Gas-phase Reaction Studies Of Organic Reactive Intermediates In ESI Mass Spectrometry

Research on the organic reactive intermediates has important significance for the elucidation of organic reaction mechanisms and exploring more efficient organic synthesis routes.Reactive intermediates are extremely active and have short lifetime,which are difficult to be isolated and studied by conventional methods.The rapid development and application of mass spectrometry technique has opened up a new way for organic reactive intermediate research.This work studied the gas-phase reactions of some organic reactive intermediates by electrospray mass spectrometry.It specifically includes four parts in the following:1.Phosphenium cation-promoted nucleophilic arylation:Diphenylphosphenium cations were generated in the gas phase by electrospray ionization tandem mass spectrometry.The gas-phase reactivity with acetone was studied in a hybrid QTrap mass spectrometer by ion-molecule reaction.The structure of 2-phenylpropan-2-ylium cation was identified by D-labeled experiments and comparing its MS2 fragmentation behavior with standard compounds.A nucleophilic arylation followed with C-C bond formation mechanism was proposed and proved by theoretical DFT calculations.Then the reactions with other ketones,acetaldehyde and other aldehydes were also proceeded.The results show it a rapid and metal-free method of nucleophilic arylation and C-C bond construction in the gas phase.2.Rapid synthesis of phosphenium cations and detection of organic molecules in the gas phase:The chapter provides a method to synthesize phosphonium cations in the gas phase,and detect organic molecules by ion-molecule reactions.The active diphenylphosphonium cations were generated from the collision induced dissociation of methyltriphenylphosphonium cations by tandem mass spectrometry.There were 10 different kinds of molecules selected to make ion-molecule reaction with diphenylphosphonium cations,including acetonitrile,formic acid,acrylonitrile,dichloromethane,ethyl acetate,n-butanol,t-butanol,triethylamine,benzene and styrene.The detection of these 10 kinds of molecules and the resolution of a pair of isomeric compounds n-butanol and t-butanol were both achieved.By adjusting the flow rate of molecules in a certain reaction time,different abundance of product peaks will be obtained.The quantitative analysis of molecules can be completed by making standard curves.This method is simple and convenient.It also offers an approach to make research of the gas phase reactivity of phosphonium cations.3.Insight into copper-catalyzed decarboxylative thiolation of carboxylic acids in the gas phase:Organocopper complexes bearing bidentate nitrogen ligands were synthesized in the gas phase by electrospray ionization mass spectrometry.Gas-phase decarboylative thiolation reaction was carried out in the ion-trap analyzer by collision-induced dissociation and ion-molecule reaction.The carboxylic acids were finally converted to thioethers as a neutral loss via collision-induced dissociation.During this process,copper acetate acted as a catalyst,and the valence state change of copper was observerd.Meanwhile,the mechanism of decarboxylative thiolation was examined.This reaction was also suitable for different carboxylic acids and bidentate nitrogen ligands in the gas phase.4.Copper-catalyzed decarboxylative iodination reaction in the gas phase:Organocopper complexes play the key role in Cu-catalyzed organic reaction.This chapter offers a method to synthesize ligand-ligated organocopper complexes.Copper acetate was used as the catalyst and 2-(aminomethyl)pyridine(2-AMP)as the ligand to react with benzoic acid to generate the organocopper complex.This complexwas easily transferred from solution to gas phase via electrospray ionization mass spectrometry(ESI-MS).During these steps,the reagent benzoic acid reacted with allyl iodide in the gas phase with Cu2+ as catalyst and 2-AMP as ligand to produce iodobenzene,thus the copper-catalyzed decarboxylative iodination reaction was created in the gas phase.From the result,the mechanism of decarboxylative iodination reaction was speculated and carefully studied.Meanwhile,this reaction was also suitable for different carboxylic acids and bidentate nitrogen ligands.