CuO-Promoted The Synthesis Of N-2-substituted-1,2,3-Trizoles

Since the remarkable discovery of Cu-catalyzed-azide-alkyne-cycloaddition (CuAAC, also referred as "click-chemistry"),1,2,3-triazoles have attracted significant attention as one of the most important heterocycles. Within the last few years, the applications of this building block have been extended widely into various research fields, such as chemical biology, material science and medicinal chemistry. This paper consists of three chapters as follows:The first chapter is to review the synthesis of1,2,3-triazoles based on positions of the substituted group.1,3-Dipolar cycloaddition of azides to alkynes is the most important one of them, which was first proposed and studied by Rolf Huisgen. Recently described methods for the catalytic direct functionalisation of triazole and its derivatives have also been proved attractive but are mainly limited to the N-1position, although few methodologies have been reported for the direct functionalisation of triazoles at the N-2position.In the second chapter, a series of1,4,5-trisubstituted1,2,3-triazoles has been prepared conveniently via1,3-dipolar cycloaddition/coupling reaction of1,3-diketone, sodium azide and aryl halides. The method does not require isolating of the azide intermediates and shows a series of advantages, for example, it is safe, efficient, convenient and environmentally benign. It fails at last for a mixture containing the N-1and N-3substituted-1,2,3-Triazoles was obtained. However, we envision one novel and operationally simple way of regioselectively synthesizing2,4,5-trisubstituted1,2,3,-triazoles via azide-chalcone oxidative cycloaddition and post-triazole arylation in one pot.In the third chapter, We have successfully developed an operationally simple way of regioselectively synthesizing2,4,5-trisubstituted1,2,3,-triazoles via azide-chalcone oxidative cycloaddition and post-triazole arylation in one pot. Compared to traditional synthesis of triazoles, this protocol uses the cheap and easy-to-prepare chalcones as substrates. Moreover, this new approach offers not only high yields under mild conditions but also highly regioselectivity for2,4,5-trisubstitued1,2,3-triazoles. The conclusion in this paper plays a role of supplement and summary for our previous work, and it deepens our understanding for applying the multi-component reaction to the cross-coupling reaction.