Acetic Anhydride → (2E)-3-(3,4-Dimethylphenyl)prop-2-enoic acid

HRID 1017136Notes

Reaction equation

HRID 1017136 reaction equation
[CH3:1][C:2]1[CH:3]=[C:4]([CH:7]=[CH:8][C:9]=1[CH3:10])[CH:5]=O.[C:11]([O-:14])(=[O:13])[CH3:12].[Na+].C(OC(=O)C)(=O)C>>[CH3:1][C:2]1[CH:3]=[C:4]([CH:7]=[CH:8][C:9]=1[CH3:10])/[CH:5]=[CH:12]/[C:11]([OH:14])=[O:13]

Participants

4

Reactant 3

HCID 7918Acetic AnhydrideHCID 222783,4-DimethylbenzaldehydeHCID 517045Sodium Acetate

Product 1

HCID 13548376(2E)-3-(3,4-Dimethylphenyl)prop-2-enoic acidYield 97%

Procedure

A 1 L single-neck round bottom flask equipped with a condenser, magnetic stir bar, and a nitrogen inlet was charged with 3,4-dimethylbenzaldehyde (Lancaster 97%, 70.0 g, 0.52 mol), sodium acetate (anhydrous, 47.1 g, 0.57 mol), and acetic anhydride (300 mL, 3.2 mol). The mixture was stirred and heated to reflux. After 48 hours heating was discontinued and the reaction mixture was quenched, while still hot, by the cautious addition of water (300 mL). Ice-water was added to double the volume and the mixture was extracted with diethyl ether (700 mL); the organic phase was separated, washed with water (4×1 L), dried over anhydrous magnesium sulfate, and evaporated to dryness. Recrystallization of the crude product from methanol gave trans-3,4-dimethylcinnamic acid (64.0 g, 97% purity by GC) as yellow crystals. 1HNMR (CD2Cl2, 500 MHz) δ7.74 (d, JAB=16 Hz, 1H); 7.36 (br s, 1H); 7.32 (d, JAB=8 Hz, 1H); 7.18 (d, JAB=8 Hz, 1H); 6.41 (d, JAB=16 Hz, 1H); 2.29 (s, 6H).

Workup

  1. customA 1 L single-neck round bottom flask equipped with a condenser, magnetic stir bar, and a nitrogen inlet
  2. temperatureheated to reflux
  3. temperatureAfter 48 hours heating
  4. customthe reaction mixture was quenched
  5. additionwhile still hot, by the cautious addition of water (300 mL)
  6. additionIce-water was added
  7. extractionthe mixture was extracted with diethyl ether (700 mL)
  8. customthe organic phase was separated
  9. washwashed with water (4×1 L)
  10. dry with materialdried over anhydrous magnesium sulfate
  11. customevaporated to dryness
  12. customRecrystallization of the crude product from methanol

Sources & evidence

ORD record
ord-2fea8119e43148ab8bb405a16273a7c0
Source dataset
uspto-grants-2002_11
Patent number
US06479424B1

Reaction notes

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