Hydrochloric Acid → Ethyl 4-oxo-4H-1-benzopyran-2-carboxylate

A 2,68 M sodium ethoxide solution in ethanol (21,9 ml) was added slowly to a solution of 2-hydroxyacetophenone (1.76 ml, 14.7 mmol) and diethyl oxalate (3.98 ml, 29.4 mmol) in a mixture of dry ethyl ether (20 ml) and absolute ethanol (20 ml). The mixture was stirred under reflux for 3 h. Afterwards it was diluted with ethyl ether (40 ml), added with 1M HCl (25 ml) and extracted with ethyl ether (3×40 ml). The combined ether phases were dried and the solvents were removed by evaporation under reduced pressure. The obtained residue was dissolved in absolute ethanol (60 ml) and 0.380 ml of concentrated hydrochloric acid were added. The resulting mixture was left under stirring at 75° C. for 1 h. After this time, 50 ml of water were poured on the mixture which was extracted with ethyl acetate (3×50 ml). The organic phase was washed successively with a sodium bicarbonate saturated solution and a NaCl saturated solution, dried and the solvents were evaporated off under reduced pressure, to obtain a crude which was purified by crystallization in ethyl ether, thereby obtaining 2.660 g of the title product (83% yield).

1. temperatureunder reflux for 3 h
2. extractionextracted with ethyl ether (3×40 ml)
3. dry with materialThe combined ether phases were dried
4. customthe solvents were removed by evaporation under reduced pressure
5. dissolutionThe obtained residue was dissolved in absolute ethanol (60 ml)
6. addition0.380 ml of concentrated hydrochloric acid were added
7. waitThe resulting mixture was left
8. stirringunder stirring at 75° C. for 1 h
9. additionAfter this time, 50 ml of water were poured on the mixture which
10. extractionwas extracted with ethyl acetate (3×50 ml)
11. washThe organic phase was washed successively with a sodium bicarbonate saturated solution
12. dry with materiala NaCl saturated solution, dried
13. customthe solvents were evaporated off under reduced pressure
14. customto obtain a crude which
15. customwas purified by crystallization in ethyl ether

ORD record

ord-b00452521c2e412e84da840da1fe7c7b

Source dataset

uspto-grants-1999_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05990142