Sonderdruckanforderungen an Prof. Dr. H. Möhrle. Fax: (0211) 811-3085. Z. Naturforsch. 54b, 913-922 (1999); eingegangen am 4. Mai 1999 Amidine, Nitrone, N-Hydroxyaminal, E/Z-Enamine, o-(Enamino)-benzaldehyde-oxime 2-Methylpapaverinium iodide (1) reacted with hydroxylamine to papaverine-N-oxide (2), but without a detectable intermediate and only in moderate yield, caused by the steric hin drance of the 1-substituent.The ring opened product of 2-dinitrophenylisoquinolinium salt with hydroxylamine, the enamine-oxime 3b gave rise to a 3-substituted cyclic nitrone (6), when heated with triethylamine. This alkali-stable compound was transformed with acid quantitatively to isoquinoline-N-oxide (4). The enaminonitrile 9c, treated with triethylamine showed cyclization to the iminoisoquinoline 10, which by loss of nitrous acid produced the tetracyclic azaindole 11. The 2-methoxyisoquinolinium salt 16 was cleaved with O-methylhydroxylamine to the resistant di(O-methyloximes) (20a/b), unable to form the amine oxide 4. From these and former results, a mechanism for the ring opening of cycliminium salts and the recyclization to amine oxides was proposed.
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