Triethylborane → {(S)-1-[hydroxy-(5-thiophen-2-yl-oxazol-2-yl)-methyl]-propyl}-carbamic acid tert-butyl ester

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Reaction Steps

To a solution of 5-thiophen-2-yl-oxazole (0.85 g, 5.62 mmol) in dry THF (4 mL) is added triethylborane (1.0 M in THF, 5.62 mmol, 5.62 mL). The mixture is stirred at room temperature for 45 min, then cooled to −78° C. and n-butyl lithium (1.6 M in hexane, 5.62 mmol, 3.51 mL) is added drop wise. The mixture is stirred at −78° C. for 45 min then a solution of (1-Formyl-propyl)-carbamic acid tert-butyl ester (2.81 mmol, 0.526 g) in dry THF (3 mL) is added slowly. The mixture is stirred at −78° C. for 4 h, then warmed to 0° C. and quenched by adding 30 mL of 10% (vol) HOAc in ethanol. The mixture is stirred at room temperature for 18 hr and then concentrated in vacuum. The residue is purified over 90 g of silica gel, eluted with ethyl acetate: heptane (1:2 then 1:1) to afford {(S)-1-[hydroxy-(5-thiophen-2-yl-oxazol-2-yl)-methyl]-propyl}-carbamic acid tert-butyl ester (363 mg, 38%) as an oil.

Provenance & Evidence