External cross-linked sulfonate-functionalized N-heterocyclic carbenes: an efficient and recyclable catalyst for Suzuki–Miyaura reactions in water
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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.
This work was supported by National Undergraduate Training Program for Innovation and Entrepreneurship (201710638031), the Key Project Funds of Science and Technology Department of Sichuan Province (2017JY0015), Fundamental Research Funds of China West Normal University (17C038) and Meritocracy Research Funds of China West Normal University (17YC031).