Synthesis of a carbene transfer organometallic polymer and application to forming a recyclable heterogeneous catalyst for the Suzuki reactions of aryl chlorides

Abstract

An efficient and versatile synthetic approach to NHC-based organometallic polymers has been developed by a simple three-step synthesis. A novel brush polymer having imidazolium salt side chains (P2) was firstly synthesized through postpolymerization modification of P1, which permits access to Ag(I)-NHC-based side chain polymer (P3) at room temperature in high yield. P3 was applied as a carbene transfer agent to form a Pd-NHC-containing polymer (P4) by the transmetallation reaction of Ag(I)-NHCs in the side chains. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis indicated that 77% of Ag(I)-NHCs in the side chains of P3 were transmetallated. The resulting Pd-NHC-containing polymer (P4) showed high catalytic activity and reusability in the Suzuki reactions of aryl chlorides and aryl boronic acids. This novel Pd-NHC-containing polymeric catalyst was used five times and still remained active giving the desired biaryl products in 70% yield in the fifth run of the cross-coupling reaction of deactivated 4-chloroanisole with phenylboronic acid.

Functionalisable N‐Heterocyclic Carbene–Triazole Palladium Complexes and Their Application in the Suzuki–Miyaura Reaction

“…Purification by flash chromatography gave the pure cross‐coupled product. The spectroscopic data were in agreement with those previously reported for 4‐methoxy‐4′‐acetyl‐biphenyl,25 4‐methoxy‐4′‐nitrobiphenyl,26 4‐methoxy‐4′‐methylbiphenyl25,27 and 4′‐(1‐naphthyl)‐acetophenone 28…”

A PdII Carbene Complex with Anthracene Side‐Arms for π‐Stacking on Reduced Graphene Oxide (rGO): Activity towards Undirected C–H Oxygenation of Arenes

“…To improve on the situation palladium N‐heterocyclic carbene catalysts have been used to stabilize the higher oxidation state, and as a further step also the heterogenization has been targeted. It turns out that these new heterogeneous catalyst materials exhibit a remarkable catalytic activity and selectivity in C–O, C–halogen, and C–C bond formation under both batch and flow conditions . There are, however, still difficulties to tackle: in many cases the additional functionalization of the ligand that aid the anchoring or immobilization step leads to high costs of preparation and sometimes lead to changes in the original reactivity of the catalyst .…”

Recent Applications of Polymer Supported Organometallic Catalysts in Organic Synthesis

“…A related polymer bound palladium species was reported by Zeng et al ., who prepared a soluble silver carbene polymer that could be used as a carbene transfer reagent for the preparation of catalyst 21b , also for application in the Suzuki coupling of aryl chlorides [ 43 ]. By using isopropanol as the solvent, the polymeric support was rendered non-soluble.…”