[RaInBowDaSh1488]

I am attempting to alkylate an aromatic azide (4-bromo-2,3-dinitrophenylazide). I've tried doing this by reacting a grignard with the desired alkylhalide, but all of my labs Mg is very old and not very reactive even after entrainment. As a result, I was going to take a shot out of making the lithiate of my compound with BuLi and reacting this with the alkylhalide.

The thing is, I don't know if BuLi will decompose aromatic azides. I've made many aromatic azides with BuLi and tosyl azide, so I'd imagine it shouldn't be an issue, but the lack of references kind of worries me. It seems like scifinder and other databases aren't too heavy on publications dealing with azide chemistry. If anyone has experience with this kind of reaction or theoretical ideas regarding azides/BuLi, input would be greatly appreciated.

[TheUnassuming]

Never tried a lithiation or lithium halogen exchange with an azide present.  I seem to remember trying a Li-Br exchange on a substrate that had an ortho-nitro group a year or two ago, and it had some unwanted side reactions... have to look back in my notebooks to see if it was the nitro or something else that was the problem. 
In any case you can always just try the exchange on a small scale and quench with D2O.  If the appropriate proton disappears in HNMR and you don't see any shifts in the other peaks, then you are golden. 

[RaInBowDaSh1488]

Never tried a lithiation or lithium halogen exchange with an azide present.  I seem to remember trying a Li-Br exchange on a substrate that had an ortho-nitro group a year or two ago, and it had some unwanted side reactions... have to look back in my notebooks to see if it was the nitro or something else that was the problem. 
In any case you can always just try the exchange on a small scale and quench with D2O.  If the appropriate proton disappears in HNMR and you don't see any shifts in the other peaks, then you are golden.

That is a brilliant idea actually! It makes perfect sense, but quenching a grignard with D2O followed by HNMR has never occurred or been suggested to me. This is a piece of advice I'll be getting heavy use out of in the future and I'm so excited at the prospect I'm going to the lab to try it now. Thanks a ton

[TheUnassuming]

Of course.  This trick works well as a check for a number of different deprotonations/lithiations/exchanges ect. 
Good luck and let us know how it goes.  I'm curious.