Synthesis and Aminolysis of 2,4-Dinitrophenyl and 5-Nitropyridine<i>N</i>-Hydroxy Oxime Derivatives
作者:Sherine N. Khattab、Ezzat Awad Hamed、Fernando Albericio、Ayman El-Faham
DOI:10.1246/bcsj.20110015
日期:2011.6.15
The 2,4-dinitrophenoxy derivatives 12–16 and the 5-nitro-2-pyridyloxy derivatives 18–22 were prepared. The products were identified by elemental analysis, IR, and NMR. The reaction of 12–16 and 18–22 with morpholine as nucleophile in CH3CN occurs through nucleophilic aromatic substitutions to give N-(2,4-dinitrophenyl)morpholine (23) and N-(5-nitro-2-pyridyl)morpholine (24) respectively. Spectrophotometric measurements of the kinetics of these reactions in CH3CN at a range of temperatures indicated that they are not morpholine-catalyzed. The Brønsted-type plots for the reactions of 12–16 and 18–22 with morpholine are linear with slopes, β12–16 = −1.58 ± 0.1 and β18–22 = −1.15 ± 0.25 respectively. The relative rate constants compared to the least reactive substrate, as well as the low negative β values, supported that the decomposition of the zwitterionic intermediate is a slow process. The low activation parameters (ΔH# and ΔS#) are in accordance with the proposed transition state (T#). The expulsion of RO− anion in the rate-determining step is assisted by intramolecular hydrogen-bonding with the ammonio-hydrogen present in the intermediate T#.
制备了 2,4-二硝基苯氧基衍生物 12-16 和 5-硝基-2-吡啶氧基衍生物 18-22。通过元素分析、红外光谱和核磁共振对产物进行了鉴定。12-16 和 18-22 以吗啉为亲核体,在 CH3CN 中发生亲核芳香取代反应,分别得到 N-(2,4-二硝基苯基)吗啉 (23) 和 N-(5-硝基-2-吡啶基)吗啉 (24)。在一定温度范围内对这些反应在 CH3CN 中的动力学进行的分光光度测量表明,这些反应不是由吗啉催化的。12-16 和 18-22 与吗啉反应的布氏曲线图呈线性,斜率分别为 β12-16 = -1.58 ± 0.1 和 β18-22 = -1.15 ± 0.25。与反应活性最低的底物相比,这些相对速率常数以及较低的负β值都表明,齐聚物中间体的分解是一个缓慢的过程。低活化参数(ΔH# 和 ΔS#)与提出的过渡态(T#)相符。在决定速率的步骤中,RO- 阴离子的排出是通过分子内氢键与中间体 T# 中的氨氢结合来实现的。