Tributyl borate → 3-(1-Carboxy-ethyl)-phenyl boronic acid

Participants

Reaction Steps

A solution of 2-(3-bromo-phenyl)-propionic acid [500 mg, 2.18 mmol, Intermediate (69)] in anhydrous ether (20 mL) is added tert-butyl lithium (1.7 M in pentane, 5.4 mL, 9.16 mmol) dropwise at −78° C. and this mixture is stirred for 30 minutes treated with tributyl borate (2.34 mL, 8.72 mmol). The reaction mixture is allowed to warm up to room temperature, stirred for 15 hours, diluted with ether, and quenched with 1 M H3PO4. After stirring for 30 minutes the ether layer is separated and extracted three times with 2 N sodium hydroxide (20 mL). The combined sodium hydroxide extracts are acidified with 6 N hydrochloric acid to pH=1 and extracted three times with ether (50 mL). The combined organic extracts are washed with brine, dried over sodium sulfate and concentrated to obtain 3-(1-carboxy-ethyl)-phenyl boronic acid [Intermediate (70)] as a solid, which is used without further purification.

Provenance & Evidence