Reaktion #5655

Reaktionsgleichung

diborane

2-valeryl furan

[1,3,2] oxazaborole

HCl

→

product

Ausbeute 70.0%

(S)-1-(2-Furyl)-1-pentanol

Ausbeute 70.0%

Lösungsmittel

methanol

THF

ether

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.STIRRINGStirred for 0.5 h
2. 2
   Sonstigewhite solid was precipitated out
3. 3
   workup.ADDITIONThe cloudy mixture was poured into 100 mL ether and 100 mL water
4. 4
   SonstigeThe organic layer was separated
5. 5
   Waschenwashed with saturated sodium bicarbonate, water, brine
6. 6
   Sonstigedried
7. 7
   Filtrationfiltered
8. 8
   SonstigeThe filtrate was evaporated to an yellowish oil which
9. 9
   Sonstigewas chromatographed
10. 10
    Wascheneluting with 10 % ethyl acetate in hexane

Vorschrift

10.4 mmol (10.4 mL) of diborane (1 M solution in THF) was added dropwise in a period of 10 m at room temperature to a solution of 2-valeryl furan (2.62 g, 17.2 mmol) and 1.68 mmol (4.2 mL) of (3aR)-1,3,3-triphenyl pyrrolidino [1,2-c] [1,3,2] oxazaborole (see E. J. Corey et al. J. Am. Chem. Soc. 1987, 109, 7925-26, 0.4M solution in THF) in 25 mL THF. The reaction mixture was stirred for 20 m and was cooled to 10° C. 6 mL methanol was cautiously added and followed by adding 62 mg HCl (by weight) in ether. Stirred for 0.5 h, white solid was precipitated out. The cloudy mixture was poured into 100 mL ether and 100 mL water. The organic layer was separated, washed with saturated sodium bicarbonate, water, brine, dried and filtered. The filtrate was evaporated to an yellowish oil which was chromatographed eluting with 10 % ethyl acetate in hexane to obtain 70% of the product. [α]25D =-13°, 60% ee by Mosher' ester analysis.

Quelle