Study On The Synthesis Of Nitrogen Heterocyclic Compounds Catalyzed By Titanocene/Br(?)nsted Acid Complex

The nitrogen-containing heterocyclic structural skeleton has become one of the important branches of organic chemistry due to its unique biological activity,physicochemical properties and wide application in many fields.The selective conversion of simple starting materials into a variety of heterocyclic structures via effectively meditating the reaction pathway is still challenging.In this dissertation,started with transition metal complex Cp2TiCl2,Lewis acid precursor,Cp2TiCl2/Br(?)nsted acid reaction systems has been established through cooperative mediation of ligand Bronsted acid and solvent,and applied to the divergent synthesis of five-and six-membered nitrogen-containing heterocycles,thus realizing the efficient conversion from aromatic amines and a-ketoesters to nitrogen-containing heterocycles.The main content and results obtained are as follows:(1)A stable metal-organic surfactant catalyst was developed by introducing the appropriate Bronsted acid ligand p-nitrobenzoic acid to the tunable Lewis acid-titanocene dichloride,bearing unique lipophilic property of the cyclopentadienyl group.The catalyst efficiently catalyzed the reaction between aromatic amine and a-ketoester in water/chlorobenzene emulsion system,with successful preparation of 3-pyrroline-2-one and its derivatives.The establishment of this method has successfully expanded the application of low-cost,air-and water-stable titanocene dichloride in emulsion catalysis,and also provides a convenient and efficient synthesis of 3-pyrrolidine-2-one derivatives.The mechanism was explored by means of modern analytical methods such as polarized light microscopy,high resolution mass spectrometry and X-Ray single crystal diffraction(2)A method for the synthesis of tetrahydroquinoline compounds between aromatic amines and a-ketoesters under the cooperative catalysis of 3,5,6-trichlorosalicylic acid and titanium dichloride in a green system of ethanol/water medium was developed.The method avoids the utilization of precious metals and prefabrication of catalysts and substrates,as well as provides a green,novel and invasive strategy for the synthesis of tetrahydroquinoline derivatives.The catalytically active species is[Cp2Ti(OOOC)PhCl3],confirmed by high resolution mass spectrometry and X-Ray single crystal diffraction analysis.(3)A method for the synthesis of 1,2-dihydroquinoline derivatives from aromatic amines and a-ketoesters under the coorperative catalysis of 5-sulfosalicylic acid and titanium dichloride was developed.The novel developed method features mild reaction conditions,high efficiency and good substrate compatibility,and through which 16 1,2-dihydroquinoline compounds have been successfully prepared,with reaction yield up to 95%.Mechanistic studies indicates that the possible catalytically active species is[Cp2Ti(OOOC)PhSO3H],which promotes intermolecular dehydration condensation by activating alpha-ketoesters,followed by accelerating the conversion of intermediates to target products.