Ethanol → Pentoxazone

Participants

Reaction Conditions

Reaction Steps

Ferric chloride hexahydrate (2.7 g, 0.01 mol), tributylamine (9.3 g, 0.05 mol) and ethyl N-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)carbamate (151 g, 0.5 mol) were introduced into a three-necked flask (1 L) equipped with a mechanical stirrer and a Dean Stark, and the resulting mixture was heated to 200° C. with stirring to form a homogeneous solution. Then, ethyl 2-hydroxy-3-methyl-3-butenoate (108 g, 0.75 mol) was added dropwise over 4.8 hours, and after the addition, the solution was stirred for another 2 hours. The ethanol generated during the heating and stirring was distilled away by means of the Dean Stark. After completion of the reaction, the reaction mixture was allowed to cool to about 100° C., and then toluene (500 mL) was added to form a solution. The solution was washed with 1N hydrochloric acid (250 mL) and water (250 mL). The organic layer was concentrated under reduced pressure, and the resulting oily crude product was crystallized in ethanol (200 mL) acidified with sulfuric acid. The precipitated crystals were collected by filtration and washed with a small amount of acidic ethanol and then hexane to obtain 3-(4-chloro-5-cyclopentyloxy-2-fluorophenyl)-5-isopropylidene-1,3-oxazolidine-2,4-dione (150.5 g, yield 85.1%) as white crystals.

Provenance & Evidence