Reaktion #305433

Reaktionsgleichung

19

2,3-Di(tert-butyldimethylsilyloxy)-5-bromo benzaldehyde

butyllithium

3,4,5-trimethoxybenzyltriphenylphosphonium bromide

→

20

Ausbeute 55.9%

4-Bromo-6-[(Z)-2-(3,4,5-trimethoxyphenyl)vinyl]-1,2-di(tert-butyldimethylsilyloxy)benzene

Ausbeute 55.9%

Lösungsmittel

tert-butylmethyl ether

tetrahydrofuran

hexane

tetrahydrofuran

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.WAITto rise to room temperature overnight, than the reaction
2. 2
   Waschenwashed with water (ca 50 mL, containing 1 mL 2N HCl)
3. 3
   TrocknenThe organic layer was dried over sodium sulphate
4. 4
   Sonstigethe solvent removed under reduced pressure
5. 5
   Sonstigeto give a crude which
6. 6
   Sonstigewas purified by column (elution with cyclohexane:AcOEt 10:1)

Vorschrift

A suspension of 3,4,5-trimethoxybenzyltriphenylphosphonium bromide (1.69 g, 3.23 mmol) in tetrahydrofuran (30 mL) was cooled to 0° C. and butyllithium (2 mL of a 1.6 N solution in hexane, 3.23 mmol) was added dropwise. The brick red solution was stirred at 0° C. for 20 min, then a solution of 19 (0.96 g, ca 2.2 mmol) in tetrahydrofuran (12 mL) was added dropwise. The temperature was allowed to rise to room temperature overnight, than the reaction was diluted with tert-butylmethyl ether (ca 100 mL) and washed with water (ca 50 mL, containing 1 mL 2N HCl) then brine (30 mL). The organic layer was dried over sodium sulphate and the solvent removed under reduced pressure to give a crude which was purified by column (elution with cyclohexane:AcOEt 10:1) to give 0.75 g of 20 still impure with 20% of the E isomer.

Quelle