Triisopropyl borate → 4-Ethoxyphenylboronic acid

Participants

Reaction Steps

A one-necked, 25-mL, round-bottomed flask equipped with a reflux condenser fitted with an argon inlet adapter was charged with magnesium powder (0.255 g, 10.5 mmol, -50 mesh), 7 mL THF, and 4-bromophenetol (1.41 g, 1.00 mL, 7.00 mmol). The resulting mixture was heated to reflux for 3 h. A second one-necked, 25-mL, round- bottomed flask equipped with a rubber septum and an argon inlet needle was charged with triisopropyl borate (3.95 g, 4.85 mL, 21.00 mmol) and cooled to -78° C. while the Grignard reagent prepared above was added dropwise via cannula over ca. 5 min. The cooling bath was removed and the reaction mixture was stirred for 3 h at room temperature. A mixture of ether (50 mL) and a 10% HCl solution (59 mL) was added and the resulting organic phase was washed with a 100-mL portion of water. The organic phase was dried over MgSO4, filtered, and concentrated to provide a yellow solid which was recrystallized from ether-hexanes to provide 0.783 g (67%) of a white solid:

Provenance & Evidence