The unusual behaviour of nitro-substituted radical σ-complexes. The reactions of alkyl radicals with 9-nitroanthracene

Abstract

Alkyl radicals react with 9-nitroanthracene to give the nitro-substituted σ-complex intermediate (III) derived from addition at the 10-position. This radical does not rearomatize, but gives rise to rearrangement of the nitro-group which eventually leads to the formation of alkylanthrones. However, in the presence of stabilized radicals, intermediate (III) is trapped to give products of addition at the 9- and 10-positions. In some cases these latter products can suffer hydrogen abstraction, followed by elimination of the NO₂· radical, to afford 9,10-dialkylanthracenes.