The reaction of meso-tetrakis(pentafluorophenyl)porpholactone with azomethine ylides and nitrones affords pyrrolidine-fused and isoxazolidine-fused dihydroporpholactones that display, respectively, isobacteriochlorin- and chlorin-type UV–Vis spectra. These reactions are site-selective, yielding, respectively, 17,18- or 12,13-dihydroporpholactones. The crystal and molecular features of pyrrolidine-fused and isoxazolidine-fused dihydroporpholactones were unveiled from single-crystal X-ray diffraction studies.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
We report an organophotocatalytic, N-CH3-selective oxidation of trialkylamines in continuous flow. Based on the 9,10-dicyanoanthracene (DCA) core, a new catalyst (DCAS) was designed with solubilizing groups for processing in flow which allowed harnessing of O2 as a benign reagent for late-stage photocatalytic N-CH3 oxidation of natural products and active pharmaceutical ingredients. These substrates bear functional groups which are not tolerated by previous methods. The organophotocatalytic process benefited from the flow parameters, affording cleaner reactions in short residence time of 13.5 mins and productivities of up to 0.65 g / day. Mechanistic studies found that catalyst derivatization not only enhanced solubility of the new catalyst compared to DCA, it profoundly diverted the photocatalytic reaction mechanism from singlet electron transfer (SET) reductive quenching with amines to energy transfer (EnT) with O2.
Abstract Electron‐deficient acridones and in situ generated acridinium salts are reported as potent, closed‐shell photooxidants that undergo surprising mechanisms. When bridging acyclic triarylamine catalysts with a carbonyl group (acridones), this completely diverts their behavior away from open‐shell, radical cationic, ‘beyond diffusion’ photocatalysis to closed‐shell, neutral, diffusion‐controlled photocatalysis. Brønsted acid activation of acridones dramatically increases excited state oxidation power (by +0.8 V). Upon reduction of protonated acridones, they transform to electron‐deficient acridinium salts as even more potent photooxidants (* E 1/2 =+2.56–3.05 V vs SCE). These oxidize even electron‐deficient arenes where conventional acridinium salt photooxidants have thusfar been limited to electron‐rich arenes. Surprisingly, upon photoexcitation these electron‐deficient acridinium salts appear to undergo two electron reductive quenching to form acridinide anions, spectroscopically‐detected as their protonated forms. This new behaviour is partly enabled by a catalyst preassembly with the arene, and contrasts to conventional SET reductive quenching of acridinium salts. Critically, this study illustrates how redox active chromophoric molecules initially considered photocatalysts can transform during the reaction to catalytically active species with completely different redox and spectroscopic properties.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract Electron‐deficient acridones and in situ generated acridinium salts are reported as potent, closed‐shell photooxidants that undergo surprising mechanisms. When bridging acyclic triarylamine catalysts with a carbonyl group (acridones), this completely diverts their behavior away from open‐shell, radical cationic, ‘beyond diffusion’ photocatalysis to closed‐shell, neutral, diffusion‐controlled photocatalysis. Brønsted acid activation of acridones dramatically increases excited state oxidation power (by +0.8 V). Upon reduction of protonated acridones, they transform to electron‐deficient acridinium salts as even more potent photooxidants (* E 1/2 =+2.56–3.05 V vs SCE). These oxidize even electron‐deficient arenes where conventional acridinium salt photooxidants have thusfar been limited to electron‐rich arenes. Surprisingly, upon photoexcitation these electron‐deficient acridinium salts appear to undergo two electron reductive quenching to form acridinide anions, spectroscopically‐detected as their protonated forms. This new behaviour is partly enabled by a catalyst preassembly with the arene, and contrasts to conventional SET reductive quenching of acridinium salts. Critically, this study illustrates how redox active chromophoric molecules initially considered photocatalysts can transform during the reaction to catalytically active species with completely different redox and spectroscopic properties.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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