Rh(?)-Catalyzed Redox-Neutral[4+1]Annulation Of Ts-amides And Gem-Difluoroacrylates

Carbon/heterocyclic structures are the core fragments of many natural products and biologically active molecules,and they have been widely applied to biomedical aspects,materials and chemical industries.Transition-metal-catalyzed annulation reactions,those directly making use of non-prefunctionalized substrates via C-H activation have been attracting increasing attention,as they enable a rapid assembly of molecular complexity from simple starting materials in a step-and atom-economical fashion.In this respect,Rh(III)catalyst has been extensively explored and numerous[n+2]annulations that tackle with alkenes,alkynes as the coupling ? systems.Nevertheless,reactions which integrate one carbon component to render[n+1]annulation patterns is far less exploited.Representative examples including the use of diazo,carbon monoxide and isonitrile as one carbon reaction partners,but several shortcomings remain such as the heavily relying on high reaction temperature and/or large stoichiometric amount of oxidants.Therefore,the development of novel[n+1]protocol that overcome these drawbacks is highly desirable.In the first part of this thesis,we summarized the research achievement of Rh(?)-catalyzed annulations,including the reactions with alkynes,alkenes,nitrogen compounds and aldehydes etc.In the second part,we describe our research in detail.By using Ts-imide directed rhodium-catalyzed C-H activation and engaging gem-difluoroacrylates as the one carbon reaction partners we have successfully developed a novel redox-neutral[4+1]annulation protocol,which provides a highly effective and straightforward route for the construction of 5-methylene-1H-pyrro]-2(5H)-one derivatives.Several shining points respect to this reaction are worth mentioning:i)An oxidant-free process due to the cleavage of C-F bonds,which render the catalyst turnover without any external oxidants;ii)High atom economical with only two molecules of hydrogen fluoride as the byproduct;iii)High stereoselectivity for the synthesis of E-products;iv)Excellent functionality tolerance owing to the very mild reaction condtion.