NH-1,2,3-三唑合成之研究

Abstract

1,2,3-triazole have found broad uses in agrochemicals, industrial applications and drugs. Many methods of preapring N-substituted 1,2,3- triazole are reported, whereas, only a few synthesis of N-unsubstituted 1,2,3-triazole were developed. In this study, we report a high yield synthesis of N-unsubstituted triazole by cycloaddition reaction of terminal acetylene and sodium azide activated by copper(I) ion. (i). The mixture of copper(I) phenyl acetylide and sodium azide dissolved in methanol was stirred at reflux temperature of 70℃ for 3 days : the yield of 4-phenyl-1H-1,2,3-triazole (2a) is less than 10% and phenyl acetylene dimer (3a) is the major product. (ii). The mixture of copper(I) azide and phenyl acetylene dissolved in methanol was stirred at reflux temperature of 70℃ for 3 days : the yield of (2a) is 33% and the yield of (3a) is 34%. (iii). The mixture of phenyl acetylene, sodium azide and copper(I) chloride dissolved in a co-solvent (methanol : 1,4-dioxane= 1 : 2) was stirred at reflux temperature of 100℃ for 2 days under nitrogen : the yield of (2a) is 81%. The same procedure was applied to terminal alkynes carrying substituents such as aryl, alkyl, hydroxyl, ester, cycloalkyl and conjugated enyne to obtain triazoles having corresponding substitutents. The yields of these products are comparable or better then those reported in literature. This reaction isregiospecific and only 4-substituted 1H-1,2,3-triazoles were obtained. The reaction must carry out under inert gases, otherwise oxidative coupling reaction is the dominated reaction, and phenyl acetylene dimmer is the major product. Reaction temperature has to be high enough (>80℃) to allow the color change of the mixture to ensure a high yield reaction. When the rate of copper(I) chloride to phenyl acetylene is 1:1, as the reactant, the optimal yield of 81% is attained. Therefore, copper(I) chloride is not a catalyst. We also synthesize 4-phenyl-1,3-diH-1,2,3-triazolium cation and its structure determined by X-ray diffraction is described.