芳烃硫醇的亲核性可以通过与“裸”卤化物阴离子的氢键结合来增强。卤化物阴离子的活性遵循F(-)>> Cl(-)约Br(-)约I(-)的顺序,并取决于抗衡阳离子(Bu(4)N约Cs约K> Na >> Li )。溶剂在亲核活化以及有效亲核试剂(例如ArS(-))的再生中起着重要作用,而那些具有高介电常数,高分子极化率,高施主数(DN)和低受体数(AN)的溶剂最有效的。烷基/芳基酯和芳基烷基醚的选择性脱保护可在非水解和中性条件下通过在催化量的KF存在下,在1-甲基-2-吡咯烷酮(NMP)中用苯硫酚处理来实现。
triplet energy was greatly improved, and then, it could markedly promote the efficient geometrical isomerization of alkenes from the E-isomer to the Z-isomer. Moreover, it was also effective for energy-transfer-mediated organometallic catalysis, which allowed realization of the cross-coupling of aryl bromides and carboxylic acids through efficient energy transfer from HiBRCP to nickel complexes. Thus, the
Aminolysis of 2,4-Dinitrophenyl X-Substituted Benzoates and Y-Substituted Phenyl Benzoates in MeCN: Effect of the Reaction Medium on Rate and Mechanism
作者:Ik-Hwan Um、Sang-Eun Jeon、Jin-Ah Seok
DOI:10.1002/chem.200500647
日期:2006.1.23
indicating that the electronic nature of the substituent X in the nonleaving group does not affect the rate-determining step (RDS) or reactionmechanism. The Hammett correlation with sigma- constants also exhibits good linearity with a large slope (rho(Y) = 3.54) for the reactions of 2 a-h with piperidine, implying that the leaving-group departure occurs at the rate-determining step. Aminolysis of 2,4-dinitrophenyl
A new boron-based photocatalyst has been applied in metallaphotoredox catalyzed carbon–oxygen bond construction reactions.
一种新的基于硼的光催化剂已被应用于金属光氧化还原催化的碳-氧键构建反应中。
Kinetics and Mechanism of Nucleophilic Displacement Reactions of Y-Substituted Phenyl Benzoates with Cyanide Ion
作者:Song-I Kim、Eun-Hee Kim、Ik-Hwan Um
DOI:10.5012/bkcs.2010.31.03.689
日期:2010.3.20
Discussion The kinetic study was performed spectrophotometrically. All reactions proceeded with quantitative liberation of Y-substituted phenoxide ion (and/or its conjugate acid) under pseudo-first- order conditions (i.e., the nucleophile concentration in excess over the substrate concentration). The reactions obeyed first- order kinetics and pseudo-first-order rate constants (
Y 取代苯甲酸苯酯 (1) 和苯硫代苯甲酸苯酯 (2) 与 CN 反应的二级速率常数汇总 - 在 80 mol % H 2 O/20 mol % DMSO 中,温度为 25.0 ± 0.1 o C a entry Y p K a 10 2 k CN- / M –1 s –1 12a 4-MeO 10.20 0.843 b 2.13 b 4-Me 10.19 0.783 b 1.89 c 3-CH 3 10.08 0.724 - d H 9.95 1.02 b 2.75 e 4-Cl 9.38 2.32 - f 3-COMe 9.19 3.59 b - g 3-Cl 9.02 4.19 - h 3-CHO 8.98 3.93 - i 4-COOEt 8.50 6.07 - j 3-NO 2 8.35 14.1 b 18.0 k 4-COMe 8.05 7.68 b 7.88 l 4-CN 7
Aminolysis of Y-Substituted Phenyl X-Substituted Cinnamates and Benzoates: Effect of Modification of the Nonleaving Group from Benzoyl to Cinnamoyl
4-dinitrophenyl X-substituted cinnamates (1a, 1c, and 1e) with amines are curved with a decreasing βnuc value from 0.65 to 0.3−0.4. The reactions of Y-substituted phenyl cinnamates (3a−g) with morpholine also result in a curved Brønsted plot, while the corresponding reactions of Y-substituted phenyl benzoates (4a−e) exhibit a linear Brønsted plot. It has been concluded that the curved Brønsted plots found