Aromatic C-H Bond Radical Transformation Enabled The Alkene Difunctionalization Reactions

Alkenes are a class of the important industrial petrochemicals,which sever as structural units that widely found in natural products,pharmaceuticals,and functional materials.Because of their low cost and high reactivity,transformations of alkenes have always been a hot area of research in organic synthesis and attract much afttention of the chemists.Among them,the alkene difunctionalization reaction enabled by aromatic C-H bond radical transtromation strategy because of its high atom-/step-economy,avoidance of use of noble transition-metal catalysts,no need of prefunctionalized substrates and directing groups,simple reaction conditions and convenient operation.It is well-known that the classical free radical reactions are initiat ed mainly by pyrolysis,photolysis,oxidation and electrochemistry.Thus,the development of new radical initiated strategies to achieve new alkene difunctionalization enabled by aromatic C-H bond radical transformations is desriable and remains a challenging area.This thesis mainly studies the aromatic C-H bond radical transformation-enabled alkene difunctionalization reactions,and new radical initiated strategies,which includes the following four aspects:(1)Recent progress in the alkene difunctionalization enabled by aryl radical transformations was systematically reviewed,which mainly introduced two topics:one is the diarylation of alkenes,and the other involves the alkylarylation of alkenes.Moreover,the mechanisms for the alkene difunctionalization were also detainedly discussed.(2)A radical-mediated diarylation of alkenes with electron-rich arenes is achieved.Using the electrochemical radical stategy allows direct activation of the electron-rich aryl C(sp²)-H bonds to form the aryl sp²?hybridized carbon-centered radical cations,followed by transformation to the aryl sp²?hybridized carbon-centered radicals in the presence of bases and addition across the alkenes,giving a series of polyaryl-functionalized alkane compounds were obtained by the reaction of aromatics radicals with olefins.Advantageously,this methodology features mild conditions,clean energy and external oxidant-free,a broad scope of styrenes and electron-rich arenes(indoles,pyrroles and O-/N-substituted arenes),a satisfactory tolerance of functional groups,and controllable chemoselectivity.(3)A nickel-catalyzed oxidative radical alkylarylation of N-arylacrylamide with alkyl bromides to access a series of indole-2-ones is developed.In contrast to the traditional radical initiation strategy,the alkyl radicals are generated through single electron transfer between the active low valence Ni^I species and alkyl bromides,which would sequntially undergo addition across the alkenes,attack the aryl C-H bonds and reductive elimiation cascades to accomplish the alkene difunctionalization and generate Ni^II species.Finally,reduction of the generate Ni^II species to the active Ni^I species by reducants,thus starting a new catalytic cycle.(4)A metal-free oxidative raical tandem[2+2+1]annulation of 1,7-enynes with disulfanes is established.The reaction employs tert-butyl peroxybenzoate(TBPB)as oxidant/initiator and diphenyl persulfide as sulfur source to allow the[2+2+1]annulation of 1,7-enynes,efficently affording 3,3a-dihydro-thieno[3,4-c]quinolin?4(5H)-ones in high yields.