[Br:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]23[O:14][C:11]([CH2:15][CH:16](C(OC)=O)[C:17]([O:19][CH3:20])=[O:18])([CH2:12][CH2:13]2)[CH2:10][CH2:9]3)=[CH:4][CH:3]=1.[Cl-].[Li+]>CS(C)=O.O>[Br:1][C:2]1[CH:3]=[CH:4][C:5]([C:8]23[O:14][C:11]([CH2:15][CH2:16][C:17]([O:19][CH3:20])=[O:18])([CH2:10][CH2:9]2)[CH2:12][CH2:13]3)=[CH:6][CH:7]=1To a solution of dimethyl 2-((4-(4-bromophenyl)-7-oxabicyclo[2.2.1]heptan-1-yl)methyl)malonate (305 mg, 0.77 mmol) in DMSO (3.0 mL) and water (0.03 mL) was added lithium chloride (98 mg, 2.3 mmol) and the reaction was stirred in a microwave reactor at 180° C. for 20 min. The resulting yellow reaction mixture was diluted with water and extracted with EtOAc. The organic phase was dried over MgSO4, filtered and concentrated by rotary evaporation in vacuo to afford 289 mg of a crude clear yellow film. Purification of the crude material by column chromatography (24 g silica gel, 0-30% EtOAc:Hept, monitor 230 nm) afforded 194 mg colorless film that solidified upon standing and which was used without further purification. 1H NMR (400 MHz, DMSO-d6): δ ppm 1.54-1.67 (m, 4H), 1.68-1.79 (m, 2H), 2.04-2.16 (m, 4H), 2.42-2.48 (m, 2H), 3.61 (s, 3H), 7.31 (d, J=8.6 Hz, 2H), 7.53 (d, J=8.6 Hz, 2H). ESI-MS m/z: 341.1 [M+H]+, retention time 1.59 min (condition E).
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