2-Nitrobenzoic acid → 3-formyl-5,8-dimethoxy-2H-chromene-2-carboxylic acid ethyl ester

HRID 1925902Notes

Reaction equation

[CH2:1]([O:3][C:4](=[O:9])/[CH:5]=[CH:6]/[CH:7]=[O:8])[CH3:2].[N+](C1C=CC=CC=1C(O)=O)([O-])=O.N1CCCC1.[OH:27][C:28]1[C:35]([O:36][CH3:37])=[CH:34][CH:33]=[C:32]([O:38][CH3:39])[C:29]=1[CH:30]=O>CS(C)=O>[CH2:1]([O:3][C:4]([CH:5]1[C:6]([CH:7]=[O:8])=[CH:30][C:29]2[C:28](=[C:35]([O:36][CH3:37])[CH:34]=[CH:33][C:32]=2[O:38][CH3:39])[O:27]1)=[O:9])[CH3:2]

Participants

Conditions

Temperature: 25 °C

Procedure

(E)-4-oxo-but-2-enoic acid ethyl ester (7.30 mL, 60.37 mmol), 2-nitro benzoic acid (1.852 g, 10.98 mmol), and pyrrolidine (0.91 mL, 10.98 mmol) were added simultaneously to a solution of commercially available 2-hydroxy-3,6-dimethoxy-benzaldehyde (10.0 g, 54.89 mmol) in dimethysulfoxide (50 mL) at 25° C. and the solution was stirred for 78 hours at 25° C. The reaction was quenched by the addition of water. The reaction mixture was then partitioned between water and ethyl acetate. The combined organics were washed with a saturated brine solution, dried over anhydrous sodium sulfate, filtered, rinsed and concentrated in vacuo. The residue obtained was purified on a silica gel flash column chromatography using ethyl acetate-hexanes (1:1.2) as eluents, yielding 3-formyl-5,8-dimethoxy-2H-chromene-2-carboxylic acid ethyl ester (3.5 g, 62.3%).

Workup

customThe reaction was quenched by the addition of water
customThe reaction mixture was then partitioned between water and ethyl acetate
washThe combined organics were washed with a saturated brine solution
dry with materialdried over anhydrous sodium sulfate
filtrationfiltered
washrinsed
concentrationconcentrated in vacuo
customThe residue obtained
customwas purified on a silica gel flash column chromatography

Sources & evidence

ORD record: ord-a6db1d6f2d8746fba985da20d2a68195
Source dataset: uspto-grants-2012_05
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US08178689B2

Reaction notes

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