[C:1]([O:16][C:17]([CH3:20])([CH3:19])[CH3:18])(=[O:15])[C:2]1[CH:14]=[CH:13][CH:12]=[C:4]([C:5]([O:7][C:8]([CH3:11])([CH3:10])[CH3:9])=[O:6])[CH:3]=1.[I:21]I>C1COCC1>[I:21][C:12]1[CH:13]=[CH:14][C:2]([C:1]([O:16][C:17]([CH3:20])([CH3:19])[CH3:18])=[O:15])=[CH:3][C:4]=1[C:5]([O:7][C:8]([CH3:11])([CH3:10])[CH3:9])=[O:6]A dry and nitrogen-flushed 10-ml-Schlenk-flask, equipped with a magnetic stirring bar and a septum, was charged with a solution of the di-tert-butyl isophthalate (278 mg, 1 mmol) in dry THF (1 ml). After cooling to 0° C., a freshly prepared (TMP)2Mg.2LiCl solution (0.6 mol/l in THF, 1.83 ml, 1.1 mmol) was added dropwise and the reaction mixture was stirred at the same temperature. The completion of the metalation (2 h) was checked by GC-analysis of reaction aliquots quenched with a solution of I2 in dry ether. Iodine (508 mg, 2 mmol) dissolved in dry THF (2 ml) was then added at 0° C. and the resulting mixture warmed to room temperature. After stirring for 1 hour, the reaction mixture was quenched with sat. aq. Na2S2O3, extracted with ether (3×20 ml) and dried over Na2SO4. After filtration the solvent was removed in vacuo. Purification by flash-chromatography (n-pentane/diethyl ether, 10:1) furnished compound 51a (380 mg, 94%) as a yellow oil.
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