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- Afewerki, Samson, et al.
(author)
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Off-Cycle Catalyst Cooperativity in Amine/Transition Metal Combined Catalysis : Bicyclo[3.2.0]heptanes as Key Species in Co-Catalytic Enantioselective Carbocyclizations
- 2022
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 364:8, s. 1394-1401
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Journal article (peer-reviewed)abstract
- The existence of off-cycle catalyst cooperativity in amine/metal combined catalysis is disclosed. The experimental and density functional theory study of the amine/metal co-catalyzed enantioselective Michael/carbocyclization cascade reaction between allenes and α,β-unsaturated aldehydes reveals that the dual catalysts can perform off-cycle cooperativity that gives access to stable bicyclo[3.2.0]heptane species that limits the carbocycle product formation. Insight into this mode of co-catalyst cooperativity sheds new light on the chiral amine/metal co-catalyzed reactions of to date and gives deeper understanding for improved future design of this type of enantioselective reactions.
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- Alimohammadzadeh, Rana, et al.
(author)
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Mild and Versatile Functionalization of Nacre-Mimetic Cellulose Nanofibrils/Clay Nanocomposites by Organocatalytic Surface Engineering
- 2020
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In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 5:31, s. 19363-19370
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Journal article (peer-reviewed)abstract
- Development of surface-engineering strategies, which are facile, versatile, and mild, are highly desirable in tailor-made functionalization of high-performance bioinspired nanocomposites. We herein disclose for the first time a general organocatalytic strategy for the functionalization and hydrophobization of nacre-mimetic nanocomposites, which includes vide supra key aspects of surface engineering. The merging of metal-free catalysis and the design of nacre-mimetic nanocomposite materials were demonstrated by the organocatalytic surface engineering of cellulose nanofibrils/clay nanocomposites providing the corresponding bioinspired nanocomposites with good mechanical properties, hydrophobicity, and useful thia-, amino, and olefinic functionalities.
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- Avella, Angelica, 1995, et al.
(author)
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Organo-Mediated Ring-Opening Polymerization of Ethylene Brassylate from Cellulose Nanofibrils in Reactive Extrusion
- 2024
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In: ACS Sustainable Chemistry & Engineering. - 2168-0485. ; 12:29, s. 10727-10738
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Journal article (peer-reviewed)abstract
- Ethylene brassylate is a renewable macrolactone from castor oil that can be polymerized via ring-opening polymerization (ROP) to obtain a fully biosourced biodegradable polyester. ROP mediated by organometallic catalysts leads to high molar mass poly(ethylene brassylate) (PEB). However, the use of metal-free organocatalysis has several advantages, such as the reduction of toxic and expensive metals. In this work, a novel cellulose nanofibril (CNF)/PEB nanocomposite fabrication process by organocatalysis and reactive extrusion (REx) is disclosed. Here, ROP was carried out via solvent-free REx in the presence of CNFs using organic 1,5,7-triazabicyclo[4.4.0]dec-5-ene as a catalyst. Neat or lactate-esterified CNFs (LACNF) were used as initiators to investigate the effect of surface topochemistry on the in situ polymerization and the properties of the nanocomposites. A molar mass of 9 kDa was achieved in the presence of both unmodified and LACNFs with high monomer conversion (>98%) after 30 min reaction in a microcompounder at 130 °C. Tensile analysis showed that both nanofibril types reinforce the matrix and increase its elasticity due to the efficient dispersion obtained through the grafting from polymerization achieved during the REx. Mechanical recycling of the neat polymer and the nanocomposites was proven as a circular solution for the materials’ end-of-life and showed that lactate moieties induced some degradation.
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- Cordova, Armando, 1970-, et al.
(author)
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Organocatalytic Dynamic Kinetic Asymmetric Transformations
- 2023
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In: Dynamic Kinetic Resolution (DKR) and Dynamic Kinetic Asymmetric Transformations (DYKAT). - : Georg Thieme Verlag KG. - 9783132453777 - 9783132453791
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Book chapter (peer-reviewed)abstract
- Dynamic kinetic asymmetric transformations (DYKAT) are an important way of converting simple organic molecules into complex small molecules as single diastereo- and enantiomers. Herein we describe selected examples that are catalyzed by small organic molecules, which utilize activation mechanisms similar to enzymes for accomplishing the high stereoselectivity. The research area of DYKAT is growing and remarkable examples for producing important organic molecules and pharmaceuticals are demonstrated. In this context, organocatalysis will play an important role.
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