One-pot Synthesis Of Alkyne Amine And Researches On The Mechanism

Alkyne amine is a generic term of compounds which nitrogen connect to functional alkyneyl group directly,and it is another important organic compound following cholestyramine.In alkyne amine molecules,nitrogen atom could polarize alkynyl bond especially when nitrogen atom attached by electron withdrawing groups it could strongly polarize alkynyl of the electron density which makes the alkyne amine have highly chemical reaction with good regional selectivity and perspective selectivity.Alkyne amines are valuable in organic synthesis precursors,organic photovoltaic materials,natural products and biologically active molecules.Especially in recent decades,the synthesis and application of alkyne amines become a hot topic.Double elimination one-pot synthesis is a simple and effective method to construct acetylenic bond.Otera has reported the preparation of aryne with one-pot synthesis method.Our laboratory have also reported the synthesis of arylethynyl sulfides by one-pot synthesis method,Recently,we have synthetised symmetrical dialkynyl selenides successfully by one-pot strategy.Based on these achievements,this paper mainly discusses the one-pot synthesis of alkynyl amine.In this paper,we mainly use cheap o-phenylene diamine,aromatic aldehyde and aryl ethyl ketone as raw materials,after o-phenylenediamine and aromatic aldehyde cyclized and aryl ethanone bromided respectively,then giving a series of high yield substrates of 2-benzimidazol-1-aryl ethanone by nucleophilic SN2 substitution.On the basis of our laboratory studies,we get a series of alkyne amine in moderate to good yields.In this experiment,the one-pot of the specific steps are as follows:under an atmosphere of nitrogen,LHMDS(1.2 eq)was added slowly to a solution of 2-benzimidazoles-1-aryl-ethanone in THF(10 mL)at-78?,and the mixture was stirred for 30 min.Then ClP(O)(OEt)2(2 eq)was added dropwise and the resulting mixture was warmed up to room temperature and stirred for 1 h.The reaction mixture was cooled to-78? and then LHMDS(2 eq)was added.After being stirred at-78? temperature for 1 h,the reaction was quenched with aqueous NH4Cl solution and the crude products was subsjected to flash column chromatography to give alkyne amine.This synthetic method has good yields,inexpensive raw material,simple operation,environmental protection and other good features,which is one of the effective method of synthesis alkyne amine compounds.This method is applicable for various non-proton substituting groups on the benzene ring(e.g.methyl,methoxy,a naphthalene ring,halogen etc.),heterocyclic(e.g.furanyl),hydrocarbon chain(e.g.2,2-dimethyl-propyl).It illustrates that this method with a wide range of versatility.To further prove the correctness that we assume the reaction mechanism,the paper also captured the reaction intermediates successfully and confirmed the characterization structure.All the target compounds synthesized and some unreported intermediates were characterized by 1H NMR,13C NMR,HRMS,MS,IR.