Reaction #1135823

Reaction equation

Acetic acid 3-(4-hydroxy-phenyl)-8-methyl-4-oxo-4H-chromen-7-yl ester

→

Acetic acid 3-(4-hydroxy-phenyl)-8-methyl-4-oxo-chroman-7-yl ester

Solvents

ethyl acetate

Conditions

Workup

1. 1
   Otherevacuated
2. 2
   Otherpurged with nitrogen gas (×5) and hydrogen gas (×5)
3. 3
   workup.ADDITION10% Pd/Al2O3 (9 g, 35%) was added to the round bottom flask at 40 hours
4. 4
   workup.ADDITION10% Pd/Al2O3 (5.69 g, 20%) was added to the round bottom flask
5. 5
   Otherreaction rate
6. 6
   OtherReaction
7. 7
   workup.WAITwas completed at 64 hours
8. 8
   FiltrationThe reaction mixture was filtered through celite
9. 9
   Otherto remove the Pd/Al2O3 catalyst
10. 10
    Washthe celite was rinsed with EtOAc (1 L)
11. 11
    Otherwas collected
12. 12
    OtherThe EtOAc was evaporated off on a rotary evaporator
13. 13
    Otherto give a yellow solid
14. 14
    OtherThe solid was re-crystallised in 95% EtOH (650 ml)
15. 15
    workup.WAITleft in the freezer overnight
16. 16
    FiltrationOff-white crystals were collected by suction filtration
17. 17
    workup.WAITThe crystals were stored in a desiccator for 24 hours

Procedure

Acetic acid 3-(4-hydroxy-phenyl)-8-methyl-4-oxo-4H-chromen-7-yl ester (26.32 g), 10% Pd/Al2O3 (12.93 g, 50%) and ethyl acetate (EtOAc) (1.5 L) were added to a hydrogenation round bottom flask (2 L). The flask was placed on the hydrogenator, evacuated, purged with nitrogen gas (×5) and hydrogen gas (×5). The reaction was monitored by HPLC. 10% Pd/Al2O3 (9 g, 35%) was added to the round bottom flask at 40 hours, indicated there was no product peak present, only starting material was present. HPLC at 62 hours indicated that the major peak was product peak with starting material peak being half height of product peak. 10% Pd/Al2O3 (5.69 g, 20%) was added to the round bottom flask to speed up reaction rate. Reaction was completed at 64 hours. The reaction mixture was filtered through celite to remove the Pd/Al2O3 catalyst, the celite was rinsed with EtOAc (1 L) to ensure majority of product was collected. The EtOAc was evaporated off on a rotary evaporator to give a yellow solid. The solid was re-crystallised in 95% EtOH (650 ml) and left in the freezer overnight. Off-white crystals were collected by suction filtration. 1HNMR in d-CDCl3 indicated the off-white crystals were 8Acetic acid 3-(4-hydroxy-phenyl)-8-methyl-4-oxo-chroman-7-yl ester with >95% purity. The crystals were stored in a desiccator for 24 hours, and weighed (18.37 g, 69%).

Source