Palladium chloride was studied for its effectiveness as a catalyst for the formation of biaryl compounds in aqueous solutions. A compliment of different bases was investigated for their effect on the formation of both the cross-coupled and the homo-coupled products. The bases that were investigated included: Na2SO4, H2KPO4, K3PO4, K2CO3, and NaHCO3 for the coupling of: Phenylboronic acid with either 4-Bromonitrobenzene or4- Bromoanisole. All the bases favored the cross-coupled products (4-nitrobiphenyl, and 4-methoxybiphenly) more than the homo-coupled (Bi-phenyl) product. The reactions were performed using a CEM discover microwave reaction unit at 80°C, in 18 MΩ deionized water. In addition all synthesis were performed using 1.0 mMol of Phenylboronic acid and 2.0 mM of either the 4-Bromonitrobenzene or Bromoanisole. The general trends observed in the study showed that both the HCO3- and the CO32- had the highest synthesis of the cross-coupled products (80-90%) and no observable effect on the product ratios from 2-16 mM of base. Whereas, the PO43- and the H2PO4- showed a decrease in the cross-coupled product with increasing base concentration from 2.0 mM up to 16 mM of base. The SO42- showed an increase in the cross-coupled products with increasing base concentration from 2.0 mM up to 8.0 mM. However, at 16 mM more homo-coupled products were observed.

Aqueous solution palladium catalyzed Suzuki cross coupling reactions: The effect of base and base concentrations

251st National Meeting (2016)

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