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Note | Regular issue | Vol 48, No. 8, 1998, pp.1649-1658
Published online, 1st January, 1970
DOI: 10.3987/COM-98-8189
Novel Synthesis of Polyfunctionalized 1,4,4a,9a-Tetrahydro-1-aza-9-oxafluorenes by Unexpected Cycloaddition of 4-(4-Methoxyphenyl)-1,4-dihydropyridines and p-Benzoquinone

Andreas Hilgeroth,* Krystina Kuna, and Uwe Kuckländer

*Institute of Pharmaceutical Chemistry, Department of Pharmacy, Martin-Luther-University Halle-Wittenberg, Wolfgang-Langenbeck-Str. 4, 06120 Halle, Germany


A surprising acid-catalysed cycloaddition reaction occurs between 3,5-diacetyl-4-(4-methoxyphenyl)-1,4-dihydropyridine (4) and p-benzoquinone in dioxane/HClO4 (5%) yielding novel polyfunctionalized 1,4,4a,9a-tetrahydro-1-aza-9-oxafluorenes (9) as exclusive products. On the other hand the corresponding 4-unsubstituted 1,4-dihydropyridine (1) is oxidized by p-benzoquinone. Novel structures are characterized by standard spectroscopy and, furthermore, confirmed by acetylation. The different reactivity of the 4-substituted and 4-unsubstituted derivatives is dicussed on the basis of semiempirical MNDO calculations and redox potentials.