B#B.[CH3:3][CH:4]([CH2:7][O:8][CH:9]1[CH2:14][CH2:13][CH2:12][CH2:11][O:10]1)[CH:5]=[CH2:6].[Br:15]Br.C[O-].[Na+]>O1CCCC1.CO.O>[Br:15][CH2:6][CH2:5][CH:4]([CH3:3])[CH2:7][O:8][CH:9]1[CH2:14][CH2:13][CH2:12][CH2:11][O:10]1
Diborane in tetrahydrofuran (125 ml, 0.150 m) at 0° C. under nitrogen is added to a mixture of 3-methyl-4-(tetrahydropyran-2-yloxy)-1-butene (72 g, 0.423 m) and tetrahydrofuran (150 ml). After the addition is complete, the mixture is allowed to warm to room temperature and then stirred for 1 hour. The reaction mixture is cooled to 0° and bromine (24 ml, 0.43 mmole) and sodium methoxide (0.565 m) in methanol (300 ml) are added slowly simultaneously. After the addition is complete, the mixture is allowed to warm to room temperature and stirred for 30 minutes. The mixture is then treated with water (100 ml) and extracted with petroleum ether (2×200 ml). The organic layer is washed with 5% sodium bicarbonate (100 ml), water (2×100 ml) and dried (Na2SO4). The solvent is removed in vacuo to give a colorless liquid. This crude product is purified by column chromatography in silica gel (500 g, 1% ether in petroleum ether) to give 1-bromo-3-methyl-4-(tetrahydropyran-2-yloxy)-butane (71 g, 65%) as a colorless liquid.
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