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

To a solution of commercially available 4-bromobutan-1-ol (16) (1 equi.) and 3,4-dihydropyran (17) (1.5 equi.) in dichloromethane (3 mL/mmole), phosphorus oxychloride (0.01 equi.) was added at room temperature. The reaction mixture was stirred at that temperature for 24 h. Then potassium carbonate (1 equi.) was added to the reaction mixture and the reaction mixture was stirred at room temperature for 1 h, quenched with water, extracted with dichloromethane, washed with brine, dried over MgSO4, and concentrated in vacuo. Purification by chromatography on silica gel (5% EtOAc (ethylacetate)/hexanes) afforded 2-(4-bromobutoxy) -tetrahydropyran (18), as a colorless oil (88%).