napoleon9
Harmless
Posts: 25
Registered: 28-1-2011
Location: viet nam
Member Is Offline
Mood: No Mood
|
|
wittig reaction by t-BuOK/THF, 5-hydroxytrphenylphosphonium bromide and 2-cis-hexenal
I made wittig reaction of 5-hydroxytrphenylphosphonium bromide and 2-cis-hexenal by t-BuOK catalyst in THF.
But I don't success with them, I don't understand what happen ? why it is no reaction.
I don't find peak alkadien conjunction by NMR.
please give me some advice.
thanks
|
|
|
Chordate
Hazard to Others
Posts: 108
Registered: 23-2-2011
Member Is Offline
Mood: No Mood
|
|
You need to tell us more than that to get an idea of what is going on.
What procedure did you use. What was your workup
What molar ratios did you use?
Where did you get your reagents, or how did you prepare them?
What do you mean by 5 hydroxytrphenylphosphonium bromide? If its not a hydrobromide salt you're probably talking about a substituted
triphenylphosphine. That numbering doesn't make sense for a substitution on the aryl groups, nor does it make any sense for a bare hydroxyl group to
be attached directly to the phosphorous. So whats substituted where, whats your full chemical's name?
Also, if you could attach a scan of your NMR, or better yet the FID it could help.
|
|
|
Nicodem
|
Thread Moved
23-9-2011 at 06:13 |
napoleon9
Harmless
Posts: 25
Registered: 28-1-2011
Location: viet nam
Member Is Offline
Mood: No Mood
|
|
sorry I write wrong.
wittig : 5-hydroxypentyltriphenylphosphonium bromide with 2-cis-hexenal in t-BuOK/THF
I wash product by NH4Cl , extracted with diethyl ether, wash brine, MgSO4.
I was add 2,1 equiv base (t-BuOK).
2-cis-hexenal (1,78 mmol)
phosohonium salt (2,5 mmol)
then the reaction is finish. It was washing with NH4Cl solution (cool), extracted with diethyl ether and washed with brine. The organic layer was
dried over magesium sulfate and filtered, and the filtrate was concentrated in vacuo to afford a yellow oil. This crude product was purified by column
chroma-
tography (silica gel) ( hexane : ethyl acetate). Rf = 0,55 (TLC , (petro ether (60:90): diethyl ether = 2:1). But I don't find peak alkadien
conjunction, I see peak -OH.
thank you for me some advices
[Edited on 26-9-2011 by napoleon9]
[Edited on 26-9-2011 by napoleon9]
|
|
|
Chordate
Hazard to Others
Posts: 108
Registered: 23-2-2011
Member Is Offline
Mood: No Mood
|
|
How did you make the wittig salt? That wittig salt is not stable. Making it would likely be tricky, and it'd be easily destroyed. Did you make it
fresh, confirm the presence of the correct salt, then run the reaction dry under inert gas?
|
|
|
napoleon9
Harmless
Posts: 25
Registered: 28-1-2011
Location: viet nam
Member Is Offline
Mood: No Mood
|
|
I made the wittig salt as "Studies on the Biomimetic Synthesis of the Manzamine Alkaloids" of Jack E. Baldwin. I controled with IR and NMR for result
exactly. Before I practice this reaction, I washed diethyl ether hot.
First I give stirred wittig salt and THF, next I give KHDMS into bottle (-78 oC). The solution is slightly yellow to bold yellow. The stirred is 30
min at temp room. Then the bottle is cold with dry ice in aceton to -78 o C, I give aldehyde into bottle. The solution is to organe for 30 min. After
the bottle is to temp room for 2 hr. The colour solution is brown. hen the reaction is finish. It was washing with NH4Cl solution (cool), extracted
with diethyl ether and washed with brine. The organic layer was dried over magesium sulfate and filtered, and the filtrate was concentrated in vacuo
to afford a yellow oil. This crude product was purified by column chroma-
tography (silica gel) ( hexane : ethyl acetate). Rf = 0,55 (TLC , (petro ether (60:90): diethyl ether = 2:1). But I don't find peak alkadien
conjunction, I see peak -OH.
thanks
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
