Br(?)nsted Acid-regulated Titanocene Lewis Acid-catalyzed CC And CN Bond Formation Reactions

Br(?)nsted acids can adjust the Lewis acid catalytic activity of titanocene complexes,and the resulting catalytic systems have shown excellent catalytic activity in the construction of C-C and C-N bonds,showing potential development and application prospects.However,the coordination chemistry of ligands Br(?)nsted acids and titanocene metal center is rarely studied,so the relationship between the structure and properties of related catalytic systems is still unclear.Therefore,the existed titanocene Lewis catalyst systems were limited to few kinds of organic reactions,which limits the development of titanocene Lewis acid catalysis methodology.In this thesis,we focused on the synergistic catalytic system constructed by ligands Br(?)nsted acids of different acidity and titanocene compounds,took the synthesis of 1,2-dihydroquinoline and ?,?unsaturated imine as model reactions,investigated the coorperative catalytic performance of titanocene dichloride with Br(?)nsted acids,explored the mechanism of those catalytic process,by which the regulation effect of Br(?)nsted acid on titanocene Lewis acid is clarified,thus the methodology of titanocene Lewis acid catalyzed C-C and C-N bond formation has been greatly enriched.Specifically,in this thesis,two types of Lewis acid catalytic systems of titanocene were successfully developed.The main contents were included as following:(1)A catalytic system where titanocene dichloride as the control center and the relatively weak acid catechol as the Br(?)nsted acid ligand was constructed,efficiently catalyzed the reaction of aniline and ?-ketoester to form 1,2-dihydroquinoline compounds.The optimal reaction conditions were established through a series of condition optimization such as reactants ratio,diacid ratio,solvent,etc.based on which 16 cases of 1,2-dihydroquinoline compounds were explored and isolated yields up to 97%was obtained.In addition to the advantages of simple operation and good substrate applicability,the catalytic system is highly efficient and has mild conditions.Through NMR,MS and control experiments,the catalytic species and reaction mechanism were further explored,and it reveales that the catalytically active species[Cp2Ti(OPhOH]+was generated in situ between catechol and titanocene dichloride,and the orthophenolic hydroxyl group of catechol and the positively charged titanocene center cooperate to activate the substrates to promote the reaction.(2)Based on the regulation strategy of titanocene Lewis acid,the Br(?)nsted acid with stronger acidity,trifluoroacetic acid,was used as a ligand to regulate titanocene dichloride to have catalyzed the condensation reaction,with fatty amine compounds involved,of pyrrolidine and aldehyde.Through optimization of conditions,18 cases of?,?-unsaturated imine compounds with yields up to 98%were obtained.Through NMR,MS and comparative experiments,the catalytic species and reaction mechanism were further explored,and it reveals that during the reaction process,titanocene dichloride coordinated with trifluoroacetic acid to generate catalytically active species[Cp2Ti(OOCCF3)]+,which catalyzed ?-hydride abstraction and transfer of pyrrole,realizing the challenging ?-position functionalization of fatty amine compounds.This work has realized the catalytic application of the titanocene Lewis acid catalyst system in the transfer reaction of ?-hydrogen for the first time.