Application of CuAAC for the covalent immobilization of homogeneous catalysts

Immobilization of Molecular Catalysts for Enhanced Redox Catalysis

“…The immobilization of homogeneous catalysts on various insoluble supports such as a siliceous material makes the immobilized catalyst insoluble in the reaction solution, providing great advantages for the easy separation of the catalyst from the reaction mixture, the fast isolation of the reaction products, and catalyst recovery and recycling by simple filtration . The immobilization of homogeneous catalysts also allows insoluble catalysts, which would otherwise be aggregated, to be well dispersed in the reaction medium such as water, resulting in the significant enhancement in the catalytic activity.…”

“…In general, the supported catalyst may be more sterically hindered and hence less accessible to substrates as compared to its non‐supported counterpart, while the selectivity may be enhanced by the steric effect. Catalyst instability in the homogeneous phase is mainly caused by bimolecular deactivation pathways, which are prevented by immobilization of the catalyst to isolate the catalyst reactive sites …”

“…The immobilization of homogeneous catalysts on various insoluble supports such as as iliceous material makes the immobilized catalysti nsoluble in the reactions olution,p roviding great advantages for the easy separation of the catalystf rom the reaction mixture, the fast isolation of the reaction products, and catalyst recovery and recycling by simple filtration. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The immobilization of homogeneous catalysts also allows insoluble catalysts, which would otherwise be aggregated, to be well dispersed in the reaction medium such as water, resultingi nt he significant enhancement in the catalytic activity.T he use of water as solvent with immobilizedc atalysts also call attentiont ot he importance of the requirements of green chemistry. [21][22][23][24][25][26] In general,t he supported catalyst may be more sterically hindered and hence less accessible to substrates as compared to its non-supported counterpart,w hile the selectivity may be enhanced by the steric effect.…”

Catalytic Enantioselective Flow Processes with Solid‐Supported Chiral Catalysts

“…In this regard, two premises are to be considered for an optimal outcome: (a) ensuring enough distance between the active site and the solid support and (b) choosing a support material, a linker and a spacer that do not interfere with the catalytic process. A few years ago, we identified the copper‐catalyzed azide‐alkyne cycloaddition (CuAAC hereafter) as an extremely valuable tool for this purpose . Indeed, this has often been our first choice to immobilize chiral catalysts because it is a clean, orthogonal reaction that takes place under mild reaction conditions and can be followed by IR spectroscopy even on the resin beads.…”

New Polymer‐Supported Mono‐ and Bis‐Cinchona Alkaloid Derivatives: Synthesis and Use in Asymmetric Organocatalyzed Reactions

“…In order to overcome these limitations, we recently introduced a simple and scalable protocol for the preparation of IPB quinidine ethers of the pyridazine class ( P9 ) 5. The key element of such an approach was the choice of the Cu‐catalyzed azide–alkyne cycloaddition (CuAAC) as the tool for linking alkyne‐functionalyzed alkaloid derivatives to insoluble azidomethylpolystyrene supports 6. Gratifyingly, this “click‐chemistry” strategy allowed a significant overall improvement of the preparation of IPB materials, including the straightforward and chromatography‐free synthesis of anchorable chiral derivatives and the attainment of unprecedentedly high anchoring yields and alkaloid loadings in the immobilization step.…”