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Topic: Synthesis of stannane compound  (Read 1166 times)

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Offline Hachiko

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Synthesis of stannane compound
« on: December 11, 2019, 11:42:14 PM »
I synthesize the stannane compound using n-BuLi and Bu3SnCl with aryl halide. I do the experiment and monitor by TLC. Firstly I add n-BuLi,I see that after Lithiation, all starting material changes (new spot appears) so I add Bu3SnCl, but there is no new spot appears(TLC seems not to change when compare with the one when I finish lithiation).
So I wonder that will the TLC change a lot from lithiation (when Li attached) to final product (when Tin attached).   Could anyone share your experience?

Offline rolnor

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Re: Synthesis of stannane compound
« Reply #1 on: December 12, 2019, 09:17:01 AM »
If you do lithio-halogen exchange with BuLi you can se a change after lithiation, if you use BuLi to pick a proton you see no change on TLC. The Bu3Sn is very lipophilic and iften you see thespots comming higher when you get stannane.

Offline Hachiko

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Re: Synthesis of stannane compound
« Reply #2 on: December 12, 2019, 07:25:11 PM »
If you do lithio-halogen exchange with BuLi you can se a change after lithiation, if you use BuLi to pick a proton you see no change on TLC. The Bu3Sn is very lipophilic and iften you see thespots comming higher when you get stannane.
So if I get the stannane, the spot of product will go higher than the spot I get when I finish lithiation process?

Offline rolnor

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Re: Synthesis of stannane compound
« Reply #3 on: December 13, 2019, 04:06:16 AM »
You must understand that the lithiated molecule will be hydrolysed when put on a TLC-plate. If you show your structure I can help you.
« Last Edit: December 13, 2019, 04:40:47 AM by rolnor »

Offline Hachiko

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Re: Synthesis of stannane compound
« Reply #4 on: December 14, 2019, 02:31:18 AM »
You must understand that the lithiated molecule will be hydrolysed when put on a TLC-plate. If you show your structure I can help you.
Thank you for your information. I really don't know that before. I synthesize tributyl(5-octylthiophen-2-yl)stannane from 2-bromo-5-octylthiophene. Could you share your experience?

Offline rolnor

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Re: Synthesis of stannane compound
« Reply #5 on: December 14, 2019, 04:52:49 AM »
Then you should se a change in RF when you lithiate because the bromo will be changed to hydrogen. I am surpised that this chemistry does not work, is there a possibility that the stannane has same Rf as the hydrogen-compound?

Offline Hachiko

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Re: Synthesis of stannane compound
« Reply #6 on: December 16, 2019, 07:32:04 PM »
Then you should se a change in RF when you lithiate because the bromo will be changed to hydrogen. I am surpised that this chemistry does not work, is there a possibility that the stannane has same Rf as the hydrogen-compound?
Yes, I see a change in TLC when I add n-BuLi, but when I add Bu3SnCL there is no change from that. I check for NMR but the structure is matched to octylthiophene. I see this kind of reaction is really straightforward with the high reaction yield, but in my case, it isn't.
 Is it about the problem from Bu3SnCl reactivity?

Offline hypervalent_iodine

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Re: Synthesis of stannane compound
« Reply #7 on: December 17, 2019, 12:32:17 AM »
I have never worked with tin, so I am not sure how stable Bu3SnCl is, but is it possible that you have a bad reagent?

Offline rolnor

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Re: Synthesis of stannane compound
« Reply #8 on: December 17, 2019, 04:59:47 AM »
The reaction can be slow, how long time do you run? I agree that the reagent can be bad if its an old bottle.

Offline OrganicDan96

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Re: Synthesis of stannane compound
« Reply #9 on: December 17, 2019, 11:36:58 AM »
You must understand that the lithiated molecule will be hydrolysed when put on a TLC-plate. If you show your structure I can help you.
Thank you for your information. I really don't know that before. I synthesize tributyl(5-octylthiophen-2-yl)stannane from 2-bromo-5-octylthiophene. Could you share your experience?
you should take a sample and quench it before you do the TLC the spot wou see will correspond to 5-octylthiophene. if you are having trouble with tlc then a crude NMR of a small sample of reaction mixture might help.

how are you visualizing the TLC?

Offline rolnor

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Re: Synthesis of stannane compound
« Reply #10 on: December 17, 2019, 01:43:45 PM »
One good way to quench this time of sample is to mix it with a dropp of acetone, RF should go down if the lithiation is successfull.

Offline Hachiko

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Re: Synthesis of stannane compound
« Reply #11 on: December 17, 2019, 09:47:24 PM »
I have never worked with tin, so I am not sure how stable Bu3SnCl is, but is it possible that you have a bad reagent?
I bought it from Sigma but I have opened for several months.

Offline Hachiko

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Re: Synthesis of stannane compound
« Reply #12 on: December 17, 2019, 09:49:28 PM »
The reaction can be slow, how long time do you run? I agree that the reagent can be bad if its an old bottle.
I added BuLi and waited till all starting material change into low Rf. Adding Bu3SnCl, keep at -78oC for 1 hour and increase to room temperature for 24hrs. 

Offline Hachiko

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Re: Synthesis of stannane compound
« Reply #13 on: December 17, 2019, 09:51:32 PM »

[/quote]
you should take a sample and quench it before you do the TLC the spot wou see will correspond to 5-octylthiophene. if you are having trouble with tlc then a crude NMR of a small sample of reaction mixture might help.

how are you visualizing the TLC?
[/quote] You mean after quenching, the spot I see will be 5-octylthiophene. I visualize TLC under UV light.

Offline Hachiko

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Re: Synthesis of stannane compound
« Reply #14 on: December 17, 2019, 10:41:16 PM »
One good way to quench this time of sample is to mix it with a dropp of acetone, RF should go down if the lithiation is successfull.
after quenching with acetone, will  I see the spot of R-Li? If I don't quench, which kind of spot will I see? Because in this case, after lithiation I see a new spot with lower Rf to compare with starting material (5-octylthiophene)
« Last Edit: December 17, 2019, 11:08:09 PM by Hachiko »

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