| Benzofurans are ubiquitous in many natural products and medicines.Studies have found that heterocyclic compounds with benzofuran rings as the core are important intermediates for various biologically active natural medicines and synthetic chemical raw materials.Their synthesis and applications have attracted considerable attention in the chemical and pharmaceutical industries.On the basis of our group’s and previous research work,this dissertation efforts focuse on the synthesis of 2-substituted benzo[b]furan derivatives compounds by the cross-coupling reaction of organoaluminum reagents and 2-halogenated benzo[b]furans catalyzed by metal palladium.A series of useful and creative achievements have been obtained.This thesis describes a simple and efficient Palladium（II）/phosphine ligand catalytic system which catalyzes cross-coupling reactions of alkyl,alkyl,alkyne and aryl aluminum reagents and with a variety of substituted 2-halogenated benzo[b]furans for the synthesis of 2-substituted benzo[b]furan derivatives compounds.Effects of metal Palladium,ligands,solvents,amounts of organoaluminum reagents,ratios of phosphine ligand to metal Palladium,reaction temperature,reaction times,different substituents of alkynyl bromides and alkynylaluminum reagents were systematically investigated.The results show that the cross-coupling reactions of 2-halogenated benzo[b]furans with arylaluminum reagents mediated by 3 mol%Pd Cl2/6 mol%Xantphos and4.0 equiv K2CO3in Hexane at 60℃for 5 hours which may led to produce 2-aryl benzo[b]furans in good to excellent isolated yields（23-93%）.The cross-coupling reactions of alkynyl aluminum reagents with 2-halogenated benzo[b]furans mediated by 3mol%Pd Cl2/6 mol%Xantphos and 1.0 equiv TMEDA in Toluene at 60℃for 4hours may produce 2-ynyl benzo[b]furans in good to excellent isolated yields（41-97%）.Furthermore,when 3 mol%Pd Cl2/6 mol%Xantphos is used as a catalyst in DCE and heated at 80℃for 4 hours,a good separation result of2-alkenylbenzo[b]furan can be obtained.Importantly,in DCE at 60℃,using 2 mol%Pd Cl2/4 mol%Xantphos as a catalyst and 1.0 equivalent of TMEDA base,a good isolated yield of 2-alkylbenzo[b]furans can be obtained.This method has the advantages of mild reaction conditions,easy separation of products,high yield and broad substrates scope.Interestingly,the corresponding scale-up reaction can also show excellent reaction results.Three compounds with antibacterial biological activity were further derived from the 5-bromo-2-（2-arylethynyl）benzo[b]furan and 1-（bis（4-fluorophenyl）methyl）piperazine.On the basis of the experimental results,a possible catalytic cycle has been proposed. |
