Reaktion #722619

Reaktionsgleichung

2,2-dimethyl-4-pentenal

diethylzinc

acetic anhydride

aminoalcohol

→

(+)-3-acetoxy-4,4-dimethylhept-1-ene

Ausbeute 78.0%

Lösungsmittel

hexane

toluene

ether

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONTo a vial containing
2. 2
   workup.ADDITIONwas added a solution
3. 3
   Sonstigethe reaction was quenched by dropwise addition of half-saturated aqueous ammonium chloride (50 mL)
4. 4
   SonstigeThe ether layer was separated
5. 5
   Extraktionthe aqueous layer was further extracted with ether (2×50 mL)
6. 6
   TrocknenThe combined ether layers were dried over magnesium sulfate whereupon the solvent
7. 7
   Sonstigewas removed at reduced pressure
8. 8
   SonstigeThe residue was purified by flash chromatography on 220-400 mesh silica with 95% hexane and 5% ether as eluant

Vorschrift

To a vial containing aminoalcohol 1 (0.05 g, 0.17 mmol) prepared as in Example 1 was added a solution containing 2,2-dimethyl-4-pentenal (0.34 g, 90% pure, 2.7 mmol), toluene (3.0 mL), and 1 M diethylzinc in hexane (6.0 mL). After 3 days at room temperature, acetic anhydride (1.2 mL, 13 mmol) was added. After 2 additional days, the mixture was diluted in ether (50 mL) and the reaction was quenched by dropwise addition of half-saturated aqueous ammonium chloride (50 mL). The ether layer was separated and the aqueous layer was further extracted with ether (2×50 mL). The combined ether layers were dried over magnesium sulfate whereupon the solvent was removed at reduced pressure. The residue was purified by flash chromatography on 220-400 mesh silica with 95% hexane and 5% ether as eluant. The product (+)-3-acetoxy-4,4-dimethylhept-1-ene (0.39 g, 78%) was isolated as a colorless liquid by distillation of the solvent at reduced pressure. Anal. for C11H20O2. Calcd: C, 71.70; H, 10.94; found: C, 71.75; H, 10.66. 1H NMR (CDCl3/TMS): δ0.84 (s+t, 6 H total), 0.87 (s, 3 H), 1.46 (m, 1 H), 1.62 (m, 1 H), 1.89-2.06 (m, 2 H), 2.07 (s, 3 H), 4.71 (dd, 1 H), 4.96-5.05 (m, 2 H), 5.81 (m, 1 H). 13C NMR (CDCl3/TMS): δ10.96, 21.02, 22.33, 23.12, 37.41, 43.46, 81.41, 117.37, 134.74, 171.11. [α]D25=+14.2, c=2.02 g/100 mL chloroform. Chiral capillary gas chromatographic analysis at 100° C. on Cyclodex B stationary phase (J & W Scientific) indicated that the enantiomeric excess of the product was 98%.

Quelle