Water → (S)-4-hydroxybutan-2-yl 2-methoxy-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenylcarbamate

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Reaction Steps

To (S)-4-(tert-butyldimethylsilyloxy)butan-2-ol (1.649 mmol, 337 mg) in dichloromethane (4 ml) were added mol sieves (4A), 2-(4-isocyanato-3-methoxyphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1.374 mmol, 378 mg) and 4-dimethylaminopyridine (0.275 mmol, 33.6 mg) were added and the mixture was stirred at 40° C. (oil bath temperature) for 18 hours. The mol sieves were removed by filtration and the filtrate washed with water, dried (sodium sulfate) and concentrated in vacuo to give a crude product which was purified by column chromatography (silica gel, heptanes with gradient 10% to 50% of ethyl acetate) to afford (S)-4-(tert-butyldimethylsilyloxy)butan-2-yl 2-methoxy-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenylcarbamate (443 mg). Tetrabutylammonium fluoride (1M in tetrahydrofuran, 1.22 mmol, 1.22 ml) was added to (S)-4-(tert-butyldimethylsilyloxy)butan-2-yl 2-methoxy-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenylcarbamate (240 mg) in tetrahydrofuran (1 ml) at room temperature. After 20 hours water was added to the reaction mixture, extracted with dichloromethane, the organic extract dried (sodium sulfate) and concentration in vacuo to yield (S)-4-hydroxybutan-2-yl 2-methoxy-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenylcarbamate (268 mg) which was used in the next step without further purification.

Provenance & Evidence