Diethyl Ether → 7,7-Dimethyl-5,8-eicosadienoic acid

HRID 1388881Notizen

Reaktionsgleichung

Reaktionsgleichung von HRID 1388881
C([Li])CCC.[Br-].[CH2:7]([P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)[CH2:8][CH2:9][CH2:10][CH2:11][CH2:12][CH2:13][CH2:14][CH2:15][CH2:16][CH2:17][CH3:18].C[O:39][C:40](=[O:51])[CH2:41][CH2:42][CH2:43]/[CH:44]=[CH:45]\[C:46]([CH3:50])([CH3:49])[CH:47]=O.CCOCC>O1CCCC1.CN(C)P(=O)(N(C)C)N(C)C.O1CCCC1>[CH3:49][C:46]([CH3:50])(/[CH:47]=[CH:18]\[CH2:17][CH2:16][CH2:15][CH2:14][CH2:13][CH2:12][CH2:11][CH2:10][CH2:9][CH2:8][CH3:7])/[CH:45]=[CH:44]\[CH2:43][CH2:42][CH2:41][C:40]([OH:39])=[O:51]

Komponenten

7

Edukt 4

HCID 3283Diethyl EtherHCID 84955Dodecyltriphenylphosphonium bromideHCID 13276466(Z)-8-Oxo-7,7-dimethyl-5-octenoic acid methyl esterHCID 178418339Butyllithium

Produkt 1

HCID 53123317,7-Dimethyl-5,8-eicosadienoic acidAusbeute 49 %

Reagenzien, Katalysatoren, Lösungsmittel 2

HCID 8028TetrahydrofuranLösungsmittelHCID 86583969tetrahydrofuran HMPALösungsmittel

Reaktionsbedingungen

Temperatur
0 °C

Versuchsvorschrift

A 1.4 ml. portion of n-butyllithium (1.6 M solution in hexane) was added to a solution of 1.4 g (2.74 mmol) of n-dodecyltriphenylphosphonium bromide in 5.5 ml of 2:1 tetrahydrofuran-hexamethylphosphorictriamide, at -78° C., under argon. The solution turned orange-red in color. To this solution was then added 0.350 g (1.77 mmoles) of (Z)-8-oxo-7,7-dimethyl-5-octenoic acid methyl ester dissolved in 1 ml of tetrahydrofuran, using a syringe. The reaction mixture was stirred for 30 minutes at -78° C. and an additional 45 minutes at 0° C. The product was isolated by ether extraction using the conventional workup procedure and then chromatographed on silica gel. Hexane-ether (19:1) eluted 0.600 g (97%) of (Z,Z)-7,7-dimethyl-5,8-eicosadienoic acid methyl ester. This material was dissolved in 6 ml of methanol and treated with 0.6 ml of 5% aqueous potassium hydroxide. After stirring at room temperature for 17 hours, 3 ml of the methanol was evaporated in vacuo. The remaining solution was acidified with oxalic acid and the product was extracted with ether. The ether extracts were washed with brine, dried over MgSO4 and the solvent evaporated at reduced pressure. Purification of the crude acid on a silica gel column provided 0.292 g (50.7%) of (Z,Z)-7,7-dimethyl-5,8-eicosadienoic acid (ca. 100% pure by GC analysis).

Aufarbeitung

  1. customchromatographed on silica gel
  2. washHexane-ether (19:1) eluted 0.600 g (97%) of (Z,Z)-7,7-dimethyl-5,8-eicosadienoic acid methyl ester
  3. dissolutionThis material was dissolved in 6 ml of methanol
  4. additiontreated with 0.6 ml of 5% aqueous potassium hydroxide
  5. stirringAfter stirring at room temperature for 17 hours
  6. custom3 ml of the methanol was evaporated in vacuo
  7. extractionthe product was extracted with ether
  8. washThe ether extracts were washed with brine
  9. dry with materialdried over MgSO4
  10. customthe solvent evaporated at reduced pressure
  11. customPurification of the crude acid on a silica gel column

Quellen und Nachweise

ORD-Eintrag
ord-59ed7aabc2ae4762b22dbab317b0f22e
Quelldatensatz
uspto-grants-1984_02
Patentnummer
US04434101

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