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

Participants

Reaction Steps

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.

Provenance & Evidence