Hydrochloric Acid → 3,7-Dimethoxy-10-methyl-phenothiazine-4-carbaldehyde

Participants

Reaction Steps

16.25 ml of n-butyllithium solution (1.6M in hexane) were added dropwise at -78° under argon to a solution of 5.46 g (10.0 mmol) of 3,7-dimethoxy-10-methylphenothiazine in 100 ml of diethyl ether/tetrahydrofuran (4:1). The reaction mixture was stirred at -70° for 15 minutes, brought slowly to 0°, stirred for 2 hours and then treated at 0° with 3.39 g (30.0 mmol) of N-formylpiperidine. After stirring at 0° for 2 hours the mixture was poured into 500 ml of ice-water, whereupon it was acidified slightly with 0.5N hydrochloric acid solution and extracted with ethyl acetate. The combined organic phases were extracted with saturated sodium chloride solution, dried over magnesium sulphate and evaporated. The residue was crystallized from acetone, whereupon, after drying, 5.42 g (90%) of 3,7-dimethoxy-10-methyl-phenothiazine-4-carbaldehyde were obtained as a red solid of m.p. 150°.

Provenance & Evidence