A tandem highly stereoselective FeCl3-promoted synthesis of a bisindoline: synthetic utility of radical cations in heterocyclic construction
摘要:
dA conceptually distinctive stereoselective construction of the novel dimer, N-[N'-acetyl-7,7'-bis-(3,4-dimethoxy-phenyl)-7,8,7',8'-tetrahydro-N'H-[8,8']biindolyl-N-yl]-ethanone 25 (bisindoline) is described below. These structures, which include 7-(3,4-dimethoxyphenyl)-indoline 24 (veratryl indoline), were obtained by the tactical combination of palladium-catalysed coupling which produced 10-acetamido-3,4-dimethoxystilbene 9, followed by FeCl3 induced oxidative cyclization/dimerization. All new structures were fully characterized by 1- and 2D NMR spectroscopy, (proton, carbon-13, COSY, HMBC, HMQC) and mass spectrometry. Configurational assignments were further supported by semi-empirical AMI calculations. Mechanistic interpretations, consistent with our results, are discussed. (C) 2004 Elsevier Ltd. All rights reserved.
The Subtle Co-catalytic Intervention of Benzophenone in Radical Cation Mediated Cyclization — An Improved Synthesis of 2-(3’,4’-Dimethoxyphenyl)indoline
作者:Noel Francis Thomas、Chin-Hui Kee、Azhar Ariffin、Khalijah Awang、Jean-Fr仕屍ic Faizal Weber、Chuan-Gee Lim、Mat Ropi Mukhtar、A. Hamid A. Hadi
DOI:10.3987/com-07-11280
日期:——
The addition of benzophenone to a FeCl 3 /CH 2 Cl 2 mixture in the presence of 3',4'-dimethoxy-2-acetamidostilbene 17 unexpectedly leads to a dramatic improvement in yield of the indoline 20 from 38% (previously reported by us) to 75.4%, after careful examination of a variety of reaction conditions. A catalytic cycle has been proposed that involves not only stilbene radical cations but also Fe 2+ promoted