Research Of Copper-Catalyzed Ullmann Condensation Reaction

The transition metal-catalyzed cross-coupling reaction to form sp² C-C or C-hetero atom bonds is one of the most important methods for modern organic synthesis. In comparison with Pd and Ni, Copper is a cheaper metal with lower-toxicity. So copper-catalyzed cross coupling, refer to Ullmann condensation, has received considerable attention in recent years.In the chapter 2 of the thesis, we studied copper-catalyzed cross coupling between sodium azide and aryl, alkenyl boronic acid, and developed a novel synthesis method for aryl and alkenyl azides from the corresponding boronic acids. Compared to the very recent procedures using aryl halides, our new method showed a milder reaction condition and improved substrate tolerance. On the basis of this finding, we next developed a one-pot procedure to prepare 1-aryl- and l-vinyl-l,2,3-triazoles directly from boronic acids and alkynes. This one-pot method was advantageous not only because it was operationally simple and high yielding, but also because it completely avoided the isolation of relatively unstable aryl and alkenyl azides.In the chapter 3 of the thesis, we developed a novel one-pot method for the synthesis of primary arylamines from the corresponding aryl halides. Crystalline 2,2,2-trifluoro-acetamide is used as ammonia surrogate and CuI is used as the catalyst to achieve the C-N coupling under mild conditions. After hydrolysis of cross coupling's intermediates, we obtained primary arylamines. An important advantage of the new procedure is that the reaction is operationally simple, economically inexpensive, and high yielding.In the chapter 4 of the thesis, we examined the possibility to carry out Cu-catalyzed cross couplings under ligandless conditions. It was found that by using K₃PO₄ as the base, the cross coupling could proceed successfully between aryl iodides and several types of nucleophiles. Aryl bromides were completely inactive under the same reaction conditions. We expected that the current procedure was valuable for realistic industrial-scale applications from the economical point of view.