Study On The Activation Of Amides C/N-H And Anilines C-H Catalyzed By Cheap Transition Metal

In recent years,transition-metal-catalyzed C-H functionalization has emerged as a facile approach to synthetize various required compounds,so it has attracted wide attention.This kind of method with simple and direct activation procedure is an effective method to improve reaction efficiency and atomic economy.In this paper,the C-H/N-H activation of amides and C-H activation of anilines catalyzed by cheap transition metals were studied.It reduces the cost of catalyst in the reaction and expands the research of C-H and N-H activation reactions.Firstly,a Ni catalyzed cross-dehydrogenative coupling of C(sp³)-H bonds in N-methylamides with C(sp³)-H bonds in cyclic alkanes was studied.In the presence of catalyst Ni Cl₂,N-methylbenzamides can be smoothly coupled with cyclohexane in medium yields.This new strategy is highly selective and tolerates a variety of functional groups.In addition,a straightforward Ni(II)-catalyzed general strategy was developed for the ortho-halogenation of benzamides with easily available halogenating reagents N-Bromosuccinimide(NBS).The transformation was highly regioselective and a wide substrate scope were observed.This discovery could be of great significance for the selective halogenation of amides with guiding groups,which is a good supplement for the study of Ni catalyzed C-H activation reactions.Next,a Ni(OTf)₂ catalyzed N–H methylation of benzenesulfonamides by using DTBP as the methylating reagent was described,providing N-methylation products in moderate to good yields.This protocol tolerated a broad range of substrates,not only various sulfonamides but also methanamides.Mechanistic study indicated that the C-H bond cleavage might proceed via a single electron transfer mediated by nickel catalyst.Meanwhile,a nickel catalyzed N–H benzylation of benzenesulfonamides by using toluene as the benzylated reagent was developed.The yield of benzylated product is 58-78%.Finally,a Co Br₂-catalyzed regioselective C–H methylation reaction of anilides using DTBP as attacking reagent was developed.This new strategy features high selectivity,a broad range of functional groups and use of green and low toxic DTBP,thus offering a good complement to previous C–H methylation reactions.In addition,a Co(acac)₂-catalyzed regioselective C–H halogenation methodology was reported.The highlight of this work is the highly selective C–H functionalization of anilides,which results in high-yielding,versatile,and practical halogenated products.Thereby,brominations,chlorinations and iodinations of many electronrich and electron-deficient anilides were achieved in a highly selective fashion.