- New in situ trapping metalations of functionalized arenes and heteroarenes with TMPLi in the presence of ZnCl2 and other metal salts
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The addition of TMPLi to a mixture of an aromatic or heteroaromatic substrate with a metal salt such as MgCl2, ZnCl2, or CuCN at -78 °C first leads to lithiation of the arene followed by transmetalation with the metal salt to afford functionalized organometallic compounds of Mg, Zn, or Cu. This in situ trapping method allows an expedited metalation (-78 °C, 5 min) of a range of sensitive pyridines (bearing a nitro, ester, or cyano group) and allows the preparation of kinetic regioisomers of functionalized aromatic compounds or heterocycles not otherwise available by standard metalating agents, such as TMPMgCl·LiCl or TMPZnCl·LiCl. Fast, faster, the fastest: Aromatic and heterocyclic substrates, when treated with TMPLi (TMP=2,2,6,6-tetramethylpiperidyl), undergo a kinetic lithiation and then a transmetalation with a metal salt such as MgCl2, ZnCl 2, or CuCN. This allows an expedited metalation of sensitive pyridines bearing a nitro, ester, or cyano group and allows the preparation of kinetic regioisomers of functionalized aromatic compounds or heterocycles.
- Frischmuth, Annette,Fernandez, Maitane,Barl, Nadja M.,Achrainer, Florian,Zipse, Hendrik,Berionni, Guillaume,Mayr, Herbert,Karaghiosoff, Konstantin,Knochel, Paul
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supporting information
p. 7928 - 7932
(2014/08/05)
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- Regiocontrolled SNAr reaction on 2,3-dihalopyridines with NaSMe to obtain bromo(methylthio)pyridines as key precursors of 3-halo-2-(hetero) arylthieno[2,3- b ]pyridines and thieno[3,2- b ]pyridines
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The synthesis of 3-halo-2-(hetero)arylthieno[2,3-b]pyridines and 3-halo-2-(hetero)arylthieno[3,2-b]pyridines has been performed through a three-step methodology from 3-bromo-2-chloropyridine or 2-bromo-3- fluoropyridine, respectively. The key step of this methodology is the formation of the required bromo(methylthio)pyridines by a regiocontrolled nucleophilic aromatic substitution (SNAr) with sodium methanethiolate (NaSMe). Then, the Sonogashira coupling with (hetero)arylalkynes followed by a halocyclization with bromine or iodine, afforded the expected 3-halo-2-(hetero)arylthienopyridines.
- Begouin, Agathe,Peixoto, Daniela,Queiroz, Maria-Joao R. P.
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p. 1489 - 1496
(2013/07/19)
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- BENZIMIDAZOLE DERIVATIVES
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A compound of formula (I) or a pharmaceutically acceptable salt or prodrug ester thereof: (I) wherein R, X and Y are as disclosed in the specification.
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Page/Page column 16
(2008/06/13)
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