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Synthesis 1993; 1993(1): 111-116
DOI: 10.1055/s-1993-25811
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Sukzessiver Aufbau polycyclischer Molekülstrukturen: 1,2,3,5,6,7-Hexahydroimidazo [1,2-a]-pyridin-8-carbonsäureethylester zur Synthese von Imidazo-naphthyridinen, -azocinen, Tri- und Tetraazaacenaphthylenen und Triazacyclooct[cd]indenen

Heinrich Wamhoff* , Wolfram Lamers
  • *Institut für Organische Chemie und Biochemie der Universität Bonn, Gerhard-Domagk-Strasse 1, D-5300 Bonn 1, Germany
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Publication Date:
17 September 2002 (online)

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Successive Construction of Polycyclic Molecules: Ethyl 1,2,3,5,6,7-Hexahydroimidazo[1,2-a]pyridine-8-carboxylate for the Synthesis of Imidazonaphthyridines, -azocines, Tri- and Tetraazaacenaphthylenes and Triazacyclooct[cd]indenes The imidazo[1,2-a]pyridine 1 gives with acetylenic esters the (imidazo [1,2-a]pyridin-8-yl)maleates 2a,b, the 4-oxoimidazo [1,2,3-ij][1,8]- naphthyridines 3a-c, and imidazo [1,2-a]azocine-8,9,10-tricarboxylates 7a,b, respectively, depending on the conditions applied. Compound 1 affords with dimethyl allene-1, 3-dicarboxylate analogously methyl 2-(1,2,4,7,8,9-hexahydro-4-oxoimidazo [1,2,3-ij][1,8]-naphthyridin-6-yl)acetate (3d). Treatment of 1 and 7b with isocyanates affords the heterocondensed 3,5-dioxo-2a,4, 8a-triazaacenaphthylenes 9a-d and 3,5-dioxo-2a,4, 10a-triazacyclooct[cd]indenes 10a,b. Analogously, 1,2,3,4,5,6,7,8- octahydro-3,5,6,8-tetraoxo-4, 7-diphenyl-2a,4,7,8a-tetraazaacenaphthylene (12) results from dimethyl (imidazolidin-2-ylidene)malonate (11). 2, 5-Dihydro-4H-1,2,4-triazole-3,5-dione 13 inserts in the 5-C-H bond of 3a,bd to give 5-(1,2,4-triazolidin-1-yl)imidazol[1,2,3-ij][1,8]naphthyridines 14a,b,d.