NOVEL COMPLEX N-HETEROCYCLES VIA INTRAMOLECULAR 1,5-ELECTROCYCLIZATIONS - 1,2,4,4A,5,5A,10-OCTAHYDROPYRIDO[4'',3'' 2',3']-CYCLOBUTA[1',2' /4,5]PYRROLO[2,3-B]PYRIDINES/

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