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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: nancy960 on February 18, 2019, 01:01:49 AM

Title: Problems on Miyaura borylation reaction
Post by: nancy960 on February 18, 2019, 01:01:49 AM

My main reactant is dibromofluorenone and I used bis(pinacolato)diboron, Pd(dppf)2Cl2, potassium acetate and dioxane as my solvent.
But even I've tried a few conditions, the conversion was remain very low.
Should I add base in aqueous solution or just in solid?
The solution after reaction shows up dark brown and muddy, the TLC test shows there is still reactant remain.

Thanks for your *delete me*

Title: Re: Problems on Miyaura borylation reaction
Post by: phth on February 19, 2019, 01:19:01 AM

If reactants remain then the conditions are not conducive to product, or the catalyst [Pd(0)] is being quenched by oxygen, for example.

Title: Re: Problems on Miyaura borylation reaction
Post by: nancy960 on February 25, 2019, 04:56:12 AM

I tried to react under Argon atmosphere but the yield was really low.From the NMR spectrum it seem to be failed and not work.

Title: Re: Problems on Miyaura borylation reaction
Post by: kriggy on February 25, 2019, 11:15:51 AM

What about trying lithium-halogen exchange and then quech with the bpin?

Title: Re: Problems on Miyaura borylation reaction
Post by: phth on February 25, 2019, 10:50:16 PM

Quote from: nancy960 on February 25, 2019, 04:56:12 AM

I tried to react under Argon atmosphere but the yield was really low.From the NMR spectrum it seem to be failed and not work.

how did you preclude oxygen and water?
https://www.chemistryviews.org/details/education/4308331/Tips_and_Tricks_for_the_Lab_Air-Sensitive_Techniques_2.html
https://www.chemistryviews.org/details/education/4360441/Tips_and_Tricks_for_the_Lab_Air-Sensitive_Techniques_3.html

It should work unless 1) reagents bad 2) experimental error

Title: Re: Problems on Miyaura borylation reaction
Post by: blackcat on November 25, 2019, 02:42:17 PM

Quote from: kriggy on February 25, 2019, 11:15:51 AM

What about trying lithium-halogen exchange and then quech with the bpin?

There is carbonyl group in the reactant

Title: Re: Problems on Miyaura borylation reaction
Post by: blackcat on November 25, 2019, 02:43:53 PM

Quote from: nancy960 on February 25, 2019, 04:56:12 AM

I tried to react under Argon atmosphere but the yield was really low.From the NMR spectrum it seem to be failed and not work.

It is not only about the atmosphere in which the reaction was conducted is important. You need to degas your solvent before the reaction. This can be by sparging or freeze-pump-thaw. The former works better for large volume, the latter for smaller volume.