Hydrochloric Acid → Retinal

HRID 845889Notes

Reaction equation

HRID 845889 reaction equation
Br[CH:2]=[CH:3][CH:4]=[C:5]([CH3:10])[CH:6]=[CH:7][O:8]C.C([Li])(C)(C)C.[CH3:16][C:17]1[CH2:22][CH2:21][CH2:20][C:19]([CH3:24])([CH3:23])[C:18]=1/[CH:25]=[CH:26]/[C:27]([CH3:29])=O.Cl>CCOCC>[CH3:16][C:17]1[CH2:22][CH2:21][CH2:20][C:19]([CH3:23])([CH3:24])[C:18]=1/[CH:25]=[CH:26]/[C:27](/[CH3:29])=[CH:8]/[CH:7]=[CH:6]/[C:5](/[CH3:10])=[CH:4]/[CH:3]=[O:2]

Participants

6

Reactant 4

HCID 313Hydrochloric AcidHCID 638014I2-IononeHCID 54250587HCID 54250587, compoundHCID 178418306HCID 178418306, compound

Product 1

HCID 638015RetinalYield 55%

Reagents, catalysts & solvents 1

HCID 3283Diethyl EtherSolvent2×

Conditions

Temperature
-30 °C

Procedure

6-Bromo-3-methyl-1-methoxy-1,3,5-hexatriene (0.257 g; 1.26 mmol) is dissolved in ether (10 cc) is introduced, under an argon atmosphere, into a 25 cc round flask fitted with a thermometer and a magnetic stirrer. The flask is cooled to -70° C. tert-Butyllithium (1.2 cc, 1.8N in pentane; 2.1 mmol, i.e. 1.7 equivalent) is then added over 7 minutes while the temperature is kept below -68° C. The solution becomes slightly coloured from pale yellow to light chestnut-brown. It is stirred for 90 minutes at 70° C. β-Ionone (0.23 g; 1.196 mmol, i.e. 0.95 equivalent) dissolved in ether (3 cc) is then added. The mixture is stirred for 90 minutes at -30° C. 1N hydrochloric acid (4.5 cc) is added at -60° C. and the mixture is then stirred vigorously for 1 hour at 10° C. After phase separation, extraction with ether and evaporation of the solvent, a crude product (0.44 g) is obtained, which is purified by flash chromatography on silica, eluting with a mixture of petroleum ether and diethyl ether (98/2 by volume). Retinal (0.187 g) is obtained in this manner in 55% yield. The structure of the product is confirmed by the infrared spectrum and the proton nuclear magnetic resonance spectrum.

Workup

  1. additionis introduced, under an argon atmosphere, into a 25 cc round flask
  2. customfitted with a thermometer and a magnetic stirrer
  3. additionis then added over 7 minutes while the temperature
  4. customis kept below -68° C
  5. additionis then added
  6. stirringthe mixture is then stirred vigorously for 1 hour at 10° C
  7. customAfter phase separation, extraction
  8. customwith ether and evaporation of the solvent
  9. customa crude product (0.44 g) is obtained
  10. customwhich is purified by flash chromatography on silica
  11. washeluting with a mixture of petroleum ether and diethyl ether (98/2 by volume)

Sources & evidence

ORD record
ord-04f5d4779ec341af8c6903ae30467ef3
Source dataset
uspto-grants-1988_07
Patent number
US04760193

Reaction notes

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