Studies on Reaction Mechanisms in Heterocyclic Compounds. II. : Chemical and Kinetic Studies on the Reaction of 2-Hydrazino-3-phenylquinoxaline with Carbonyl Compounds. (2)

Azoloquinoxaline N-oxides

“…o-Nitrobenzyl bromide (6) was converted to o-nitrobenzyltriphenylphosphonium bromide (7) in excellent yield.…”

“…Attempts by others to prepare these N-oxides by oxidation of the known azoloquinoxalines with hydrogen peroxide in acetic acid, alkaline potassium permanganate, or acidic chromic anhydride resulted in oxidation at C-4 instead of N-oxidation (eq l).1 We rea-H R = H, CH3; X = N R = H, CH3; X = CH soned that these compounds could be prepared from iV-oxide precursors, thereby avoiding the necessity for N-oxidation at a late stage in the synthesis. Until recently, there were few methods available for the selective synthesis of suitable 3substituted quinoxaline 1-oxide (1) precursors, but it has been demonstrated in these laboratories that certain quinoxaline 1,4-dioxides bearing an electron-withdrawing group in the 2 position can be selectively monodeoxygenated to afford good yields of the desired starting materials.14 Following this concept, we have developed general procedures for the synthesis of i'-triazolo[l,5-a]quinoxaline 5-oxides (3), s-triazolo [4,3c]quinoxaline 5-oxides (6), and tetrazolo[l,5-o]quinoxaline 5-oxides (7).…”