Study On The Synthesis Of N-aryl Carbazole From Cyclohexanone Under Transition Metal-free Condition

Carbazole compounds are important organic nitrogen heterocyclic compounds,which are ubiquitous in nature and widely used in pharmaceuticals,dyes and organic optoelectronic materials.It is of great significance in our daily life.Based on this,developing a kind of high efficient and green synthesis method has become one of research hotspot in organic synthesis.The cheap and non aromatic cyclohexanone compounds which can be used as aryl source by "dehydrogenation aromatization" have been widely used in organic synthesis.Taking the heavy metal residues in the synthesis of pharmaceutical drugs and light-emitting materials into consideration,it affords an effective methodto synthetise carbazole through cyclohexanone dehydroaromatization strategy undertransition-metal-freecondition.In this paper,we use cyclohexanones as raw materials to synthesize a series of unsymmetrical N-arylcarbazole compounds under transition-metal-free condition.The main contents are as follows:1.Developed an efficient strategy for N-arylcarbazole synthesis from arylureas and cyclohexanones under transition metal-free conditions.In this kind of transformation,on one hand,there is no need to add any transition metal catalyst and getting a good stability for functional group;on the other hand,thewhole carbazole moiety(except the nitrogen atom)comes from two equivalents of non aromaticcyclohexanones.Thecombined use of potassium iodide and iodine couldsignificantly improve the reaction efficiency to provide 2,6-disubstituted9-arylcarbazoles in moderateto good yields.This method affords anovel approach forunsymmetrical N-arylcarbazole synthesis.2.Developed an efficient strategy for carbazoles and 1,2,4-triarylpyrroles synthesis from anilines and cyclohexanonesor acetophenones under transition metal-free conditions.A variety of 2,6-disubstituted-9-aryl-carbazoles were synthesized in moderate to good yields promoted by KI/I2 using anilines as the nitrogen and aryl source.Meanwhile,avariety of 1,2,4-triarylpyrroles were selectively synthesized from anilines and acetophenones in the presence of KI alone.This method affords a simple approach for unsymmetrical carbazoles and pyrroles from readily available starting materials.