Can Amine (such as Et3N) be used as solvent as well as base for the Sonogashira Coupling?
How to decide the amount of solvent to be used in any reaction? Does the amount of solvent affect the reaction ?
Yes, you can absolutely use an amine as solvent for Sonogashira couplings. In fact, I know more examples without any additional solvents other than the amine than with additional ether or others.
The amount of solvent definitely affects your reaction, within a certain span at least. Too little solvent, and your reagents might not be properly solved. When the solvent is also a reagent itself (as it's the case here), you might have issues with the stochiometry. And when using too much solvent, your solution becomes too dilute and the reagents no longer can "find" each other.
As the Sonogashira coupling is a well established procedure with many published examples, I would choose an amount of solvent based on these published examples.
thank you for explaining it more precisely - Simon Janich
But, is it possible to explain - why usually "ether" solvents are preferred for Sonogashira? Is it because ether solvents have more polarity?
I agree with you that amine can be used as a solvent as well as base in sonogashira ( I have been working on this, and used only amine for the reaction, and got the product). But, then a question arises into my mind - Is ether solvent not really important, and how amine works as solvent ?
In other words, solvents are chosen in a way that the reactant and reagents are soluble in it, and it supports the stability of the intermediate formation. Do you think this explanation is good enough?
Yes, that seems to cover it pretty well.
By adding ethers, you can tweak the polarity/solvent properties. Ethers are also aprotic, so you don't have to worry about unwanted protonation/deprotonation. In addition, they are coordinating, so they can act as labile ligands.
And unlike other solvents with similar properties (like DMF) they are fairly easy to remove after the reaction.
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