Quinones. Part 11. The reaction of o-aminothiophenol with o-benzo- and o-naphtho-quinones: a new route to 1H-phenothiazin-1-ones

Abstract

1H-Phenothiazin-1-ones can be obtained by the condensation of o-aminothiophenol with 3,5-di-t-butyl- and 3-t-butyl-5-phenyl-o-benzoquinones. In the absence of large blocking groups the phenothiazinones are unstable. A methyl group at C-4 leads via the quinone-methide tautomer, to formation of a spiro-dimer the crystal structure of which was determined by X-ray analysis. By further reaction with o-aminothiophenol, 1H-phenothiazin-1-ones yield triphenodithiazines (benzothiazino-phenothiazines).

o-Naphthoquinones do not form benzo-1H-phenothiazin-1-ones with o-aminothiophenol. The parent compound yields 4-hydroxy-3H-benzo[a]phenothiazin-3-one by initial thiol addition at C-4 followed by rearrangement.