Sulfuric Acid → 6-chloro-5,7-dimethyl-4-oxo-4H-1-benzopyran-2-carboxylic acid

HRID 461822

Reaction equation

HRID 461822 reaction equation
[OH-].C([N+](C)(C)C)C1C=CC=CC=1.[Cl:13][C:14]1[C:19]([CH3:20])=[CH:18][C:17]([OH:21])=[CH:16][C:15]=1[CH3:22].[C:23]([C:29](OC)=[O:30])#[C:24][C:25]([O:27]C)=[O:26].[OH-].[Na+].S(=O)(=O)(O)O>CO.O1CCOCC1>[Cl:13][C:14]1[C:19]([CH3:20])=[CH:18][C:17]2[O:21][C:24]([C:25]([OH:27])=[O:26])=[CH:23][C:29](=[O:30])[C:16]=2[C:15]=1[CH3:22]

Participants

8

Reactant 5

HCID 1118Sulfuric AcidHCID 27234-Chloro-3,5-dimethylphenolHCID 12980Dimethyl acetylenedicarboxylateHCID 14798Sodium HydroxideHCID 66854Benzyltrimethylammonium hydroxide

Product 1

HCID 213925966-chloro-5,7-dimethyl-4-oxo-4H-1-benzopyran-2-carboxylic acid

Reagents, catalysts & solvents 2

HCID 887MethanolSolventHCID 312751,4-DioxaneSolvent

Conditions

Temperature
0 °C

Procedure

0.5 Parts of benzyl trimethylammonium hydroxide were added dropwise to a mixture of 156.6 parts of 4-chloro-3, 5-xylenol, 149.1 parts of dimethyl acetylene dicarboxylate and 30 parts of dioxan. The reaction mixture was heated for 1/2 hour on the steam bath, cooled, and basified with 320 parts of 25% aqueous sodium hydroxide solution. After addition of 100 parts of methanol the red solution was heated at reflux for 3 hours on the steam bath, cooled, and acidified with excess dilute sulphuric acid. The precipitated yellow solid was filtered, washed with a little water, and dried. The solid was added portionwise to 850 parts of stirred chlorosulphonic acid cooled to 0° C. When all the solid had dissolved, the dark red solution was added cautiously dropwise to excess ice-water. The precipitated solid was filtered, washed with water, and recrystallised from a dioxan aqueous ethanol mixture to give 157.1 parts of 6-chloro-5,7-dimethyl-4-oxo-4H-1-benzopyran-2-carboxylic acid as a colourless solid, melting point 289°-290° C.

Workup

  1. temperatureThe reaction mixture was heated for 1/2 hour on the steam bath
  2. temperaturecooled
  3. temperaturewas heated
  4. temperatureat reflux for 3 hours on the steam bath
  5. temperaturecooled
  6. filtrationThe precipitated yellow solid was filtered
  7. washwashed with a little water
  8. customdried
  9. additionThe solid was added portionwise to 850 parts of stirred chlorosulphonic acid
  10. dissolutionWhen all the solid had dissolved
  11. additionthe dark red solution was added cautiously dropwise to excess ice-water
  12. filtrationThe precipitated solid was filtered
  13. washwashed with water
  14. customrecrystallised from a dioxan aqueous ethanol mixture

Sources & evidence

ORD record
ord-39b0c557d23b47318e7ee8c4f9597455
Source dataset
uspto-grants-1977_12
Patent number
US04064256

Linked notes

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