Reaction #4080

Reaction equation

sodium borohydride

calcium chloride

cholesta-1,4,6-trien-3-one

isopropenyl acetate

→

cholesta-1,5,7-trien-3-ol

Yield 63.0%

Solvents

acetic acid

ethanol

methanol

Conditions

Workup

1. 1
   Temperaturethe mixture was heated
2. 2
   Temperatureunder reflux for 3 hours
3. 3
   WashThe reaction solution was thoroughly washed with water until it
4. 4
   Dryingdried over sodium sulfate A solution of the
5. 5
   Otherthus obtained
6. 6
   Concentrationconcentrate in 600 ml of ether
7. 7
   workup.ADDITIONwas added dropwise at a temperature of -5° C. to -10° C. to a reducer solution
8. 8
   Otherbeing prepared
9. 9
   workup.ADDITIONadding dropwise
10. 10
    workup.ADDITIONwas added to the reaction mixture
11. 11
    Extractionthe resultant solution was extracted with ether
12. 12
    OtherThe ethereal layer separated
13. 13
    Washwas washed with water
14. 14
    Dryingsodium bicarbonate solution, dried over sodium sulfate
15. 15
    workup.DISTILLATIONdistilled under reduced pressure
16. 16
    Otherto remove ether
17. 17
    OtherThe residue was recrystallized from acetone

Procedure

To a mixture of 38 g (0.1 mol) of cholesta-1,4,6-trien-3-one and 17 g (0.1 mol) of paratoluenesulfonic acid were added 400 g (4 mol) of isopropenyl acetate, and the mixture was heated under reflux for 3 hours. The reaction solution was thoroughly washed with water until it was neutral, and dried over sodium sulfate A solution of the thus obtained concentrate in 600 ml of ether was added dropwise at a temperature of -5° C. to -10° C. to a reducer solution and stirred at 0° C. for 6 hours, said reducer solution being prepared by cooling a solution of 90 g of calcium chloride in 1,500 ml of methanol to a temperature of -5° C. to -10° C., then adding dropwise thereto a solution of 45 g of sodium borohydride in 2,000 ml of ethanol, and stirring the reaction solution at a temperature of -5° C. to -10° C. for 60 minutes. After completion of the reaction, 50% acetic acid was added to the reaction mixture and the resultant solution was extracted with ether. The ethereal layer separated was washed with water and then sodium bicarbonate solution, dried over sodium sulfate and distilled under reduced pressure to remove ether therefrom. The residue was recrystallized from acetone to yield 23.9 g of cholesta-1,5,7-trien-3-ol (IV), m.p. 126°-127° C. The yield was 63%.

Source