On the utility of the azido transfer protocol: synthesis of 2- and 5-azido N-methylimidazoles, 1,3-thiazoles and N-methylpyrazole and their conversion to triazole–azole bisheteroaryls
作者:Paolo Zanirato、Stefano Cerini
DOI:10.1039/b500634a
日期:——
The azido transfer procedure of heteroaryllithium and tosyl azide was used to synthesize selected 2- and 5-azidoazoles. This procedure, which is based on the fragmentation of the appropriate lithium triazene salts 1aâ7a, successfully afforded 2-azido-N-methylimidazole 1, 2-azido-1,3-thiazole 2, 2-azidobenzo-1,3-thiazole 3, 5-azido-N-methylpyrazole 4, 5-azido-N-methylimidazole 6 [via 2-(trimethylsilyl)-5-azido-N-methylimidazole 5], and 5-azido-1,3-thiazole 7 (via 5-lithio-1,3-thiazole), but attempts to prepare 5-azido-2-(trimethylsilyl)-1,3-thiazole 8 from the corresponding triazene 7a failed, affording only the desilylated azide 7 in poor yield. Azides 1â7 underwent 1,3-dipolar cycloaddition when mixed with neat (trimethylsilyl)acetylene, giving 1-heteroaryl-4-trimethylsilyl-1,2,3-triazoles 1bâ7b generally in very high yields.
利用杂芳基锂和对甲苯基叠氮化物的叠氮转移程序合成了部分 2-和 5-叠氮唑。该步骤基于适当的三氮烯锂盐 1aâ7a 的碎裂,成功地得到了 2-叠氮-N-甲基咪唑 1、2-叠氮-1,3-噻唑 2、2-叠氮苯并-1,3-噻唑 3、5-叠氮-N-甲基吡唑 4、5-叠氮-N-甲基咪唑 6 和 5-叠氮-N-甲基咪唑 7、但从相应的三嗪 7a 中制备 5-叠氮-2-(三甲基硅基)-1,3-噻唑 8 的尝试失败了,只得到了脱硅叠氮化物 7,收率很低。叠氮化物 1â7 与纯净的(三甲基硅基)乙炔混合后发生 1,3-二极环加成反应,得到 1-heteroaryl-4- 三甲基硅基-1,2,3-三唑 1bâ7b,收率通常非常高。