Proximity effects in diaryl derivatives. Part III. The formation of phenazines and dibenzothiadiazepines by reduction of 2,2′-dinitrodiaryl sulphides, sulphoxides, and sulphones

Abstract

Reduction of 2,2′-dinitrodiaryl sulphides, sulphoxides, and sulphones with zinc and sodium hydroxide in aqueous dioxan afforded phenazines (V), dibenzo[b,f][1,4,5]thiadiazepines (IV; X = S or SO₂), dibenzo[b,f][1,4,5]-thiadiazepine N-oxides, and other products. Phenazines arise by intramolecular nucleophilic rearrangement of a partially reduced species, followed by loss of the sulphur-containing group. Studies of the reduction of 2-amino-2′-nitrodiphenyl sulphone and of dibenzothiadiazepine derivatives show that these compounds are not intermediates in the formation of phenazines.