[herrhansen]

Hi.

I was doing an Suzuki reaction, but ends up with a yield of around 50 %. TLC is pretty clean. Not much starting product and only small amounts of catalyst is visible at the apolar position. So I was wondering if the spot, which looks like the starting product could be formed by some homo coupling? I have attached the sideproduct suggested. I dont know if it is possible for amines to attack palladium (II) complexes forming amines?

Thanks guys and girls.

[Telamond]

Homocoupling is a possibility. The catalytic cycle for Suzuki-Miyaura coupling is usually via Pd(0) - Pd (II) cycle and you start out with a Pd(II) complex, so it has to form the Pd(0) complex somehow. But you usually use a small amount of catalyst, so it shouldn't effect the yield that much.

The reaction that you're describing is a Buchwald-Hartwig amination. I don't know much about it practically, and about their rates, just knows that it works. Perhaps you need to protect the amine somehow? Also, how come you're running the reaction in ethanol? Won't you just re-esterify your ester?


Have you tried separating the two dots and running a 1H NMR to see which is the byproduct?

[OC pro]

Boronic acids also tend to dimerize during Suzuki coupling. Depends on the nature of them.

[BobfromNC]

Another common side product is the dehalogenated starting material.  So if you are reacting bromobenzene with a boronic acid, you might get some benzene as a side product.  If your SM is low enough MW, the dehalogenated material may evaporate in the workup.  Most side products are best solved by using a larger excess of the boronic acid or different catalyst ligand. 

Bob