Improved synthesis of 2-methoxyphenothiazine

A procedure for synthesis of 2-methoxyphenothiazine (1) has been developed, starting from resorcinol and aniline by condensation, following methylation and cyclization. p-Toluenesulfonic acid and polysubstituted aromatics were employed as the catalyst of condensation and the solvent of cyclization, respectively, to improve the yield. The use of parallel experiments, statistical experimental design, and multivariate modeling made the total yield of the procedure as high as 74.2%. J. Heterocyclic Chem., (2012).