[Br:1][C:2]1[C:6](=[CH:7][Br:8])[O:5][C:4](=[O:9])[C:3]=1[CH:10]([OH:14])[CH2:11][CH2:12][CH3:13].CC(C)=O.OS(O)(=O)=O.O=[Cr](=O)=O>CC(C)=O.S(=O)(=O)(O)O.O.[O-2].[O-2].[O-2].[Cr+6]>[Br:1][C:2]1[C:6](=[CH:7][Br:8])[O:5][C:4](=[O:9])[C:3]=1[C:10](=[O:14])[CH2:11][CH2:12][CH3:13]To an ice cooled situation of 4-bromo-5-(bromomethylene)-3-(1-hydroxybutyl)-2(5H)-furanone (2.77 g, 8.5 mmol) in acetone (75 ml) was added dropwise with stirring Jones reagent (12 ml, prepared by dissolving chromium trioxide (13.36 g) in sulfuric acid (11.2 ml) and water (38.5 ml). The mixture was stirred at room temperature for 1 h and the progress of the reaction monitored by thin layer chromatography. After the completion of the reaction, the mixture was poured into water (200 ml) and extracted with ether (3×100 ml). The combined ether extracts were washed with brine (100 ml), dried over sodium sulfate and evaporated to yield the crude ketone (2.23 g, 81%) as a yellow solid. Recrystallisation of the crude ketone from dichloromethane/hexane gave the pure ketone as yellow plates, m.p. 83-84° C. νmax 1700, 1680, 1630, 1540, 1310, 1000 cm−1. 1H n.m.r. δ (CDCl3) 0.97, t, J 7.2 Hz, (H4′)3; 1.70, m, (H3′)2; 2.93, t, J 7.2 Hz, (H2′)2; 6.74, s, 5-CHBr. 13C n.m.r. δ (CDCl3): 13.6, C4′; 16.7, C3′; 44.4, C2′; 99.3, 5-CHBr; 125.7, C4; 138.1, C3; 150.4, C5; 163.5, CO; 194.1, C1′. Mass spectrum: m/z 326, (M(81Br2), <5%); 324 (M(81Br, 79Br), 5); 320, (M(79Br2), <5); 298 (10); 296 (22); 281 (16); 279 (8); 225 (4); 131 (14); 77 (32); 71 (52); 43 (100).
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