficult to control and many by-products.In this paper,photocatalysis was applied to the synthesis of a series of 1,3-disubstituted benzimidazolone and the selective oxidation of benzyl alcohol.The mechanism of photocatalysis in these two reaction systems was explored through catalyst design,preparation,characterization and performance evaluation.The research contents and results are as follows:1.A series of 1,3-disubstituted benzimidazolone compounds were obtained by the C-N coupling reaction of benzimidazolone compounds with brominated hydrocarbons via photocatalysis.The yields of products was 41%-98%.The structure of the compounds was further determined by H NMR,IR and HRMS.Through the exploration of reaction conditions,the highest yield was obtained under the following conditions:reaction in anhydrous acetonitrile for 12 h at room temperature,with CuBr and t-BuOK as photosensitizer and alkali assistant.It is found that the electron cloud density of N can be increased for the monosubstituted benzimidazolone containing allyl and benzyl electron donating groups compared with that containing methyl and ethyl,which makes the nucleophilic substitution reaction of SN2 easier to take place.Meanwhile,the brominated hydrocarbon with lower steric hindrance has higher yield than that of bromocyclohexane and 2-bromopropane with higher steric hindrance.The photocatalytic mechanism in the reaction system was explored.It was determined that light in the reaction system can activate Cu(?)to form an activation state,reduce the activation energy of forming SN2 transition intermediate,and make the reaction occur under mild conditions.2.A series of binary Ag3PO4 QDs/g-C3N4 nanosheet composite photocatalysts were prepared at room temperature for the first time with the ultrathin g-C3N4 nanosheet exfoliated by thermal oxidation as the support.The photocatalytic selective oxidation of benzyl alcohol was investigated.The results show that quantum dots of well-crystallized Ag3PO4 with the particle size of 3-5 nm are homogeneously dispersed on the g-C3N4 nanosheet.For the photocatalysts with the mass ratio of 0.6 Ag3PO4 to g-C3N4 in acetonitrile solvent,the maximum conversion of benzyl alcohol is 32.1%,and the highest selectivity of benzaldehyde is 90%.The results of active species capture experiment show that the main active species of photogenerated hole are responsible for the selective oxidation.3.A mild,efficient and controllable new organic synthesis method has been developed for the photocatalytic synthesis of benzimidazolone compounds and benzaldehyde,which has changed the harsh synthesis conditions under the traditional conditions,simplified the reaction process,and is of great significance for the realization of green organic synthesis.