54 g of carbromal (2-bromo-2-ethylbutyryl-urea) in 600 cc of isopropanol was
stirred and refluxed for 3 hours with 27.8 g of anhydrous silver oxide. The
reaction mixture was filtered and the silver residue was extracted with 100 cc
of boiling isopropanol. The filtered and dried solids which separated weighed
22.5 g and melted at 189°C to 190.5°C. Concentration of the filtrate yielded
an additional 3.3 g of product which melted at 160°C to 170°C. These two
crops were separately obtained as white needles by crystallization from
alcohol and exhibited slight solubility in water. The first crop gave 21.7 g of 2-
ethyl-cis-crotonyl urea with a melting point of 191°C to 193°C, and the
second crop gave 0.9 g with a melting point of 191°C to 193°C for a total
yield of 42.4 g or 63% of the theoretical.
