Citric Acid → 4-(3,4-Difluoro-phenyl)-6-methoxymethyl-2-oxo-1,2,3,4-tetrahydro-pyrimidine-5-carboxylic acid methyl ester

Participants

Reaction Conditions

Reaction Steps

A solution of methyl 4-methoxyacetoacetate (702 g, 4.8 mol), urea (433 g, 7.2 mol), 3,4-difluorobenzaldehyde (670 g, 4.7 mol), boron trifluoride diethyl etherate(1126 g, 7.9 mol), copper(II) acetate (94 g, 0.52 mol), and acetic acid (36 mL) in THF (7.5 L) was heated to reflux for 8 hours. The reaction mixture was cooled to 20° C. Ethyl acetate (8 L) and 10% citric acid aqueous solution (7.5 kg) was added. The two layers were separated and the aqueous layer was extracted with ethyl acetate (4 L). The combined organic layers were washed with 10% aqueous sodium carbonate (2×5 L) and with 5% brine (1×5 L). The organic layer was concentrated under reduced pressure, with toluene being added continuously and the mixture was concentrated until the level of THF and ethyl acetate was <0.5% volume to toluene, to a final volume was about 2.5 L. The toluene slurry was warmed to 80° C. to dissolve the solids. The solution was cooled slowly to 60° C. and seeded. The slurry was aged at 60° C. for 1 hour and cooled slowly to 20° C. over 4 hours. Hexane (700 mL) was added over 30 minutes. The slurry was aged for 1 hour and filtered. The solid was washed with toluene (1.5 L) and dried to afford (+)-2 as a white solid.

Provenance & Evidence