To a solution of 2-bromo-5-methylbenzoic acid (5.00 g, 23.3 mmol) in DME (100 mL) were added 3-carboxyphenylboronic acid (3.86 g; 23.3 mmol), a solution of Na2CO3 (9.90 g, 93 mmol) in H2O and tetrakis(triphenylphosphine)palladium. The mixture was stirred at 90° C. for 4 days. The mixture was allowed to cool to rt, diluted with EtOAc (50 mL), and washed with a saturated NaHCO3 solution. The aqueous layer was separated, acidified with 10% HCl, and extracted with EtOAc (3×20 mL). The combined extracts were dried over MgSO4 and concentrated. The crude material was purified by column chromatography (9:1 hexanes/EtOAc 1% acetic acid) to afford 4-methyl-[1,1′-biphenyl]-2,3′-dicarboxylic acid (2.20 g, 37%) as a solid: 1H NMR (DMSO-d6) δ2.40 (s, 3H), 7.30 (m, 1H), 7.42 (m, 1H), 7.52-7.57 (m, 2H), 7.60 (s, 1H), 7.85 (s, 1H), 7.91-7.92 (m, 1H).
