2-Methoxy-4-(trifluoromethyl)phenyl boronic acid (2.05 g, 9.32 mmol; Combi-Blocks, San Diego, Calif.), methyl 5-bromo-2-formylbenzoate (1.51 g, 6.21 mmol; GLSyntech, LLC, Hatfield, Pa.), tripotassium phosphate (5.27 g, 24.9 mmol; freshly ground) and THF (31.1 mL) was added to a vial. The vial was purged with argon. Then chloro(1,5-cyclooctadiene)rhodium(i) dimer (0.153 g, 0.311 mmol; Strem Chemicals, Inc., Newburyport, Mass.) was added. The vial was sealed and stirred at RT. After 1 h, the reaction was filtered and the filtrate was concentrated under a vacuum. The crude material was absorbed onto a plug of silica gel and purified by chromatography through a silica gel column (80 g), eluting with a gradient of 0% to 10% EtOAc in heptane, to provide 6-bromo-3-(2-methoxy-4-(trifluoromethyl)phenyl)isobenzofuran-1(3H)-one (2.06 g, 86% yield) as a brown solid. 1H NMR (400 MHz, CDCl3) δ ppm 3.92 (s, 3H), 6.72 (s, 1H), 7.11-7.17 (m, 3H), 7.25 (dt, J=8.2, 0.7 Hz, 1H), 7.65 (dd, J=8.3, 1.7 Hz, 1H), 8.00 (d, J=1.8 Hz, 1H). m/z (ESI) 405.0 (M+H)+. This lactone was not stable on MS.
