Acetic Anhydride → 6-Bromo-2-methyl-4H-3,1-benzoxazin-4-one

Reaction equation

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

Participants

Reactant 2

HCID 7918Acetic Anhydride

HCID 798582-Amino-5-bromobenzoic acid

Product 1

HCID 27971426-Bromo-2-methyl-4H-3,1-benzoxazin-4-oneYield 85%

Procedure

2-Amino-5-bromobenzoic acid (25 g, 116 mmol) was added in portions to acetic anhydride (150 mL) giving a slightly exothermic reaction to 30° C. The suspension was heated at reflux for 2 h. The product crystallized spontaneously upon cooling. After stirring in ice for 30 min, the crystals were filtered off and washed twice with heptane. The crystals were thoroughly dried at 0.1 mbar/50° C. One obtained 22.4 g (85%) of beige crystals. MS: m/z=239/241 (M).

Workup

customgiving
customa slightly exothermic reaction to 30° C
temperatureThe suspension was heated
temperatureat reflux for 2 h
customThe product crystallized spontaneously
temperatureupon cooling
filtrationthe crystals were filtered off
washwashed twice with heptane
customThe crystals were thoroughly dried at 0.1 mbar/50° C

Sources & evidence

ORD record: ord-c8e59a2becb04486bdd9575972ab5d27
Source dataset: uspto-grants-2010_06
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US07728142B2

Reaction notes

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