Synthesis of Benzimidazoles Condensed with, or Linked to, Nitroxides or Heterocyclic N-Oxides
作者:Kálmán Hideg、Balázs Bognár、Tamás Kálai
DOI:10.1055/s-2008-1067158
日期:2008.8
Pyrazino[1,2-a]benzimidazoles were synthesized starting from 2-acetyl-1H-benzimidazole. Benzimidazoles were linked to nitroxides by lithiation and ring-closure and cross-coupling reactions leading to pH-sensitive EPR probes and a paramagnetic analogue of antiviral agent HBB.
Nickel(II)-Catalyzed [5 + 1] Annulation of 2-Carbonyl-1-propargylindoles with Hydroxylamine To Synthesize Pyrazino[1,2-<i>a</i>]indole-2-oxides in Water
作者:Hong-Yan Bi、Min Du、Cheng-Xue Pan、Yuhong Xiao、Gui-Fa Su、Dong-Liang Mo
DOI:10.1021/acs.joc.9b00784
日期:2019.8.16
the efficient synthesis of various pyrazino[1,2-a]indole-2-oxides was developed through a nickel(II)-catalyzed [5 + 1] annulation of 2-carbonyl-1-propargylindoles with hydroxylamine in water without using an organic solvent. The reaction involved an initial condensation of 2-carbonyl-1-propargylindoles with hydroxylamine to afford oxime intermediates, which then underwent a nickel(II)-catalyzed 6-exo-dig
通过镍(II)催化的2-羰基-1-炔丙基吲哚的[5 +1]环化反应,开发了一种原子经济实用的方法,可有效合成各种吡嗪并[1,2 - a ]吲哚-2-氧化物。在不使用有机溶剂的情况下与羟胺一起使用。该反应涉及2-羰基-1-炔丙基吲哚与羟胺的初始缩合以提供肟中间体,然后将其进行镍(II)催化的6-exo-dig环化。初步研究表明(n -Bu)4NI用作相转移催化剂,并促进了活性镍(II)物种的形成。更重要的是,镍(II)盐和水中的相转移催化剂可以循环使用七次,并且通过过滤和洗涤方案可以容易地以高收率获得克级可缩放产品。