Trimethyl orthoformate → 1,3-Benzoxazole-7-carboxylic acid

Reaction equation

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

Participants

Reactant 2

HCID 9005Trimethyl orthoformate

HCID 684433-Aminosalicylic acid

Product 1

HCID 183553101,3-Benzoxazole-7-carboxylic acid

Procedure

A solution of 3-amino-2-hydroxy-benzoic acid (12.5 mmol) in trimethyl orthoformate (19.2 mL) is heated to reflux for 20 h and concentrated in vacuo. The residue is washed three times with hot MeOH, the filtrates are combined and the solvent is removed in vacuo to give the desired product which is used without further purification. 1H-NMR (DMSO-d6): δ=13.4 (bs, 1H); 8.87 (s, 1H); 8.08 (d, J=8.0 Hz, 1H); 7.96 (d, J=7.5 Hz, 1H); 7.52 (t, J=7.9 Hz, 1H).

Workup

temperatureto reflux for 20 h
concentrationconcentrated in vacuo
washThe residue is washed three times with hot MeOH
customthe solvent is removed in vacuo

Sources & evidence

ORD record: ord-a3fc63cda01540df82fa25a92ae279d7
Source dataset: uspto-grants-2012_10
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US08288435B2

Reaction notes

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