Alkynes Participate In Cycloaddition Reactions To Construct Heterocyclic Compounds

Heterocyclic compounds are widely found in various fields of chemical science and materials science.Isoxazole,quinazoline,and pyridine structural units are the core building blocks of many natural products and drugs.In this paper,we carried out studies on the alkyne's participation in the construction of isoxazole,quinazoline and pyridine derivatives.The following three tasks were mainly carried out.The[3+2]cycloaddition reaction of indole and diacetyl promoted by PIFA?[bis?trifluoroacetoxy?iodo]benzene?was studied and a series of isoxazole derivatives were successfully constructed.The reaction takes PIFA as oxidant and CF₃CH₂OH/H₂O as solvent,and the maximum yield can reach 94%.The reaction is applicable to various diacetylenes and asymmetric diacetylenes,and the target product can be obtained with high selectivity.Whether it is an electron-withdrawing group or an electron-donating group,the target product can be obtained at medium to higher yields.Rh?III?catalyzed C-H activation/[5+1]annulation/5-exo-cyclization reaction was successfully achieved for the first time,and various quinazoline derivatives has been achieved.The reaction took[Cp*RhCl₂]₂ as tcatalyst,DMA/EtOH/NMP as solvent,Ag₂CO₃ and2,6-dimethylbenzoic acid as additives to effectively construct the quinazoline ring,and at the same time built a 5-membered ring.The electronic effect and steric hindrance effect of the substituents on the ruthenium of the reaction have a great influence on the reaction,and the large hindered oxime does not participate in the reaction.The quinazoline products can be obtained in high yields by NTs-,O-linked diynes,while the reaction efficiency of alkyl,ester-linked diacetylenes is relatively poor.Under optimal conditions,we synthesized 53different functionalized quinazoline derivatives with a maximum yield of 91%.Cu-MOF-catalyzed amination/cyclization/aromatization cascade reactions were performed to synthesize a variety of pyridine derivatives.This system uses HKUST-1 as catalyst and the environmentally friendly EtOH as solvent.Cyclopentanone,cyclohexanone,and aryl benzyl ketones are all suitable for use in this catalytic system,and heterocyclic compounds containing pyridine structural units can be obtained in moderate yields.The reaction does not require high temperatures and there is no need for a large excess of reaction material.The maximum yield can reach 85%.