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DOI: 10.1055/s-1989-27164
Indoliziniumsalze und Heteroanaloga durch Anellierung heterocyclischer α-Methylimine mit 3-Alkoxyacroleinen
Publikationsverlauf
Publikationsdatum:
17. September 2002 (online)
Indolizinium Salts and Heteroanalogues by Annulation of Heterocyclic α-Methylimines with 3-Alkoxyacroleins Lithiated 2-Methyl-Δ1-pyrroline(1), 2-methyl-2-oxazoline(2), 2-methyl-2-thiazoline(3), and 1,2-dimethylimidazole (4) add to 3-alkoxyacroleins 5 to yield 3-alkyl-4-ethoxy-3-buten-2-ols 6, 7, 8, and 9 substituted by the starting heterocycles. These intermediates undergo cyclization with hydroiodic acid to afford dihydroindolizinium-, dihydrooxazolo[3,2-a]pyridinium-, dihydrothiazolo[3,2-a]pyridinium-, and imidazol[1,2-a]pyridinium iodides 10, 11, 12, and 14 in moderate to good yields. Thus a pyridinium ring is annulated on to a five-membered nitrogen heterocycle. 1H-NMR and 13C-NMR assignments are tabulated.