Diels-Alder reactions using supercritical water as an aqueous solvent medium
作者:Michael B. Korzenski、Joseph W. Kolis
DOI:10.1016/s0040-4039(97)01274-4
日期:1997.8
A variety of Diels-Alderreactions have been performed in supercritical water as a reaction medium. The rapid reaction of Diels-Alderreactions of cyclopentadiene and various electron poor dienophiles such as diethyl fumarate and acrylonitrile is observed in supercritical water, and leads to high yields of clean products without added catalysts.
characterisation of new hydrogen-bond-rich ionicliquids and studies of their catalytic performance in Diels–Alderreactions are described. D-Glucose and chloroalcohols were used as the raw materials and as the sources of hydroxyl groups for the synthesis of ionic-liquid cations, whereas weakly coordinating bis(trifluoromethylsulfonyl)imide was used as the anion. The new ionicliquids were analysed by 1H and 13C
描述了新型富氢键离子液体的合成,表征以及它们在Diels–Alder反应中的催化性能的研究。D-葡萄糖和氯醇被用作合成离子-液体阳离子的原料和羟基的来源,而弱配位的双(三氟甲基磺酰基)酰亚胺被用作阴离子。用1 H和13分析新的离子液体通过13 C NMR光谱和ESI-MS实验,证实了它们的结构。此外,通过差示扫描量热法和热重分析法测得的离子液体的热数据表明,这些化合物在-29°C至-16°C的温度范围内倾向于形成玻璃,并且在环境温度下具有热稳定性。到至少430°C,最有可能是因为存在双(三氟甲基磺酰基)酰亚胺阴离子。研究了离子液体在环戊二烯与马来酸二乙酯或丙烯酸甲酯的模型反应中的性能。所研究的离子液体即使以催化量存在(相对于亲双烯体为4摩尔%)也显示出高活性。离子液体结构中存在的羟基数目的增加导致更高的反应速率。
Design, Synthesis, and Self-Assembly of Polymers with Tailored Graft Distributions
作者:Alice B. Chang、Tzu-Pin Lin、Niklas B. Thompson、Shao-Xiong Lennon Luo、Allegra L. Liberman-Martin、Hsiang-Yun Chen、Byeongdu Lee、Robert H. Grubbs
DOI:10.1021/jacs.7b10525
日期:2017.12.6
polymerization (ROMP). One-pot copolymerization of an ω-norbornenyl macromonomer and a discrete norbornenyl comonomer (diluent) provides opportunities to control the backbone sequence and therefore the side chain distribution. Toward sequence control, the homopolymerizationkinetics of 23 diluents were studied, representing diverse variations in the stereochemistry, anchor groups, and substituents. These
接枝密度和接枝分布影响聚合物的链尺寸和物理性能。然而,实现对这些结构参数的精确控制提出了长期的综合挑战。在本报告中,我们介绍了一种通过接枝开环复分解聚合(ROMP)来合成具有定制结构的聚合物的通用策略。ω-降冰片烯大分子单体和离散的降冰片烯基共聚单体(稀释剂)的一锅共聚提供了控制主链序列并因此控制侧链分布的机会。为了控制序列,研究了23种稀释剂的均聚动力学,这些动力学代表了立体化学,锚定基团和取代基的各种变化。这些修饰将均聚速率常数调整到2个数量级以上(0。–1 s –1 < k homo <82 M –1 s –1)。通过互补的机理和密度泛函理论(DFT)研究确定并阐明了速率趋势。在此基础上,通过将选定的稀释剂与聚(d,l-丙交酯)(PLA),聚二甲基硅氧烷(PDMS)或聚苯乙烯(PS)大分子单体。交叉传播速率常数是根据Mayo-Lewis终端模型通过瞬时共聚单体浓度的非线性最小二乘拟合
Stereospecificity and Concertedness of Retro-Diels-Alder Fragmentation in Some Diester Systems Upon Chemical Ionization
Retro-Diels-Alder (RDA) fragmentation of cis- and trans-2,3-diethoxycarbonyl-5,6,7,8-dibenzobicyclo[2.2.2]octanes under isobutane and methane chemical ionization conditions is highly stereospecific, giving rise to protonated diethyl maleate and fumarate, respectively. This behaviour indicates a single-step concerted mechanism, analogous to the ground-state RDA process that occurs in neutral molecules in the condensed phase. The analogous dissociation is partially stereospecific in stereoisomeric endo-, exo- and trans-2,3-diethoxycarbonylbicyclo[2.2.1]heptanes and non-stereospecific in endo-, exo- and trans-2,3-diethoxycarbonyl-5,6-benzobicyclo[2.2.2]octanes, indicating the involvement of a stepwise mechanism in the latter two systems. The different behaviour of the above systems is explained in terms of the energy of the RDA fragmentation. The differentiation and quantitative estimates of protonated diethyl maleate and fumarate were obtained from collision-induced dissociation measurements.