- Acylation of 2-benzylpyridine N-oxides and subsequent in situ [3,3]-sigamatropic rearrangement reaction
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An effective method for the acylation of 2-benzylpyridine N-oxides and their fast in situ [3,3]-sigmatropic rearrangement was reported. This transformation has a wide substrate scope under mild conditions, giving moderate to excellent yields. The application for the synthesis of chiral phenyl-2-pyridylmethanol products was briefly explored. Furthermore, an interesting example of tandem substitution and in situ [3,3]-sigamatropic rearrangement of 2-benzylpyridine N-oxide with benzenecarboximidoyl chloride was reported.
- Antilla, Jon C.,Jing, Hua-qing,Li, Hong-liang
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- Visible-Light-Promoted Copper-Catalyzed Regioselective Benzylation of Pyridine N-Oxides versus Thermal Acylation Reaction with Toluene Derivatives
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Copper-catalyzed visible light mediated direct C–H bond benzylation of pyridine N-oxides with toluene derivatives was accomplished by recent developments in photochemical carbon–carbon bond formation through a photo-induced bond-dissociation strategy. Thi
- Kianmehr, Ebrahim,Gholamhosseyni, Maral
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p. 1559 - 1566
(2018/04/20)
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- Copper-Catalyzed Aerobic Oxygenation of Benzylpyridine N-Oxides and Subsequent Post-Functionalization
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A copper-catalyzed aerobic oxidation of benzylpyridine N-oxides is reported. The N-oxide moiety acts as a built-in activator for the benzylic methylene oxidation, without requirement of additives. Reaction conditions were identified which suppress undesired benzoylpyridine formation via N-deoxygenation involving intermolecular oxygen transfer. The versatility of the N-oxide group of the benzoylpyridine N-oxide reaction products for post-functionalization of the pyridine ring is demonstrated through efficient C–C, C–N, C–O and C–Cl bond forming procedures, with both nucleophiles and electrophiles. Finally, the applicability of the new synthetic methodology is demonstrated in an alternative route towards the antihistaminic drug Acrivastine via three consecutive N-oxide activated C–H functionalization processes, starting from picoline N-oxide. (Figure presented.).
- Sterckx, Hans,Sambiagio, Carlo,Médran-Navarrete, Vincent,Maes, Bert U. W.
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p. 3226 - 3236
(2017/09/13)
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- Palladium-catalyzed regioselective benzylation-annulation of pyridine N -oxides with toluene derivatives via multiple c-h bond activations: Benzylation versus arylation
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A palladium-catalyzed cross-dehydrogenative coupling (CDC) reaction of pyridine N-oxides with toluenes has been developed that operates under mild conditions. 2-Benzylpyridines can be obtained directly by this method via a CDC reaction between unactivated toluenes and pyridine N-oxides. In addition, azafluorene N-oxides, of value for future medicinal chemistry applications, can be obtained successfully by this procedure via four tandem C-H bond activations.
- Kianmehr, Ebrahim,Faghih, Nasser,Khan, Khalid Mohammed
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supporting information
p. 414 - 417
(2015/03/05)
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- Catalyst and base controlled site-selective sp2 and sp3 direct arylation of azine N-oxides
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Site-selective direct arylation of both sp2 and sp3 sites on azine N-oxide substrates is described. The arylation reactions are carried out in either a divergent manner or a sequential manner. The sp3 arylation reaction is applied to the synthesis of the natural products, papaverine and crykonisine, and a 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.
- Schipper, Derek J.,Campeau, Louis-Charles,Fagnou, Keith
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experimental part
p. 3155 - 3164
(2009/08/15)
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- Site-selective sp2 and benzylic sp3 palladium-catalyzed direct arylation
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Palladium-catalyzed site selective 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 for sp3 arylation. From these studies, the choice of base emerged as a pivotal component for site selectivity, pointing to its intimate involvement in the mechanism of direct arylation. These site selective reactions have been validated in both divergent and sequential derivatizations of heterocyclic compounds represent an attractive alternative to other routes to this class of molecule. Copyright
- Campeau, Louis-Charles,Schipper, Derek J.,Fagnou, Keith
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p. 3266 - 3267
(2008/10/09)
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