6.9 parts of sodium are dissolved in 100 parts of absolute ethyl alcohol in a
vessel provided with a reflux condenser. After the sodium is dissolved, 9.6
parts of urea and 20.9 parts of the ethyl ester of ethyl (1-methyl-δ 1 -
butenyl)cyanoacetic acid are added. The mixture is refluxed for twelve hours,
after which the alcohol is removed by vacuum distillation and the residue is
dissolved in 100 parts of water. The resulting solution is extracted with ether
in three successive 25 part portions. The nitrile which is formed as a by-
product from the cyanoacetate used is recovered from the ether extract by
washing with water, evaporating the ether and distilling. The combined water
solutions containing 5-ethyl-5-(1-methyl-δ 1 -butenyl)-4-imino barbituric acid,
are acidified until acid to Congo red with concentrated hydrochloric acid, after
which the mixture is transferred, if necessary, to another vessel, and an equal
volume of concentrated hydrochloric acid is added. The solution is then
refluxed for one hour to hydrolyze the imino compound. The 5-ethyl-5-(1-
methyl-δ 1 -butenyl)barbituric acid crystallizes out on cooling. It is filtered and
washed with two 25 part portions of ice water. By this process, 8 parts of the
crude product (35% yield) have been obtained. After two crystallizations from
50% alcohol, the yield of the purified product is 6.5 parts (29%). The product
melts at 160°C to 162°C.
The sodium salt of 5-ethyl-5-(1-methyl-δ 1 -butenyl)barbituric acid is prepared
by dissolving 23 parts of sodium in 350 parts of absolute alcohol in a vessel provided with a reflux condenser containing a drying tube, and adding the
resulting solution to a solution of 224 parts of 5-ethyl-5-(1-methyl-δ 1 -
butenyl)barbituric acid dissolved in 300 to 400 parts of absolute alcohol. The
resulting solution is concentrated in vacuo, with heating on a warm water
bath. About 200 parts of dry benzene are then added and the mixture is again
concentrated, If this evaporation is carried out to an extent such that all of
the solvent is removed, no further washing is required. If all of the solvent is
not removed by evaporation, the residue is washed with dry ether. The
resulting sodium salt is then dried in an oven at 90°C and then is dried in
vacuo (2 mm) at 78°C. The yield is 97% to 99%.
5-Ethyl-5-(1-methyl-1-butenyl)-2,4,6-(1H,3H,5H)-
pyrimidinetrione sodium salt
