Nitric Acid → 6-Nitro-2H-pyrido[3,2-B][1,4]oxazin-3(4H)-one

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Reaction Steps

2H-Pyrido[3,2-b]-1,4-oxazin-3 (4H)-one (2.5 g) was dissolved in acetic acid (6 mL) and acetic anhydride (30 mL). Fuming nitric acid (3 mL) was added dropwise to the reaction solution in ice-bath. The reaction solution was stirred in ice-bath overnight. Solution was poured into crashed ice. The light yellow precipitation was collected by filtration, washed with water and dried to give a mixture of nitrated products (regio-isomers). The mixture was crystallized from dichloromethane to give 6-nitro-2H-pyrido[3,2-b]-1,4-oxazin-3 (4H)-one (1 g) as a light yellow solid. 6-Nitro-2H-pyrido[3,2-b]-1,4-oxazin-3 (4H)-one (1 g) was reduced under hydrogenolysis conditions using 10% Pd—C in methanol (50 mL) and 1N HCl solution (10 mL) at 50 psi for 2 h. The catalyst was filtered off and washed with methanol and 1N HCl solution. The filtrate was evaporated to give 6-amino-2H-pyrido[3,2-b]-1,4-oxazin-3 (4H)-one.

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