Reaktion #508672

Reaktionsgleichung

4-fluorobenzylamine

sodium cyanoborohydride

Diisobutylaluminum hydride

2-ethyl-malonic acid diethyl ester

→

rac-2-[(4-fluoro-benzylamino)-methyl]-butyric acid ethyl ester

Ausbeute 22.0%

Lösungsmittel

acetic acid

toluene

dichloromethane

ethanol

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstigewas quenched with saturated aqueous ammonium chloride (35 mL)
2. 2
   SonstigeThe cold bath was removed
3. 3
   workup.ADDITION1.0 M aqueous hydrochloric acid solution (90 mL) and DL-tartaric acid (4.25 g) were added sequentially
4. 4
   SonstigeThe biphasic mixture was then partitioned between 1.0 M aqueous hydrochloric acid solution (350 mL) and dichloromethane (350 mL)
5. 5
   TrocknenThe organic layer was dried over sodium sulfate
6. 6
   Einengenwas concentrated in vacuo
7. 7
   Sonstigeto afford crude product (1.64 g, 11.4 mmol, 59%)
8. 8
   workup.STIRRINGThe mixture was stirred at 25° C. for 20 h
9. 9
   Einengenwas concentrated in vacuo
10. 10
    SonstigeThe residue was partitioned between half-saturated aqueous sodium bicarbonate solution (150 mL) and ethyl acetate (2×150 mL)
11. 11
    TrocknenThe combined organic layers were dried over sodium sulfate
12. 12
    Einengenwere concentrated in vacuo
13. 13
    SonstigeThe residue was purified by flash column chromatography (Teledyne Isco RediSep column; 0-60% ethyl acetate in hexanes)

Vorschrift

Diisobutylaluminum hydride (38.4 mL of a 1.0 M solution in toluene, 38.4 mmol) was added over 5 min to a solution of 2-ethyl-malonic acid diethyl ester (3.50 g, 19.2 mmol) in dichloromethane (35 mL) at −78° C. The reaction mixture was stirred at that temperature for 3.5 h, and then was quenched with saturated aqueous ammonium chloride (35 mL). The cold bath was removed, 1.0 M aqueous hydrochloric acid solution (90 mL) and DL-tartaric acid (4.25 g) were added sequentially, and the mixture was allowed to warm to 25° C. over 1.5 h with vigorous stirring. The biphasic mixture was then partitioned between 1.0 M aqueous hydrochloric acid solution (350 mL) and dichloromethane (350 mL). The organic layer was dried over sodium sulfate and was concentrated in vacuo to afford crude product (1.64 g, 11.4 mmol, 59%). This material was dissolved in ethanol (40 mL) at 25° C. and 4-fluorobenzylamine (1.30 mL, 11.4 mmol), glacial acetic acid (1.5 mL), and sodium cyanoborohydride (1.43 g, 22.8 mmol) were added sequentially. The mixture was stirred at 25° C. for 20 h, and then was concentrated in vacuo. The residue was partitioned between half-saturated aqueous sodium bicarbonate solution (150 mL) and ethyl acetate (2×150 mL). The combined organic layers were dried over sodium sulfate and were concentrated in vacuo. The residue was purified by flash column chromatography (Teledyne Isco RediSep column; 0-60% ethyl acetate in hexanes) to afford rac-2-[(4-fluoro-benzylamino)-methyl]-butyric acid ethyl ester (0.630 g, 2.49 mmol, 22%) as a pale yellow oil. 1H NMR (400 MHz, CDCl3) δ: 0.92 (3H, t, J=7.4 Hz), 1.27 (3H, t, J=7.0 Hz), 1.52-1.69 (2H, m), 2.47-2.54 (1H, m), 2.68 (1H, dd, J=4.7 Hz, J2=11.7 Hz), 2.86 (1H, dd, J=9.2 Hz, J2=11.7 Hz), 3.73 (1H, d, J=13.2 Hz), 3.77 (1H, d, J=13.2 Hz), 4.12-4.20 (2H, m), 6.96-7.00 (2H, m), 7.24-7.27 (2H, m).

Quelle