| The use of photochemistry for organic synthesis reaction is an important part of modern organic chemistry,the main content of the study is a series of reactions of organic matters under lighting condition.Light-excited molecules are a kind of intermediate with high reactivity,which can realize many reactions that are difficult to occur in thermochemistry,so it is of high economic value and research significance to use photochemistry to carry out organic synthesis reactions.Proton transfer process exists in many organic synthesis reactions,the[1,3]-proton transfer process（PT）has been the focus of research by many scholars at home and abroad,by the dehydration of amines and carbonyl compound to obtain Schiff base that contain imine structure,and using acid or base catalysts catalyze Schiff base to achieve proton transfer process under heating condition,and then hydrolysis to contain a specific group of primary amines chemical and pharmaceutical intermediates,which is one of the ways to prepare primary amines.The disadvantage of this process is that the product of proton transfer under heating conditions is a raceme,which results in lower optical activity of the hydrolysis of the primary amine compound and the use of acid-base catalysts that are not environmentally friendly.Therefore,it is necessary to find new process methods to realize the proton transfer of the imine Schiff bases,and how to achieve stereochemical control in the process has always been a challenging subject in the field of asymmetric catalysis.This paper studies the use of near-neutral organic solvents under lighting conditions to promote the realization of proton transfer of a variety of Schiff bases,and the transfer mechanism was preliminarily studied in this paper.It was found that using solvents such as alcohols,aldehydes and carbon tetrachloride which contain strong electronegative atoms such as O and Cl,had better effect on[1,3]-proton transfer of Schiff base molecule than other solvents under higher light intensity,and the yield could reach more than 90%.Through experimental verification and chemical energy calculation and analysis,the protons transfer process of Schiff base is determined in two steps:（1）the dissociation ofα-active hydrogen in the excited state of the Schiff base;（2）Isomerism rearrangement of hydrogen ions.And using a variety of chiral catalysts catalyze the proton transfer process of 1,1-diphenyl-N-（1-phenylethylidene）methylamine Schiff base in CCl4,through experiments found that the effect of divalent tin porphyrin chiral metal catalyst was the best,and the product yield and enantiomeric excess percentage were as high as 98%and 91.49%respectively.Moreover,the course of asymmetric proton transfer of Schiff base is studied theoretically,and the aromatic structure contained in Schiff base molecules will produce weak interaction with solvent molecules.The presence of chiral catalyst causes Schiff base molecules to be in a stable hand environment,solvent molecules containing more electro-negative atoms or groups will form a hydrogen bond structure with Schiff base active hydrogen.Illumination provides energy source for the reaction process and promotes the dissociation and rearrangement of theα-active hydrogen of Schiff base,so as to achieve the asymmetrical proton transfer process of Schiff base.In short,the use of photochemistry instead of traditional thermodynamic reactions for organic synthesis will help reduce production costs and environmental pollution.The process of asymmetric proton transfer of Schiff base molecules is realized by hand catalysis in near-neutral solvents,which provides a new process method for the industrialization of industrialization proton transfer of Schiff base pharmaceutical and chemical intermediates.The mechanism of proton transfer is also studied,which enriches the theory of proton migration in organic chemistry. |
