Enantioselective direct Mannich-type reactions of 2-benzylpyridine N-oxides catalyzed by chiral bis(guanidino)iminophosphorane organosuperbase
作者:Qiupeng Hu、Azusa Kondoh、Masahiro Terada
DOI:10.1039/c8sc00808f
日期:——
pronucleophiles for the first time in enantioselective addition reactions under Brønsted base catalysis. A chiral bis(guanidino)iminophosphorane was able to overcome the inherent issue of low acidity of the pronucleophiles, establishing the diastereo- and enantioselective direct Mannich-type reaction with N-Boc imines. The control experiments indicated that the N-oxide moiety of the substrates played
Palladium-catalyzed C-H couplings (C SP ³ -C SP ² ) of pyridine N-oxides with benzyl chloride derivatives is reported. It provides a novel and easy process for the synthesis of 2-benzylpyridine derivatives through benzylic cross-couplings of pyridine N-oxides.
Site-Selective sp<sup>2</sup> and Benzylic sp<sup>3</sup> Palladium-Catalyzed Direct Arylation
作者:Louis-Charles Campeau、Derek J. Schipper、Keith Fagnou
DOI:10.1021/ja710451s
日期:2008.3.1
Palladium-catalyzed siteselective arylation reactions of both sp2 and benzylic sp3 sites on azine and diazine N-oxide substrates are described that occur in good to excellent yield and with complete selectivity for reaction at the desired position. These studies have uncovered the need to properly control the metal to ligand ratio in sp2 arylation and necessitated a complete reinvestigation of all reaction parameters
Catalyst and base controlled site-selective sp2 and sp3 direct arylation of azine N-oxides
作者:Derek J. Schipper、Louis-Charles Campeau、Keith Fagnou
DOI:10.1016/j.tet.2008.12.004
日期:2009.4
Site-selective direct arylation of both sp(2) and sp(3) sites on azine N-oxide substrates is described. The arylation reactions are carried out in either a divergent manner or a sequential manner The sp arylation reaction is applied to the synthesis of the natural products, papaverine and crykonisine, and. rationale for low reactivity of electron-deficient aryl halides is provided. Mechanistic investigations point toward the intimate involvement of the base in the mechanism of these reactions. (C) 2008 Published by Elsevier Ltd.
Palladium-Catalyzed (<i>N</i>-Oxido-2-pyridinyl)methyl Transfer from 2-(2-Hydroxyalkyl)pyridine<i>N</i>-Oxide to Aryl Halides by β-Carbon Elimination