Hydrochloric Acid → Pentoxazone

Participants

Reaction Steps

Ethyl N-(4-chloro-5-cyclopentyloxy-2-flourophenyl)carbamate (3.01 g, 10 mmol), ethyl 2-hydroxy-3-methyl-3-butenoate (2.02 g, 14 mmol) and stannous acetate (23.7 mg, 0.1 mmol) were introduced into a flask (25 cc) equipped with an air condenser tube (20 cm), and the reaction was conducted at 200° C. for 2.5 hours under such a reduced pressure that the ethyl butenoate was refluxed below the middle of the air condenser tube. After the reaction solution was cooled to room temperature, toluene (20 mL) was added, and the reaction solution was washed with water (20 mL), then 1N hydrochloric acid (20 mL), 1N sodium hydroxide (20 mL) and 1N hydrochloric acid (20 mL). The organic layer was dried over magnesium sulfate. After the drying agent was filtered off, the filtrate was concentrated under reduced pressure. Acidic methanol (3.5 mL) was added to the resulting oily crude product to form a homogeneous solution. Then, 6N hydrochloric acid (0.4 mL) was further added, and the solution was left to stand at room temperature. The precipitated crystals were collected by filtration, washed with a 20:1 mixed solvent consisting of methanol and 6N hydrochloric acid and dried to obtain 3-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)-5-isopropylidene-1,3-oxazolidine-2,4-dione (1.97 g, yield 55.6%).

Provenance & Evidence