Kinetic Investigation of Oxidation of Aromatic Anils by Potassium Peroxymonosulfate in Aqueous Acidic Medium
作者:R. Venkatesh、K. Karunakaran
DOI:10.1002/kin.20794
日期:2013.8
The kinetics of oxidation of aromaticanils to benzaldehyde and azobenzene by potassium peroxymonosulfate has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. It has been found that the variation in the ionic strength of the reaction has a negligible effect on the rate. Similarly, polymerization was not observed when acrylonitrile was
在过乙酸水溶液中,研究了过氧一硫酸钾将芳香族苯酚氧化为苯甲醛和偶氮苯的动力学。介质的低介电常数有助于反应。已经发现,反应离子强度的变化对速率的影响可以忽略。类似地,当将丙烯腈添加到反应混合物中时,未观察到聚合。该观察结果排除了反应中任何自由基的形成。Mn(II)的添加增加了反应速率,这表明参与了两个电子转移。高度负∆ S #值表示结构化的过渡状态。注意到哈米特图的偏差,并且获得了在苯胺部分中具有取代基的茴香的凹向下曲线。观察到的log k obs对σ的断裂归因于过渡态,而对于苯甲醛部分以及苯胺和苯甲醛部分的组合中的取代基观察到了向上凹的曲线,并提出了合适的机理。
Oxidation of Aromatic Anils by Sodium Perborate in Aqueous Acetic Acid Medium
作者:R. Venkatesh、K. Karunakaran
DOI:10.14233/ajchem.2014.15506
日期:——
The kinetics of oxidation of 9 meta- and 15 para- substituted aromatic anils by sodium perborate were investigated in aqueous acetic acid medium. The reaction was second order with respect to aromatic anil and first order with respect to the sodium perborate. The increase of [H+] in this oxidation retards the rate of the reaction. The observed rate constant for the substituents were plotted against the Hammett constant, s and a non-linear concave downward curve was obtained for the anils with substituents in the aniline moiety. The observed break in the log kobs versus s was attributed to the transition state whereas the non-linear concave upward curve was observed for the substituents in the benzaldehyde moiety and a non-linear concave upward curve was observed for the substituents in the combination of aniline and benzaldehyde moiety. The electron withdrawing substituents fall on one side of the curve, having a negative r value and the electron releasing substituents fall on the other side, with a positive r value and a suitable mechanism was proposed.
<i>tert</i>-Butyl
Isocyanide as a Convertible Reagent in Ugi Reaction: Microwave-Assisted
Preparation of 5,6-Dihydropyrazolo[1,5-<i>a</i>]pyrazine-4,7-diones
tert-Butyl amides resulting from Ugi MCR of t-BuNC and 5-substituted-1H-pyrazole-3-carboxylic acids with various aldehydes and amines undergo cyclization into 5,6-dihydropyrazolo[1,5-a]pyrazine-4,7-diones in glacial acetic acid under microwave irradiation. This reaction is a remarkable case of neighboring-group-assisted cleavage of tert-butyl amides and demonstrates utility of t-BuNC as a new convertible isocyanide.
在微波辐照下,t-BuNC 和 5-取代-1H-吡唑-3-羧酸与各种醛类和胺类的 Ugi MCR 生成的叔丁基酰胺在冰醋酸中环化成 5,6-二氢吡唑并[1,5-a]吡嗪-4,7-二酮。该反应是邻位基团辅助叔丁基酰胺裂解的一个显著案例,并证明了 t-BuNC 作为一种新的可转化异氰酸酯的实用性。
The Willgerodt-Kindler Reaction in Water: High Chemoselectivity of Benzaldehydes over Acetophenones
作者:Kioumars Aghapoor、Farshid Mohsenzadeh、Golriz Khanalizadeh、Hossein R. Darabi
DOI:10.1007/s00706-006-0560-7
日期:2007.1
Water has been found for the first time as a useful solvent in the Willgerodt-Kindler (WK) reaction for the synthesis of benzothiomorpholides in high yield at 80 degrees C for 3h. This novel approach confronts the WK protocol with a new situation in which water not only is not regarded as a serious disadvantage but also is applied in this case as a useful solvent in the reaction. The basis of this finding is the presence of a methylene chain in the carbonyl substrates, which leads to the high reaction selectivity of benzaldehydes over acetophenones.
SmI<sub>2</sub>MEDIATED ALLYLATION OF ALDIMINES WITH ALLYL BROMIDE
作者:Byeong Hyo Kim、Rongbi Han、Ryun Ju Park、Kyung Ho Bai、Young Moo Jun、Woonphil Baik
DOI:10.1081/scc-100104829
日期:2001.1
In a mild reaction with SmI2, aldimines have been converted into homoallyl amines in good yields.