Aromatic hydroxylation. Part 6. Oxidation of naphthalene by dioxygen in the presence of iron(II) salts

Abstract

The major products from the oxidation of naphthalene with dioxygen in the presence of an iron(II) salt and an organic reducing agent are cis- and trans-1,2-dihydroxy-l,2-dihydronaphthalene, 2,3-epoxy- 3,4-dihydro-cis- and -trans-4-hydroxynaphthalen-1(2H)-one, cis-2-formylcinnamaldehyde, and 1- and 2-naphthol. A series of labelling experiments using ¹⁸O₂, and deuterionaphthalenes reveal the origin of the oxygen in the dihydrodiols and quinone epoxides and the absence of a large value of the NIH shift for formation of 1- or 2-naphthol. The suggested mechanism involves a free radical co-oxidation of naphthalene and the organic reducing agent by dioxygen with iron–oxygen complexes, behaving as oxy-radicals. as the active oxidising species.