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Search Results (3)

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Keywords = chlorine as electrophilic center

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20 pages, 6566 KiB  
Review
Chlorine in an Organic Molecule, a Universal Promoter—Workhorse—Of Reactions
by Mieczysław Mąkosza and Michał Fedoryński
Molecules 2023, 28(24), 7957; https://doi.org/10.3390/molecules28247957 - 5 Dec 2023
Cited by 2 | Viewed by 2979
Abstract
Due to the electronic configuration of the atom and charge of the nucleus, the chlorine in organic molecules can exert a variety of effects. It can depart as a chloride anion in the process of substitution and elimination, facilitates the abstraction of protons [...] Read more.
Due to the electronic configuration of the atom and charge of the nucleus, the chlorine in organic molecules can exert a variety of effects. It can depart as a chloride anion in the process of substitution and elimination, facilitates the abstraction of protons and stabilizes generated carbanions, exerts moderate stabilizing effect of carbenes, carbocations and radicals. There are frequent cases where chlorine substituent promotes more than one transformation. These rich effects of chlorine substituent will be illustrated by examples of our work. Full article
(This article belongs to the Special Issue Featured Reviews in Organic Chemistry 2024)
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17 pages, 3010 KiB  
Article
Synthesis and Catalytic Activity of Bifunctional Phase-Transfer Organocatalysts Based on Camphor
by Luka Ciber, Franc Požgan, Helena Brodnik, Bogdan Štefane, Jurij Svete, Mario Waser and Uroš Grošelj
Molecules 2023, 28(3), 1515; https://doi.org/10.3390/molecules28031515 - 3 Feb 2023
Cited by 4 | Viewed by 3098
Abstract
Ten novel bifunctional quaternary ammonium salt phase-transfer organocatalysts were synthesized in four steps from (+)-camphor-derived 1,3-diamines. These quaternary ammonium salts contained either (thio)urea or squaramide hydrogen bond donor groups in combination with either trifluoroacetate or iodide as the counteranion. Their organocatalytic activity was [...] Read more.
Ten novel bifunctional quaternary ammonium salt phase-transfer organocatalysts were synthesized in four steps from (+)-camphor-derived 1,3-diamines. These quaternary ammonium salts contained either (thio)urea or squaramide hydrogen bond donor groups in combination with either trifluoroacetate or iodide as the counteranion. Their organocatalytic activity was evaluated in electrophilic heterofunctionalizations of β-keto esters and in the Michael addition of a glycine Schiff base with methyl acrylate. α-Fluorination and chlorination of β-keto esters proceeded with full conversion and low enantioselectivities (up to 29% ee). Similarly, the Michael addition of a glycine Schiff base with methyl acrylate proceeded with full conversion and up to 11% ee. The new catalysts have been fully characterized; the stereochemistry at the C-2 chiral center was unambiguously determined. Full article
(This article belongs to the Special Issue New Approaches to Synthetic Organic Chemistry)
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14 pages, 1539 KiB  
Article
Separating Electronic from Steric Effects in Ethene/α-Olefin Copolymerization: A Case Study on Octahedral [ONNO] Zr-Catalysts
by Francesco Zaccaria, Roberta Cipullo, Andrea Correa, Peter H. M. Budzelaar, Vincenzo Busico and Christian Ehm
Processes 2019, 7(6), 384; https://doi.org/10.3390/pr7060384 - 20 Jun 2019
Cited by 10 | Viewed by 4464
Abstract
Four Cl/Me substituted [ONNO] Zr-catalysts have been tested in ethene/α-olefin polymerization. Replacing electron-donating methyl with isosteric but electron-withdrawing chlorine substituents results in a significant increase of comonomer incorporation. Exploration of steric and electronic properties of the ancillary ligand by DFT confirm that relative [...] Read more.
Four Cl/Me substituted [ONNO] Zr-catalysts have been tested in ethene/α-olefin polymerization. Replacing electron-donating methyl with isosteric but electron-withdrawing chlorine substituents results in a significant increase of comonomer incorporation. Exploration of steric and electronic properties of the ancillary ligand by DFT confirm that relative reactivity ratios are mainly determined by the electrophilicity of the metal center. Furthermore, quantitative DFT modeling of propagation barriers that determine polymerization kinetics reveals that electronic effects observed in these catalysts affect relative barriers for insertion and a capture-like transition state (TS). Full article
(This article belongs to the Special Issue Computational Methods for Polymers)
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