Manufacturing Process
A solution of methylcarbazate (48.0 mg) in methanol (250 ml) is added all at
once at room temperature to a well stirred solution of 2-formylquinoxaline-
1,4-dioxide (100 g) in methanol (2.5 liters). Two drops of concentrated
hydrochloric acid are added. The mixture is stirred for 3 hours then filtered to remove the yellow crystalline product. The crystals of (2-
quinoxalinylmethylene)hydrazinecarboxylic acid methyl ester are washed with
methanol then air dried; M.P. 234.5-236°C (dec.). Yield=121.8 g. The product
is purified by refluxing in chloroform for 2 hours, followed by filtration and air
drying; M.P. 239.5-240°C (dec.).
The ultraviolet absorption spectrum (water) exhibits maxima at 236, 251,
303, 366 and 373 nm with extinction coefficients of 11,000, 10,900, 36,400,
16,100 and 16,200, respectively.
