Acetyl chloride → (11aS)-8-Benzyloxy-7-methoxy-2-methylidene-1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one

Participants

Reaction Steps

To a solution of (2S)-4-(methylene)-1-[5-methoxy-2-nitro-4-(phenylmethoxy)benzoyl]-2-pyrrolidinecarboxaldehyde (1.0 equivalent) in THF/H2O (v/v, 1.7:1, 0.03 M) was added sodium hydrosulfite (5˜8 equivalent) in portions within 2 minutes at room temperature. The mixture was further stirred for 6˜20 hours and monitored by TLC (hexanes/AcOEt 1:2 and CH2Cl2/MeOH 5:1). After the aldehyde was almost consumed, the reaction was quenched with methanol (about same volume as THF used). The solvents were removed by rotary evaporation in vacuo (temperature <40° C.) and the remainder solid was put on high vacuum to make it completely dry. The solid was suspended in anhydrous methanol (0.03 M) and AcCl (8˜10 equivalent) was added dropwise at room temperature. After stirred for 15 minutes, the cloudy solution was filtered and the solid was washed with anhydrous methanol. The clear yellow filtrate was stirred at room temperature for 1 to 2 hours and was quenched with saturated sodium bicarbonate. After most of the methanol was removed by rotary evaporation, the remainder was diluted with dichloromethane and water. The aqueous layer was extracted with AcOEt. The combined organic layers were dried over anhydrous sodium sulfate and filtered. The solvents were removed and the residue was purified by flash chromatography (hexanes/AcOEt, 1:3, 1:5) to give (11aS)-7-methoxy-2-methylene-8-(phenylmethoxy)-1,2,3,11a-tetrahydro-5H-pyrrolo[2,1-c][1,4]benzodiazepin-5-one in 70% to 85% yield. The NMR spectra are consistent with the literature reported. MS (ESI): m/z 371.2 (M+Na)+. MS (ESI, with CH3OH): m/z 403.3 (M+CH3OH+Na)+. MS (ESI, with H2O): m/z 389.2 (M+H2O+Na)+.

Provenance & Evidence