Ethyl Acetate → 10-(1-Diethylamino-2-propyl)-2-phenothiazinecarbonitrile

Participants

Reaction Conditions

Reaction Steps

Sodium hydride (19.2 g; in 50% strength dispersion in vaseline) is added in the course of 20 minutes to a solution of 2-phenothiazinecarbonitrile (44.86 g) in N,N-dimethylformamide (600 cc). The mixture obtained is then heated to 110° C., after which the solution of 1-diethylamino-2-propyl p-toluenesulphonate hydrochloride prepared above is added in the course of 35 minutes. The reaction mixture is stirred at 110° C. for 7 hours and then diluted, after cooling, with ethyl acetate (2 liters). The mixture is washed with distilled water (5×1 liter). The organic phase is extracted with 4N hydrochloric acid (240 cc) and the acid aqueous phase is washed with ethyl acetate (750 cc) and then alkalinized with 5N caustic soda (250 cc). The alkaline medium is then extracted with ethyl acetate (1250 cc). The organic phase is washed with distilled water (3×300 cc), dried over magnesium sulphate, filtered and concentrated to dryness under reduced pressure (30 mm Hg; 4 kPa) at 40° C. The residue is stirred in the presence of ethyl ether (100 cc); a precipitate forms and this is filtered off, and the filtrate is purified by chromatography on a column of silica gel (0.2-0.063 mm) (height: 82 cm; diameter: 4.5 cm), eluting with an 80:20 (by volume) mixture (7 liters) of cyclohexane and ethyl acetate and collecting 100-cc fractions. After concentration to dryness under reduced pressure (30 mm Hg; 4 kPa) at 50° C., 10-[(2RS)-1-diethylamino-2-propyl]-2-phenothiazinecarbonitrile (6.76 g) is obtained from fractions 4 to 9, and a mixture (8.5 g) of 10-[(2RS)-1-diethylamino-2-propyl]-2-phenothiazinecarbonitrile and 10-[(1RS)-2-diethylamino-1-propyl]-2-phenothiazinecarbonitrile is obtained from fractions 10 to 22. The mixture is purified by chromatography on column of silica gel (0.2-0.063 mm) (height: 67 cm; diameter: 3.0 cm), eluting with an 85:15 (by volume) mixture (3 liters) of cyclohexane and ethyl acetate and collecting 50-cc fractions. Fractions 22 to 29 are combined and concentrated to dryness at 50° C. under reduced pressure (30 mm Hg; 4 kPa) to give 10 -[(2RS)-1-diethylamino-2-propyl]-2-phenothiazinecarbonitrile (2.76 g).

Provenance & Evidence