General procedure for the synthesis of 2,3-dimethyl-4-bromopyridine from 2,3-dimethyl-4-hydroxypyridine: 2,3-dimethylpyridin-4-ol (2.0 g, 20 mmol) and phosphorus tribromide (14.0 g, 49 mmol) were stirred and reacted for 4 hours at 130 °C under nitrogen protection. After completion of the reaction, the reaction mixture was slowly poured into ice water and adjusted to alkaline with aqueous sodium hydroxide. Subsequently, the mixture was extracted with ether and water. The organic phase was concentrated under reduced pressure to remove the ether to give a brown needle-like solid product (2.03 g, 90% purity, 60% yield). The structure of the product was confirmed by 1H NMR (CDCl3) and LC/MS: 1H NMR (CDCl3) δ 8.10 (d, 1H), 7.34 (d, 1H), 2.58 (s, 3H), 2.39 (s, 3H); LC/MS: retention time (5-100-7 method) = 3.555 min; m/z 185.7 ([M + H ]+, 100%), 187.7 ([M + H + 2]+, 97%).
