Imidazole → Ethyl (S)-(-)-2-(tert-butyldimethylsilyloxy)propionate

To a solution of (S)-(−)-ethyl lactate (20 mL, 191.06 mmol) in DMF (191 mL) was added tert-butyldimethyl silyl chloride (39.6 g, 262.59 mmol) and imidazole (41.6 g, 612.72 mmol). After stirring at room temperature for 20 hr, the reaction mixture was diluted with a saturated aqueous NaCl solution (600 mL) and extracted with petroleum ether (3×400 mL). The organic layer was washed with a cold 3% HCl solution (200 mL) and a saturated aqueous NaCl solution (200 mL), dried over Na2SO4 and concentrated. The remaining residue was purified by silica gel (700 g) with petroleum ether (2 L), followed by 3% ethyl acetate in petroleum ether (4 L). The 3% ethyl acetate in the petroleum ether fractions was collected and the solvent was removed to give 36.57 g of (S)-(−)-ethyl 2-(tert-butyldimethylsilyloxy)propanoate as colorless oil (82% yield). 1H NMR (CDCl3): δ 4.23 (q, 1H, J=6.8 Hz, H2, —CH—), 4.11 (q, 2H, J=7.2 Hz, —CH2—), 1.32 (d, 3H, J=6.8 Hz, H3, —CH3), 1.21 (t, 3H, J=7.2 Hz, —CH3), 0.83 (s, 9H, Si—(CH3)3), 0.03 (s, 3H, Si—CH3), 0.00 (s, 3H, Si—CH3).

1. extractionextracted with petroleum ether (3×400 mL)
2. washThe organic layer was washed with a cold 3% HCl solution (200 mL)
3. dry with materiala saturated aqueous NaCl solution (200 mL), dried over Na2SO4
4. concentrationconcentrated
5. customThe remaining residue was purified by silica gel (700 g) with petroleum ether (2 L)
6. customThe 3% ethyl acetate in the petroleum ether fractions was collected
7. customthe solvent was removed

ORD record

ord-6f07c4a35869425880fa3a572965f337

Source dataset

uspto-grants-2012_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08168648B2