The DDQ-Mediated CDC Reaction To Synthesize Nitrogen-Containing Heterocycles

Construction of N-containing heterocycles have been the research focus on organic synthesis,because they are extensively used in pharmaceutical chemistry,drug synthesis and functional materials.From the perspective of atomic economy,cross dehydrogenation coupling?CDC?as the most direct and economical way to form C-C and C-N bonds can avoid the pre-functionalization of materials.Based on long-term research for DDQ mediated-oxidative coupling reaction,here,we aim to utilize chloranil and DDQ as oxidants.The main content was as follows:?1?Chloranil mediated the oxidative cyclization of o-allylaniline compounds.First,the effects of different solvents,reaction temperature,oxidants on the reaction result were investigated.The optimal reaction condition was obtained at 80°C for 2 hours,which used chloranil of 2.1 equivalents as oxidant and 1,2-dichloroethane as solvent.Then,the substrate scope was investigated and a series of 2,4-diarylquinolines were obtained.Meanwhile,a one-pot method for the synthesis of 2,4-diarylquinolines was developed,which involves using aniline and 1,3-diarylpropylene as reaction substrates.In the reaction,DDQ mediated oxidative coupling,Fe Cl₃ catalyzed rearrangement,Chloranil promoted oxidative annulation.In addition,a gram-scale experiment showed desired 2,4-diarylquinolines could be provided in good yield.Finally,the possible reaction mechanism was proposed by the control experiment and corresponding results.?2?DDQ-mediated oxidative coupling of 1,3-diarylphenylpropylene and 4-amino coumarin.First,the effects of different solvents,reaction temperature,oxidant equivalent on the reaction results were screened.The optimal reaction conditions were determined at room temperature for 4 hours,which used DDQ of 1.2 equivalent as oxidant and 1,2-dichloroethane as solvent.Then,the substrate scope was investigated and a series of 3-allylcoumarins were obtained.Based on coupling reaction,the oxidative annulation of 4-aminocoumarins and 1,3-diphenylpropene was developed with 5 coumarins fused with pyridines as product.Besides,the oxidative coupling between?-enaminoester and 1,3-diphenylpropene is tried,and only the hydrolyzed products were obtained.Finally,the possible reaction mechanism was proposed by the control experiment and corresponding results.?3?DDQ mediated the tandem reaction of 1,3-diarylpropylene and o-aminobenzamide.First,the effects of different solvents,reaction temperature,oxidant equivalent on the reaction results were screened.The optimal reaction conditions were determined,which used chloroform as solvent,1.2 equivalent DDQ as oxidant,the reaction was at room temperature for 10 minutes,then continued to add DDQ of 1.0equivalent,stiring at 50°C for 1 to 4 hours,cyclization products were obtained in good yield.The reaction conditions are mild,the operation is simple,and the substrates of various functional groups are well tolerated.Finally,the possible mechanism was propossed by control experiment and corresponding results.A total of 55 compounds were synthesized from above research methods,of which37 were new compounds.And the structures of all compounds were identified by NMR,mass spectrometry and other methods.In this paper,DDQ or chloranil were used as oxidants to provide a simple and novel approach for the synthesis of nitogen-containing heterocycles,which is of great significance for the construction of C-N bonds.