Sodium hydride → (2E,4E)-5-(2-bromo-cyclopent-1-enyl)-3-methyl-penta-2,4-dienoic acid ethyl ester

HRID 2392947Notes

Reaction equation

HRID 2392947 reaction equation
[H-].[Na+].[CH2:3]([O:5][C:6](=[O:19])[CH:7]=[C:8]([CH3:18])[CH2:9]P(OCC)(OCC)=O)[CH3:4].[Br:20][C:21]1[CH2:25][CH2:24][CH2:23][C:22]=1[CH:26]=O>CN(C=O)C>[CH2:3]([O:5][C:6](=[O:19])/[CH:7]=[C:8](\[CH3:18])/[CH:9]=[CH:26]/[C:22]1[CH2:23][CH2:24][CH2:25][C:21]=1[Br:20])[CH3:4]

Participants

5

Reactant 3

HCID 24758Sodium hydrideHCID 2773818Ethyl 4-(diethoxyphosphoryl)-3-methylcrotonateHCID 117690601-Cyclopentene-1-carboxaldehyde, 2-bromo-

Product 1

HCID 86753065(2E,4E)-5-(2-bromo-cyclopent-1-enyl)-3-methyl-penta-2,4-dienoic acid ethyl esterYield 36.6%

Reagents, catalysts & solvents 1

HCID 6228DimethylformamideSolvent2×

Procedure

2.03 g of NaH (50% in mineral oil) was suspended in 120 ml of DMF. 12.9 g of 4-(diethoxy-phosphinyl)-3-methyl-but-2-enoic acid ethyl ester was added at 0°. The mixture was stirred for 15 min at 0° and for 30 min at RT. After recooling to 0°, 5.72 g of 2-bromo-cyclopent-1-enecarbaldehyde, dissolved in 11 ml of DMF, was added drop by drop and allowed to react for 10 min. at 0° and for 2 h at RT. The mixture was then poured onto crushed ice, extracted with EtOEt, washed with sat. NaCi-solution, dried over Na2SO4, and evaporated to dryness. Purification of the residue by flash chromatography (silica gel, hexane/AcOEt=97/3) and crystallization from hexane/trace amounts of AcOEt yielded finally 3.408 g of pure (2E,4E)-5-(2-bromo-cyclopent-1-enyl)-3-methyl-penta-2,4-dienoic acid ethyl ester as yellowish crystals of mp. 85°-86°.

Workup

  1. customAfter recooling to 0°
  2. additionwas added drop by drop
  3. customto react for 10 min. at 0° and for 2 h at RT
  4. additionThe mixture was then poured
  5. customonto crushed ice
  6. extractionextracted with EtOEt
  7. washwashed with sat. NaCi-solution
  8. dry with materialdried over Na2SO4
  9. customevaporated to dryness
  10. customPurification of the residue
  11. customby flash chromatography (silica gel, hexane/AcOEt=97/3) and crystallization from hexane/

Sources & evidence

ORD record
ord-660fe1c391c64162a010261e347ac11c
Source dataset
uspto-grants-1998_09
Patent number
US05801253

Reaction notes

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