| 1. |
- Artacho Ruiz, Josep, et al.
(författare)
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Tröger's Base Twisted Amides: Endo Functionalization and Synthesis of an Inverted Crown Ether
- 2012
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7052 .- 1523-7060. ; 14:18, s. 4706-4709
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Tidskriftsartikel (refereegranskat)abstract
- Taking advantage of the unconventional reactivity of twisted mono- and bis-amides of Tröger's base (TB), rac-6 and rac-7, respectively, the first synthesis of a 6-endo-monosubstituted TB analogue, rac-9, and the first rational synthesis of a 6,12-endo,endo-disubstituted TB analogue, rac-11, have been achieved. The bis-TB crown ether, meso-13, was prepared starting from rac-7. Meso-13 constitutes a rare example of a crown ether with an inverted methylene bridge-to-bridge bis-TB conformation both in solution and in the solid state, resulting in a reluctance to act as a receptor for cations.
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| 2. |
- Dawaigher, Sami, et al.
(författare)
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A Protocol for the exo-Mono and exo,exo-Bis Functionalization of the Diazocine Ring of Tröger's Base.
- 2015
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 1520-6904 .- 0022-3263. ; 80:24, s. 12006-12014
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Tidskriftsartikel (refereegranskat)abstract
- An efficient protocol has been developed for the exo-mono and exo,exo-bis functionalization of Tröger's base in the benzylic 6 and 12 positions of the diazocine ring. The lithiation of Tröger's base using s-BuLi/TMEDA followed by electrophilic quench affords exo-mono- and exo,exo-bis-substituted derivatives of Tröger's base in good to excellent yields. The variation of the number of equivalents of s-BuLi/TMEDA and the order of addition of the electrophile strongly govern the outcome of the reaction for each electrophile.
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| 3. |
- Dawaigher, Sami
(författare)
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Improving Tröger's Base Chemistry : Developing the Chemistry of Tröger's base
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Tröger’s base framework has been implemented in two different receptors. The first of these receptors, incorporating two 18-crown-6 moities, was used as a host in a binding study together with a sieries of bisammonium salts that yielded different binding constants that were then used as a benchmark to compare different computational methods (Molecular Mechanics (MM) and Density Functional Theory (DFT)) in predicting the correct results where the MM methods proved more effective. The second of the receptors incorporated two Tröger’s base moieties linked together with two crown ether straps. This receptor was tested for it’s affinity towards different metal cations, the receptor proved too hindered to accomodate any cations except Fe3+. Furthermore, the reactivity of Tröger’s base with lithium amide bases has been investigated extensively. A new protocol for preparing mono- and bissubstistuted Tröger’s base derivatives has been developed where Tröger’s base is treated with sBuLi/TMEDA followed by an electrophilic quench resulting in a Tröger’s base derivative substituted in the exo-6 and exo-12 positions. In addition to this method, a method for converting exo-6- and exo-12 substituted Tröger’s base amides into endo-6 and endo-12 substituted Tröger’s base amide has been developed. A study of the reduction of Tröger’s base amides is described herein.
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| 4. |
- Dawaigher, Sami, et al.
(författare)
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Mono endo-6- And bis endo,endo-12-N,N-diethylcarbamoyl derivatives of Tröger’s Base. Synthesis and exo-endo isomerization study
- 2020
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Ingår i: Arkivoc. - 1551-7004. ; 2020:7
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Tidskriftsartikel (refereegranskat)abstract
- An efficient synthetic route to the mono-endo-6- and bis-endo,endo-6,12-N,N-diethylcarbamoyl derivatives of Tröger’s base (TB), endo-7 and endo-8, is reported. Studies of reaction time, proton source, and additive allowed establishment of optimized conditions for the conversion of exo-7 into the corresponding isomer endo-7. With a longer reaction time, the exo,exo-6,12 bis-carbamoyl derivative exo-8 was converted into the corresponding endo,endo-bis-carbamoyl product endo-8. Single crystal X-ray crystallographic analysis confirmed the structural and stereochemical assignments made on the basis of 1H NMR, mechanistic, and calculational studies. Deuterium quench experiments using LDA, CD3ONa/CD3OD and DCl/CD3OD conditions of both exo-7 and exo-8 afforded exo-7d1 and exo-8d2, respectively (> 95% deuterium incorporation), supporting an enolate mechanism for the isomerization. In contrast, when repeating the experiment with DCl/CD3OD, no deuterium was incorporated, suggesting the traditional ring-opening mechanism involving an iminium ion.
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| 5. |
- Li, Yutang, et al.
(författare)
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Enantiotopic Discrimination by Coordination-Desymmetrized meso-Ligands
- 2020
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Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 12:6, s. 1575-1579
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Tidskriftsartikel (refereegranskat)abstract
- The first examples of enantiopure catalysts that are chiral merely due to coordination of different metal ions at enantiotopic positions of an achiral meso-ligand are reported. These catalysts exhibit a pseudo-Cs symmetry and are able to catalyze reactions demanding simultaneous involvement of two catalytic sites. The latter was demonstrated by application in the asymmetric ring-opening of meso-epoxides.
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| 6. |
- Lidskog, Anna, et al.
(författare)
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Experimental and Computational Models for Side Chain Discrimination in Peptide–Protein Interactions
- 2021
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 27:42, s. 10883-10897
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Tidskriftsartikel (refereegranskat)abstract
- A bis(18-crown-6) Tröger's base receptor and 4-substituted hepta-1,7-diyl bisammonium salt ligands have been used as a model system to study the interactions between non-polar side chains of peptides and an aromatic cavity of a protein. NMR titrations and NOESY/ROESY NMR spectroscopy were used to analyze the discrimination of the ligands by the receptor based on the substituent of the ligand, both quantitatively (free binding energies) and qualitatively (conformations). The analysis showed that an all-anti conformation of the heptane chain was preferred for most of the ligands, both free and when bound to the receptor, and that for all of the receptor-ligand complexes, the substituent was located inside or partly inside of the aromatic cavity of the receptor. We estimated the free binding energy of a methyl- and a phenyl group to an aromatic cavity, via CH-π, and combined aromatic CH-π and π-π interactions to be −1.7 and −3.3 kJ mol−1, respectively. The experimental results were used to assess the accuracy of different computational methods, including molecular mechanics (MM) and density functional theory (DFT) methods, showing that MM was superior.
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| 7. |
- Lindbäck, Emil, et al.
(författare)
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A Double Conformationally Restricted Dynamic Supramolecular System for the Substrate-Selective Epoxidation of Olefins-A Comparative Study on the Influence of Preorganization
- 2015
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Ingår i: ChemCatChem. - : Wiley. - 1867-3880. ; 7:2, s. 333-348
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Tidskriftsartikel (refereegranskat)abstract
- A double conformationally restricted kinetically labile supramolecular catalytic system, the third generation, was designed and synthesized. We investigated the substrate selectivity of this system by performing competitive pairwise epoxidations of pyridyl-and phenyl-appended olefins. We compared the obtained substrate selectivities to previous less preorganized generations of this system. Five different substrate pairs were investigated, and the present double conformationally restricted system showed higher normalized substrate selectivities ( pyridyl versus phenyl) for two of the substrate pairs than the previous less conformationally restricted generations. As for the preorganization of the components of the system, the catalyst, and the receptor part, it was shown that for each substrate pair there was one generation that was better than the other to generate substrate-selective catalysis.
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| 8. |
- Lindbäck, Emil, et al.
(författare)
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Substrate-selective catalysis.
- 2014
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Ingår i: Chemistry: A European Journal. - : Wiley. - 1521-3765 .- 0947-6539. ; 20:42, s. 13432-13481
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Forskningsöversikt (refereegranskat)abstract
- Substrate selectivity is an important output function for the validation of different enzyme models, catalytic cavity compounds, and reaction mechanisms as demonstrated in this review. In contrast to stereo-, regio-, and chemoselective catalysis, the field of substrate-selective catalysis is under-researched and has to date generated only a few, but important, industrial applications. This review points out the broad spectrum of different reaction types that have been investigated in substrate-selective catalysis. The present review is the first one covering substrate-selective catalysis and deals with reactions in which the substrates involved have the same reacting functionality and the catalysts is used in catalytic or in stoichiometric amounts. The review covers real substrate-selective catalysis, thus only including cases in which substrate-selective catalysis has been observed in competition between substrates.
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| 9. |
- Lindbäck, Emil, et al.
(författare)
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Synthesis of Cr(III) Salen Complexes as Supramolecular Catalytic Systems for Ring-Opening Reactions of Epoxides
- 2016
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Ingår i: ChemistrySelect. - : Wiley. - 2365-6549. ; 1:8, s. 1789-1794
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of two conformationally restricted Cr(III) salen complexes, 2 and 3, is described. Together, they constitute a supramolecular hydrogen-bonding catalytic system for the recently reported asymmetric ring-opening reactions of epoxides by a dynamic supramolecular catalyst. The synthesis involves state-of-the art transformations in frontline synthetic chemistry applied to heterocyclic chemistry. Hence, palladium-catalyzed reactions were employed, including carbonylative annelation and Suzuki cross-coupling reactions, for the formation of one of the heterocyclic rings (quinolone) and the functionalization of the formed rings. For the construction of the second heterocyclic ring (isoquinolone), a Curtius rearrangement was employed. The corresponding salen ligands were then prepared by Schiff-base reactions, yielding the final complexes after metal insertion. For reference purposes the less conformationally restricted Cr(III) complexes 4 and 5 were also synthesized.
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