Trimethyl borate → 4-Methyl-3-(2,2,6,6-tetramethyl-3,5-dioxo-tetrahydropyran-4-yl)phenylboronic acid

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Reaction Conditions

Reaction Steps

4-(5-Bromo-2-methyl-phenyl)-2,2,6,6-tetramethyl-pyran-3,5-dione (5 g, 0.0147 mol) is dissolved in anhydrous tetrahydrofuran (150 ml), the reaction mixture is cooled to 0° C. and sodium hydride (708 mg, 0.0294 mol, 60% dispersion in oil) is added. The mixture is stirred for 30 minutes, then cooled to −78° C. n-Butyl lithium (14.7 ml, 0.0294 mol, 2M solution in cyclohexane) is added, dropwise over approximately 10 minutes and reaction mixture is stirred for 15 minutes before trimethylborate (4.95 ml, 0.0442 mol) is added. The reaction mixture is stirred for a further 45 minutes, allowed to warm to ambient temperature and then stirred a further 1.5 hours before quenching with 2M aqueous hydrochloric acid. The reaction mixture is stirred for 1 hour and then extracted with dichloromethane. After separation of the organic phase solvents are removed under reduced pressure to give a pale yellow gum. Trituration with iso-hexane affords 4-methyl-3-(2,2,6,6-tetramethyl-3,5-dioxo-tetrahydropyran-4-yl)phenylboronic acid (2.01 g) as a white solid.

Provenance & Evidence