Construction Of Five Membered Heterocyclic Frameworks Via The Strategy Of [3+2] And [4+2] Cycloaddition

Five membered heterocyclic compounds containing oxygen or nitrogen are important heterocyclic derivatives.The construction of these skeleton has been widely concerned by organic chemists.So far,many strategies have been developed and applied for the construction of this kind of skeleton.In this dissertation,we have successfully constructed the skeletons of benzodihydrofuran,indoline and oxatricyclic[3,2,1,02,7]octane via the[3+2]or[4+2]cycloaddition of novel electrophiles,it include three parts:(1)Study on Lewis acid-catalyzed[3+2]cycloaddition Using In(OTf)3 as Lewis acid catalyst,the[3+2]cycloaddition reaction of 3-hydroxy-3-aryloxyheterocyclobutanes and arylamines was realized,and indoline derivatives were successfully constructed.The reaction conditions were mild,and the corresponding indoline derivatives could be synthesized in 46%-91%yields with good functional group tolerance.Subsequently,under the same conditions,we also achieved[3+2]cycloaddition of 3-hydroxy-3-aryloxyheterocyclobutane and phenols to give benzodihydrofuran with 40%-91%yields.Through the later conversion,the product can realize the synthesis of indole and benzofuran.(2)Cu/chiral phosphoric acid-catalyzed asymmetric[3+2]cycloaddition The asymmetric[3+2]cycloaddition of 3-hydroxy-3-aryloxyheterocyclobutane with phenols catalyzed by Cu(OTf)2 and chiral phosphoric acid was successfully constructed.Benzodihydrofuran derivatives can be synthesized in 45%-90%yields and 78-98%ee value with good functional group tolerance.The control experiment showed that the catalytic mechanism of this reaction was the process of copper and chiral phosphoric acid co-catalysis,that is,copper contributed to the formation of the intermediate of p-methylenequinone,and chiral phosphoric acid controlled the enantioselectivity of the subsequent ring opening process of oxacyclobutane.(3)Bronsted acid catalyzed[4+2]cycloaddition of isobenzopyan salts.Using diphenyl phosphate as Bronsted acid,the[4+2]cycloaddition reaction of 1-arylethenylboronic acid with isobenzopyran salt as electrophilic reagent was achieved.In this reaction,a multi-component bridged ring derivative based on oxatricyclic[3,2,1,02,7]octane skeleton was successfully constructed.This reaction has a capability with 41-85%yields,which showed good substrate compatibility.This reaction mode is a new reaction strategy for isobenzopyranoates.