Hypercrosslinked Polymer Platform-Anchored Single-Site Heterogeneous Pd–NHC Catalysts for Diverse C–H Functionalization

Abstract

We demonstrate a new class of hypercrosslinked polymer (HCP) platform-anchored single-site heterogenized Pd–NHC catalysts for multipurpose C–H functionalization reactions. This new class is represented by a set of three catalysts, viz., HCP-B- Me NHC-Pd, HCP-B- Bn NHC-Pd, and HCP-TPM- Me NHC-Pd, having a variation on the structural feature of the anchoring polymeric platform. All three catalysts were fully characterized via diverse solid-state characterization and analytical techniques such as X-ray photoelectron spectroscopy, 13C cross-polarization magic-angle-spinning nuclear magnetic resonance, field-emission scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetric analysis, and inductively coupled plasma–optical emission spectrometry. Three types of regularly practiced and very useful C–H functionalization reactions, viz., C–H halogenation, acetoxylation, and arylation, are tested with the new catalysts and found to be highly compatible and successful. With the HCP-TPM- Me NHC-Pd catalyst, up to 85, 75, and 70% yields of the functionalized products were achieved for the halogenation, acetoxylation, and arylation reactions, respectively. Demanding attributes such as enhanced activity, heterogeneity, and recyclability are offered by this new system, making it a promising candidate in the field of heterogeneous C–H functionalization, where only a few efficient catalysts are available.

Eco-Friendly Production of Hyper-Cross-Linked Polymers Using Mechanosynthesis and Bioresources: A Critical Review

“…(K) N,N′-dimethyl-benzimidazolium iodide and triphenylmethane-based HCP catalyst with Pd as the active site . (L) Several examples of halogenation reactions promoted by a catalyst developed by Mandal et al, including yields. Reprinted with permission from ref .…”

“…(L) Several examples of halogenation reactions promoted by a catalyst developed by Mandal et al, including yields. Reprinted with permission from ref . Copyright 2021, American Chemical Society.…”

“…In another study, Pd-derived HCPs (Figure K) catalyzed C–H halogenation, acetoxylation, and arylation with yields up to 85%, 75%, and 70%, respectively (see some examples of halogenation reactions in Figure L). These HCPs were based on N,N′-dimethyl-benzimidazolium iodide and triphenylmethane . Suzuki–Miyaura reactions were also catalyzed by Pd-based HCPs with very low Pd contents of only 0.03 mol % achieving up to six complete cycles without significant loss of activity .…”

“…These HCPs were based on N,N′-dimethyl-benzimidazolium iodide and triphenylmethane. 61 Suzuki−Miyaura reactions were also catalyzed by Pd-based HCPs with very low Pd contents of only 0.03 mol % achieving up to six complete cycles without significant loss of activity. 65 Other reactions have also been subjected to the use of Pd-based catalysts associated with HCPs.…”

Evaluation of CO2and H2O Adsorption on a Porous Polymer Using DFT and In Situ DRIFT Spectroscopy

“…HCPs exhibit a permanent porosity and high surface area, and their synthesis is straightforward, requiring only common Lewis acid catalysts to initiate polymerization, such as Fe­(III) chloride and Al­(III) chloride, or organic Brønsted acids. , This simplicity and potential for scale-up explain the scientific interest around these materials. In fact, some HCPs are already commercially available (e.g., ion-exchange polymeric resins) while others are being developed and tailored for different applications related to gas separation/storage, − liquid phase adsorption, , and catalytic organic transformations. − In particular, HCPs have recently been investigated for CO 2 capture ,,− and CO 2 photoconversion to value-added chemicals. , Martin et al reported a biphenyl–xylene HCP with CO 2 uptake capacity of 1.7 and 13.4 mmol g –1 under atmospheric pressure and 30 bar, respectively, exceeding that of commercial adsorbents like zeolite 13X and activated carbons BPL and Norit R under similar conditions . Su et al studied an amine-functionalized HCP that displayed selective CO 2 uptake over N 2 , a feature they attributed to the high density of primary amines and the relatively small pore size of the material .…”