Yield: 100%

Reaction Conditions:

with acetic acid at 50; for 12 h;

Steps:

A
Example A; Maleuric acid; Maleuric acid was prepared according to the procedure of US2717908. A mixture of 500 g of maleic anhydride (5.1 moles) and 300 g of urea (5 moles) in 1000 mL of acetic acid was heated to 50°C. The mixture was a homogeneous solution until maleuric acid began to precipitate out. After 12 hours, the mixture was cooled to room temperature overnight. The maleuric acid was filtered and washed with acetic acid to afford 530 g (67% yield). Additional maleuric acid precipitates from the mother liquor over lime to afford nearly a quantitative yield.1H NMR (DMSO-d6): δ 12.8 (br s, 1 H), 10.4 (brs. 1 H), 7.6 (brs, 1 H), 7.3 (br s, 1 H), 6.4 (s, 2 H).

References:

Cytec Technology Corp. EP925283, 2003, B1 Location in patent:Page/Page column 9