Functionalized 4-benzylated pyridines can be efficiently prepared by a transition-metal-freecross-coupling between various benzylic zinc chlorides and substituted 4-cyanopyridines in THF/DMPU under microwave irradiation (40 °C, 0.5–1.5 h). Selective benzylations on polycyano-aromatics have also been achieved under these mild conditions. We also report a novel oxidative nucleophilic substitution of
Lewis Acid Promoted Benzylic Cross-Couplings of Pyridines with Aryl Bromides
作者:Stéphanie Duez、Andreas K. Steib、Sophia M. Manolikakes、Paul Knochel
DOI:10.1002/anie.201103074
日期:2011.8.8
Either ZnCl2, Sc(OTf)3 , or BF3⋅OEt2 can promote the palladium‐catalyzed arylation of methylpyridines and related heterocycles (see example). The complexation of the Lewisacid to the nitrogen atom in the heterocycle facilitates the reductive elimination, leading to various arylated pyridines in high yields. BF3⋅OEt2 was also found to promote highly regioselective metalations in the case of 2,4‐lutidine
Synthesis of 4-benzylpyridines via Pd-catalyzed CH<sub>3</sub>-arylation of 4-picoline
作者:Jing Wu、Dadian Wang、Xiang Chen、Qingwen Gui、Hua Li、Ze Tan、Genping Huang、Guangwei Wang
DOI:10.1039/c7ob01726j
日期:——
A highly efficient synthesis of 4-benzylpyridines was developed via Pd-catalyzed C(sp3)–H arylation between 4-picoline and aryl halides. It was found that the best yields were achieved with a simple Pd(PPh3)4 catalyst and Cs2CO3 as the base.
Palladium‐Catalyzed Benzylic C(sp<sup>3</sup>)−H Carbonylative Arylation with Aryl Bromides
作者:Bowen Hu、Haoqiang Zhao、Yu Wu、Patrick J. Walsh
DOI:10.1002/anie.202300073
日期:2023.6.5
A novel, selective and high-yielding palladium-catalyzedcarbonylative arylation of a variety of weakly acidic (pKa 25–35 in DMSO) benzylic and heterobenzylic C(sp3)−H bonds with arylbromides has been achieved. Comprehensive mechanistic studies identified the catalyst resting state and the turnover-limiting step while catalytic intermediates were also isolated.