<i>N</i>-Demethylation of <i>N,N</i>-Dimethylanilines by the Benzotriazole <i>N</i>-Oxyl Radical: Evidence for a Two-Step Electron Transfer−Proton Transfer Mechanism
作者:Enrico Baciocchi、Massimo Bietti、Osvaldo Lanzalunga、Andrea Lapi、Daniele Raponi
DOI:10.1021/jo100040y
日期:2010.3.5
The reaction of the benzotriazole N-oxyl radical (BTNO) with a series of 4-X-N,N-dimethylanilines (X = CN, CF3, CO2CH2CH3, CH3, OC6H5, OCH3) has been investigated in CH3CN. Product analysis shows that the radical, 4-X-C6H4N(CH3)CH2•, is first formed, which can lead to the N-demethylated product or the product of coupling with BTNO. Reaction rates were found to increase significantly by increasing the
苯并三唑N-氧基自由基(BTNO)与一系列4-X- N,N-二甲基苯胺(X = CN,CF 3,CO 2 CH 2 CH 3,CH 3,OC 6 H 5,OCH 3)已在CH 3 CN中进行了研究。产物分析表明,首先形成了自由基4-XC 6 H 4 N(CH 3)CH 2 •,这可能导致生成N-脱甲基产物或与BTNO偶联的产物。发现反应速率通过增加芳基取代基的供电子能力而显着提高(ρ + = -3.8)。使用给电子性取代基(X = CH 3,OC 6 H 5,OCH 3),未观察到分子间氘动力学同位素效应(DKIE)和基本的分子内DKIE。在具有吸电子取代基(X = CN,CF 3,CO 2 CH 2 CH 3)的情况下,观察到分子间和分子内DKIE的实质值。这些结果可以根据N的电子转移机理来解释,N-二甲基苯胺到BTNO自由基,然后使苯胺自由基阳离子去质子化(ET-PT机理)。通过将Marcus方程应用于X