[Br:1][C:2]1[CH:3]=[C:4]([OH:8])[CH:5]=[CH:6][CH:7]=1.[CH3:9][C:10]1([CH3:19])[O:15][CH2:14][C:13]([CH3:18])([CH2:16]O)[CH2:12][O:11]1.C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.N(C(OC(C)C)=O)=NC(OC(C)C)=O>C1COCC1>[CH3:9][C:10]1([CH3:19])[O:15][CH2:14][C:13]([CH3:18])([CH2:16][O:8][C:4]2[CH:5]=[CH:6][CH:7]=[C:2]([Br:1])[CH:3]=2)[CH2:12][O:11]1
To a mechanically stirred mixture of 3-bromophenol (26.14 g, 0.1511 mol), 2,2,5-trimethyl-5-hydroxymethyl-1,3-dioxane (31.98 g, 0.20 mol), triphenylphosphine (59.32 g, 0.226 mol), and THF (250 mL), cooled to −2° C., a solution of diisopropyl azodicarboxylate (DIAD), 4.6 mL, 0.2265 mol) in THF (50 mL) was added dropwise over 45 min, and the mixture was allowed to warm up to room temperature. After 3 days, THF was removed, and the residue was stirred in a mixture of toluene and heptane (1:1, 300 mL), and filtered. The solids were washed with the same mixture of solvents (200 mL), and the combined filtrates were washed with dilute sodium hydroxide solution, water, and saturated sodium chloride solution, dried, and concentrated. The residue was chromatographed over silica gel. Elution with toluene-heptane (1:1) removed some unreacted triphenylphosphine. The product came in toluene-heptane (3:1) eluates and, on standing with pentane, solidified, 40.69 g (85% yield), m.p. 67-70° C. Mass spec: m/z 314, 316 (M+). Anal Calcd for C14H19BrO3: C, 53.34; H, 6.08; Br, 25.35%. Found: C, 53.37; H, 5.97; Br, 25.35%.
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