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

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.

1. customfor 2 h
2. filtrationThe catalyst was filtered off
3. washwashed with methanol and 1N HCl solution
4. customThe filtrate was evaporated

ORD record

ord-c1065368744b40b6a35273cbce4edde1

Source dataset

uspto-grants-2010_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07642351B2