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Topic: Bromination of a propargyl alcohol  (Read 3462 times)

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Offline AlphaScent

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Bromination of a propargyl alcohol
« on: September 11, 2014, 11:00:08 AM »
I am trying to figure the cheapest way to brominate 2-pentyn-1-ol. 

I first thought Finkelstein may be the way to go via the mesylate.  It is two steps though.

Then I thought triphenylphosphosphine and bromine, but it is costly.

Lastly, I thought about Phosphorus Tribromide.  Will this work easily for propargly alcohols??

Does anyone have any experience??

This is done neat, right?  With pyridine as an HBr scavenger???
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Offline discodermolide

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Re: Bromination of a propargyl alcohol
« Reply #1 on: September 11, 2014, 11:05:11 AM »
Finkelstein needs low temp to avoid allene formation.
PBr3 is probably the way to go.

Have not done either for a long time now :(
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Offline AlphaScent

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Re: Bromination of a propargyl alcohol
« Reply #2 on: September 11, 2014, 02:58:15 PM »
I am not doing finkelstein.

I found a great procedure in a book by a chemist named Brandsma.  Has exactly what I need.

Done in ether with a bit of pyridine at -35.  Then bring to rt and reflux for 30 min.

Not bad.
If you're not part of the solution, then you're part of the precipitate

Offline orgopete

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Re: Bromination of a propargyl alcohol
« Reply #3 on: September 11, 2014, 07:14:06 PM »
I cannot tell you whether this is good advice or not, but I'd look up your target compound. It looks simple enough that I assume it is known. (For kicks, I'd sometimes compare what they were paying me with the cost of trying a "new" route to a known compound. I didn't try too many new routes. It just wasn't worth it. That is also why I bought something if I could. Just sayin.)
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Offline AlphaScent

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Re: Bromination of a propargyl alcohol
« Reply #4 on: September 12, 2014, 09:32:06 AM »
ORgopete,

I understand.  We are trying to make starting materials so it is cheaper.  On scale, it will be cheaper.

The PBr3 is the route to take here. 
If you're not part of the solution, then you're part of the precipitate

Offline zsinger

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Re: Bromination of a propargyl alcohol
« Reply #5 on: September 15, 2014, 06:09:19 PM »
PBr3 SURELY!  As stated, you will get the allene with Finkelstein if the temp is not uber cold!  Too expensive to conduct, and 2 steps as you said.
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