August 24, 2019, 02:11:03 PM
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Topic: Vilsmeier Complex Bromination  (Read 190 times)

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Offline AlphaScent

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Vilsmeier Complex Bromination
« on: July 12, 2019, 03:36:00 PM »
Why is the reaction of PBr3 with DMF, producing the Vilsmeier complex, not more widely used as a brominating reagent?

I have done two brominations of primary alcohols and both reactions gave >90% yield and the work up could not be easier. 

Is it simply the use of PBr3?  This is just a discussion really about this methodology.  Has anyone else done this reaction?

Cheers!
If you're not part of the solution, then you're part of the precipitate

Offline wildfyr

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Re: Vilsmeier Complex Bromination
« Reply #1 on: July 12, 2019, 07:48:40 PM »
I was under the impression that this is a common way to convert alcohols to bromides.

I have done this reaction. What other methods do you feel are more common for this direct conversion?

Offline AlphaScent

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Re: Vilsmeier Complex Bromination
« Reply #2 on: July 18, 2019, 11:51:27 AM »
I guess I do not really see it in the literature that often.  I feel like I see Appel (Br2/PPh3) a lot more often.  Also Finkelstein I feel like is used much more often (MEsylate/Tosylate reacted with NaBr in acetone)
If you're not part of the solution, then you're part of the precipitate

Offline hollytara

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Re: Vilsmeier Complex Bromination
« Reply #3 on: July 18, 2019, 01:11:12 PM »
Straight up HBr works too - if it is primary alcohol not usually any issues since no sterepochemistry or SN1/rearrangement issues.

If you want gentle, CBr4 and PPh3.


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