Trimethyl borate → (4-Chloro-2,5-difluorophenyl)methanol

To a mixture of 4-chloro-2,5-difluoro-benzoic acid (15 g, 78 mmol) tetrahydrofuran (THF)(75 mL) and trimethylborate (26 mL, 230 mmol) was added borane-methylsulfide complex (86 mL, 86 mmol, 10 M solution in DMS), and the mixture was stirred for 18 hours at ambient temperature. Additional borane-methylsulfide complex (2.47 mL, 24.7 mmol) was added to drive the reaction to completion. The mixture was poured into 1M aqueous NaOH, extracted 3× with ether, and the combined organic layers were dried over anhydrous MgSO4, filtered and concentrated in vacuo. Trituration of the solid residue with ether-hexane afforded 14 g of (4-chloro-2,5-difluoro-phenyl)-methanol as a colorless solid. 1H NMR (400 MHz, CDCl3) δ 7.26 (dd, 1H, J=6, 8.8 Hz), 7.11 (dd, 1H, J=6, 9.2 Hz), 4.71 (d, 2H, J=6.0 Hz), 1.80 (t, 1H, J=6.0 Hz) ppm.