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Ketone with Py ring bromination problems

fireoncells
in Organic Chemistry

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Hello !

I am doing some research on thiazole chemistry. I have to brominate 1-(2-(pyridin-4-yl)thiazol-5-yl)ethanone to obtain the corresponding bromoketone. I've tried this with elemental bromine in CCl4 (stirring, r.t) and obtained a red powder after vacuum filtration . The problem is that this molecule has to 2 aromatic N atoms and the bromine is actually incorporated into the molecule (probably like in pyridinium tribromide?). The 1HNMR spectra shows that there has no bromination occured.

I have tried to brominate it with NBS/CCl4 + 2 drops HCl conc under reflux. TLC shows that the bromination is incomplete.

I don't like CCl4 at all-it is toxic and it doesn't work so I have to try some other system like NBS/MeCN or NBS/DMF with an appropriate catalyst. One of them is HBr but I don't have HBr so I have to make it. TsOH might also be a very good idea but the problem is that can form salt with my haloketone complicating isolation.

 

So my questions are: Which is the best method to brominate this molecule with pronounced basicity ? (no Br2 please ! ) ) and how to isolate the product (in base form not pyridinum salt) ?

 

I really need the oppinion of an expert....

Edited by fireoncells

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