General procedure for the synthesis of 2,6-dichloropyridine-4-boronic acid pinacol ester from 2,6-dichloropyridine and bis-boronic acid pinacol ester: Under nitrogen protection, 2,6-dichloropyridine (3 g, 20.3 mmol), 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl (5.92 g, 23.3 mmol), 1,10-phenanthroline (145 mg, 0.81 mmol) and chlorobis(1,5-cyclooctadiene)iridium(I) dimer (267 mg, 0.30 mmol) were dissolved in 1,2-dichloroethane (20 mL). After passing nitrogen for 5 minutes, the reaction mixture was heated at 100 °C for 1 hour. Upon completion of the reaction, the cooled mixture was poured into a mixture of ether (150 mL) and 4 M aqueous sodium hydroxide (200 mL) to separate the organic and aqueous phases. The aqueous phase was cooled with an ice bath and acidified with 5 M aqueous hydrochloric acid, and the resulting precipitate was filtered, washed with water and dried to afford 2,6-dichloropyridine-4-boronic acid pinacol ester (4.9 g, 17.9 mmol, 88% yield).LCMS (Method A): retention time 0.74 min; m/z 192,194 (as MH+ for boronic acid ionization).1H NMR ( 400 MHz, DMSO-d6) δ 1.28 (12H, s), 7.57 (2H, s).
