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Paper | Regular issue | Vol 48, No. 8, 1998, pp.1581-1591
Published online, 1st January, 1970
DOI: 10.3987/COM-98-8190
Novel Complex N-Heterocycles via Intramolecular 1,5-Electrocyclizations: 1,2,3,4,4a,5,5a,10-Octahydropyrido-[4",3":2',3']cyclobuta[1',2':4,5]pyrrolo[2,3-b]pyridines

Harald Walter* and Carsten Sundermann

*Chemical Research Crop Protection, Business Unit Fungicides, Novartis Crop Protection AG, Postfach, CH-4002 Basel, Switzerland

Abstract

The synthesis of 2-amino-3-isopropenylpyridine (5) and 2-amino-5-chloro-3-isopropenylpyridine (6) and their toluenesulfonic acid catalyzed reactions in refluxing toluene with some 1-substituted piperidin-4-ones are described. The toluenesulfonic acid catalyzed reaction of the pyridine derivatives (5) and (6) with 1-benzyl-, 1-benzoyl- and 1-methylpiperidin-4-one lead to novel pyrrolo[2,3-b]pyridines (7-12) in good to excellent yields in diastereoisomeric pure form (Scheme 2, Table 1). An intramolecular 1,5-electrocyclization of the dipolar reactive intermediate (13) as a key step (Scheme 3) is proposed for the formation of the compounds (7-12).