| Pyrrole and carbazole derivatives are very important five-member heterocyclic compounds. Pyrrole derivatives are abundant as constituents of natural products and have broad synthetic utility in both material science and medicine. Many pyrrole-containing compounds display a variety of physiological activities and interesting biological properties. Carbazole derivatives are characteristic of their excellent fluorescent properties due to the extended π-electron bond. They are widely used in luminescence chemistry as a photosensitizing and charge transport material. Therefore, many efforts of synthetic chemists have been directed to the syntheses of this class of heterocycles. The critical step of the synthesis is the formation of C-N bond.Ullmann reaction is one of the most important methods to form C-N bond. But usually high temperature, normally over 200°C, strong base and long reaction time were required. Therefore, the development of novel catalytical system for C-N bond forming reaction with high yield and high selectivity was highly desired. In recent years, Pd and Cu catalyzed C-N bond formation reactions have drawn considerable attention.However, no examples of a copper-catalyzed combination of N-alkenylation and N-alkylation of amides had been reported. Our research focused on the synthesis of heterocyclic compounds through the reaction between the dihalogen compounds and amides or carbamates. The best condition was use CuI as catalyst,rac-trans-N,N'-dimethylcyclohexane-1,2-diamine as ligand, potassium carbonate as base and toluene as solvent. Under the optimized reaction condition, the desired dihydropyrroles were obtained in 38%-84% yield. This reaction was further extended to the coupling reaction of amide with diiodo biphenyl; and the carbazole derivatives were synthesized in 53%-95% yield. |
