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1. New 1,2,3-Triazoles from (R)-Carvone: Synthesis, DFT Mechanistic Study and In Vitro Cytotoxic Evaluation

   https://doi.org/10.3390/molecules27030769  

   Oubella, Ali ; Bimoussa, Abdoullah ; N’ait Oussidi, Abdellah ; Fawzi, Mourad ; Auhmani, Aziz ; Morjani, Hamid ; Riahi, Abdelkhalek ; Esseffar, M’hamed ; Parish, Carol ; Ait Itto, Moulay Youssef ( February 2022 , Molecules)

   Aseries of novel 1,4-disubstituted 1,2,3-triazoles were synthesized from an (R)-carvone terminal alkyne derivative via a Cu (I)-catalyzed azide–alkyne cycloaddition reaction using CuSO4,5H2O as the copper (II) source and sodium ascorbate as a reducing agent which reduces Cu (II) into Cu (I). All the newly synthesized 1,2,3-triazoles 9a–h were fully identified on the basis of their HRMS and NMR spectral data and then evaluated for their cell growth inhibition potential by MTS assay against HT-1080 fibrosarcoma, A-549 lung carcinoma, and two breast adenocarcinoma (MCF-7 and MDA-MB-231) cell lines. Compound 9d showed notable cytotoxic effects against the HT-1080 and MCF-7 cells with IC50 values of 25.77 and 27.89 µM, respectively, while compound 9c displayed significant activity against MCF-7 cells with an IC50 value of 25.03 µM. Density functional calculations at the B3LYP/6-31G* level of theory were used to confirm the high reactivity of the terminal alkyne as a dipolarophile. Quantum calculations were also used to investigate the mechanism of both the uncatalyzed and copper (I)-catalyzed azide–alkyne cycloaddition reaction (CuAAC). The catalyzed reaction gives complete regioselectivity via a stepwise mechanism streamlining experimental observations. The calculated free-energy barriers 4.33 kcal/mol and 29.35 kcal/mol for the 1,4- and 1,5-regioisomers, respectively, explain the marked regioselectivity of the CuAAC reaction. 

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2. Photoswitchable Sol–Gel Transitions and Catalysis Mediated by Polymer Networks with Coumarin‐Decorated Cu 24 L 24 Metal–Organic Cages as Junctions

   https://doi.org/10.1002/anie.201913297  

   Oldenhuis, Nathan J. ; Qin, K. Peter ; Wang, Shu ; Ye, Hong‐Zhou ; Alt, Eric A. ; Willard, Adam P. ; Van Voorhis, Troy ; Craig, Stephen L. ; Johnson, Jeremiah A. ( January 2020 , Angewandte Chemie International Edition)

   Photoresponsive materials that change in response to light have been studied for a range of applications. These materials are often metastable during irradiation, returning to their pre‐irradiated state after removal of the light source. Herein, we report a polymer gel comprising poly(ethylene glycol) star polymers linked by Cu₂₄L₂₄metal–organic cages/polyhedra (MOCs) with coumarin ligands. In the presence of UV light, a photosensitizer, and a hydrogen donor, this “polyMOC” material can be reversibly switched between Cu^II, Cu^I, and Cu⁰. The instability of the MOC junctions in the Cu^Iand Cu⁰states leads to network disassembly, forming Cu^I/Cu⁰solutions, respectively, that are stable until re‐oxidation to Cu^IIand supramolecular gelation. This reversible disassembly of the polyMOC network can occur in the presence of a fixed covalent second network generated in situ by copper‐catalyzed azide‐alkyne cycloaddition (CuAAC), providing interpenetrating supramolecular and covalent networks.

    

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3. Photoswitchable Sol–Gel Transitions and Catalysis Mediated by Polymer Networks with Coumarin‐Decorated Cu 24 L 24 Metal–Organic Cages as Junctions

   https://doi.org/10.1002/ange.201913297  

   Oldenhuis, Nathan J. ; Qin, K. Peter ; Wang, Shu ; Ye, Hong‐Zhou ; Alt, Eric A. ; Willard, Adam P. ; Van Voorhis, Troy ; Craig, Stephen L. ; Johnson, Jeremiah A. ( January 2020 , Angewandte Chemie)

   Photoresponsive materials that change in response to light have been studied for a range of applications. These materials are often metastable during irradiation, returning to their pre‐irradiated state after removal of the light source. Herein, we report a polymer gel comprising poly(ethylene glycol) star polymers linked by Cu₂₄L₂₄metal–organic cages/polyhedra (MOCs) with coumarin ligands. In the presence of UV light, a photosensitizer, and a hydrogen donor, this “polyMOC” material can be reversibly switched between Cu^II, Cu^I, and Cu⁰. The instability of the MOC junctions in the Cu^Iand Cu⁰states leads to network disassembly, forming Cu^I/Cu⁰solutions, respectively, that are stable until re‐oxidation to Cu^IIand supramolecular gelation. This reversible disassembly of the polyMOC network can occur in the presence of a fixed covalent second network generated in situ by copper‐catalyzed azide‐alkyne cycloaddition (CuAAC), providing interpenetrating supramolecular and covalent networks.

    

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4. Ultrasound Promoted Step‐Growth Polymerization and Polymer Crosslinking Via Copper Catalyzed Azide–Alkyne “Click” Reaction

   https://doi.org/10.1002/anie.201804451  

   Mohapatra, Hemakesh ; Ayarza, Jorge ; Sanders, Emily C. ; Scheuermann, Angelique M. ; Griffin, Philip J. ; Esser‐Kahn, Aaron P. ( July 2018 , Angewandte Chemie International Edition)

   Mechano‐activated chemistry is a powerful tool for remodeling of synthetic polymeric materials, however, few reactions are currently available. Here we show that using piezochemical reduction of a Cu^II‐based pre‐catalyst, a step‐growth polymerization occurs via the copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction to form a linear polytriazole. Furthermore, we show that a linear polymer can be crosslinked mechanochemically using the same chemistry to form a solid organogel. We envision that this chemistry can be used to harness mechanical energy for constructive purposes in polymeric materials.

    

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5. Ultrasound Promoted Step‐Growth Polymerization and Polymer Crosslinking Via Copper Catalyzed Azide–Alkyne “Click” Reaction

   https://doi.org/10.1002/ange.201804451  

   Mohapatra, Hemakesh ; Ayarza, Jorge ; Sanders, Emily C. ; Scheuermann, Angelique M. ; Griffin, Philip J. ; Esser‐Kahn, Aaron P. ( July 2018 , Angewandte Chemie)

   Mechano‐activated chemistry is a powerful tool for remodeling of synthetic polymeric materials, however, few reactions are currently available. Here we show that using piezochemical reduction of a Cu^II‐based pre‐catalyst, a step‐growth polymerization occurs via the copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction to form a linear polytriazole. Furthermore, we show that a linear polymer can be crosslinked mechanochemically using the same chemistry to form a solid organogel. We envision that this chemistry can be used to harness mechanical energy for constructive purposes in polymeric materials.

    

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