[Cooper]

Hi,

Just a quick question. I see a lot of people trying to add an alkyne to an alkylbromine so they add something like LDA and an alkylbromine at the same time to the alkyne (this is all on paper). I thought that the LDA could react with the alkylbromine as well as the alkyne, so you should add the LDA first, then the alkylbromine. Is this correct to say or do some bases like LDA only deprotonate things like alkynes? I'll attach a drawing in case you are confused.

Thanks

[Calicum]

In your case, the alkylation of a terminal alkyne, two separate steps are required. Putting both in the same reaction flask would most likely produce unwanted products.

[Dan]

I thought that the LDA could react with the alkylbromine as well as the alkyne, so you should add the LDA first, then the alkylbromine.

That would be the sensible way to do it, yes. This general strategy of using a very strong base for the stoichiometric deprotonation of a compound to generate an anionic nucleophile, followed by addition of an electrophile that would otherwise react with the strong base, is a common type of protocol.