Hydrochloric Acid → 2-(Tert-butyldimethylsilanyloxymethyl)-4-fluoro-5-trimethylsilanylfuran-3-yl-boronic acid

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Reaction Conditions

Reaction Steps

tert-Butyl-(4-fluorofuran-2-ylmethoxy)dimethylsilane (prepared according to Heffernan et al, US2008 0058395, 6.75 g) was dissolved in anhydrous THF (100 mL), under an atmosphere of nitrogen and cooled to −78° C. n-Butyllithium (2.5M in hexanes, 11.74 mL) was added and the mixture was stirred at −78° C. for 10 minutes. Chlorotrimethylsilane (3.19 g) was added and the mixture was stirred at −78° C. for 40 minutes. Further n-butyllithium (2.5M in hexanes, 11.74 mL) was added and the mixture was stirred at −78° C. for 40 minutes, before triisopropyl borate (11.04 g) was added. The resultant mixture was stirred at −78° C. for 5 minutes then allowed to warm to room temperature. 1M aqueous hydrochloric acid (100 mL) and diethyl ether (50 mL) were added and the mixture was stirred vigorously for 5 minutes. The layers were separated and the organic layer was dried (MgSO4) and filtered. The filtrate was concentrated in vacuo and the residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and cyclohexane, with a gradient of 0-20% to give 2-(tert-butyldimethylsilanyloxymethyl)-4-fluoro-5-trimethylsilanylfuran-3-yl-boronic acid (6.01 g) as a brown oil which was used without further characterisation.

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