Benzopyran → 4H-1-Benzopyran-2-carboxylic acid, 6-nitro-4-oxo-, ethyl ester

HRID 1071195Notes

Reaction equation

[O:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[C:4](=[O:11])[CH:3]=[C:2]1[C:12]([O:14][CH2:15][CH3:16])=[O:13].[N+:17]([O-])([O-:19])=[O:18].[K+].O1C2C=CC=CC=2C=CC1>S(=O)(=O)(O)O>[N+:17]([C:7]1[CH:6]=[C:5]2[C:10](=[CH:9][CH:8]=1)[O:1][C:2]([C:12]([O:14][CH2:15][CH3:16])=[O:13])=[CH:3][C:4]2=[O:11])([O-:19])=[O:18]

Participants

Conditions

Temperature: 0 °C

Procedure

To a solution of ethyl chromone-2-carboxylate (Example 16) in about 3 mL of sulfuric acid cooled to −10° C. is added about 1 mL potassium nitrate in sulfuric acid. The molar ratio of potassium nitrate to the benzopyran is slightly greater than 1:1. The reaction mixture is stirred at 0° C. for 1 h, the ice bath removed, and the reaction stirred at room temperature until the reaction is complete by HPLC (<3% benzopyran): about 4-6 h. The nitrated benzopyran precipitates as the reaction progresses. The reaction mixture is poured onto ice, and the precipitate is dissolved in ethyl acetate. The ethyl acetate layer is dried, filtered, and evaporated to afford ethyl 6-nitrochromone-2-carboxylate as a light yellow solid (about 90% yield).

Workup

customthe ice bath removed
stirringthe reaction stirred at room temperature until the reaction
customabout 4-6 h
customThe nitrated benzopyran precipitates as the reaction progresses
additionThe reaction mixture is poured onto ice
dissolutionthe precipitate is dissolved in ethyl acetate
dry with materialThe ethyl acetate layer is dried
filtrationfiltered
customevaporated

Sources & evidence

ORD record: ord-7e1f096c064f4d1bab6461c279be65e7
Source dataset: uspto-grants-2005_06
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US06903227B2

Reaction notes

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