Ethanol → Pentoxazone

Participants

Reaction Conditions

Reaction Steps

Ethyl N-(4-chloro-5-cyclopentyloxy-2-fluorphenyl)carbamate (674 g, 2.24 mmol), ferric chloride (3.7 g, 22.8 mmol) and tributylamine (21 g, 0.113 mol) were introduced into a three-necked flask (3 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 (484 g, 3.51 mol) was added dropwise over 5.5 hours, and after the addition, the solution was stirred for another 2.5 hours. The ethanol generated during the heating and stirring was distilled away by mean s of the Dean Stark . After completion of the reaction, the reaction mixture was allowed to cool to about 100° C., and then toluene (2.0 L) was added to form a solution. The solution was washed with 1N hydrochloric acid (1 L) and water (1 L). The organic layer was concentrated under reduced pressure, and the resulting oily crude product was crystallized in ethanol (3.85 L) 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 (590 g, yield 74.5%) as white crystals.

Provenance & Evidence