Synthesis of 1- and 3-methyl phenothiazines

Article abstract of DOI:10.1515/HC.2002.8.4.343

Synthesis of 1-methyl/3-methyl phenothiazines is reported by Smiles rearrangement of 2-formamido-3-methyl/5-methyl-2′-nitro diphenylsulfides. The latter were obtained by the condensation of 2-amino-3-methyl/5-methylbenzenethiols with o-halonitrobenzenes followed by formylation. However 2-amino-3-methyl/5-methylbenzenethiols on condensation with halonitrobenzenes containing a nitrogroup at ortho positions to the reactive halogen atom directly yields 9-nitrophenothiazines as Smiles rearrangement and ring closure occur simultaneously in situ due to combined resonance and inductive effect reinforced by two nitrogroups.