The oxygenation of enamines. Ketonization at the .beta. position to give .alpha.-amino ketones

Superoxide Free Radical Generation by Amadori Compounds: The Role of Acyclic Forms and Metal Ions

“…Thus, the one-electron oxidation of an Amadori compound leading eventually to glucosone and free amino acid could proceed without metal redox catalysis given that the appropriate organic electron-transfer catalyst is present (). Uncatalyzed autoxidation of enamines has also been reported previously ( , ). It is unclear, however, whether the superoxide formation in our experiments under metal-free conditions was uncatalyzed; this is currently under investigation.…”

“…The sequence of reactions (Scheme 4) which was previously accepted as the mechanism for the metalcatalyzed autoxidation of Amadori compounds can only partly explain superoxide generation by Schiff bases 1 and 2 since at similar conditions Schiff bases do not enolize as readily as corresponding Amadori compounds 4 and 6. It was found earlier that enamines were less susceptible to autoxidation than the structurally similar Schiff bases (32), possibly because the initial step of electron transfer from the Schiff base nitrogen to O 2 is more favored than the electron transfer from the amino nitrogen of enamine. Iron(III), which forms stable soluble complexes with Amadori compounds at pH >2 (V. V. Mossine, unpublished results and ref 34) and which has been reported to accelerate superoxide formation during the autoxidation of glycated polypeptides (9), was incapable of acting as an autoxidation catalyst in our experiments, at least at concentrations of <100 µM.…”

Studies on the oxidation of enamines with molecular oxygen. I. Oxidation of Some Piperidino Alkenes

“…We regard 5 as the rearrangement product of the corresponding epoxide, 6 as a product of the further oxidation of 5 (via 2-piperidino-2-hydroperoxy cyclo-hexanone) and 7 as a secondary product of the oxidative C=C scission, formed by the further oxidation of adipic hemialdehyde piperidide. b and 6 were already described as oxidation products of 1 [6], but 7 was first detected by us. A further product which was detected in small amounts by GC/MS coupling is 1,2-dipiperidino cyclohex-1-ene…”

“…Enamines are olefins with especially low ionization energies ( Table I), and therefore we must expect the attack a t the C=Cdouble bond as the main reaction of the oxidation of enamines. Indeed, both JERUSSI [6] and WINBERG [ 71 found waminoketones (rearrangement products of the corresponding epoxides) and lower acid amides (products of the oxidative scission of the C=C double bond) as the main products of enamine oxidation.…”

Captodative aminoalkenes

“…In addition, these reactions are of limited application and of no particular preparative value. The formation of the aminoalkenes 2c containing the geminal carbonyl group was observed upon hydrolysis of enediamines, 143,144 oxidation of enamines 145,146 or aminoalcohols 147 and removal of protective groups. 148,149 Thus analogues of one of the natural components of the smell of freshly backed bread, viz., compounds 45a,b, were synthesised by careful acid hydrolysis of the corresponding ketal 46 148 or azomethine derivative 47.…”