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Lithiation of arylethers

  1. May 15, 2014 #1
    Is it possible someone can explain the point of doing this, I am having a really hard time grasping the concept. For example if I have anisole and I use butyl litium as a reagent, my understanding is that it will behave like a base and deprotanate the ring, resulting in a lithium bonded to the ring. Since OMe is an activating group it is para/meta directing. One might expect the lithium to therefore go to the para position, but I think I am right in saying it goes to the meta position due to a stabilised transition state where the Li coordinates with the oxygen.

    I am not sure what the point of doing this is, what is to be done with the lithiated anisole? Can the reaction be done without OMe, will any EWG do, or indeed could it be done with plain benzene? And what is the point of lithiating? Do we treat a lithiated ring as being analogous to a negative charge stuck on a carbon and it can therefore behave like a nucleophile?

    Rings are nucleophilic anyway so what is the point?
  2. jcsd
  3. May 15, 2014 #2
    This was an interesting question that I wanted to know about also so I did a quick literature scan. Apparently the RLi reagent is very selective for the ortho product. This reaction may not proceed through a typical electrophilic aromatic substitution type of mechanism. You can read a bit about it here: J. Org. Chem. 1997, 62, 3024-3025. It is a short communication and very accessible, in my opinion. The author makes some statements about potential complication with the ether moiety being responsible for the predominant ortho product. Unfortunately I've about used up my free time, so you're on your own from here.
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