Abstract
The isomerization reaction of N-nonsubstituted (1 and 3), N-benzylated (4 and 5), and N-benzoylated octahydro-7 (1H)-quinolones (6 and 7) and decahydroquinoline-2, 7-dione derivatives (8-15) was investigated under various acidic and basic conditions. Except for the N-benzoyl-7-ones (6 and 7), isomerization features were interpreted as the phenomenon associated both with the facility of the cis-isomers and the difficulty of the trans-ones in the retro-Michael ring opening to form amino enone intermediates and with predominance of the cis-ring junction over the trans-one in the subsequent recyclization of the intermediates. Isomerization of N-benzoyloctahydro-7 (1H)-quinolone resulted in the exclusive formation of the cis-ketone (6) and in the successful isolation of the intermediate (18). The contrasting feature was interpreted by assuming both the facile ring opening of the trans-ketone (7) possibly via a cyclic process (7') and the retarded recyclization of 18, due to a reduced nucleophilicity of the amido nitrogen, resulting in a failure in the formation of 7.
