Transition-metal-catalyzed C\N Hydrocarbylation Based On Cross Dehydrogenation Coupling

Hydrocarbylation is a very important reaction in organic synthesis and chemical production,and is an important means to construct C-X（X=C,N,O,S,etc.）bond.Compared with traditional hydrocarbylation reactions,the transition metal-catalyzed cross dehydrogenation coupling（CDC）hydrocarbylation reaction has the advantages of high efficiency,atomic economy and environmental friendliness,and is more in line with the concept of green synthesis.The main work of this paper was to explore new methods of introducing hydrocarbon groups into the C（sp²）in aromatic ring and N atom in aromatic amine under the catalysis of cheap transition metals,and used the new methods to prepare some important compounds in fine chemical synthesis.The specific work table is shown in the following aspects:1.A novel and efficient approach for the amine-directed dehydrogenative C（sp²）-C（sp³）coupling of arylamines with acetonitrile was reported by using iron as the catalyst.In this method,α-aryl nitriles were prepared conveniently under relatively simple reaction from cheap and readily available raw materials which without pretreatment.Electron-withdrawing or electron-donating groups substituted anilines,aminopyridines,naphthylamines and some nitrogen containing heterocyclic aromatic amine are suitable for this reaction system.This is the first example of direct dehydrogenation coupling of cyanomethylation on the electron-deficient pyridines and the electron-withdrawing groups containing benzenes.,which has great innovation significance and theoretical significance.In this paper,Fe Cl₂ was selected as the most suitable catalyst for this reaction,and then the reaction conditions were optimized.More than 60α-aryl nitrile compounds were synthesized by this new method,and have been identified by ¹H NMR,¹³C NMR,and ESI-TOF-MS.The KIE study showed that the Csp³-H bond cleavage in acetonitrile was the rate-determining step in this reaction.The results of control experiments illustrated that a radical process is possibly involved in the reaction.2.A new method of C（sp²）-C（sp³）cross dehydrogenation coupling between imidazolo[1,2-a]pyridines and methyl ketone has been developed.In this method,C3-alkylated imidazo[1,2-a]pyridines can be prepared with cheap and readily available methyl ketones which without pretreatment.Cheaply manganese acetate was selected was the most suitable catalyst for this reaction,and then the reaction conditions were optimized.Both electron-donating and electron-withdrawing groups at different positions of imidazo[1,2-a]pyridines are tolerated in the reaction,and they provided the target alkylation products in moderate to good yields.The results of control experiments indicate that a radical process is possibly involved in the reaction.3.A new method of copper catalyzed N-C（sp³）cross dehydrogenation coupling reaction between aromatic primary amines and toluene was developed.The method directly uses commercial aromatic amines and toluene as raw materials without pretreatment,and realizes the coupling of C-N bond under the catalysis of copper to prepare secondary amines.This method is structure single and has good selectivity and the products has a single structure,which overcomes the defects of traditional method for preparing secondary amine,such as many by-products,serious pollution,harsh reaction conditions,poor selectivity and so on.Aniline compounds containing electron withdrawing substituents and nitrogen-containing heterocyclic aromatic amines showed good tolerance in this reaction.In addition to toluene,ethylbenzene,xylene,trimethylbenzene and cyclohexane all showed good reactivity in this reaction.The results of controlled reaction experiment showed that the reaction may have experienced free radical process.This reaction provides a potential route for the selective C–N coupling functionalization from simple substrates to functionalized aromatic secondary amines.The results of control reaction experiments indicate that the reaction may undergo a free radical process.