[CH2:1]1[CH2:17][O:16][C:3]2([CH2:9][O:8][C:7]([CH2:11][CH2:12][CH2:13][CH2:14][OH:15])([CH3:10])[CH2:6][CH2:5][CH2:4]2)[O:2]1.N1C=CC=CC=1>C(Cl)Cl.N1C=CC=CC=1.[O-2].[O-2].[O-2].[Cr+6].[O-2].[O-2].[O-2].[Cr+6]>[CH2:17]1[CH2:1][O:2][C:3]2([CH2:9][O:8][C:7]([CH3:10])([CH2:11][CH2:12][CH2:13][CH:14]=[O:15])[CH2:6][CH2:5][CH2:4]2)[O:16]1Dry celite (40 g) and 6,6-ethylenedioxy-2-(4'-hydroxybutyl)-2-methyloxepane (4.88 g, 0.0196 mol) in methylene chloride (100 ml) are added to a pyridine-chromium trioxide solution [prepared from pyridine (18.6 g, 0.0284 mol) and chromium trioxide (11.8 g, 0.118 mol)]in dry methylene chloride (500 ml) at 10° C. in a nitrogen atmosphere. After 5 hours the mixture is filtered and the celite is washed with methylene chloride (10×50 ml). The solvent is removed at reduced pressure. The residue is diluted with ether (200 ml), filtered and the ether is removed at reduced pressure. The crude product (4.7 g) is chromatographed on SilicAR CC-7 (100 g) in hexane. Elution with 20% ethyl acetate/hexane gives 6,6-ethylenedioxy-2-methyl-2-(4'-oxobutyl)-oxepane (14) as a clear colorless oil (3,3 g, 70%): ir (neat) 1725 cm-1 (CHO).
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