Selective Monodeoxygenation of Methyl 3-(2-Quinoxalinylmethylene)carbazate N1, N4-Dioxide (Carbadox)

Article abstract of DOI:10.1055/s-1996-4420

The veterinary drug methyl 3-(2-quinoxalinylmethylene)carbazate N¹, N⁴-dioxide (Carbadox) has been selectively reduced in good yield at either N¹ or N⁴ with the reagents sodium dithionite or phosphorus trichloride, respectively. The identity of the products, which are important metabolites, was established by ¹H NMR and by an X-ray crystal structure of the N¹-monodeoxygenated product. The further metabolite, bis(desoxy) Carbadox, was prepared by reduction of Carbadox with a slight excess of sodium dithionite/ acetic acid. When a large excess of this reagent was used, a new compound, methyl 3-(2-quinoxalinylmethyl)carbazate, was also formed.