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1. Enzymatic Knoevenagel condensation in dual‐functionalized water‐mimicking ionic liquids and tertiary amide solvents

   https://doi.org/10.1002/jctb.7603  

   Zhao, Hua ; Campbell, Chante' D. ( February 2024 , Journal of Chemical Technology & Biotechnology)

   Knoevenagel condensation is an important tool for building carbon–carbon (CC) bonds, especially when catalyzed by enzymes to enable a potentially high chemo‐, regio‐ and/or stereoselectivity. Although many Knoevenagel condensation reactions are carried out in aqueous solutions, insoluble hydrophobic substrates often lead to poor catalytic efficiencies. The use of water‐miscible organic solvents improves the substrate solubilization, but usually induces activity suppression or inactivation of enzymes. There is a great need to develop alternative solvents for both substrate dissolution and enzyme compatibility in CC bond formation reactions.

   Our group previously developed dual‐functionalized water‐mimicking ionic liquids (ILs) for the activation and stabilization of hydrolases (e.g. lipase and protease). In the present study, we evaluated the Knoevenagel condensation of 4‐chlorobenzaldehyde with acetylacetone, and found that porcine pancreas lipase in water‐mimicking ILs carrying ammonium, imidazolium and benzimidazolium cations enabled higher reaction rates (up to 3.22 μmol min⁻¹ g⁻¹lipase) and better yields thantert‐butanol, glymes and [BMIM][Tf₂N]. Interestingly, tertiary amide solvents such asN‐methyl‐2‐pyrrolidone (NMP),N,N‐dimethylformamide (DMF) andN,N‐dimethylacetamide (DMAc) led to 8.2‐ to 11.1‐fold increases in the initial rate (up to 35.66 μmol min⁻¹ g⁻¹lipase) when compared with dual‐functionalized ILs, which is likely due to some synergistic effect of these tertiary amides with the lipase.

   Dual‐functionalized ILs based on ammonium, imidazolium and benzimidazolium cations improved Knoevenagel condensation reaction rates and yields when compared withtert‐butanol and glymes. Tertiary amides (NMP, DMF and DMAc) significantly increased the reaction rate. © 2024 The Authors.Journal of Chemical Technology and Biotechnologypublished by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

    

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2. Taming Nitrene Reactivity with Silver Catalysts

   https://doi.org/10.1055/s-0040-1707197  

   Vine, Logan E. ; Zerull, Emily E. ; Schomaker, Jennifer M. ( December 2020 , Synlett)

   null (Ed.)

   Nitrene transfer (NT) is a convenient strategy to directly transform C–H bonds into more valuable C–N bonds and exciting advances have been made to improve selectivity. Our work in silver-based NT has shown the unique ability of this metal to enable tunable chemo-, site-, and stereoselective reactions using simple N-dentate ligand scaffolds. Manipulation of the coordination environment and noncovalent interactions around the silver center furnish unprecedented catalyst control in selective NT and provide insights for further improvements in the field. 1 Introduction 1.1 Strategies for Nitrene Transfer 1.2 Brief Summary of Chemocatalyzed Nitrene Transfer 1.3 Focus of this Account 2 Challenges in Chemocatalyzed Nitrene Transfer 2.1 Reactivity Challenges 2.2 Selectivity Challenges 2.3 Chemoselective Nitrene Transfer 2.4 Site-Selective Nitrene Transfer 2.5 Enantioselective Nitrene Transfer 3 Summary and Perspective 3.1 Future Opportunities and Challenges 3.2 Conclusion 

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3. Protocol for Palladium/N-Heterocyclic Carbene-Catalyzed Suzuki–Miyaura Cross-Coupling of Amides by N–C(O) Activation

   https://doi.org/10.1055/s-0040-1705956  

   Lei, Peng ; Li, Guangchen ; Ling, Yun ; An, Jie ; Nolan, Steven P. ; Szostak, Michal ( January 2021 , Synthesis)

   null (Ed.)

   Abstract Amides are among the most important and ubiquitous functional groups in organic chemistry and process development. In this Practical Synthetic Procedure, a protocol for the Suzuki–Miyaura cross-coupling of amides by selective N–C(O) bond activation catalyzed by commercially available, air- and moisture-stable palladium/N-heterocyclic carbene (NHC) complexes is described. The procedure described involves [Pd(IPr)(cin)Cl] [IPr = 2,6-(diisopropylphenyl)imidazol-2-ylidene, cin = cinnamyl] at 0.10 mol% at room temperature and is performed on decagram scale. Furthermore, a procedure for the synthesis of amide starting materials is accomplished via selective N-tert-butoxycarbonylation, which is the preferred method over N-acylation. The present protocol carries advantages of operational simplicity, commercial availability of catalysts, and excellent conversions at low catalyst loadings. The method is generally useful for activation of N–C(O) amide bonds in a broad spectrum of amide precursors. The protocol should facilitate the implementation of amide cross-coupling reactions. 

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4. Generation and Stabilization of a Dinickel Catalyst in a Metal‐Organic Framework for Selective Hydrogenation Reactions

   https://doi.org/10.1002/ange.202306905  

   Guo, Qing‐Yun ; Wang, Zitong ; Feng, Xuanyu ; Fan, Yingjie ; Lin, Wenbin ( July 2023 , Angewandte Chemie)

   Although many monometallic active sites have been installed in metal–organic frameworks (MOFs) for catalytic reactions, there are no effective strategies to generate bimetallic catalysts in MOFs. Here we report the synthesis of a robust, efficient, and reusable MOF catalyst, MOF‐NiH, by adaptively generating and stabilizing dinickel active sites using the bipyridine groups in MOF‐253 with the formula of Al(OH)(2,2′‐bipyridine‐5,5′‐dicarboxylate) forZ‐selective semihydrogenation of alkynes and selective hydrogenation of C=C bonds in α,β‐unsaturated aldehydes and ketones. Spectroscopic studies established the dinickel complex (bpy⋅⁻)Ni^II(μ₂‐H)₂Ni^II(bpy⋅⁻) as the active catalyst. MOF‐NiH efficiently catalyzed selective hydrogenation reactions with turnover numbers of up to 192 and could be used in five cycles of hydrogenation reactions without catalyst leaching or significant decrease of catalytic activities. The present work uncovers a synthetic strategy toward solution‐inaccessible Earth‐abundant bimetallic MOF catalysts for sustainable catalysis.

    

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5. Generation and Stabilization of a Dinickel Catalyst in a Metal‐Organic Framework for Selective Hydrogenation Reactions

   https://doi.org/10.1002/anie.202306905  

   Guo, Qing‐Yun ; Wang, Zitong ; Feng, Xuanyu ; Fan, Yingjie ; Lin, Wenbin ( July 2023 , Angewandte Chemie International Edition)

   Although many monometallic active sites have been installed in metal–organic frameworks (MOFs) for catalytic reactions, there are no effective strategies to generate bimetallic catalysts in MOFs. Here we report the synthesis of a robust, efficient, and reusable MOF catalyst, MOF‐NiH, by adaptively generating and stabilizing dinickel active sites using the bipyridine groups in MOF‐253 with the formula of Al(OH)(2,2′‐bipyridine‐5,5′‐dicarboxylate) forZ‐selective semihydrogenation of alkynes and selective hydrogenation of C=C bonds in α,β‐unsaturated aldehydes and ketones. Spectroscopic studies established the dinickel complex (bpy⋅⁻)Ni^II(μ₂‐H)₂Ni^II(bpy⋅⁻) as the active catalyst. MOF‐NiH efficiently catalyzed selective hydrogenation reactions with turnover numbers of up to 192 and could be used in five cycles of hydrogenation reactions without catalyst leaching or significant decrease of catalytic activities. The present work uncovers a synthetic strategy toward solution‐inaccessible Earth‐abundant bimetallic MOF catalysts for sustainable catalysis.

    

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