Potassium Hydroxide → (E)-5-Boronopent-4-enoic acid

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Reaction Steps

Methyl (E)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pent-4-enoate (2.0 g, 8.33 mmol) was dissolved in MeOH (100 ml), a 0.8 M aqueous potassium hydroxide solution (52.1 ml, 41.6 mmol) was added and the mixture was stirred at room temperature overnight. MeOH was removed by concentration under reduced pressure, and 3 M hydrochloric acid was then added until the pH was 3. This aqueous solution was washed with tert-butyl methyl ether and then concentrated under reduced pressure. The resulting residue was purified by column chromatography (10 mM aqueous ammonium acetate solution:methanol). Obtained fractions were concentrated under reduced pressure, and the resulting solid was washed with tert-butyl methyl ether again to afford the title compound (674.6 mg, 56.3%).

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