trans-2-Methyl-2-butenal → 3,5,7-Trimethyl-2E,4E,6E,8E-decatetraene

HRID 1085768Notes

Reaction equation

HRID 1085768 reaction equation
[Br-].[CH3:2]C([P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1)/C=C/C.[CH2:26]([Li])[CH2:27][CH2:28][CH3:29].[CH3:31]/[C:32](=[CH:35]\[C:36](\[CH3:39])=[CH:37]\[CH3:38])/[CH:33]=O.C/C(=C\C)/C=O>CCCCCC.O.O1CCCC1>[CH3:26]/[C:27](/[CH:31]=[C:32](\[CH3:33])/[CH:35]=[C:36](\[CH3:39])/[CH:37]=[CH:38]/[CH3:2])=[CH:28]\[CH3:29]

Participants

8

Reactant 4

HCID 5321950trans-2-Methyl-2-butenalHCID 11133375(1-Methyl-(E)-2-butenyl)triphenylphosphonium bromideHCID 113324592,4-Dimethyl-2E,4E-hexadienalHCID 178418339Butyllithium

Product 1

HCID 146560443,5,7-Trimethyl-2E,4E,6E,8E-decatetraene

Reagents, catalysts & solvents 3

HCID 962WaterSolvent2×HCID 8028TetrahydrofuranSolventHCID 8058HexaneSolvent

Procedure

(1-Methyl-(E)-2-butenyl)triphenylphosphonium bromide from Example 9 (0.62 g, 0.0015 mole) was added to a dry flask with 5 ml tetrahydrofuran. The flask was equipped with magnetic stirrer and septum; the reaction was carried out under nitrogen. The salt did not dissolve completely but became a sticky suspension. The mixture was cooled over ice, and butyllithium (2.5M in hexane) was added dropwise, with stirring, until the color change became permanent; then an additional 0.0015 mole was added. The solid in the flask dissolved as it was converted to the ylide. One hundred milligrams of 2,4-dimethyl-(E,E)-2,4-hexadienal (0.0008 mole), compound 4, R1 =H, prepared previously by Pattel and Pattenden (1985), was added to the Wittig reagent, and the mixture was allowed to warm to room temperature. The mixture was stirred for 2 hr, and it was again cooled over ice. Water was added dropwise until the red color of the solution had disappeared, and ca. 2 ml more water was added. The mixture was diluted with hexane and the organic layer dried over sodium sulfate. The solvent was removed and the product passed through a silica column with hexane. By capillary GC the product was 61% the (E,E,E,E) isomer, ca. 31% the (E,E,Z,E) isomer, and ca. 8% by-products, after clean-up on silica. Further purification on the AgNO3HPLC column yielded the (E,E,E,E) isomer in >97% purity.

Workup

  1. customThe flask was equipped with magnetic stirrer
  2. dissolutionThe salt did not dissolve completely
  3. additionwas added dropwise
  4. additionthen an additional 0.0015 mole was added
  5. dissolutionThe solid in the flask dissolved as it
  6. stirringThe mixture was stirred for 2 hr
  7. temperatureit was again cooled over ice
  8. dry with materialthe organic layer dried over sodium sulfate
  9. customThe solvent was removed
  10. customFurther purification on the AgNO3HPLC column
  11. customyielded the (E,E,E,E) isomer in >97% purity

Sources & evidence

ORD record
ord-e354825b2dc64ee39283573924021e0e
Source dataset
uspto-grants-1991_04
Patent number
US05011683

Reaction notes

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