Anomalous acetoxylation of aromatic nuclei: some structural requirements in the substrate

Abstract

For certain aromatic nuclei, bromination in acetic acid and in the presence of pyridine is accompanied by nuclear acetoxylation. As first observed with galbulin, when two alkoxyl groups, one meta and one para to a benzylic centre of the substrate are present, acetoxylation occurs at the intervening ortho position. Under the given conditions, acetoxylation occurs at position 8 of 6,7-dimethoxy-1-phenyl-1,2,3,4,-tetrahydronaphthalene, and at position 2 of 3,4,-dimethoxy diphenyl- and triphenyl-methanes. Acetoxylation does not occur in the absence of either of the alkoxy groups or in the absence of pyridine, nor does it occur in the pendant ring of 1-(3´,4´-dimethoxypheny1)- 1,2,3,4-tetrahydronaphthalene. These results are consistent with the earlier suggestion that the reaction occurs by way of initial oxidative formation of a doubly benzylic cation.