Hydrochloric Acid → 5-(1-Propynyl)pyridine-3-boronic Acid (contains varying amounts of Anhydride)

Participants

Reaction Conditions

Reaction Steps

To a solution of 3-bromo-5-(prop-1-ynyl)pyridine (2.96 g, 15.10 mmol) and triisopropyl borate (4.21 ml, 18.12 mmol) in THF and toluene at −40° C. was added n-BuLi (2.5 M solution in hexanes, 7.25 mL, 18.12 mmol) drop wise over a period of 7 min, and the reaction mixture was stirred at −40° C. for 30 min and then warmed up to −20° C. over a period of 8 min. The reaction was quenched with HCl (15.10 ml, 2 M solution, 30.2 mmol), and a reddish solution was formed. The two layers were separated, and the organic layer was extracted with water (3×10 mL). To the combined organic layers were added NaOH (5M solution, 2.416 ml, 12.08 mmol) (to adjust pH to 7). During the addition, a very white cloudy solution was formed. THF (30 mL) was added, but the layers did not separate. Solid sodium chloride was added to make the solution saturated, and the two layers were formed. The layers were separated, and the aqueous layer was extracted with THF (3×20 mL), and the combined THF layers were dried over sodium sulfate and then filtered. The filtrate was evaporated in vacuo, and the residue was concentrated to give a white powder (553 mg). This material was used without further purification.

Provenance & Evidence