1,4-Naphthoquinones, XXV: Reaction of the redox 5-lipoxygenase inhibitor 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-3-hydroxy-1,4-naphthoquinone with O2.- and 3O2

Article abstract of DOI:10.1002/ardp.19953280510

The 5-lipoxygenase inhibitor 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-3-hydroxy-1,4-naphthoquinone, its deoxygenation product 1 as well as the oxygenated species 3 are O₂^.- quenchers with different power in aqueous solution. In alcoholic solution the antioxidative capacity of 1 does not change, 2 indeed is still only a weak O₂·^- quencher while 3 shows prooxidative properties. This phenomenon was explored in the O₂·^- generating oxygenation system (OS) DMSO-CO₃^2--O₂ by preparative techniques. The following reaction sequence could be proven: 3 → 2 → 4 (2,6-di-tert-butyl-1,4-benzoquinone). While the step 3 → 2 would be O₂·^- dependent the transition 2 → 4 occurs on two levels: 1. retro Michael reaction with release of 2,6-di-tert-butylphenol, 2. base catalysed oxygenation of 5 → 4 by ³O₂. The diphenoquinone 6 occurring as byproduct is split with the OS - in contrast to the reaction with ¹O₂ - in considerable yield to give 4.