Acetic Anhydride → 6,8-dimethoxyisochroman-1,3-dione

HRID 432945Notes

Reaction equation

HRID 432945 reaction equation
[C:1]([CH2:4][C:5]1[CH:13]=[C:12]([O:14][CH3:15])[CH:11]=[C:10]([O:16][CH3:17])[C:6]=1[C:7]([OH:9])=[O:8])(O)=[O:2].C(OC(=O)C)(=O)C>C1(C)C=CC=CC=1>[CH3:15][O:14][C:12]1[CH:13]=[C:5]2[C:6](=[C:10]([O:16][CH3:17])[CH:11]=1)[C:7](=[O:9])[O:8][C:1](=[O:2])[CH2:4]2

Participants

4

Reactant 2

HCID 7918Acetic AnhydrideHCID 41666254778-99-8

Product 1

HCID 118168976,8-dimethoxyisochroman-1,3-dioneYield 83.1%

Reagents, catalysts & solvents 1

HCID 1140TolueneSolvent

Conditions

Temperature
110 °C

Procedure

2-Carboxymethyl-4,6-dimethoxybenzoic acid (60) (3.97 gm) was stirred in toluene (40.0 mL) at ambient temperature in a 100 mL flask with magnetic stirring. Acetic anhydride (1.72 mL) was added and the mixture heated to 110° C. Monitoring by HPLC revealed that the reaction was complete within 2.5 hours. Heat was then removed. Crystallization of 6,8-dimethoxyisochroman-1,3-dione (25) occurred as the solution cooled. The mixture was cooled to 2° C. After a short hold time, yellow crystalline solids were filtered, washed with fresh toluene and then dried on high vacuum. 6,8-Dimethoxyisochroman-1,3-dione (25) (3.05 g) was isolated as a yellow crystalline solid.

Workup

  1. temperatureHeat
  2. customwas then removed
  3. customCrystallization of 6,8-dimethoxyisochroman-1,3-dione (25)
  4. temperaturecooled
  5. temperatureThe mixture was cooled to 2° C
  6. filtrationAfter a short hold time, yellow crystalline solids were filtered
  7. washwashed with fresh toluene
  8. customdried on high vacuum

Sources & evidence

ORD record
ord-847e912df363482db53662f3d2be951e
Source dataset
uspto-grants-2003_12
Patent number
US06664401B2

Reaction notes

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