methyl (E)-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pent-4-enoate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 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%). 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 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 the resulting solid was washed with tert-butyl methyl ether again

Conditions: temp:65.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Methyl pent-4-ynoate (5.0 g, 44.6 mmol) and 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (7.42 g, 58.0 mmol) were mixed, zirconocene chloride hydride (1.18 g, 4.46 mmol) and triethylamine (0.622 ml, 4.46 mmol) were added and the mixture was stirred at 65° C. overnight. The reaction solution was left to cool and then diluted with diethyl ether, and the precipitated white solid was removed by filtration through celite. The filtrate was concentrated under reduced pressure, and the resulting residue was purified by column chromatography (hexane:ethyl acetate) to afford the title compound (5.36 g, 50.1%). The reaction solution was left to cool the precipitated white solid was removed by filtration through celite The filtrate was concentrated under reduced pressure the resulting residue was purified by column chromatography (hexane:ethyl acetate)