(R)-2-Methyl-CBS-oxazaborolidine → (S)-2-(4-t-butyldimethylsilyloxy-1,3-dihydro-6-ethyl-7-methyl-3-oxoisobenzofuran-5-yl)-1-cyclopentenyl-1-hydroxyethane

HRID 1757213Notizen

Reaktionsgleichung

Reaktionsgleichung von HRID 1757213
[CH:1]1([C:6]([CH2:8][C:9]2[C:10]([O:22][Si:23]([C:26]([CH3:29])([CH3:28])[CH3:27])([CH3:25])[CH3:24])=[C:11]3[C:15](=[C:16]([CH3:20])[C:17]=2[CH2:18][CH3:19])[CH2:14][O:13][C:12]3=[O:21])=[O:7])[CH2:5][CH2:4][CH2:3][CH2:2]1.CB1N2CCC[C@@H]2C(C2C=CC=CC=2)(C2C=CC=CC=2)O1>C1(C)C=CC=CC=1>[Si:23]([O:22][C:10]1[C:9]([CH2:8][C@@H:6]([C:1]2[CH2:5][CH2:4][CH2:3][CH:2]=2)[OH:7])=[C:17]([CH2:18][CH3:19])[C:16]([CH3:20])=[C:15]2[C:11]=1[C:12](=[O:21])[O:13][CH2:14]2)([C:26]([CH3:27])([CH3:28])[CH3:29])([CH3:25])[CH3:24]

Komponenten

4

Edukt 2

HCID 9838490(R)-2-Methyl-CBS-oxazaborolidineHCID 53886302Cyclopentyl (4-t-butyldimethylsilyloxy-1,3-dihydro-6-ethyl-7-methyl-3-oxoisobenzofuran-5-yl methyl)methanone

Produkt 1

HCID 70213482(S)-2-(4-t-butyldimethylsilyloxy-1,3-dihydro-6-ethyl-7-methyl-3-oxoisobenzofuran-5-yl)-1-cyclopentenyl-1-hydroxyethane

Reagenzien, Katalysatoren, Lösungsmittel 1

HCID 1140TolueneLösungsmittel

Reaktionsbedingungen

Temperatur
-30 °C

Versuchsvorschrift

Cyclopentyl (4-t-butyldimethylsilyloxy-1,3-dihydro-6-ethyl-7-methyl-3-oxoisobenzofuran-5-yl methyl)methanone (4.2 g) was treated with a 1M toluene solution of (R)-tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborole (3 ml). The toluene was evaporated in vacuo and methylene chloride added (2 ml). The reaction mixture was cooled to -30° C. and borane/dimethyl sulfide (0.33 ml) was added three times at 45 minute intervals. The reaction mixture was stirred 16 hours at -30° C. and quenched by addition of 1M hydrogen chloride/ether (3 ml). Toluene was added (10 ml) and the solution filtered, diluted with ether (200 ml), washed with aqueous hydrochloric acid, aqueous sodium bicarbonate and brine. Drying and evaporation gave an oil which was purified by silica gel chromatography to give (S)-2-(4-t-butyldimethylsilyloxy-1,3-dihydro-6-ethyl-7-methyl-3-oxoisobenzofuran-5-yl)-1-cyclopentenyl-1-hydroxyethane. Further purification by crystallization from t-butylmethyl ether gave material with an enantiomeric excess of 97.8% (Chiracel OD-H, 85:15 hexane:i-propanol, 0.8 ml/minute, minor 8.3 minutes, major 9.2 minutes).

Aufarbeitung

  1. customThe toluene was evaporated in vacuo and methylene chloride
  2. additionadded (2 ml)
  3. additionborane/dimethyl sulfide (0.33 ml) was added three times at 45 minute intervals
  4. customquenched by addition of 1M hydrogen chloride/ether (3 ml)
  5. additionToluene was added (10 ml)
  6. filtrationthe solution filtered
  7. additiondiluted with ether (200 ml)
  8. washwashed with aqueous hydrochloric acid, aqueous sodium bicarbonate and brine
  9. customDrying
  10. customevaporation
  11. customgave an oil which
  12. customwas purified by silica gel chromatography

Quellen und Nachweise

ORD-Eintrag
ord-2d142d713296406190b71cf65074198d
Quelldatensatz
uspto-grants-1995_08
Patentnummer
US05444072

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