Synthesis
General procedure for the synthesis of 10-methylphenothiazine from phenothiazine and iodomethane: NaH (60% purity, 1.0 g, 25.1 mmol) was slowly added to a 50 ml round-bottomed flask containing DMF (10 ml) under ice-water bath conditions. Iodomethane (1.3 g, 11.04 mmol) and phenothiazine (2 g, 10.0 mmol) were then added sequentially. The reaction mixture was transferred to room temperature and stirred for 2 h. The progress of the reaction was monitored by TLC. After completion of the reaction, the reaction was quenched by addition of water and extracted with dichloromethane (50 ml x 3). The organic phases were combined and dried with magnesium sulfate and subsequently concentrated to remove the solvent. Purification by silica gel column chromatography afforded the target product 10-methylphenothiazine (2.1 g, white solid) with a melting point of 96 °C in 97% yield.
Purification Methods
Recrystallise it (three times) from EtOH to give the -form (prisms). Recrystallisation from EtOH/*benzene gives the .-form (needles). It has also been purified by vacuum sublimation and is carefulmax 255nm (log 4.60) (pH 6.3) and 255nm in hexane. [Cymerman-Craig & Warburton Aust J Chem 9 294 1956, Beilstein 27 II 33, 27 III/IV 1215.]
References
[1] Molecular Crystals and Liquid Crystals, 2010, vol. 520, p. 36 - 43
[2] Patent: CN106045986, 2016, A. Location in patent: Paragraph 0039; 0040; 0041
[3] Patent: CN106045987, 2016, A. Location in patent: Paragraph 0039; 0040; 0041
[4] Journal of Heterocyclic Chemistry, 1980, vol. 17, p. 1053 - 1056
[5] ACS Chemical Neuroscience, 2017, vol. 8, # 4, p. 798 - 806
