Research On Iron-Catalyzed 1,3-Dipole Cycloaddition And Arylation Coupling

As a cheap,non-toxic and abundant catalyst,iron has attracted extensive attention from organic chemists,and iron catalysts were applied to various organic chemical reactions.However,there are relatively few reports on 1,3-dipolar cycloaddition and arylation coupling reactions by iron-catalysis.In this paper,the iron-mediated 1,3-dipolar cycloaddition reaction and iron-catalyzed arylation coupling reaction were studied.Then the reactions were applied to the synthesis of 3-acyl-1,2,4-oxadiazole derivatives,nitrobenzene derivatives and phenol derivatives.This dissertation includes three parts:In the first part:With the mediation of iron nitrate,the selective synthesis of 3-acyl-1,2,4-oxadiazole derivatives were achieved by 1,3-dipolar cycloaddition using alkyne and nitrile as substrates.The reaction mechanism was proposed.First,iron nitrate nitrates alkynes to form ?-nitroacetophenone,?-nitroacetophenone dehydrates to form nitrile oxide(1,3-dipole),nitrile oxide and nitrile were synthesized by 1,3-dipolar cycloaddition to 3-acyl-1,2,4-oxadiazole derivatives.Iron nitrate plays dual roles in the reaction,which can nitrate alkynes to form 1,3-dipoles and effectively inhibit the formation of by-products of isoxazole and pyrimidine.Besides,the Lewis acidity of iron(?)has a better activation effect on nitrile and promotes the cyclization of the reaction.In the second part:nitrobenzene derivatives were synthesized by ipso-nitrations of aryl halides with potassium nitrite under photoinduced and iron-catalyzed conditions.The reaction mechanism was proposed:At first,iron(?)complexes were formed from iron salt and nitrites,and then under light conditions,aryl halides obtain electrons from excited iron(?)complexes to form aryl radicals and iron(?)complexs.Later the aryl radicals were combined with the iron(?)complexes to form the nitrobenzene derivatives.In this reaction,iron complexes not only realized efficient conversion of aryl iodide to nitrobenzene derivatives,but also realized efficient conversion of aryl bromide and part of aryl chloride to nitrobenzene derivatives by adding NaI.In the third part:Phenol derivatives were synthesized by aerobic oxidation of aryl halides under photoinduced and iron-catalyzed conditions.The reaction mechanism was speculated:Under light conditions,aryl halides first obtained electrons from triphenylphosphine to form aryl radicals,and then aryl radicals capture oxygen to form Peroxyaryl radicals,which further react with triphenylphosphine to form phenol derivatives.In this reaction,O2 as an oxygen source,providing oxygen atoms to from the phenolic hydroxyl group.