[CH3:1][O:2][C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][C:4]=1B(O)O.[Br:12][C:13]1[CH:14]=[CH:15][C:16]([CH:23]=[O:24])=[C:17]([CH:22]=1)[C:18]([O:20]C)=O.P([O-])([O-])([O-])=O.[K+].[K+].[K+]>C1CC=CCCC=C1.C1CC=CCCC=C1.[Cl-].[Cl-].[Rh].[Rh].C1COCC1>[Br:12][C:13]1[CH:22]=[C:17]2[C:16]([CH:23]([C:4]3[CH:5]=[CH:6][CH:7]=[CH:8][C:3]=3[O:2][CH3:1])[O:24][C:18]2=[O:20])=[CH:15][CH:14]=1
(2-Methoxyphenyl)boronic acid (4.69 g, 30.9 mmol), methyl 5-bromo-2-formylbenzoate (5.00 g, 20.6 mmol; GLSyntech, LLC), tripotassium phosphate (17.5 g, 82.0 mmol) and THF (103 mL) were added to a pressure tube. The tube was purged with argon. Then chloro(1,5-cyclooctadiene)rhodium(I) dimer (0.507 g, 1.03 mmol) was added. The tube was sealed and stirred at rt. After 30 min, LCMS showed lactone product. TLC confirmed a complete conversion of methyl 5-bromo-2-formylbenzoate to a lower spot. The reaction was filtered with the aid of EtOAc. The filtrate was concentrated and the crude material was absorbed onto a plug of silica gel and purified by chromatography through a Redi-Sep pre-packed silica gel column (120 g), eluting with a gradient of 0% to 30% EtOAc in hexanes, to provide 6-bromo-3-(2-methoxyphenyl)isobenzofuran-1(3H)-one (5.15 g, 78% yield). m/z (ESI) 319.0 (M+H)+, 321.0 (M+3H)+.
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