Trimethyl borate → 2,2'-Bithiophene-5-boronic acid

Participants

Reaction Conditions

Reaction Steps

In a flame-dried, 3-neck, 250 mL rbf, 2,2′-bithiophene (5.0 g, 30.1 mmol) was dissolved in anhydrous THF (100 mL) and cooled to −78° C. (dry ice/acetone). A solution of n-BuLi in hexanes (2.5 M, 12.6 mL, 31.6 mmol) was added slowly over a period of ˜5 minutes. The reaction mixture was allowed to stir at −78° C. for 15 minutes, and then trimethyl borate (10.1 mL, 90 mmol) was added dropwise over a period of 5 minutes. The reaction was allowed to stir at −78° C. for 2 hours, then warm to RT and stir for a further 1 hour. The yellow reaction mixture was quenched by pouring it into a 10% HCl solution (250 mL). The mixture was extracted with ether (2×100 mL) and the combined organic portions were washed with water (500 mL), dried over MgSO4, filtered and solvent removed by rotary evaporation. The resulting yellow solid was washed with water, filtered and air dried to afford (109) (6.15 g, 97%). The material was used in the next step without further purification.

Provenance & Evidence