3,4-dihydro-2H-pyran → 2-But-3-enoxyoxane

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Reaction Steps

To a chilled solution (0° C.) of 3,4-dihydro-2H-pyran (117 g, 1.4 mol) in anhydrous ether (600 mL) were added p-toluensulfonic acid (0.5 g) and 3-buten-1-ol (25.0 g, 0.35 mol). The resulting mixture was stirred at room temperature for 5 h and was then quenched by the addition of concentrated ammonium hydroxide (5 mL) and methanol (50 mL). The solvent was evaporated in vacuo, and ether was added to the residue. The precipitated ammonium p-toluenesulfate was filtered, the filtrate was concentrated, and the crude product was purified by flash column chromatography on silica gel (0-5% ethyl acetate in hexanes) to give 2-(3-butenyloxy)tetrahydropyran (49 g, 90%) as colorless viscous liquid: 1H-NMR (CDCl3, 300 MHz,) δ 5.80-5.89 [m, 1H, ═CH—C], 5.02-5.06 [m overlapping, 2H, ═CH2], 4.59-4.60 [m, 1H, 2-H of THP], 3.77-3.83 [m, 2H, —CH2O], 3.44-3.50 [m, 2H, CH2O of THP], 2.33-2.38 [m, 2H, CH2—CH═CH2], 1.51-1.71 [m, 6H, Hs of THP].

Provenance & Evidence