Research On The Synthesis Of N-heterocyclic Compounds Via Palladium-catalyzed Reactions

N-heterocyclic Compounds are widely found in nature and bioactive products,which are often used as intermediates in medicine,dyes,pesticides or other fine chemical products and play an important role in organic synthesis.Indole,as an important N-heterocyclic compound,has drew much attention due to its unique biological and pharmacological properties,huge quantity and wide application.Therefore,the synthesis of indole and its derivatives have been a hot topic in the field of organic synthesis.In this paper,palladium-catalyzed synthesis of indole N-heterocyclic has been studied,aiming at developing more novel,more efficient and more practical syntheses of indole derivatives.There are three parts in this article:In part I,the properties and uses of N-heterocyclic compounds and indoles are sketched,and some common synthesis methods of indole and its derivatives are summarized.In part II,an efficient method for the synthesis of 1H-indole-3-sulfonates via palladium-catalyzed tandem reactions of 2-alkynyl arylazides with sulfonic acids has been developed.The desired products were obtained in good to excellent yields under mild reaction conditions.The reactions were shown to proceed very fast,in most cases,within 10 min.It's confirmed that the reaction occurred with various structures of 2-alkynyl arylazides,after examining the substrates scope under the optimal conditions.Finally,the possible reaction mechanism is put forward.In part III,a novel method for the synthesis of C2-quaternary indole-3-ones via palladium-catalyzed one-pot transformation of 2-alkynyl arylazides is described.The optimization of reaction and examining of substrates scope are used in the same method.And reaction mechanism is proposed: 1H-indole-3-sulfonate is synthesized as a intermediate from2-alkynyl arylazides and sulfonic acid.Under heating and basic conditions,1H-indole-3-sulfonate could undergo a 1,3-sulfonyl shift followed by reductive desulfonation to form the desired product indole-3-one.The mechanism is verified by some experiments.An simple,efficient and general method for the synthesis of 1H-indole-3-sulfonates via palladium-catalyzed tandem reactions of 2-alkynyl arylazides with sulfonic acids has been developed.C2-quaternary indole-3-ones are synthesized by tandem reaction of 1,3-sulfonyl shift and reductive desulfonation.This novel rearrangement of 1-H-indole-3-sulfonates represents an important contribution to the application of aryl sulfonates.