An environmental catalyst derived from biological waste materials for green synthesis of biaryls via Suzuki coupling reactions

Synthesis of bio-macromolecular supported catalysts has gained much recent attention due to their greener nature. Among the biopolymers, chitosan is widely used as a support material due to its high affinity for metal ions. In this study, chitosan-Ulva sp. (green alga) composite microbeads were prepared as a support material for palladium catalyst. Ulva sp. particles were incorporated into chitosan matrix to enhance the interaction with palladium ions. The catalytic performance of chitosan-Ulva supported Pd(II) catalyst was investigated in the synthesis of biaryls via the Suzuki coupling reaction. All the experiments were conducted without using any solvent under the microwave irradiation, which is also considered as a green technique. This green catalyst exhibited high selectivity and efficiency in the reactions of phenyl boronic acid with different aryl halides in only 4 min at low temperature (50 °C). Excellent TON and TOF values were achieved for the catalyst; 4950 and 75000. In addition, the catalyst did not lose its activity even after 8 cycles. It showed high thermal stability (216.8 °C) and durability in presence of oxygen. This green catalyst has a potential to be used in pharmacology, medicine and cosmetics.