text: A mixture of bromo acetal 1 (549 mg, 1.78 mmol), AIBN (30.3 mg, 0.185 mmol), and BuSnH (0.65 mL, 2.42 mmol) in dry benzene (12 mL) was heated under reflux for 1 hour and then evaporated under reduced pressure. Silicagel column chromatography of the crude product with hexane–EtOAc (92:8) as eluant gave tetrahydropyran 2 (395 mg, 97%) as an oily mixture of two diastereomers.  (c 0.43, CHCl); IR (CHCl):1732 cm–1;1H NMR (CDCl)δ 4.77–4.89 (m, 0.6H), 4.66–4.69 (m, 0.4H), 3.40–4.44 (m, 4H), 3.68 (s, 3H), 2.61 (dd, J = 15.2, 4.2 Hz, 1H), 2.51 (dd, J = 15.2, 3.8 Hz, 1H), 0.73–1.06 (m, 3H); mass spectrum: m/z 215 (M+–Me); Anal. Calcd for CHO: C, 62.6; H, 9.65. Found: C, 62.6; H, 9.7.