Radical Reactions Based On Sp~3 C-H Activation

C-H bond is the most common chemical bond in organic compounds.The direct activation and functionalization of C-H bond is an important research content in the field of organic synthesis,because of the high atom-and step-economy.However,due to the low polarity and high bond dissociation energy of C-H bond,the activation and functionalization of C-H bond is difficult and challenging,which has attracted the attentions from many chemical researchers.In recent decades,radical reaction has become an effective tool in organic synthesis owing to its high efficiency and cleanness.And great progress has been witnessed in the radical C-H activation and functionalization.For example,in the presence of peroxide initiators,oxidants or visible light photoredox catalysts,the cleavage of C-H bond gives the corresponding radicals,and then it reacts with unsaturated bond to obtain useful structures or cyclic compounds.Based on this,the main research content of this paper is to obtain heterocyclic molecules with potential bioactivities based on the radical addition or addition/cyclization processes.The research content of this paper is mainly divided into the following two parts:(1)Radical tandem cyclization reaction of N-allylbenzamide and etherA radical-initiated cascade addition and cyclization of N-allylbenzamides with simple ethers to construct ether-substituted dihydroisoquinolinones was performed in the presence of CuI as the catalyst and DTBP as the oxidant.The cleavage of the sp~3 C–H bond in ethers and the sp~2 C–H bond in phenyls was involved in this reaction.Moreover,the arylalkylation of N-allylanilines was also realized under similar reaction conditions,providing ether-functionalized indolines in good to moderate yields.(2)1,4-addition reaction of oxygenα-position radical and chromoneA very simple and direct method for the C-H functionalization of ethyl acetates was developed,delivering a variety of 1-(4-oxochroman-2-yl)ethyl acetate derivatives by reacting with chromones.The reaction has wide substrate scope with the excellent site-selective activation at the inactiveα-hydrogen of the alkoxyl group instead of theα-hydrogen of carbonyl groups under radical conditions.A distinguishing feature of this reaction is that no metal catalyst was required with DTBP as the sole oxidant.