Regioselectivity of N-substitution in bis-alkylation of 1,2,4-triazolo[1,5-a]benzimidazole-2-thione
作者:T. A. Kuz’menko、V. V. Kuz’menko、L. N. Divaeva、A. S. Morkovnik、G. S. Borodkin
DOI:10.1007/s11172-012-0158-7
日期:2012.6
Cyclization of the corresponding N-substituted 1,2-diaminobenzimidazoles with carbon disulfide in refluxing DMF leads to 3-methyl- and 3-benzyl-1,2,4-triazolo[1,5-a]benzimidazole-2-thiones. Based on the results of their S-alkylation, quantum chemical calculations by the density functional theory method, and 1D and 2D NMR spectroscopic studies, it was concluded that the bis-alkylation of N-unsubstituted 1,2,4-triazolo[1,5-a]benzimidazole-2-thione in the presence of a base proceeds with the formation of N(4)-derivatives of 2-alkylthio-1,2,4-triazolo[1,5-a]benzimidazole, rather than N(3)-derivatives as was believed earlier.
将相应的N-取代1,2-二氨基苯并咪唑与二硫化碳在回流的DMF中环化得到3-甲基和3-苄基-1,2,4-三唑并[1,5-a]苯并咪唑-2-硫酮。根据它们的S-烷基化结果、密度泛函理论方法的量子化学计算以及一维和二维核磁共振波谱研究,得出的结论是,在碱存在的条件下,N-未取代的1,2,4-三唑并[1,5-a]苯并咪唑-2-硫酮的双烷基化反应是通过形成2-烷硫基-1,2,4-三唑并[1,5-a]苯并咪唑的N(4)衍生物进行的,而不是像之前认为的那样形成N(3)衍生物。