Phosphoric Acid → 4-(4-BOC-Piperazino)phenylboronic acid

Participants

Reaction Conditions

Reaction Steps

To tert-butyl 4-(4-bromophenyl)-1-piperazinecarboxylate (118.30 g, 346.9 mmol) in dry THF/MePh (1/1, 1.5 L) at −78° C. under dry nitrogen was added n-BuLi (2.5 M, 160 mL, 398.9 mmol) dropwise and the reaction was stirred at −78° C. for 20 minutes. Triisopropyl borate (96.1 mL, 416.3 mmol) was added dropwise and the reaction was warmed to 0° C. and stirred for 2 hours. Aqueous sat. NH4Cl (400 mL), water (100 mL) and 1 equivalent of H3PO4 (20 ML) were added and the mixture stirred for 15 minutes and then concentrated to a volume of approximately 200 mL (at which stage the mixture became bluish and a precipitate formed). A dropping funnel was charged with heptane (800 mL) and the solvent was added to the reaction mixture with vigorous stirring over a period of one hour and the resulting suspension was stirred overnight. The suspension was filtered, washed with heptane (2×200 mL), and dried over the weekend in vacuo to afford 4-[4-(tert-butoxycarbonyl)-1-piperazinyl]phenylboronic acid.

Provenance & Evidence