Oxidative Transformations of Heteroaromatic Iminium Salts

Atropisomers of Cofacial Heteroaromatic Rings with Two Positive Charges. Derivatives of 1,8-Di(3‘-pyridyl)naphthalene

“…Three isomeric pyridones are possible from the oxidation of 2a by way of the formation of pseudobase intermediates: those resulting from the addition of hydroxide ion to the two α (H2‘ and H6‘) and one γ (H4‘) positions followed by ferricyanide oxidation to a pyridone. − The simplicity of the proton spectrum of 3 in DMSO- d 6 indicated that each ring had oxidized to a common structure; the spectrum did not show a triplet signal for H5‘ and the 2‘-pyridone isomer therefore was eliminated. An NOE difference experiment in which the N -methyl protons were irradiated caused only the broadened singlet at δ 7.1 for H2‘ to be enhanced (12%), thereby favoring the 6‘-pyridone and eliminating the 4‘ isomer, the latter expected to show enhanced signals for both H2‘ and H6‘.…”

7-alkyl-1,3,7-triazapyrenium salts: Rare event of oxidative hydroxylation under the conditions of acid catalysis

“…This reaction was later extended to numerous other heteroaromatic cations [3,4]. The potassium ferrocyanide remains the classic oxidant in this reaction, more seldom oxygen [5] and other oxidants [6] are employed.…”