反应详情

温度

0 °C

Aldimine (2.00 g, 7.47 mmol) and O-allyl-N-benzylcinchonidinium bromide (0.38 g, 0.75 mmol, 0.10 equiv) were mixed with toluene (20 mL) at ambient temperature. The mixture was stirred for 30 min and then was cooled to 0° C. Powdered KOH (2.10 g, 37.35 mmol, 5 equiv) was added at once to convert the thin slurry into a yellow solution. The mixture was stirred for 5 min and 4-methoxybenzyl bromide (7.51 g, 37.35 mmol, 5 equiv) was added at 0 to 1° C. The solution was allowed to warm and was stirred at ambient temperature for 16 h. The reaction mixture was sequentially washed with water (20 mL) and brine (20 mL), separated, and treated with a 5-6 N HCl solution in IPA (7 mL) for 1 h at ambient temperature. The reaction mixture was washed with water (20 mL). The aqueous phase was separated and treated with toluene (20 mL). The aqueous phase was separated, treated with a 2 N NaOH solution until basic, and the product was extracted with toluene (20 mL). The toluene phase was washed with brine (20 mL), separated, and dried over Na2SO4. The solid was filtered and the solvent was stripped to dryness to afford tert-butyl 2-amino-3-(4-methoxyphenyl)-2-methylpropanoate; 1.70 g; 85.8% as a clear oil. 1H NMR (500 MHz, CDCl3): δ 7.13 (d, J=8.7 Hz, 2H, Ar), 6.81 (d, J=8.7 Hz, 2H, Ar), 3.78 (s, 3H, CH3), 3.05 (d, J=13.3 Hz, 1H, CH2), 2.71 (d, J=13.3 Hz, 1H, CH2), 1.62 (br. s, 2H, NH2), 1.45 (s, 9H, 3×CH3), 1.32 (s, 3H, CH3). 1H NMR analysis, carried out in the presence of 1.2 equiv of BINOL, resulted in 47.6% ee. Optical rotation (α25D, chloroform, c=1.38): −9.06°.

1. stirringThe mixture was stirred for 5 min
2. temperatureto warm
3. stirringwas stirred at ambient temperature for 16 h
4. washThe reaction mixture was sequentially washed with water (20 mL) and brine (20 mL)
5. customseparated
6. additiontreated with a 5-6 N HCl solution in IPA (7 mL) for 1 h at ambient temperature
7. washThe reaction mixture was washed with water (20 mL)
8. customThe aqueous phase was separated
9. additiontreated with toluene (20 mL)
10. customThe aqueous phase was separated
11. additiontreated with a 2 N NaOH solution until basic
12. extractionthe product was extracted with toluene (20 mL)
13. washThe toluene phase was washed with brine (20 mL)
14. customseparated
15. dry with materialdried over Na2SO4
16. filtrationThe solid was filtered