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Journal ArticleDOI

An Alternative Synthesis of Cycloalkyl-Substituted CPA Catalysts and Application in Asymmetric Protonation Reactions**

21 Sep 2021-European Journal of Organic Chemistry (John Wiley & Sons, Ltd)-Vol. 2021, Iss: 35, pp 4943-4945
About: This article is published in European Journal of Organic Chemistry.The article was published on 2021-09-21 and is currently open access. It has received 2 citations till now. The article focuses on the topics: Protonation & Catalysis.
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TL;DR: This article showed that dispersion interactions are the main arbiter of the 3 to 2 equilibrium and showed that 2 is favored in solution at higher temperature (345 K or above) whereas 3 is preferred near 298 K. Van't Hoff analysis revealed the 3-to-2 conversion has a ΔH = 33.36 kcal and ΔS = 0.102 kcal mol-1 K-1.
Abstract: Reaction of {LiC6H2-2,4,6-Cyp3·Et2O}2 (Cyp = cyclopentyl) (1) of the new dispersion energy donor (DED) ligand, 2,4,6-triscyclopentylphenyl with SnCl2 afforded a mixture of the distannene {Sn(C6H2-2,4,6-Cyp3)2}2 (2), and the cyclotristannane {Sn(C6H2-2,4,6-Cyp3)2}3 (3). 2 is favored in solution at higher temperature (345 K or above) whereas 3 is preferred near 298 K. Van't Hoff analysis revealed the 3 to 2 conversion has a ΔH = 33.36 kcal mol-1 and ΔS = 0.102 kcal mol-1 K-1, which gives a ΔG300 K = +2.86 kcal mol-1, showing that the conversion of 3 to 2 is an endergonic process. Computational studies show that DED stabilization in 3 is -28.5 kcal mol-1 per {Sn(C6H2-2,4,6-Cyp3)2 unit, which exceeds the DED energy in 2 of -16.3 kcal mol-1 per unit. The data clearly show that dispersion interactions are the main arbiter of the 3 to 2 equilibrium. Both 2 and 3 possess large dispersion stabilization energies which suppress monomer dissociation (supported by EDA results).
Journal ArticleDOI
TL;DR: In this paper , the dispersion energy donor (DED) donor for 2,4,6-triscyclopentylphenyl with SnCl2 ligand was analyzed and shown to be the main arbiter of the 3 to 2 equilibrium.
Abstract: Reaction of {LiC6H2−2,4,6-Cyp3⋅Et2O}2 (Cyp=cyclopentyl) (1) of the new dispersion energy donor (DED) ligand, 2,4,6-triscyclopentylphenyl with SnCl2 afforded a mixture of the distannene {Sn(C6H2−2,4,6-Cyp3)2}2 (2), and the cyclotristannane {Sn(C6H2−2,4,6-Cyp3)2}3 (3). 2 is favored in solution at higher temperature (345 K or above) whereas 3 is preferred near 298 K. Van't Hoff analysis revealed the 3 to 2 conversion has a ΔH=33.36 kcal mol−1 and ΔS=0.102 kcal mol−1 K−1, which gives a ΔG300 K=+2.86 kcal mol−1, showing that the conversion of 3 to 2 is an endergonic process. Computational studies show that DED stabilization in 3 is −28.5 kcal mol−1 per {Sn(C6H2−2,4,6-Cyp3)2 unit, which exceeds the DED energy in 2 of −16.3 kcal mol−1 per unit. The data clearly show that dispersion interactions are the main arbiter of the 3 to 2 equilibrium. Both 2 and 3 possess large dispersion stabilization energies which suppress monomer dissociation (supported by EDA results).
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1,801 citations

Journal ArticleDOI
TL;DR: A number of chiral acid catalysts have been developed recently as discussed by the authors, with a focus being placed on thiourea, TADDOL, and phosphoric acids, which are rapidly growing areas in organocatalysis.
Abstract: Hydrogen bond catalysis and Bronsted acid catalysis are rapidly growing areas in organocatalysis. A number of chiral acid catalysts has been developed recently. Recent progress in the chiral Bronsted acid catalysis has been reviewed with a focus being placed on thiourea, TADDOL, and phosphoric acids. 1 Introduction 2 Hydrogen Bond Catalysis 2.1 Monofunctional Thiourea Catalysts 2.2 Bifunctional Thiourea Catalysts 2.3 TADDOL Derivatives 2.4 BINOL Derivatives 3 Bronsted Acid Catalysis 3.1 Ammonium Salts 3.2 Phosphoric Acids 4 Conclusion

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TL;DR: This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction.
Abstract: Charged intermediates and reagents are ubiquitous in organic transformations. The interaction of these ionic species with chiral neutral, anionic, or cationic small molecules has emerged as a powerful strategy for catalytic, enantioselective synthesis. This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction.

751 citations

Journal ArticleDOI
TL;DR: This Review closes this gap by providing a clear definition of ACDC and by examining both clear cases as well as more ambiguous examples to illustrate the differences and overlaps with other catalysis concepts.
Abstract: Recently, the use of enantiomerically pure counteranions for the induction of asymmetry in reactions proceeding through cationic intermediates has emerged as an exciting new concept, which has been termed asymmetric counteranion-directed catalysis (ACDC). Despite its success, the concept has not been fully defined and systematically discussed to date. This Review closes this gap by providing a clear definition of ACDC and by examining both clear cases as well as more ambiguous examples to illustrate the differences and overlaps with other catalysis concepts.

651 citations