3,4-dihydro-2H-pyran → 2-(4-Bromobutoxy)tetrahydro-2H-pyran

16.0 g (105.0 mmols) of 4-bromobutanol was dissolved in 140 ml of chloroform, and a solution prepared by dissolving 13.9 ml (1.5-fold equivalent weight) of 3,4-dihydro-2H-pyran in 40 ml of chloroform was dropwise added thereto at 0° C. in an atmosphere of argon. The solution obtained was stirred for 4 hours while keeping it at 0° C., followed by addition of an aqueous sodium hydrogencarbonate, and the resulting solution was extracted with chloroform (100 ml×2). The organic layer obtained was dried with anhydrous sodium sulfate, and thereafter concentrated under reduced pressure to obtain 24.0 g of 4-(tetrahydropyran-2-yl)oxybutyl bromide (yield: 96%).