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Topic: Stilbene  (Read 7797 times)

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puru

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Stilbene
« on: February 02, 2005, 10:52:55 AM »
guys
how do i prepare stilbene C6H5-CH=CH-H5C6
is this right:
2 C6H5CHCl2 + 4NaOH---Ether--->C6H5-CH=CH-H5C6
                                                   + 4NaCl +etc.

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Re:Stilbene
« Reply #1 on: February 02, 2005, 11:16:09 AM »
First, it depends whether you want the cis or trans olefin isomer of stilbene.

The scheme that you have written has the starting materials in the wrong oxidation state.

There are lots of different ways to approach this synthesis.  What sort of reactions do you know that can make alkenes?

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Re:Stilbene
« Reply #2 on: February 02, 2005, 11:32:50 AM »
I'm more of a brute force Chemist. I would of just done the Wurtz reaction, a one step elimination, and a Chlorine-to-Hydrogen exchange. But that would be one of the ugliest synthesis of all time.

What did you have in mind movies?
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Re:Stilbene
« Reply #3 on: February 02, 2005, 06:44:20 PM »
I was thinking Wittig reaction with benzaldehyde to get the cis isomer.

For the the trans I would have to go with cross-metathesis of styrene, but that's probably way beyond the scope of this question.   ;D

Other fancy alternatives:

1) Sonogashira coupling of phenyl acetylene and bromobenzene.  Then you could reduce the alkene to get either the cis or the trans (Lindlar reduction and Li/NH3 reduction, respectively.  The Birch reduction might not work though).

2) Takai reaction on benzaldehyde to get trans-beta-iodostyrene, the a Suzuki coupling with phenyl boronic acid.  (trans-stilbene)  You could also make the iodostyrene from phenylacetlyene and the Schwartz reagent, quenching with iodine after the hydrozirconation.

3) Start with benzoin and reduce both carbonyls with NaBH4 to get the meso diol, then eliminate to the alkene via the Corey-Winter reaction.  (cis-stilbene)

4) McMurray coupling with benzaldehyde. (trans-stilbene)

5) Julia olefination with benzaldehyde and phenylbenzylsulfonate.  (trans-stilbene)

6) I know you can convert trans-stilbene to cis-stilbene (or vice-versa!) by epoxidizing, adding lithium diphenylphosphide, and then methyl iodide.  You end up losing diphenylmethylphosphine oxide in either case.  Pretty cool, huh?

puru

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Re:Stilbene
« Reply #4 on: February 03, 2005, 11:04:16 AM »
there was a mistake in my equations as i was typing it astray.I have also found that wittig reactions is what i wanted
thanks a lot guys

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