- Radical chain monoalkylation of pyridines
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The monoalkylation of N-methoxypyridinium salts with alkyl radicals generated from alkenes (via hydroboration with catecholborane), alkyl iodides (via iodine atom transfer) and xanthates is reported. The reaction proceeds under neutral conditions since no acid is needed to activate the heterocycle and no external oxidant is required. A rate constant for the addition of a primary radical to N-methoxylepidinium >107 M-1 s-1 was experimentally determined. This rate constant is more than one order of magnitude larger than the one measured for the addition of primary alkyl radicals to protonated lepidine demonstrating the remarkable reactivity of methoxypyridinium salts towards radicals. The reaction has been used for the preparation of unique pyridinylated terpenoids and was extended to a three-component carbopyridinylation of electron-rich alkenes including enol esters, enol ethers and enamides.
- Dénès, Fabrice,Jangra, Harish,Meléndez, Camilo,Mulliri, Kleni,Renaud, Philippe,Rieder, Samuel,Zipse, Hendrik
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p. 15362 - 15373
(2021/12/14)
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- The AZARYPHOS family of ligands for ambifunctional catalysis: Syntheses and use in ruthenium-catalyzed anti-markovnikov hydration of terminal alkynes
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The family of AZARYPHOS (aza-aryl-phosphane) phosphane ligands, containing a phosphine unit and sterically shielded nitrogen lone pairs in the ligand periphery, is introduced as a tool for developing ambifunctional catalysis by the metal center and nitrogen lone pairs in the ligand sphere. General synthetic strategies have been developed to synthesize over 25 examples of structurally diverse (6-aryl-2pyridyl)phosphanes (ARPYPHOS), (6alkyl-2-pyridyl)phosphanes (ALPY-PHOS), 4,6-disubsituted l,3-diazin-2ylphosphanes or l,3,5-triazin-2- ylphosphanes, quinazolinylphosphanes, quinolinylphosphanes, and others. The scalable syntheses proceed in a few steps. The incorporation of AZARYPHOS ligands (L) into complexes [RuCp(L)2(MeCN)][PF6] (Cp = cyclopentadieny1)gives catalysts for the anti-Markovnikov hydration of terminal alkynes of the highest known activities. Electronic and steric ligand effects modulate the reaction kinetics over a range of two orders of magnitude. These results highlight the importance of using structurally diverse ligand families in the process of developing cooperative ambifunctional catalysis by a metal and its ligand.
- Hintermann, Lukas,Dang, Tuan Thanh,Labonne, Aurelie.,Kribber, Thomas,Xiao, Li,Naumov, Pance
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supporting information; experimental part
p. 7167 - 7179
(2010/02/28)
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- 6-Alkyl-N,N-disubstituted-2-pyridinamines as anticonvulsant agents
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The anticonvulsant effect of a series of 6-alkyl-N,N-disubstituted-2-pyridinamines is described. An investigation was carried out to optimize the anticonvulsant activity and reduce behavioral side effects in this series. Three compounds (7, 8, 10; Table I) were selected from initial screening for a more complete pharmacological evaluation. While each of these compounds was a potent anticonvulsant agent with ED50 values from 5 to 10 mg/kg, the activity was accompanied by significant behavioral side effects including decreased spontaneous locomotion, ataxia, and ptosis.
- Pavia,Taylor,Lobbestael
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p. 1237 - 1242
(2007/10/02)
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