Palladium-Catalyzed Decarboxylative Cyclization To Access Indoloisoquinolines And Tribenzo[7]annulenes

C,C-Palladacycle as a highly reactive intermediate has attracted widely attention from organic chemists.The two C-Pd bonds can be readily functionalized by coupling reagents to construct two new chemical bonds due to their high reactivity.Despite great progress has been made in the research of palladacycle with coupling reagents in the construction of cyclic compounds,the scope of coupling reagents reported is relatively limited.Therefore,developing new coupling reagents is extremely necessary.In the past few decades,the research on carboxylic acids as substrate has been increasing.Compared with other reagents,carboxylic acids,as a kind of cheap,stable and readily available substrate,have been widely used in decarboxylated cross-coupling reactions.However,methods to construct cyclic compounds via a decarboxylative cyclization strategy are still rare.Therefore,in this paper,methods of synthesis cyclic compounds(such as indole[2,1-a]isoquinolines and tribenzo[7]anunenes)via decarboxylative cyclization of palladacycle with different carboxylic acids were developed.The main content of the paper is divided into the following parts:Chapter one:In this paper,the recent research progress involving palladacycle formed by aryl C(sp~2)-H activation with coupling reagents is summarized.Chapter two:A novel palladium-catalyzed cascade cyclization of alkene-tethered 2-(2-halophenyl)indole with o-bromobenzoic acids is described,which provides an efficient avenue for building various fused indolo[2,1-a]isoquinolines.The method enables the construction of three C-C bonds via an intramolecular Heck reation,C-H activation,and decarboxylation sequence.Chapter three:A palladium-catalyzed[4+3]decarboxylative annulation of 2-iodobiphenyls with 2-(2-halophenyl)acrylic acids is reported.The method enables the construction of tribenzo[7]anunenes by employing 2-(2-bromophenyl)acrylic acids as C3 unit insertion in moderate to excellent yield.Moreover,tribenzo[7]annulenes can be also synthesized via a[2+2+3]decarboxylative annulation strategy by employing readily available 1-bromo-2-iodobenzene,phenylboronic acids,and 2-(2-halophenyl)acrylic acids.