[Scintillation]

Hi all!

Can you think of functional groups that tolerate LiAlH4, but not organolithium reagents (alkyllithium, aryllithium etc.) ?

You'll probably want to know why I'm asking this, since these reagents are used for totally different purposes. Imagine that reacting LiAlH4 with substrate 1 will lead to the same product as you would get if you used n-BuLi on substrate 2.

Thanks a lot

[tmartin]

This is an interesting question.  Is this of your own curiosities or is this a question for a class?

At first glance I read this and wanted to say an alcohol or water (they would both give the same product with either, right?)... but I don't think that's the nature of your question.

I suppose this question is not really asking for a group that will react exclusively with LAH or BuLi, but more so about the inherent reactivity of each?  I consider LAH to be a hydride source, and best for reductions of carbonyls, while I consider BuLi a base (or nucleophile depending on conditions).  I can think of a few different compounds that would give the same product, you just have to set up your starting materials to match.

[Scintillation]

Hi TMartin!

This is not for a class, but I would say it's more important than just a curiosity. I'm currently working on a research project in which I use organolithium compounds to create a new C-C bond. We have observed that LAH does the same reaction, except instead of adding an extra carbon chain to the substrate, it only adds a hydride. So, if we set up the substrates to match, as you suggested, we can synthesize one compound by both methods (RLi or LAH). All is needed is that the substrate carries the extra carbon chain before the reaction, when using LAH.

I was thinking of substrates that would fit well in the article I'm about to write, and I wanted to show that in some cases, LAH is not only a surrogate that can lead to the same compounds synthesized with R-Li, but that is has particular advantages. For instance, if a substrate carries a functional group (elsewhere in the molecule) that will be attacked by an organolithium, but not LAH, then the LAH pathway would be the best option for this particular substrate.

I have actually found one case in which the use of LAH is the only possible choice. In this case, the substrate possesses a very acidic proton that is removed by R-Li but hopefully not by LAH.

If you're thinking of more ideas, they would be greatly appreciated.

Thanks anyways for your answer!

S.

[pacifyer]

Perhaps an alkyne... it will tolerate LAH, but will be deprotonated by any Li-R...

[bolo]

Ferrocene, bromofuran...

[Åke]

Hi all!

Can you think of functional groups that tolerate LiAlH4, but not organolithium reagents (alkyllithium, aryllithium etc.) ?

Hi,

Compounds that contain those functional groups which make them undergo latheral and/or directed ortho lithiation upon treatment with R-Li, let's say anisole as a simple example. Pyridine is another example; n-BuLi adds to it (1,2-nucleophilic addition).