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Topic: Lithium-halogen exchange  (Read 3893 times)

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Offline Baerchen

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Lithium-halogen exchange
« on: July 21, 2010, 09:32:56 PM »
Hi!
I am trying to do a lithium exchange with an allylic iodide. Does anyone have some practical tips to help out as so far I cannot get the reaction to occur.

I have been hammering the lithium then dipping it in MeOH then X4 before chucking it in the flask with a bit of dry ether. I've tried refluxing the mixture and sonication but nothing happens.

I have been able to form the organolithium with tBuLi but it's so reactive I am getting the Wurtz coupling product despite trying cooler temps, more and less equivs of tBuLi. That's why I think the lithium metal would be the way to go - if I can initiate the rn!

Thank you in advance

Offline 408

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Re: Lithium-halogen exchange
« Reply #1 on: July 22, 2010, 01:24:16 AM »
Try adding lithium chloride in addition to the Li metal.

Offline stewie griffin

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Re: Lithium-halogen exchange
« Reply #2 on: July 23, 2010, 01:15:23 PM »
Have you tried sec-BuLi or looked at the conditions Knochel uses (he uses LiCl alot... as 408 suggests). Maybe just make the Grignard?

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