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.
Einleitung
azeutische C hem ie, H ein rich -H ein e-U n iversität, U niversitätsstr. 1, D -40225 D ü sseld orf H errn Prof. Dr. G. W illuhn zum 65. G eburtstag gew idm et Z. N aturforsch. 54b, 5 3 2 -5 4 0 (1999); ein gegan gen am 1. D ezem b er 1998 O xim e, D io x im e, E /Z -E n am in e, R ing-C hain Isom erism , A m in e O xide The N -alkyl-and N -aryl-isoquinolinium salts 7, 15-17 reacted with free hyd roxylam ine in pyridine to give the isoq u in olin e-2-oxid e (9) as final product. The interm ediate d ioxim es 8 w ere isolated and characterized by derivatisation with acetic anhydride to the oxim e ester nitrile 10. From the reaction o f 8 with trifluoroacetic anhydride/triethylam ine 3-am in o-isoq u in olin e-2-oxid e (12) resulted after hydrolysis. D u e to the electronic influence the 5-nitroisoqu inolin iu m salts 1 -3 react faster than the 5-hydroxy derivative 20. but w ith the sam e course o f con version via d ioxim es to am ine oxides. A n optim ized m eth od for preparation o f the am ine ox id es was d evelop ed .
Amide, Amidine, Isoxazole 1-Methylpyridinium salts showed no reaction with excessive hydroxylamine, but nicotinic acid derivatives in HM PT gave the corresponding N-oxides. 3-Acetyl-1-methylpyridinium iodide generated the hydroximino-pyridine 1-oxide 13 and the isoxazoles 14, 15E, and 15Z. 2-and 4-Cyano-l-methylpyridinium iodides underwent no ring cleavage, but altered only the functional group. However, the 3-cyano compound was converted into the corresponding pyridine N-oxides with carboxamide, hydroxyamidine and carbaldoxime groups.
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