I'm trying to synthesise a product through suzuki coupling using 5-bromo-2-thiophenecarboxylic acid and 2-fluoro-4-methoxyphenylboronic acid.
I tried using Cs2CO3, K2CO3, Na2CO3 as base and regarding solvents I used 1,4-dioxane-water ( 10: 1 ) and THF-water ( 10:1 ). I respected inert atmosphere (degassing and Argon bubbling) in organic solvent as well as in aqueous basic carbonate solution. Temperatures tried were 95, 90, 80 degrees Celsius. As workup, I directly, after cooling down the mixture, add HCl 15% and do the rest of the workup to initiate the isolation of carboxylic acid product. I used boronic acid in excess to avoid purification of 2 carboxylic acids(which is almost ridiculously hard, even with AcOH in column).
Catalyst: Pd(PPh3)4
My percentage yields of pure product were : 14% , 18,9%, 22% and 22%.
I really can't think of something that might increase the yield of the reaction since it's the starting point of many synthesis steps.
Can I get some help/opinions/tips/suggestions please? My next try i want to use 1,4-dioxane and increase temperature to 110-120 degrees celsius, maybe temperature is the main reason. I really don't know. I'm looking forward to read anything you can think of.
Thanks a lot ! It's a huuuuge text and I'm sorry for that, but I wanted to include everything so you have all the informations you need to provide any help.
What kind of palladium catalyst are you using? I have seen great difference between Pd(PPh4)3 vs PdCl2, for example.
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