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| PAPER | Synthesis 2006: 1283-1288
DOI: 10.1055/s-2006-926407 |
© Georg Thieme Verlag Stuttgart · New York
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Microwave-Assisted Oxidative Aromatization of Hantzsch 1,4-Dihydropyridines using Manganese Dioxide
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| Mark C. Bagley*, M. Caterina Lubinu |
School of Chemistry, Main Building, Cardiff University, Park Place, Cardiff, CF10 3AT, UK
Fax: +44(29)20874030; e-Mail: Bagleymc@cardiff.ac.uk;
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Received
14 October 2005 |
Abstract
4-Aryl- and 4-alkyl-1,4-dihydropyridines, prepared by microwave-assisted Hantzsch reaction, are readily and efficiently aromatized in only one minute using commercial manganese dioxide in the absence of an inorganic support at 100 °C under microwave irradiation. This rapid procedure is more efficient than microwave-assisted aromatization using Pd/C, iodine or o-iodoxybenzoic acid (IBX) and gives the dehydrogenated or 4-dealkylated product in 91-100% yield (13 examples). Key words
aromatization - Hantzsch dihydropyridines - heterocycles - microwave synthesis - oxidation
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