Synthesis Of Imines By Pd(?)-Catalyzed Dearomatization Of N-Arylureas

As one kind of organic compounds,imine is always considered to be that a carbonyl oxygen atom is replaced by nitrogen atom of the primary amines,which include a primary aliphatic amine and an aromatic one,so the activity of the imine varies a lot.The derivatives of imine are extensively found in the natural products,and are widely used in organic synthetic intermediates and pharmaceutical industries because of their special properties.With the continuous improvement of the imine synthesis,the method of imine formation has been extended to more wide range of substrates.This has laid a good foundation for the deep understanding of the reaction mechanism and a practical application.In this thesis,we will mainly optimize the conditions of the reaction of the Pd?II?-catalyzed dearomatization of N?arylureas to imines.And the mechanism of the reaction has also been confirmed by means of density functional theory.This thesis is divided into four parts:In the first part,we made a comparatively systematic literature review on the methods of the synthesis of imines.In addition to the traditional methods,where the use of aldehydes or ketones and primary amines leads to the formation of imines,there has been coming the new methods to produce imines,for example,the high efficiency of imine formation from primary alcohols and amines in the presence of metal catalysts has been extensively developped.In the second part,we found a new kind of imine derivative with spiral ring structure when we studied the structures of the products seperated from the reaction between N?arylureas and diphenyl acetylene catalyzed by Pd?II?.By expanding the substrates,we can obtain several imine derivatives with different aromatic ring substituents,and the maximum separated yield can reach 88%.At the same time,we proposed a possible reaction mechanism for the process of the transition metal catalyzed N?arylureas and diphenyl acetylene to imines.This discovery provides a new way for the synthesis of imines and studying dearomatization of aromatic compounds.In the third part,we accidentally got a special kind of new compounds in the second part,and analyzed by X-ray single crystal structure to find that the new compound comes from the rearrangement of our previous imine compounds.To know more information of such a rearrangement,we designed a model reaction.We finally found that the rearrangement is essentially Cope rearrangement.However,it is too difficult to determine the intermediates in the process of rearrangement.Therefore,we puts forward the possible reaction mechanism on the rearrangement process according to the experimental results and experience.In the fourth part,based on the second chapter,we first studied theoretically the mechanism of reaction between N?arylureas derivatives and diphenyl acetylene catalyzed by Pd?II?complex by density functional theory calculation.The results showed that:1)the most advantageous position in the naphthalene ring interacts with the catalyst Pd?II?complex was?position.2)the catalytic process is divided into four stages.3)thermodynamically,the complexing reaction of naphthyl urea and catalyst is endothermic,but the addition of diphenyl acetylene is exothermic,and the heat released is greater than the heat absorbed.So the whole reaction goes smoothly at room temperature.the conversion rate is determined by the transition state Ts_a'formed by Pd?OAc?₂ and 2-naphthylurea,and the conversion rate is determined by the intermediate Mid_a.