- Manganese-Catalyzed Kumada Cross-Coupling Reactions of Aliphatic Grignard Reagents with N-Heterocyclic Chlorides
-
Herein we report the use of manganese(II) chloride for the catalytic generation of C(sp 2)-C(sp 3) bonds via Kumada cross-coupling. Rapid and selective formation of 2-alkylated N-heterocyclic complexes were observed in high yields with use of 3 mol% MnCl 2 THF 1.6 and under ambient reaction conditions (21 °C, 15 min to 20 h). Manganese-catalyzed cross-coupling is tolerant toward both electron-donating and electron-withdrawing functional groups in the 5-position of the pyridine ring, with the latter resulting in an increased reaction rate and a decrease in the amount of nucleophile required. The use of this biologically and environmentally benign metal salt as a catalyst for C-C bond formation highlights its potential as a catalyst for the late-stage functionalization of pharmaceutically active N-heterocyclic molecules (e.g., pyridine, pyrazine).
- Petel, Brittney E.,Purak, Merjema,Matson, Ellen M.
-
supporting information
p. 1700 - 1706
(2018/07/13)
-
- Fused pyrazino[2,3-b]indolizine and indolizino[2,3-b]quinoxaline derivatives; synthesis, structures, and properties
-
The synthesis of six new compounds incorporating either a pyrazino[2,3-b]indolizine or indolizino[2,3-b]quinoxaline core are reported in good yield (58-87%). The intermediates for the key cyclization reaction for one set of compounds (5a-c), with a sterically demanding 3,5-dimethylpyrazole group in the 5-position of the core, were found to be mono-substituted. These intermediates could be isolated and cyclized by heating under acid-catalyzed conditions. To further demonstrate the versatility of the chemistry, compounds 6a-c were synthesized in 58-68% yields. Compounds 5a-c are non-planar in solution and the solid-state, while 6a-c have close to planar conformations, pointing to weak hydrogen bonds between the acidic C-Hs and the adjacent azine nitrogen atoms. The cytotoxicity of the six newly synthesized and three previously prepared compounds was assessed against a human glioblastoma multiforme cell line.
- Bloch, Witold M.,Derwent-Smith, Stephanie M.,Issa, Fatiah,Morris, Jonathan C.,Rendina, Louis M.,Sumby, Christopher J.
-
scheme or table
p. 9368 - 9375
(2011/12/03)
-
- Homolytic alkylation of heteroaromatic bases : The problem of monoalkylation
-
The silver-catalyzed decarboxylation of carboxylic acids by persulphate leads to alkyl radicals, which have been utilized for the selective alkylation of heteroaromatic bases. The method is particularly efficient in a water-chlorobenzene two-phase system for two reasons : it considerably increases the selectivity in monoalkylation when more positions of high nucleophilic reactivity (i.e. α and γ) are available in the heterocyclic ring (i.e. quinoline , 4-cyano- and 4-ethylpyridine, pyrazine , quinoxaline etc.) and it determines a much higher efficiency for the radical sources when the silver salt catalysis is deactivated by complexation of the salt with the heterocyclic compound . The high selectivity in monoalkylation has been obtained by the combination of polar effects and the increased lipophilicity of the alkylated product, which makes its extraction from the aqueous solution by the organic solvent easier.
- Fontana,Minisci,Barbosa, M. C. Nogueira,Vismara
-
p. 2525 - 2538
(2007/10/02)
-
