Alcohol (preparation recently submitted),

allyl bromide (ReagentPlus, Sigma Aldrich),

sodium hydride (60% dispersion in mineral oil, Sigma Aldrich),

N,N-dimethylformamide (ACS reagent, Sigma Aldrich)

The tetrahydropyran 3-ol (0.093 g, 0.32 mmol) and dry DMF (22 mL) were sequentially added to a 50 mL round bottom flask fitted with a septum under nitrogen atmosphere. The flask was placed on an ice bath with stirring and then solid sodium hydride (0.016 g, 0.67 mmol) was added portion-wise. The solution was stirred for 30 min while maintaining the temperature at 0°C and then allyl bromide (0.078 g (56 µL), 0.64 mmol) was added dropwise. The reaction mixture was allowed to slowly warm to room temperature and with stirring that was continued overnight. After, the reaction was once again placed on an ice bath and the septum was removed. The reaction was quenched by the dropwise addition of ice-cold water (2 mL). Additional water (10 mL) was added and mixture was extracted with ethyl acetate (3 x 15 mL) using a separatory funnel. The combined organic fractions were dried with Na₂SO₄, filtered and the solvent was removed under reduced pressure. Purification of the residue by flash chromatography using 7:3 hexanes:ethyl acetate as eluent yielded 0.098 g (92%) of product as a clear, colorless oil.

Particular care should be taken when handling sodium hydride.