Kinetics and mechanism of the oxidation of heteroaromatic cations by ferricyanide ion

A rate and equilibrium study of the addition of acetone enolate ion to the 2-methyl-5-nitroisoquinolinium cation in aqueous solution

“…Although in this pH region the concentration of the acetone enolate ion nucleophile is proportional to [-OH], the concentration of the isoquinolinium cation is inversely proportional to [-OH] and so there is no net increase in rate of adduct formation with increasing pH. In these more basic solutions the yield of adduct also suffers because its formation must compete with the disproportionation of the pseudobase to 2-methyl-5-nitro-lisoquinolinone and 1,2-dihydro-2-methyl-5-nitroisoquinoline (16). Since this disproportionation is an irreversible process, whereas adduct formation from the cation is reversible, extended reaction periods (especially at high temperatures) will result in reduced yields of adduct and increased amounts of disproportionation products.…”

Characteristics of the oxidative hydroxylation reaction of 7-alkyl-1,3,7-triazapyrenium salts

“…The likely mechanism of formation of compounds 3a,b includes a stepwise addition of nucleophiles to cations 1a,b with subsequent oxidation involving the addition of cyanide ion in the first step and water in the second. The limiting step is evidently the oxidation process since, in both stages, it involves a neutral particle and not an anion as in the classically used Decker reaction [13]. The absence of cyanoamide 3c as a result of the reaction of salt 1c is not fully clear but it can be partially explained by the greater inductive effect and steric hindrance from the ethyl group when compared with a methyl.…”

“…Kinetic studies of the Decker reaction [13,14] have shown that this is a first order reaction in both the heterocyclic cation and the oxidant. However our attempt to speed up the oxidative hydroxylation process of salts 1a-c in basic medium using K 3 [Fe(CN) 6 ] excess led to complete degradation of the reaction mixture.…”

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

“…In such reactions occurring in alkaline medium the anion of the pseudobase 7-ALKYL-1,3,7-TRIAZAPYRENIUM SALTS is subjected to oxidation and not the pseudobase proper (see the Scheme) [8].…”