synthesis of 6-nitroderivatives of oxazolo[3,2-a]-pyridines and their reactions with nucleophiles合成的6-nitroderivatives oxazolo(3 a)-pyridines和他们的反应与亲核试剂.pdfVIP

Molecules 2003, 8, 460-466 molecules ISSN 1420-3049 Second Eurasian Meeting on Heterocyclic Chemistry ìHeterocycles in Organic and Combinatorial Chemistryì Synthesis of 6-Nitroderivatives of Oxazolo[3,2-a]-pyridines and Their Reactions with Nucleophiles Alexander A. Bush and Eugene V. Babaev* Chemistry Department, Moscow State University, Moscow 119899, Russia * Author to whom correspondence should be addressed; e-mail: babaev@org.chem.msu.su Received: 13 May 2003; in revised form: 17 June 2003 / Accepted: 17 June 2003 / Published: 30 June 2003 Abstract: 5-Nitro-2-pyridone can be selectively N-phenacylated, and the resulting phenacylpyridones I undergo cyclization to 6-nitrooxazolo[3,2-a]pyridinium salts II. These salts II readily react with ammonia and aliphatic amines leading to the products of pyridine ring opening - previously unknown 1-amino-2-nitro-4-(oxazole-2-yl)butadienes-1,3. Reaction of salts II with water lead to hydrolytic cleavage of the oxazole fragment. Keywords: 5-Nitro-2-pyridone, oxazolo[3,2-a]pyridine, butadiene, nitrodiene, aminodiene, oxazolyldiene. Introduction The aromatic oxazolo[3,2-a]pyridinium ring system, first prepared by Bradsher [1] and Kroehnke [2], has attracted recent attention due to its several modes of reaction with nucleophiles and the possibility of obtaining a wide variety of heterocyclic structures (oxazoles, pyridines, indolizines, various azolopyridines and azinopyridines) starting from this bicyclic system (for a review, see [3]). The key feature of the reactivity of the oxazolo[3,2-a]pyridi