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Author Topic: Preparation of Vinyl Lithium  (Read 4523 times)

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stevet

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Preparation of Vinyl Lithium
« on: April 06, 2010, 08:43:13 AM »

I have been trying for a few weeks to prepare vinyl lithium in order to prep a higher order cuprate, to do a carbon-carbon bond formation with a tosylate. The reaction requires Vinyl lithium. This is where the problem starts...
Vinyl lithium can be purchased, but due to shipping regulations, would take about two months to arrive. Most of the methods available require the use of t-butyl lithium, which we also don't have available, and is subject to the same shipping restrictions as vinyl lithium.
We have tried metal-halogen exchange (n-BuLi and vinyl bromide) which has been done before, but conditions are unclear, and were not successful.
We have also tried direct metallation, with vinyl bromide and fine Li metal (1% Na as catalyst), however this was also unsuccessful.
Any suggestions for its preparation? Preferably from Vinyl bromide (as this is what i have available). There are other methods, such as deprotonation of ethene with superbase, however, reagent availability is a problem.

We got an alternate synthetic route, so its not urgent to find a solution, but some help in solving this problem would be appreciated!

Steve
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cpncoop

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Re: Preparation of Vinyl Lithium
« Reply #1 on: April 06, 2010, 10:49:53 AM »

I'm not sure if you've given this a shot already, but treatment of tetravinyltin with butyl lithium will give you the desired material.  According to a paper in JACS, you carefully combine tetravinyltin with butyl lithium in pentane (at 0C), and vinyllitium precipitates from solution.  It can then be filtered (under N2), and dissolved in dry THF to make your reagent solution.  Hope this helps
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stevet

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Re: Preparation of Vinyl Lithium
« Reply #2 on: April 25, 2010, 07:15:14 AM »

Thanks. I had seen that way, just forgot to mention it. I'm not too keen on using the tetrachlorotin for safety reasons, but if all else fails, I'll give it a go. In the meantime i have managed to work around the use of the vinyl lithium, using a Wittig reaction instead.
Steve
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