Metalloporphyrin-catalyzed oxidations 3. Expoxidation and aldehyde formation by oxidative carboncarbon bond cleavage in squalene

Abstract

Hemin dimethylester and cobalt(II/III) octaethylporphyrins have been found to catalyze the autoxidation of squalene, C 30H 50. Three isomeric epoxides and two α, β-unsaturated aldehydes with 27 and 25 carbon atoms were the main products (⩾=60% of the oxidation products). These compounds were isolated and characterized by various spectroscopic techniques. The use of cobalt(III) and iron(III) acetylacetonates as catalysts for squalene autoxidation led mainly to epoxides. With the low molecular weight analoque of squalene, 2-methyl-2-pentene, the cobalt(II/III) octaethylporphyrin-catalyzed autoxidation produced ketones and alcohols derived from allylic hydroperoxides. The differences are explained by aggregation phenomena.