Radical adamantyldenitration in polynitrobenzenes. Selectivity of homolytic aromatic ipso substitution

Abstract

1-Adamantyl radicals react with 3,5-dinitro-1-X-benzenes (Ia–d), 2,4-dinitro-1-X-benzenes (IIa–e), and 2,4,6-trinitro-1-X-benzenes (IIIa–c) to effect selectively the displacement of the nitro group. This adamantyl-denitration represents a further example of the ease of radical substitution at an ipso position. The same substrates react with phenyl and methyl radicals, but the reaction takes a completely different course; the only products obtained derive from attack at the unsubstituted nuclear positions. This drastic change of behaviour is attributed to the different polar character of adamantyl and phenyl or methyl radicals which determines a change in the nature of the transition state of the radical addition to the aromatic substrate.