Reaction #2146735

Reaction equation

ethyl bromide

magnesium

(5Z)-3-methylnon-5-en-1-ol

2-methylbut-3-yn-2-ol

→

(9Z)-2,7-dimethyltridec-9-en-3-yne-2,5-diol

Yield 77.1%

Solvents

tetrahydrofuran

tetrahydrofuran

tetrahydrofuran

tetrahydrofuran

Conditions

Workup

1. 1
   Temperatureby occasional heating with a heat gun
2. 2
   Temperatureunder reflux
3. 3
   Temperatureto cool down to room temp.
4. 4
   workup.STIRRINGwith stirring
5. 5
   TemperatureThe reaction mixture was then again refluxed for 3 h
6. 6
   Otherthe heating bath removed
7. 7
   workup.STIRRINGwith stirring over a period of 30 min
8. 8
   TemperatureThe reaction mixture was refluxed
9. 9
   workup.STIRRINGwith stirring overnight
10. 10
    Temperatureto cool to room temp.
11. 11
    Otherquenched
12. 12
    workup.ADDITIONby pouring into 100 mL of an aqueous satd
13. 13
    OtherThe organic layer was separated
14. 14
    Extractionthe aqueous one extracted three times with 500 mL of ether each
15. 15
    DryingThe combined organic extracts were dried with sodium sulphate
16. 16
    Concentrationconcentrated to dryness in a rotary evaporator
17. 17
    OtherThe resulting residue (10.8 g) was purified by flash chromatography (200 g of silica gel, pentane/ether, 1:1, Rf=0.22)

Procedure

A solution of 10.4 g (95.6 mmol) of ethyl bromide in 40 mL of dry tetrahydrofuran was added dropwise over a period of 30 min to a vigorously stirred suspension of 2.32 g (95.6 mmol) of magnesium turnings in 15 mL of dry tetrahydrofuran, with the reaction being initiated by occasional heating with a heat gun. After stirring the reaction mixture for 90 min under reflux, it was allowed to cool down to room temp., and a solution of 3.54 g (42.2 mmol) of 2-methylbut-3-yn-2-ol in 40 mL of dry tetrahydrofuran was added dropwise with stirring. The reaction mixture was then again refluxed for 3 h, the heating bath removed and a solution of 6.50 g (42.2 mmol) of (5Z)-3-methylnon-5-en-1-ol in 40 mL of dry tetrahydrofuran added at room temp. with stirring over a period of 30 min. The reaction mixture was refluxed with stirring overnight, allowed to cool to room temp., and quenched by pouring into 100 mL of an aqueous satd. NH4Cl solution. The organic layer was separated, and the aqueous one extracted three times with 500 mL of ether each. The combined organic extracts were dried with sodium sulphate, and concentrated to dryness in a rotary evaporator. The resulting residue (10.8 g) was purified by flash chromatography (200 g of silica gel, pentane/ether, 1:1, Rf=0.22) to furnish 7.76 g (77%) of (9Z)-2,7-dimethyltridec-9-en-3-yne-2,5-diol as a colourless oil.

Source