Pinacol → 5-(Tetramethyl-1,3,2-dioxaborolan-2-yl)-2-(tris(propan-2-yl)silyl)-1,3-oxazole

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Reaction Conditions

Reaction Steps

2-Triisopropylsilanyl-oxazole (intermediate 16, 10 g, 44.365 mmol) is dissolved in 40 mL abs. diethylether under argon. The solution is cooled to −78° C. and n-butyllithium (1.6 M solution in hexane, 100 mL, 160 mmol) is added slowly at that temperature. After stirring for 1 h boronic acid triispropylester (12 mL, 52.193 mmol) 20 mL abs. THF is added slowly. The mixture is stirred for 2 h, and is warmed to r.t. The mixture is quenched with methanol. 2,3-Dihydroxy-2,3-dimethylbutane (pinacole, 5.243 g, 44.365 mmol) is dissolved in 10 mL THF and injected to the mixture at 18° C. within 3 min. The mixture is acidified to pH 5 with acetic acid and stirred for 12 h. After addition of 150 mL diethylether and filtration over silica gel, the solvent is evaporated in vacuo. Yield: 15.2 g; ESI mass spectrum: [M+H]+=352; retention time HPLC: 1.334 min (HPLC method Z001_002).

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