Acetic Acid → 7,8-Dimethoxyquinazoline-2,4(1H,3H)-dione

Participants

Reaction Conditions

Reaction Steps

Acetic acid (177.4 ml., 3.1 moles) was added to a vigorously stirred suspension of 3,4-dimethoxyanthranilic acid (436.5 g., 2.21 moles) in 10 liters of water. Then 2.24 liters of 20% potassium cyanate (5.53 moles) solution was gradually added and the mixture was stirred for one hour at 40° C. After cooling the reaction mixture to 20° C., 3.54 kg. sodium hydroxide pellets were added maintaining the temperature below 40° C. The reaction mixture was heated to 90° C. for 45 minutes and then slowly cooled in an ice bath. The sodium salt of the product was filtered, resuspended in 6 liters of water, acidified with concentrated hydrochloric acid (370 ml.), cooled and filtered to yield 404 grams (82%) of the product. Recrystallization from dimethylformamide gave colorless crystals, M.P. 314°-6° C.

Provenance & Evidence