Benzoic Acid → 3-Fluoro-4-methoxybenzoic acid

3-fluoro-4-methoxyacetophenone (11.5 g) was dissolved in 100 ml dioxane and NaOBr solution (as prepared below) was added dropwise, with constant stirring with a stir bar at room temperature. The NaOBr solution was prepared by dissolving 40 g of NaOH in 500 ml of water, cooling to 0° C. in an ice bath, and adding bromine (12.5 ml) dropwise while stirring with stir bar; bromine was added slowly so that the reaction mixture did not exceed 5° C. After overnight stirring of the 3-fluoro-4-methoxyacetophenone, dioxane and NaOBr solution, the reaction mixture was diluted with water (200 ml). Since the reaction mixture was basic, the product, benzoic acid, was in water as its sodium salt. The resultant mixture was partitioned between ether and water. The ether layer was washed with dilute aqueous NaOH to extract any remaining product as Na salt. The aqueous layers were combined and acidified to pH 1 to precipitate the benzoic acid. The resulting acid was extracted with ether. The ether layer was washed with water a few times, dried with MgSO4, and filtered. Rotary evaporation of the ether fraction afforded 3-fluoro-4-methoxybenzoic acid (IV) in 85% yield.

1. temperaturecooling to 0° C. in an ice bath
2. stirringwhile stirring
3. stirringwith stir bar
4. customdid not exceed 5° C
5. customThe resultant mixture was partitioned between ether and water
6. washThe ether layer was washed with dilute aqueous NaOH
7. extractionto extract any remaining product as Na salt
8. customto precipitate the benzoic acid
9. extractionThe resulting acid was extracted with ether
10. washThe ether layer was washed with water a few times
11. dry with materialdried with MgSO4
12. filtrationfiltered
13. customRotary evaporation of the ether fraction

ORD record

ord-93fc24620c104a2c9d3ba2a8256382e3

Source dataset

uspto-grants-1995_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05422037