A solid-phase synthesis of substituted cyclic urea derivatives as potential heterocyclic library scaffolds is described. 2-Amino-3-nitropyridine is attached to Wang resin via a carbamate linkage. Reduction of the nitro group was achieved with SnCl(2).2H(2)O. Reductive alkylation with a range of substituted benzaldehydes followed by cyclative cleavage afforded a small library of 3-substituted imidazo[4,5-b]pyridine-2-ones in 33-45% yield and 59-88% purity. Subsequently, this methodology was applied to the synthesis of 3-substituted imidazo[4,5-f]quinolin-2-ones.
Die Oxidationsstabilität von einzelnen Fettsäuremethylestern kann durch die Bestimmung der Induktionsperiode mittels der Active Oxygen Method verglichen werden. Die Bestimmung der flüchtigen und öllöslichen Säuren über einen Zeitraum weit über die Induktionsperiode hinaus zeigt, daß sich die Werte einem Grenzwert nähern. Selbst wenn sich die Proben im Fettsäuremuster nur unwesentlich unterscheiden, ist ersichtlich, daß sich die verschiedenen Herstellungsverfahren mehr oder weniger ungünstig auf den Gehalt der Tocopherole auswirken. Versuche unter Lichteinfluß haben deutlich gemacht, daß bei der Lagerung ein Ausschluß von Licht bei weitem entscheidender ist als ein Ausschluß von Luft.
Use of Polymer-Supported Thiophenol for the Synthesis and Purification of a Benzimidazol-2-one Library.-Monosubstituted benzimidazol-2-ones (III) are prepared by an efficient solution-phase synthesis involving alkylation or acylation of the benzimidazole-1-carboxylate (I), purification with polymer-supported thiophenol to remove excess halides, and hydrolysis of the carboxylate ester. The methodology can be extended to the alkylation of the second nitrogen [cf. (IV)] in order to increase the diversity of molecules in the library. -(ERMANN, MONIKA; SIMKOVSKY, NADJA M.; ROBERTS, STANLEY M.; PARRY, DAVID M.; BAXTER, ANDY D.; MONTANA, JOHN G.; Tetrahedron Lett. 41 (2000) 14, 2483-2485; Dep. Chem., Univ. Liverpool, Liverpool L69 3BX, UK; EN)
Pyridine derivativesPyridine derivatives R 0380 Some Regioselective Cross-Coupling Reactions of Halopyridines and Halopyrimidines. -Several N-heterocyclic biaryls are prepared from bromides (I) or (IV) by lithiation in the appropriate solvent (Et 2 O or THF), generation of intermediate organozinc bromides via metal-metal exchange of the lithiated compounds, and palladium-catalyzed coupling with mono-and dichloro pyridines and pyrimidines. In the cases of dichloro compounds, regioselective coupling occurs. -(SIMKOVSKY*, N. M.; ERMANN, M.; ROBERTS, S. M.; PARRY, D. M.; BAXTER, A. D.; J.
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