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Renewable Vitrimer—A Novel Route Towards Reprocessable and Recyclable Thermosets from Biomass-Derived Building Block
Published in Anandhan Srinivasan, Selvakumar Murugesan, Arunjunai Raj Mahendran, Progress in Polymer Research for Biomedical, Energy and Specialty Applications, 2023
Arunjunai Raj Mahendran, Mohammed Khalifa, Günter Wuzella, Herfried Lammer
The chemistry behind associative CAN is recently reviewed by several authors (Jin 2019;Krishnakumar et al., 2020; Guerre, Taplan, Winne, & Du Prez, 2020; Zou, Dong, Luo, Zhao, & Xie, 2017). Vitrimers can be synthesized via many different chemistries and the major associative covalent adaptable networks are based on carboxylic acid chemistry (transesterification), imine amine exchange chemistry, olefin metathesis, disulfide exchange chemistry, transamination of vinylogous urethane, and boronic acid chemistry. As mentioned earlier, most of the vitrimer networks are from fossil fuel–derived chemicals and currently due to environmental concern, bio-based polymer networks are acquiring attention among industries and consumers. Renewable resources like vegetable oils, lignin, tannins, isosorbide, furan, etc., are the suitable raw material for replacing fossil fuel–derived chemicals either partially or fully in bio-based thermosets. Therefore, this review focuses on preparing various renewable vitrimers from biomass-derived building blocks and their properties. Initially, the chemistry behind the different exchangeable covalent networks is explained and then the research works done by several authors in the area of renewable vitrimers are summarized. Finally, the shortcoming and the future perspective of this vitrimer is discussed.
Structural Design for Molecular Catalysts
Published in Qingmin Ji, Harald Fuchs, Soft Matters for Catalysts, 2019
Qingmin Ji, Qin Tang, Jonathan P. Hill, Katsuhiko Ariga
Schneider et al. developed a second-generation 2,2′-dihydroxy-1,1′-binaphthyl (BINOL)-based phosphoric acid and further optimized as an enantioselective organocatalyst of vinylogous Mannich reaction of acyclic silyl dienolates [97]. They investigated BINOL-based phosphoric acids with varied the size of the ortho and para substituents within the 3,3′-aryl groups, as these positions were of prime importance for the enantioselectivity of the reaction. Placing a tBu group instead of a methyl group in the para position was shown to significantly increase the selectivity to 96% ee with a high yield production of the vinylogous Mannich reaction. Upon protonation of the imines, chiral contact ion pairs are generated in situ and attacked highly diastereoselectively by the nucleophile. One of the 3-aryl groups within the Brønsted acid catalyst shields the Re face of the imine, thereby directing the incoming nucleophile to the opposite side. They found that γ-substituted silyl dienolates are suitable substrates for this process, thus giving rise to products with two new chiral centers in good diastereo- and enantiocontrol.
Catalytic Asymmetric Synthesis of Cycloalkanes via Cascade Reactions of Nitroalkenes
Published in Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera, Catalytic Asymmetric Reactions of Conjugated Nitroalkenes, 2020
Irishi N. N. Namboothiri, Meeta Bhati, Madhu Ganesh, Basavaprabhu Hosamani, Thekke V. Baiju, Shimi Manchery, Kalisankar Bera
The Enders group reported a sequential 1,4-/1,6-/vinylogous 1,2-addition cascade reaction of β-dicarbonyl compounds 34, β-nitroalkenes 1 and 4-nitro-5-styrylisoxazoles 35 by employing cinchona-derived squaramide C6a in the presence of an achiral base, resulting in the formation of cyclohexane derivatives 36 with good yields and high enantiomeric excess (Scheme 10.12).46
A review on DBU-mediated organic transformations
Published in Green Chemistry Letters and Reviews, 2022
Shashi Kanth Boddu, Najeeb Ur Rehman, Tapan Kumar Mohanta, Anjoy Majhi, Satya Kumar Avula, Ahmed Al-Harrasi
An efficient and atom-economic transformation of enones with electron-deficient alkenes in the presence of DBU under mild conditions has been developed by Tian et al. This protocol offers a direct access to 1,5-dicarbonyl compounds in synthetically useful yields using vinylogous strategy via dienolate intermediates (Scheme 54) (71).