An unprecedented intramolecular to intermolecular mechanistic switch in 1,1-diaminoazines leading to differential product formation during the I<sub>2</sub>-induced tandem oxidative transformation
作者:Deepika Kathuria、Pankaj Gupta、Sumit S. Chourasiya、Subash C. Sahoo、Uwe Beifuss、Asit K. Chakraborti、Prasad V. Bharatam
DOI:10.1039/c9ob00610a
日期:——
been developed via tandem oxidative transformation of guanylhydrazones (in its preferentially existing azine tautomeric form) with distinct advantages such as wide substrate scope, use of substoichiometric amounts of iodine, no requirement of external oxidizing agents, base free reaction conditions, short reaction time and moderate to good yields. The role of silver salt in improving the yield and
在I 2催化的氧化转化过程中,胍基towards嗪对嗪形式的互变异构偏好诱导了空前的分子内到分子间的机械转换,与之相比,它导致了4,5-二取代的-3-氨基-1,2,4-三唑的反应。半咔唑酮和硫代半咔唑酮形成1,3,4-氧杂/噻二唑。分子内至分子间环化转变是通过对照实验确定的,这归因于对嗪互变异构体采取分子内反应必不可少的顺式构象的高能量需求(〜22 kcal mol -1)。我2通过串联氧化转化胍基hydr(优先存在的嗪互变异构体形式),开发了一种有效,直接合成4,5-二取代-3-氨基-1,2,4-三唑的诱导方法,具有广泛的优势。底物范围,使用亚化学计量的碘,无需外部氧化剂,无碱反应条件,反应时间短且产率中等至良好。还强调了银盐在提高产率和缩短反应时间中的作用。