1643-69-2Relevant academic research and scientific papers
Meta C-H Arylation of Electron-Rich Arenes: Reversing the Conventional Site Selectivity
Liu, Luo-Yan,Qiao, Jennifer X.,Yeung, Kap-Sun,Ewing, William R.,Yu, Jin-Quan
, p. 14870 - 14877 (2019/10/02)
Controlling site selectivity of C-H activation without using a directing group remains a significant challenge. While Pd(II) catalysts modulated by a mutually repulsive pyridine-type ligand have been shown to favor the relatively electron-rich carbon centers of arenes, reversing the selectivity to favor palladation at the relatively electron-deficient positions has not been possible. Herein we report the first catalytic system that effectively performs meta C-H arylation of a variety of alkoxy aromatics including 2,3-dihydrobenzofuran and chromane with exclusive meta site selectivity, thus reversing the conventional site selectivity governed by native electronic effects. The identification of an effective ligand and modified norbornene (NBE-CO2Me), as well as taking advantage of the statistics, are essential for achieving the exclusive meta selectivity.
Structural Effects on the Transition States of Imine-Forming Eliminations in N-Substituted O-(Arylsulfonyl)hydroxylamines
Hoffman, Robert V.,Shankweiler, Jean M.
, p. 4019 - 4022 (2007/10/02)
A series of amines with various alkyl and aryl substituents at C-1 were converted to the corresponding N-(arylsulfonoxy)amines, which served as precursors for base-promoted, imine-forming elimination.By varying the bases used to promote the elimination and by varying the leaving groups attached to nitrogen, the Broensted parameters β and βlgCH3 were determined.These were used to locate the transition state on the More O'Ferrall-Jencks energy surface for elimination.Substituents were found to influence the structure of the activated complex markedly.Resonance effects were most important, while inductive effects had little influence .
