Mechanism of Catalytic Oxidation of Styrenes with Hydrogen Peroxide in the Presence of Cationic Palladium(II) Complexes
作者:Katherine L. Walker、Laura M. Dornan、Richard N. Zare、Robert M. Waymouth、Mark J. Muldoon
DOI:10.1021/jacs.7b05413
日期:2017.9.13
Kinetic studies, isotope labeling, and in situ high-resolution mass spectrometry are used to elucidate the mechanism for the catalytic oxidation of styrenes using aqueous hydrogen peroxide (H2O2) and the cationicpalladium(II) compound, [(PBO)Pd(NCMe)2][OTf]2 (PBO = 2-(pyridin-2-yl)benzoxazole). Previous studies have shown that this reaction yields acetophenones with high selectivity. We find that
Supercritical Carbon Dioxide: A Promoter of Carbon-Halogen Bond Heterolysis
作者:Thais Delgado-Abad、Jaime Martínez-Ferrer、Ana Caballero、Andrea Olmos、Rossella Mello、María Elena González-Núñez、Pedro J. Pérez、Gregorio Asensio
DOI:10.1002/anie.201303819
日期:2013.12.9
Amazing reaction medium: Supercritical carbon dioxide, with zero dipole moment, lower dielectric constant than pentane, and non‐hydrogen‐bonding behavior, ionizes carbon–halogen bonds, dissociates the resulting ion pairs, and escapes from capture by the carbocation intermediates at temperatures above 40 °C. These properties allow the observation of carbocation chemistry in the absence of acids.
We herein report a transition-metal-free cross-coupling between secondaryalkylhalides/mesylates and aryl/alkenylboronic acid, providing expedited access to a series of nonchiral/chiral coupling products in moderate to good yields. Stereospecific SN2-type coupling is developed for the first time with alkenylboronic acids as pure nucleophiles, offering an attractive alternative to the stereospecific
Isotope effects in nucleophilic substitution reactions. V. The mechanism of the decomposition of 1-phenylethyldimethylphenylammonium halides in chloroform
作者:Helen Alma Joly、Kenneth Charles Westaway
DOI:10.1139/v86-200
日期:1986.6.1
Secondary α and β hydrogen–deuterium kinetic isotopeeffects have been used together to show that the SN reaction between 1-phenylethyldimethylphenylammonium ion and bromide or iodide ion in chloro...
The discovery of a new [1,5] sigmatropic rearrangement is described. With the aid of a borane-based Lewis acid, the transiently generated C3 ammonium enolates undergo a sigmatropic [1,5] shift of benzylic, allylic and propargylic groups to provide access to trans-configured tetrahydroquinoline-4-ones with diastereoselectivity of >99 : 1. The reaction is investigated in kinetic, mechanistic and computational