Pd-catalyzed Dearomative Polycyclization Reactions

Polycyclic skeleton molecules containing quaternary carbon center are important component of all kinds of natural products and biological pharmaceutical intermediate units,how to use chemical methods to construct this system efficiently is the challenge faced by chemists.In recent years,transition-metal-catalyzed reactions have became one of the hot research spots.Chemists also work hard in transition-metal-catalyzed reactions for constructing the spiro systems and had made great progress.This dissertation mainly discusses from the following five parts:The first chapter mainly introduces the discovery of aromatic compounds and the development of aromaticity,and then briefly expounds the progress of dearomatization by traditional chemical methods.The second chapter mainly introduces the transition-metal-catalyzed dearomative cyclization of aromatic compounds and detaily represents the deromative cycliation of benzyl chloride compounds,phenolic compounds,indole compounds,aromatic amine compounds,and some kinds of aromatic heterocyclic compounds.The third chapter discusses a novel palladium(0)-catalyzed dearomative polycyclization reaction of bromophenols.In this reaction,diynes were used as the coupling segments,and the tricyclic scaffolds containing spiro ring skeleton were effectively constructed by [2+2+1] and [2+2+2] routes.The reaction realized the dearomative polycyclization of para-bromophenols and meta-bromophenols,and obtained tricyclic architectures including spirofused and fused rings.It is worth noting that the research work has preliminarily realized asymmetric transformation,which provides a basis for the asymmetric synthesis of natural products and functional materials containing this skeleton.In chapter four,Pd/NBE-catalyzed C-H activation/dearomative cyclization of indoles is described.This new ptotocol,using NBE as a transient media,through a sequence of C-H alkylation/alkyne insertion/indole dearomatization,efficiently built three new chemical bonds in a single chemical operation.This reaction provides a diverse range of pentacyclic molecules containing a spiroindolenine fragments in good yields and high chemoselectivity.In addition,preliminary mechanistic studies have been studied and this research provides a theoretical basis for the study of this kind of reaction.The fifth chapter introduces a novel Pd(II)-catalyzed [5+2] annulation of o-arylanilines.The reaction used o-arylanilines as the substrates and 1,3-dienes as coupling compounds.The conjugated 1,3-dienes were employed as two-carbon synthons,leading to a new class of intriguing dibenzo[b,d]azepines.In addition,because of the conjugate effect of the olefinic bond and the metal,the elimination of β-H is suppressed,preventing Heck-type byproduct.The [5+2] annulation was realized with high chemoselectivity.