Synthesis Of Heterocyclic Compounds Through The Radical-Initiated Cascade Cyclizations

Heterocycles constitute by far one of the largest group of organic compounds.Various heterocyclic structures are widely found in biologically active nature products,organic materials,agrochemicals,and pharmaceuticals,which exhibites the importance of heterocyclic compounds.Therefore,the synthesis of heterocycles scaffold has gained considerable attention of organic chemists.It is well known that the radical-initiated tandem cyclization is a powerful tool for the construction of heterocyclic compounds.It has the advantages of atomic economy,chemical selectivity,region-selectivity and stereoselectivity.In this paper,we mainly studied the synthesis of heterocyclic compounds via radical-initiated tandem cyclization in the absence of transition-metal.1.Visible-light-induced strategy to access sulfonated chromanes and sulfonated1,2,3,4-tetrahydroquinolines via a radical cascade cyclization of1-(arylethynyl)-2-(vinyloxy)benzenes and N-allyl-2-(arylethynyl)anilines with aromatic and aliphatic sulfinic acids has been developed.In the presence of TBHP(7.5 mol%)as an oxidant and Eosin Y(3.0 mol%)as a photocatalyst,the reactions undergo smoothly to afford the corresponding products in good yields at room temperature under metal-free conditions.This transformation features low loading of TBHP,mild reaction conditions,simple operation,broad functional-group tolerance,and good yields of products.2.A highly efficient synthesis of carbamoylated benzimidazo[2,1-a]isoquinolin-6(5H)-ones using 2-arylbenzoimidazoles and oxamic acids was developed.This strategy tolerated various substrates on the starting materials to generate the corresponding products in good yields under metal-free conditions.However,N-sulfonyl substituted oxamic acids(monosubstituted ones)is different from results with 2-arylbenzoimidazoles under the optimized reaction conditions,affording the corresponding sulfonyl-substituted benzimidazoisoquinolinones in high yields.