Influence of the Position of tert-Butyl Substituents on Reactivity of Quinone Dimers Yielding Dibenzofuran-1,4-diones
摘要:
Reactivity of two isomeric quinone dimers, 5,5'-di-tert-butyl-2,2'-bisbenzoquinone (2) and 6,6'-di-tert-butyl-2,2'-bisbenzoquinone (3) have been compared. Both quinone dimers underwent thermal cyclization in ethanol to give dibenzofuran-1,4-diones exclusively, the reaction proceeding faster for 3 than for 2. Molecular modeling analysis indicates that the different reactivity should be explained in terms of the steric hindrance of tert-butyl group in 2, which prevents approaching of solvent molecules to C=O moiety so that the solvent-assisted proton transfer occurs more slowly.
Synthesis, Structure, and Properties of Benzoquinone Dimer and Trimers Bearing t-Bu Substituents
摘要:
Highly soluble and stable quinone dimer and trimers were successfully yielded by introduction of t-Bu substituents. In X-ray structure analysis, the dimer quinone moiety was distorted into the boat shape, which was clarified by MO calculations. X-ray and UV/vis studies indicated that the covalently linked quinone moieties bear a large torsional angle. Nevertheless, the reduction potentials rose significantly with the order of monomer < dimer < trimer, indicating that the negative charge was efficiently delocalized within the radical anions.
Substituent effects in the oxidation of 2-alkyl-1,4-dialkoxybenzenes with ceric ammonium nitrate
作者:Brian E. Love、Alexander L. Simmons
DOI:10.1016/j.tetlet.2016.11.042
日期:2016.12
Increased steric size of alkyl groups and the presence of coordinating atoms on alkoxy groups have both been found to contribute to decreasing yields of diquinones upon reaction of 2-alkyl-1,4-dialkoxybenzenes with CAN. The overall hydrophilicity of the substrates does not appear to be a significant factor in determining the diquinone yield for these reactions.
Preparation of a series of substituted diquinones is reported. In most examples, inverse order of addition (addition of a dimethoxybenzene derivative to a CAN solution) has been found to produce higher yields of diquinones than the traditional protocol in which the oxidant is added to the arene.
A mixture of biquinone (QQn) and bihydroquinone (HHn) bearing tert-butyl substituents at 5,5′- (n = 1) and 6,6′-positions (n = 2) yields hydroquinonylquinone (HQn) as an equilibrium product by quinone/hydroquinone exchange. The equilibrium constants for the formation of HQ1 are higher than those of HQ2 in all solvents. While the exchange between QQ1 and HH1 is slow, that between HQ1s occurs so rapidly in CDCl3 that it is observed in phase-sensitive 2D NOESY NMR spectra.
Rechargeablebatteries using organiccathodematerials are expected to afford high mass energy densities since these materials can undergo multiple electron redox reactions per molecule. Although the batteries using benzoquinone (BQ) derivatives as organiccathode active materials exhibited high theoretical capacity, their practical capacities and cycle retention were far from satisfactory. To overcome
使用有机阴极材料的可充电电池有望提供高质量的能量密度,因为这些材料每个分子可以经历多次电子氧化还原反应。尽管使用苯醌(BQ)衍生物作为有机阴极活性材料的电池具有较高的理论容量,但其实际容量和循环保持率仍远远不能令人满意。为克服这些问题,合成了基于2,2'-双-对-苯醌(BBQ)骨架的二聚BQ衍生物,并研究了使用BBQs作为正极活性物质制备的电池的充放电行为。与基于BQ单体的电池相比,基于BBQ的电池表现出出色的性能。例如,烧烤室提供了358 A h kg -1的高初始容量(比使用LiCoO 2作为正极活性材料的现有锂离子电池的两倍多)和在50次循环下的198 A h kg -1的高循环保持率。电化学测量和密度泛函理论(DFT)计算表明,烧烤衍生物中通常会发生三个电子氧化还原反应,尽管(OMe)2 -BBQ似乎经历了四电子氧化还原反应。
Effects of reaction conditions on quinone/diquinone product ratios in the oxidation of 1,4-dimethoxybenzene derivatives with ceric ammonium nitrate
作者:Brian E. Love、Brian C. Duffy、Alexander L. Simmons
DOI:10.1016/j.tetlet.2014.02.017
日期:2014.3
Proper choice of reaction conditions allows formation of either the quinone or corresponding diquinone as the major product upon treatment of 2-alkyl-1,4-dimethoxybenzenes with ceric ammonium nitrate. (c) 2014 Elsevier Ltd. All rights reserved.