Reaktion #2348120

Reaktionsgleichung

water

3,5-dimethoxybenzaldehyde

4-methoxy-benzyltriphenylphosphonium bromide

n-butyllithium

→

solid

Ausbeute 86.0%

5[(E)-2-(4-Hydroxyphenyl)-vinyl]benzene 1,3-diol

Ausbeute 86.0%

Lösungsmittel

tetrahydrofuran

tetrahydrofuran

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.STIRRINGthe mixture stirred for 6-15 h
2. 2
   Extraktionextracted with dichloromethane
3. 3
   WaschenThe organic phase was washed with water, and removal of the solvent in vacuo
4. 4
   Sonstigeafforded an oil
5. 5
   SonstigeThe oil was separated by flash column chromatography (49:1 hexane/ethyl acetate)
6. 6
   WaschenThe cis-stilbene eluted first as a clear oil
7. 7
   workup.ADDITIONTo a solution of the trans isomer (3.1. g) in anhydrous dichloromethane (150 mL) at −78° C. was added (dropwise) boron tribromide (1.0 M, 34.5 mL)
8. 8
   workup.STIRRINGthe resulting red solution was stirred under argon for 30 min
9. 9
   workup.ADDITIONThe solution was poured into water
10. 10
    Extraktionextracted with dichloromethane
11. 11
    WaschenThe organic phase was washed with water, and removal of the solvent in vacuo
12. 12
    Sonstigeafforded an oil, which
13. 13
    Sonstigewas separated by flash column chromatography (1:1 hexane/ethyl acetate)

Vorschrift

To a solution of 4-methoxy-benzyltriphenylphosphonium bromide (12.5 g) in anhydrous tetrahydrofuran (200 mL) at −78° C. was added n-butyllithium (2.44 M, 1.0 equiv), and the resulting red solution was stirred under argon for 2-4 h. A solution of 3,5-dimethoxybenzaldehyde (4.5 g) in tetrahydrofuran was added dropwise over 30 min and the mixture stirred for 6-15 h. The resulting cream suspension was poured into water and extracted with dichloromethane. The organic phase was washed with water, and removal of the solvent in vacuo afforded an oil. The oil was separated by flash column chromatography (49:1 hexane/ethyl acetate). The cis-stilbene eluted first as a clear oil followed by the trans isomer as a colorless solid or oil. Overall yield: 91%. To a solution of the trans isomer (3.1. g) in anhydrous dichloromethane (150 mL) at −78° C. was added (dropwise) boron tribromide (1.0 M, 34.5 mL), and the resulting red solution was stirred under argon for 30 min. The solution was poured into water and extracted with dichloromethane. The organic phase was washed with water, and removal of the solvent in vacuo afforded an oil, which was separated by flash column chromatography (1:1 hexane/ethyl acetate) to afford a colorless solid (2.26 g, 86%): mp 260° C.

Quelle