Cobalt-catalyzed [5+2] Cycloaddition Reaction For The Construction Of 7H-dibenzo[b,d]azepine

The seven-membered compounds this thesis report are a kind of7H-dibenzo[b,d]azepines,which represents an important class of medium-sized N-heterocycles.It exists in various intermediates with important activity and can be converted to bioactive and more structurally complicated compounds.Therefore,it is required to find a feasible and straightforward method with readily available starting materials to prepare 7H-dibenzo[b,d]azepines.Metal-catalyzed C-H bond cyclization is the most convenient and efficient way for the synthesis of heterocycles.Cobalt has been greatly developed as a catalyst in C-H activation.As a cheap metal,it has natural advantage over precious metals.Content of this thesis:based on the review of various metal-catalyzed C-H bond activation and results our group already have,we propose a reasonable reaction design.Condensation of 2-picolinic acid with benzidine to form niacinamide as a directing group,activates the C-H activated intercalation reaction under cobalt catalysis.By investigating the effects of catalyst type,catalyst amount,oxidants,additives,temperature and solvents on the reaction,the optimal reaction conditions are as follows:the catalyst is CoCl₂,the amount of catalyst is20 mol%,the oxidant is 0.2 eq of manganese acetate and 0.1 bar O₂,the reaction temperature is 120?,the solvent is trifluoroethanol and the reaction time is 18 h.Under the optimal condition,the influence of various substrates on the yields of products was examined.The experimental results show that the 1,2-diphenylethyne and the substrates participate in the reaction with a relatively higher yield,while the reaction of the terminal alkyne can only reach about 50%.Finally,according to the previous research results and the experimental results,a plausible reaction mechanism is proposed.