New Methods Of C-N Bond Formation From Cyclohexanones And Amines

The nitrogen-containing heterocycles represent an important class of organic compounds and exhibit valuable bioactivities.The compounds have a broad application in drugs,pesticides and functional materials.Based on the importance of nitrogen-containing heterocycles,the C-N bond formation has alway been a vital research direction in the chemistry field.With the rise and development of green chemistry,the high selective synthesis of nitrogen-containing compounds with cheap and available raw materials has aroused wide interest of chemists.Aiming at the current challenging problems existing in the C-N bond formation,we investigated the method of C-N bond formation with cyclohexanones and amines as starting materials.The main research was described as follows:1.The transition-metal-free catalyzed heterocyclic generation reaction was developed,the efficient four-component synthesis of N-substituted phenothiazines by cyclohexanones,elemental sulfur and amines has been realized.Both of the aryl rings in the phenothiazine moiety came from clohexanones via a condensation,dehydrogenation,tautomerization and aromatization sequence.The combination use of KI/DMSO in an oxygen atmosphere significantly improved the reaction yields.The elemental sulfur not only acts substrate but also serves as oxidant.In this reaction,two C-N and two C-S bonds were achieved in one pot.Furthermore,the unsymmetrical N-substituted phenothiazines has been acquired,and the reaction of diamine with cyclohexanone afforded the corresponding product.Since amines,cyclohexanones and sulfur were inexpensive and readily available starting materials,this four-component procedure affords an efficient method for the rapid construction of N-substituted phenothiazines without the use of a noble metal catalyst.2.A series of N-substituted octahydrocarbazoles were synthesized from cyclohexanones and 2-aminobenzenethiols via C-N bond formation.The preliminary results show that the N-substituted octahydrocarbazoles were formed in good yields and high selectivity by using Pd(TFA)2 as the catalyst,NHC as the ligand,cyclohexane as the solvent and oxygen as the oxidant.It will provide a novel method for the synthesis of carbazoles.