Formylation reaction of an arylbromide derivative using Butyl Lithium and 1-formylpiperidine is usually carried out in dry THF. Here if the arylbromide derivative is insoluble in THF will the formylation occur. If not what other solvents can be employed.
You can try to add another ether (diethylether or similar) to THF to enhance the solubility.
Hello Geetmani,
many thanks for sharing this very interesting technical question with the RG community. My personal experience tells me that if your aryl bromide is not even soluble in THF it will be insoluble in diethyl ether as well. However, if you are not sure about this, you can make a quick test by placing a small amount of your aryl bromide in a vial and add a few ml of diethyl ether to see if it perhaps dissolves easier than in THF. Quick solubility tests can also be carried out with other solvents as well.
Are you following a procedure described in the literature? If the authors do not give a hint regarding a suitable solvent, you can try two variants. First of all you could run the reaction with a suspension of your aryl bromide in THF or diethyl ether. Chances are that it will dissolve in the course of the reaction. The driving force here is the insolubility of LiBr (lithium bromide) which gradually precipitates as the reaction proceeds.
Yet another option would be to use DME (1,2-dimethoxyethane) as solvent. It is well established that DME coordinates to the lithium as chelating ligands and enhances the reactivity of n-butyllithium.
Good luck with your experiments and best wishes, Frank Edelmann
Thank you, Dr. Gal and Dr. Edelmann. I very much appreciate your insights into my query. My aryl bromide derivative is insoluble in both ether as well as in THF. However, the idea of using DME is interesting.
My aryl bromide is soluble in DMF, so I was thinking of using THF as solvent and adding a few drops of DMF to solubilize the aryl bromide. I hope there won't be any complications.
Dear Geetmani,
many thanks for your kind response and explanation. Actually, I would strongly suggest to stay away from DMF (dimethylformamide) in this case, because it is well known that DMF can react with organolithium reagents. Check if your arylbromide precursrs is soluble in DME and then use this solvent. You can also prepare a suspension in THF and place it in an ultrasound bath for a few minutes to make finely divided particles. Then I would try to run the reaction in suspension and hope that the starting material will dissolve over time. After a while, LiBr will certainly precipitate. I any case I would try to avoid DMF.
Dear Dr. Edelmann
I would like to thank you once again for your wise suggestions. Ultrasonication with THF solvent seems to be a good option for now. I will try the aforesaid reaction without using DMF.
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