[Br:1][C:2]1[CH:3]=[CH:4][C:5]2[O:9][CH:8]([CH3:10])[C:7](=O)[C:6]=2[CH:12]=1.[CH2:13]([O:15][C:16](=[O:37])[CH:17]=P(C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)[CH3:14]>C1(C)C=CC=CC=1.Cl.C(O)C>[CH2:13]([O:15][C:16](=[O:37])[CH2:17][C:7]1[C:6]2[CH:12]=[C:2]([Br:1])[CH:3]=[CH:4][C:5]=2[O:9][C:8]=1[CH3:10])[CH3:14]A mixture of 5-bromo-2-methyl-benzofuran-3-one (6.8 g, 29.9 mmol) and (triphenyl-phosphanylidene)-acetic acid ethyl ester (17.4 g, 44.9 mmol) in anhydrous toluene is heated for 40 h at 120° C. under an argon atmosphere. After cooling to room temperature the volatiles are removed by rotary evaporation. The residue is purified by flash column chromatography (silica gel, gradient of cyclohexane/EtOAc 100:0 to 90:10) to afford a mixture of two regioisomeric products. The product mixture (7.1 g, 31.3 mmol) is dissolved in a 1.25 M solution of HCl in ethanol and heated at reflux for 1 h. After cooling to room temperature the solvent is removed by rotary evaporation to yield the title compound as a pale yellow oil (6.9 g, 23.2 mmol, 78%). 1H NMR (400 MHz, CDCl3, 298 K): δ=7.59 (d, J=2.0 Hz, 1H), 7.31-7.22 (m, 2H), 4.15 (q, J=7.1 Hz, 2H), 3.54 (s, 2H), 2.42 (s, 3H), 1.25 (t, J=7.1 Hz, 3H). MS (ES+): 297 (M(C13H1379BrO3)+H)+.
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