[CH3:1]C(C)([O-])C.[K+].[CH3:7][O:8][CH2:9][C:10]([CH3:14])([OH:13])[C:11]#[CH:12].CI>O1CCCC1.CCOCC.O>[CH3:1][O:13][C:10]([CH3:14])([CH2:9][O:8][CH3:7])[C:11]#[CH:12]17.5 ml of the 1.0M solution of potassium tert-butoxide in tetrahydrofuran (Aldrich; 17.52 mmol) are added to a solution, cooled with an ice bath, of 2 g of (±)-1-methoxy-2-methyl-3-butyn-2-ol (17.52 mmol) in 6 ml of tetrahydrofuran. Stirring is carried out at ambient temperature for 30 minutes and then 0.55 ml of methyl iodide (35.04 mmol) is added. The reaction mixture is stirred at ambient temperature for 3 hours and then is diluted with ether and water. After separation by settling, the organic phase is washed with water, dried over sodium sulfate, filtered and concentrated under limited vacuum. 2.4 g of the expected product are obtained in the form of a yellow oil comprising residual ether and residual tetrahydrofuran. The (±)-3,4-dimethoxy-3-methylbut-1-yne obtained is used in the following stage without subsequent purification.
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