p-Toluenesulfonic acid → 4-Diethoxymethyl-10-methyl-phenothiazine

Participants

Reaction Steps

15.0 ml of triethyl orthoformate were added at room temperature to a solution of 4.90 g (20.3 mmol) of 10-methylphenothiazine-4-carbaldehyde and 50 mg of p-toluenesulphonic acid×1H2O in 15 ml of methanol. The reaction mixture was boiled at reflux for 45 minutes, cooled and poured into 30 g of ice, 30 ml of saturated aqueous sodium hydrogen carbonate solution and 100 ml of diethyl ether. The organic phase was washed with 50 ml of saturated sodium chloride solution, dried over magnesium sulphate and concentrated. The residue was chromatographed on 300 g of silica gel with diethyl ether/hexane (1:4), whereupon, after crystallization from diethyl ether/hexane in a refrigerator, 6.16 g (96.2%) of 4-diethoxymethyl-10-methyl-phenothiazine were obtained as a white solid of m.p. 44.6°-46.2°.

Provenance & Evidence