Bromination of 10-Phenylphenothiazine and 10-Phenylphenoxazine

Article abstract of DOI:10.1021/jo00185a011

The reaction of either 10-phenylphenothiazine (1) with bromine in acetic acid or the cation radical of 1 with bromide ion gives ring substitution only and in accord with customary stoichiometry for nucleophilic substitution of aromatic cation radicals.However, the reaction of 1 with pyridinium bromide perbromide (2) gives predominantly 10-phenyl ring substitution and a small amount of ring substitution products.Evidence is presented which indicates that ring substitution occurs via cation radical whereas 10-phenyl substitution proceeds via electrophilic attack on the neutral molecule 1.Substitution of 10-phenylphenoxazine (4) occurs predominantly but not exclusively on the phenoxazine ring; some bromination does occur on the 10-phenyl ring.In contrast, the reaction of 4 with bromine gives only ring mono- and disubstitution products.These results indicate that both 1 and 4 react similarly under the same conditions.