External cross-linked sulfonate-functionalized N-heterocyclic carbenes: an efficient and recyclable catalyst for Suzuki–Miyaura reactions in water

A sulfonate-functionalized N-heterocyclic carbene (NHC) was successfully attached to a hyper-cross-linked polymer via an external cross-linking reaction. The structure of Poly-BBIS was confirmed by FTIR spectroscopy, TEM, FESEM, and BET. The Poly-BBIS show a large surface areas (up to 563 m2 g−1) and hydrophilicity, as well as abundant micro-mesoporous, tunable and versatile active sites. The catalytic activity of the Pd derivative Poly-BBIS-Pd2+ was examined for Suzuki–Miyaura cross-coupling reactions in water, followed by an investigation of the reaction mechanism. The Poly-BBIS-Pd2+ gives a yield of 98% for the reaction between bromobenzene and phenylboronic acid with a loading of 0.057 mmol % Pd in water after approximately 2 h. Also, the catalyst can be reused for 5 times without significant loss of activity. This work highlights a low-cost route to the synthesis of heterogeneous catalysts based on hydrophilic sulfonate-functionalized NHC polymers for the Suzuki–Miyaura cross-coupling reaction in water.