A PMMA-based heterogeneous photocatalyst for visible light-promoted [4 + 2] cycloaddition

Abstract

Macromolecular organic photocatalysts consisting of a PMMA network with integrated conjugated moiety have broad and promising applications in visible light-promoted photoredox catalysis.

Photocatalytic polymer nanomaterials for the production of high value compounds

“…Here, photocatalytic gels have been produced to allow easy partitioning of reagents into the gel network, where they can be readily transformed. To date conjugated, 47 polymer/inorganic, 48 polymer/metal 49 and classical polymer 18 gel networks have been investigated. Similar to the previously discussed porous polymeric nanomaterials, photocatalytically modified gels exhibit significant advances over linear, bulk polymers.…”

“…Here, photocatalytic gels have been produced to allow easy partitioning of reagents into the gel network, where they can be readily transformed. To date conjugated, 47 polymer/inorganic, 48 polymer/metal 49 and classical polymer 18 gel networks have been investigated.…”

“…3,4 Furthermore, the incorporation of small molecule photocatalysts into classical polymers has recently been reported as new heterogeneous photocatalytic systems. 5 Photocatalytic systems use visible light to enable a broad range of chemical reactions to proceed including water splitting, [6][7][8][9] CO 2 reduction, [10][11][12][13] C-C coupling reactions, 14,15 C=C bond cleavage, 16,17 pericyclic reactions, 18,19 metal reduction, 20,21 enzyme co-factor activation, 22,23 trifluoromethylation of arenes, 24 oxidation of sulfides, 25,26 dehalogenation of haloketones, 27 heterocycle formation 28 and enantioselective alpha-alkylation. 29 These reactions proceed through the formation of photogenerated radical species within the photocatalytic material.…”

“…Bulk gel photocatalytic materials have been reported that have photocatalytic sites incorporated into the gel structure. 18 These gel networks allow for the diffusion of reagents into the networks, enabling their catalytic conversion. Similarly, to conjugated porous polymers, mass-transfer is once again a challenge limiting these materials.…”

Molecular Rubies in Photoredox Catalysis

“…For Cr III photocatalysts and organic thioxanthylium and benzothiadiazole photocatalysts ( Tanaka, et al, 2020 ; Huber, et al, 2020 ), oxygen is required for the regeneration of the reduced photocatalyst PC (n−1)+ ( Scheme 1A , mediator cycle). Interestingly, Rappé and Shores suggested that singlet oxygen 1 O 2 is required to regenerate the chromium(III)-based PC 3+ forming superoxide O 2 •– , which in turn reduces the cyclohexenyl radical DAP •+ ( Scheme 1A ) ( Higgins, et al, 2016 ) According to the suggested mechanism, 1 O 2 forms in a separate energy transfer photocycle ( Scheme 1A , photocycle #2) so that two photons would be required for a single turnover.…”