Reacción #2348120

Ecuación de reacción

water

3,5-dimethoxybenzaldehyde

4-methoxy-benzyltriphenylphosphonium bromide

n-butyllithium

→

solid

Rendimiento 86.0%

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

Rendimiento 86.0%

Disolventes

tetrahydrofuran

tetrahydrofuran

Condiciones de reacción

Tratamiento posterior

1. 1
   workup.STIRRINGthe mixture stirred for 6-15 h
2. 2
   Extracciónextracted with dichloromethane
3. 3
   LavadoThe organic phase was washed with water, and removal of the solvent in vacuo
4. 4
   Otroafforded an oil
5. 5
   OtroThe oil was separated by flash column chromatography (49:1 hexane/ethyl acetate)
6. 6
   LavadoThe 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
    Extracciónextracted with dichloromethane
11. 11
    LavadoThe organic phase was washed with water, and removal of the solvent in vacuo
12. 12
    Otroafforded an oil, which
13. 13
    Otrowas separated by flash column chromatography (1:1 hexane/ethyl acetate)

Procedimiento

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.

Fuente