| Solvothermal in-situ ligand reaction,as a bridge connecting organic chemistry and inorganic chemistry,has important research value in developing new reactions and synthesizing organic compounds and coordination compounds with novel structures.Under suitable conditions,organic ligands can also undergo multi-step domino reactions under the catalysis of transition metals,and new transition-metal complexes or organic compounds with complicated structures can be obtained from "one pot" reaction of simple ligands.These compounds may have potential applications on catalysis,optical,electrical,and magnetic chemistry.The study of the process and mechanism of this kind of reaction is conducive to the directional construction of molecules with special structures and properties has always been the goal pursued by chemists.However,the "black box" system of solvothermal reaction has brought challenges to the tracking of the reaction process and mechanism research.When the reaction system contains paramagnetic transition metal ions or organic free radicals,traditional nuclear magnetic resonance technology cannot realize the reaction process tracking.Fortunately,due to its soft ionization character,electrospray ionization mass spectrometry(ESI-MS)has little effect on the reaction system,and can quickly give the mass-to-charge ratio of ionic species in the reaction system,which has become an important technology for studying chemical reaction processes.In addition,at suitable conditions,single crystals of products and intermediates can be obtained,from which accurate structural information can be easily obtained,providing a basis for the analysis of mass spectra fragments.In this thesis,process and mechanisms of two solvothermal domino reaction systems which produce compounds with novel structures are studied.Through the combination of electrospray ionization mass spectrometry and X-ray crystallography,the reaction process is analyzed,and key intermediates are intercepted,from which possible reaction mechanisms are proposed.The main contents of this paper are as follows:1)The first chapter is the introduction,which introduces the progress of solvothermal in-situ reactions and tandem reactions,the application of mass spectrometry in the study of reaction processes and mechanisms,and the progress of organic free radicals..Then the topic of this thesis is proposed.2)The second chapter introduces the solvothermal domino synthesis of four unsymmetric triarylmethyl radicals(compounds 1,2,3,4)from L2(4-methyl-1-(1-methyl-1H-benzo[d]imidazol-2-yl)-4H-benzo[d]imidazo[1,5-a]imidazole)catalyzed by Fe Cl3·6H2O in Et OH.All the products are characterized by high resolution mass spectrometry and their structures are further confirmed by X-ray single crystal diffraction.For compound L6-4-Py,the reaction process was tracked by ESI-MS,a series of key intermediates of L2 and aromatic aldehyde to form hydroxyl,such as [CH(L2-H)(C5H4N)OH+H] +(m/z=409.17)And by reacting with pyridine-2 formaldehyde to obtain the intermediate carbonyl structure complex are intercepted and the possible reaction mechanism was proposed.In addition,the optical properties of the product were initially characterized.L6' exhibits dual emission at room temperature.Compared with the emission wavelength of L6((4-methyl-3-((4-methyl-1-(1-methyl-1Hbenzo[d]imidazol-2-yl)-3a,4,4a,8a-tetrahydro-1H-benzo[d]imidazo[1,5-a]imidazol-3-yl)(4-methyl-1-(1-methyl-1H-benzo[d]imidazol-2-yl)-3a,4-dihydro-1H-benzo[d]imidazo[1,5-a]imidazol-3-yl)methyl)-1-(1-methyl-1Hbenzo[d]imidazol-2-yl)-4H-benzo[d]imidazo[1,5-a]imidazole),the emission wavelength is red-shifted.In addition,a novel reaction of L2 at solvothermal condition in the absence of Fe Cl3·6H2O was discovered to produce a substituted ethylene derivative.The mechanism was preliminarily studied via control experiments and a plausible mechanism was proposed.To our knowledge,this is a rare C=C double bond formation reaction and further study is ongoing.In the reactivity study of L2,coupling reaction with aryl bromide was performed and Under the conditions of tricyclohexylphosphine tetrafluoroborate as ligand,pivalic acid as additive,DMA as reaction solvent,and potassium carbonate as basethree products(compounds 6,7,8)were obtained,indicating L2 is potentially useful in the coupling chemistry.3)In the third chapter,the domino reaction of N-methylbenzimidazole-and pyridine-2-methylamine catalyzed by Mn X2(X = Cl,Br)under solvothermal conditions was investigated.Using electrospray ionization mass spectrometry,three key intermediate fragments involving self-condensation of primary amine to imine(intermediate 1,m/z=484.09),the pyridoimidazole structure from intramolecular nucleophilic addition cyclization(intermediate 2,m/z=441.09),and the carbonyl compound(intermediate 3,m/z=291.60)from intermediate 2 were captured.Then,the reaction was studied at a series of temperatures(room temperature,reflux in methanol,80 ?,100 ?,and 120 ?).ESIMS was used to track these reactions and the effect of temperature and time on the reaction was evaluated.It is found that at room temperature,Mn2+ coordinated with the substrates aldehyde and amine respectively.Under reflux condition,three intermediates can be generated,however,no product was formed.At 80 ?,the target product started to form and the higher the temperature,the faster the reaction(80 ?,10 h;100 ?,2 h;120 ?,0.5 h).Based on these results,a possible reaction mechanism is proposed,including the following key steps: coordination,oxidative self-coupling to generate imine intermediate,intramolecular nucleophilic addition,oxidation,and reduction. |
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