Acetic Anhydride → 2-methyl-5-nitro-4H-benzo[d][1,3]oxazin-4-one

HRID 1409612Notes

Reaction equation

[NH2:1][C:2]1[CH:10]=[CH:9][CH:8]=[C:7]([N+:11]([O-:13])=[O:12])[C:3]=1[C:4]([OH:6])=[O:5].[C:14](OC(=O)C)(=O)[CH3:15]>>[CH3:14][C:15]1[O:5][C:4](=[O:6])[C:3]2[C:7]([N+:11]([O-:13])=[O:12])=[CH:8][CH:9]=[CH:10][C:2]=2[N:1]=1

Participants

Reactant 2

HCID 7918Acetic Anhydride

HCID 957952-Amino-6-nitro-benzoic acid

Product 1

HCID 666429832-methyl-5-nitro-4H-benzo[d][1,3]oxazin-4-oneYield 85%

Conditions

Temperature: 200 °C

Procedure

A mixture of 2-amino-6-nitro-benzoic acid (1.5 g, 8.2 mmol) in acetic anhydride (15 mL) was heated at 200° C. for 30 minutes in a microwave oven. The mixture was filtered and washed with ethyl acetate (20 mL). The filtrate was concentrated in vacuo. The solid was stirred in ether (20 mL) for 2 hours. The suspension was filtered and washed with ether (20 mL) to give 2-methyl-5-nitro-benzo[d][1,3]oxazin-4-one as a light brown solid (1.4 g, 85% yield): HPLC: Waters Symmetry C18, 5 μm, 3.9×150 mm, 1 mL/min, 240 nm, CH3CN/0.1% H3PO4, 5% grad 95% in 5 min, 5.36 min (92%); 1H NMR (DMSO-d6) δ 2.42 (s, 3H, CH3), 7.79 (dd, J=1, 8 Hz, 1H, Ar), 7.93 (dd, J=1, 8 Hz, 1H, Ar), 8.06 (t, J=8 Hz, 1H, Ar); 13C NMR (DMSO-d6) δ 20.87, 107.79, 121.54, 128.87, 137.19, 147.12, 148.46, 155.18, 161.78; LCMS: MH=207.

Workup

filtrationThe mixture was filtered
washwashed with ethyl acetate (20 mL)
concentrationThe filtrate was concentrated in vacuo
filtrationThe suspension was filtered
washwashed with ether (20 mL)

Sources & evidence

ORD record: ord-38567dd511f347e09493e69e81b8b91f
Source dataset: uspto-grants-2014_12
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US08921385B2

Reaction notes

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