A convenient synthesis of 2‐amino‐4 H ‐1,3,4‐oxadiazino[5,6‐ b ]‐quinoxaline derivatives

The reaction of 6‐chloro‐2‐(1‐methylhydrazino)quinoxaline 4‐oxide 5 with a 2‐fold molar amount of ethyl chloroglyoxalate gave ethyl 8‐chloro‐4‐methyl‐4 H ‐1,3,4‐oxadiazino[5,6‐ b ]quinoxaline‐2‐carboxylate 6 , whose reaction with hydrazine hydrate afforded the C 2 ‐hydrazinocarbonyl derivative 7 . The reaction of compound 7 with nitrous acid provided the C 2 ‐acylazide derivative 8 , which was converted into the C 2 ‐amino 9 , C 2 ‐carbamate 11a‐c, 12a,b , and C 2 ‐ureido 13a‐c, 14 derivatives. The mass spectral fragmentation patterns were examined for compounds 10–14 , wherein the molecular ion peak did not appear in the mass spectra of compounds 10c, 11a‐c, 12a,b, 13c , and 14.