The Smiles rearrangement of 2-aryloxy-5-nitrophenoxides. Attempted routes to benzoxirens and tribenzo[b,e,h]trioxonins
Abstract
Formation of dibenzo-p-dioxins by the pyrolysis of 2-halogenophenoxides does not appear to involve intermediate benzoxirens. Thermal self-condensation of potassium 2-bromo-5-nitrophenoxide (1b) gave a mixture of 2,7- and 2,8-dinitrodibenzo-p-dioxins (6d) and (6e). The mechanism of formation of the 2,8-isomer (6e) is shown to involve Smiles rearrangement of potassium 2-(2-bromo-5-nitrophenoxy)-5-nitrophenoxide (9a). Further examples of Smiles rearrangements of 2-aryloxy-5-nitrophenoxides and an attempted synthesis of the tribenzo-[b,e,h]trioxonin derivatives (16) are described.