Heterocyclic Compounds Are Constructed By Radical Addition To Carbon-carbon Triple Bonds

Radical cascade cyclization reaction to synthesize heterocyclic compounds has become one of the important research fields of organic methodology.The method involves intramolecular or intermolecular reactions and undergoes two or more successive steps.Multiple bonds can be constructed in a single operation to avoid the separation and purification of intermediate products.Among them,the construction of heterocyclic compounds by radical addition/cyclization of C≡C triple bonds has a wide range of application value.In this paper,the methods of synthesis of different heterocyclic skeletons via radical addition of C≡C triple bonds in recent years are reviewed.Moreover,the efficient synthese of dihydrobenzofuran and benzothiazazepine skeleton was achieved by designing a new substrate and a new reaction process under mild reaction conditions.This paper mainly includes the following two aspects:1.Visible Light-induced Radical Addition/Annulation to Construct Phenylsulfonyl-functionalized Dihydrobenzofurans Involving an Intramolecular 1,5-HAT ProcessA visible light-induced radical cascade reaction of 2-alkynylarylethers with sodium sulfinates was established for the synthesis of sulfonyl-functionalized dihydrobenzofurans,and it goes through an intramolecular 1,5-HAT process.This process provided an efficient and convenient C-C formation protocol for the construction of a dihydrobenzo-furan ring.Various substituents on 2-alkynylarylethers and sodium sulfinates were tolerated in the reaction,and the target product can be obtained with medium to good yields.2.Radical Cascade Reaction of Three Components to Synthesize Benzothiazazepine DerivativesBenzothiazazepines were synthesized by 2-(1H-pyrrole-1-yl)arylamine,elomeric sulfur and alkynes.In this method,Aryl radicals are vulcanized by C(sp~2)-H bonds with elemental sulfur,and then radical addition/annulation to form a sulfur-containing seven-member skeleton.This reaction has a wide range of substrate scope and good functional group compatibility,which offers a novel strategy to constructing seven-member sulfur-containing heterocyclic skeletons.