Trimethyl borate → 3-(2,4-Dioxobicyclo[3.2.1]oct-3-yl)-4-ethylphenylboronic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of 3-(2-ethyl-5-iodophenyl)bicyclo[3.2.1]octane-2,4-dione (0.65 g, 1.77 mmol) in anhydrous tetrahydrofuran (15 ml) at −10° C. is added iso-propyl magnesium chloride lithium chloride complex (10.6 ml, 10.6 mmol, 1M in tetrahydrofuran) dropwise over 10 minutes. The reaction mixture is stirred at this temperature for 1.5 hours, then cooled to −78° C., at which point trimethyl borate (1.39 ml, 12.4 mmol) is added dropwise to maintain a temperature below −60° C. After re-cooling to −78° C. the mixture is further stirred for 5 minutes, then additionally at room temperature for 1 hour. The solution is quenched with 2M hydrochloric acid and extracted with ethyl acetate (×3). All organic fractions are combined, dried over magnesium sulfate, filtered and the filtrate concentrated in vacuo to give an orange-coloured gum. This crude product is dissolved in a minimum amount of dichloromethane then precipitated with iso-hexane to afford 3-(2,4-dioxo-bicyclo[3.2.1]oct-3-yl)-4-ethylphenylboronic acid (0.46 g, 90%) as a cream-coloured solid.

Provenance & Evidence