- One-pot double functionalisation of π-deficient heterocyclic lithium reagents
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Herein, we report an efficient method for the double functionalisation of lithiated halogenopyridines, -pyrazines or -furopyridines through a convenient one-pot electrophilic trapping/nucleophilic substitution sequence.
- Chartoire, Anthony,Comoy, Corinne,Fort, Yves
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experimental part
p. 1839 - 1845
(2011/04/26)
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- TMSCH2Li-LiDMAE: a new nonnucleophilic reagent for C-2 lithiation of halopyridines
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A new superbasic reagent has been discovered by combining TMSCH2Li and LiDMAE in hexane. This reagent was found highly efficient for the C-2 lithiation of sensitive chloro- and fluoropyridines. The metallation occurred chemo- and regioselectively at 0 °C avoiding the nucleophilic addition or substrate degradation commonly obtained with other alkyllithiums even at lower temperatures.
- Doudouh, Abdelatif,Gros, Philippe C.,Fort, Yves,Woltermann, Christopher
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p. 6166 - 6171
(2007/10/03)
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- Lithiation of 2-heterosubstituted pyridines with BuLi-LiDMAE: Evidence for regiospecificity at C-6
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The determination of the initial deprotonation site of 2-chloro- and 2-methoxypyridine during reaction with BuLi-LiDMAE has been investigated. A series of experiments on deuterated regioisomers revealed a direct lithiation at C-6 excluding a potential first classical ortholithiation and lithium equilibration in the reaction medium. These results suggested that the formation of lithium aggregates at the neighboring of the pyridinic nitrogen atom favored BuLi delivery at C-6 as well as 6-lithio intermediate stabilization.
- Gros, Philippe,Choppin, Sabine,Mathieu, Julien,Fort, Yves
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p. 234 - 237
(2007/10/03)
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- Unusual C-6 lithiation of 2-chloropyridine-mediated by BuLi-Me2N(CH2)2OLi. New access to 6-functional-2-chloropyridines and chloro-bis-heterocycles
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Formula Presented The reaction of 2-chloropyridine with alkylithium generally results in nucleophilic addition leading to the loss of chlorine atom while exclusive directed ortho metalation is obtained using LDA. Herein it is shown that the BuLi-Me2
- Choppin, Sabine,Gros, Philippe,Fort, Yves
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p. 803 - 805
(2007/10/03)
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- LIGAND EXCHANGE AND LIGAND COUPLING VIA THE ?-SULFURANE INTERMEDIATE IN THE REACTION OF ALKYL 2-PYRIDYL SULFOXIDE WITH GRIGNARD REAGENTS: CONVENIENT PREPARATION OF 2,2'-BIPYRIDINES
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The reaction between methyl 2-pyridyl sulfoxide (1) with Grignard reagents afforded 2,2'-bipyridine (2) in moderate yield.The reaction is considered to involve initial ligand exchange to generate 2-pyridylmagnesium halide which in the subsequent step attacks the original sulfoxide to form the ?-sulfurane that undergoes ligand coupling to afford 2.The reaction of t-butyl-2-pyridyl sulfoxide (3) with C6H5MgBr, however, gave only 2-phenylpyridine (4).This may due to steric hindrance to the initial ligand exchange.Formation of 2 is a convenient process for preparation of 2,2'-bipyridines bearing various substituents.
- Oae, Shigeru,Kawai, Tsutomu,Furukawa, Naomichi
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p. 123 - 132
(2007/10/02)
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- ipso-Substitution of a Sulphinyl or Sulphonyl Group Attached to Pyridine Rings and its Application for the Synthesis of Macrocycles
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A sulphinyl or sulphonyl group directly bound to the 2- or 4-position of a pyridine ring was readily displaced by several nucleophiles such as RO-, RS-, and CN- to afford the corresponding ipso-substitution products.Similarly, 2-halogeno-6-methylsulphinyl- or -methylsulphonyl-pyridines also react with nuclephiles to afford 2-halogeno-6-substituted pyridine derivatives.Thus, the leaving abilities of the leaving groups fall in the order RSO2 > RSO > Br ca.Cl >> RS (R = alkyl or benzyl).The ipso-substitution can be applied to the synthesis of 2,6-disubstituted pyridino macrocycles containing both carbon-oxygen and carbon-sulphur bridges, resulting in several new macrocycles in moderate yields.
- Furukawa, Naomichi,Ogawa, Satoshi,Kawai, Tsutomu,Oae, Shigeru
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p. 1839 - 1845
(2007/10/02)
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- SELECTIVE IPSO-SUBSTITUTION IN PYRIDINE RING AND ITS APPLICATION FOR THE SYNTHESIS OF MACROCYCLES CONTAINING BOTH OXA- AND THIA-BRIDGES
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Both the sulfinyl and sulfonyl groups directly bound to 2 or 4 position in pyridine were readily displaced by several nucleophiles such as RO(1-) and RS(1-) .The facility of the leaving groups is RSO2 = RSO > Br = Cl >> RS (R:alkyl or benzyl).The ipso-substitution could be applied for the synthesis of new type of 2,6-disubstituted macrocycles containing both carbon-oxygen and carbon-sulfur bridges in moderate yields.
- Furukawa, Naomichi,Ogawa, Satoshi,Kawai, Tsutomu,Oae, Shigeru
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p. 3243 - 3246
(2007/10/02)
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