Reaction #1815

Reaction equation

Ethanol

toluene

diethyl carbonate

sodium hydride

toluene

water

→

7-Benzyloxy-4-hydroxy-coumarin

Yield 84.0%

Conditions

Workup

1. 1
   Temperaturewas heated
2. 2
   workup.DISSOLUTIONto dissolve the starting material
3. 3
   OtherThis solution was then taken in an addition funnel
4. 4
   Otherequipped with a mechanical stirrer
5. 5
   Othera distillation apparatus (double jacketed-splitter heads) with a condenser, a thermocouple, and a thermometer to read
6. 6
   TemperatureThe reaction flask was heated to 110°-115° C. with a heating mantle during the addition
7. 7
   Otheris removed as an azeotrope with toluene
8. 8
   workup.ADDITIONAdditional toluene was added through the addition funnel
9. 9
   TemperatureThe reaction mixture was refluxed for ~5 hrs
10. 10
    Otherthe reaction
11. 11
    OtherThe contents of the reaction flask were transferred to a separatory funnel
12. 12
    Otherto separate into two phases
13. 13
    Filtrationfiltered under vacuum
14. 14
    OtherThe crude product was recrystallized from hot methanol

Procedure

4-Benzyloxy-2-hydroxy-acetophenone (20 g, 0.0825 mol), prepared in accordance with Example 4, was dissolved in 150 mL of toluene. To this solution was added diethyl carbonate (25.3 g, 0.21 mol) and the entire contents taken in a beaker was heated while stirring to dissolve the starting material. This solution was then taken in an addition funnel and was added at a rate of 7-8 mL/min (addition time=1.5 hrs) to a suspension of sodium hydride (4.3 g, 10.1 mol) in toluene (100 mL) taken in a 500 mL 4-neck flask equipped with a mechanical stirrer, a distillation apparatus (double jacketed-splitter heads) with a condenser, a thermocouple, and a thermometer to read the temperature of the distillate under N2 atmosphere. The reaction flask was heated to 110°-115° C. with a heating mantle during the addition. Ethanol produced during this reaction is removed as an azeotrope with toluene. Additional toluene was added through the addition funnel to have enough of toluene in the reaction flask. The reaction mixture was refluxed for ~5 hrs to complete the reaction. The contents of the reaction flask were transferred to a separatory funnel and 400 mL of distilled water was added to separate into two phases. The aqueous layer was acidified to pH 2.0 with 1:1 dil. HCl and filtered under vacuum. The crude product was recrystallized from hot methanol; yield 84%.

Source