Vibrational CD study on the solution phase structures of the MacMillan catalyst and its corresponding iminium ion

Golub, Tino P.; Merten, Christian

doi:10.1039/d1cp04497d

Cited by 11 publications

(13 citation statements)

References 53 publications

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“…For chiral thiourea catalysts, we utilized VCD spectroscopy to reveal their binding mode and the relative orientation of catalyst and substrate in hydrogen‐bonded complexes [15] . Jørgensen–Hayashi‐type prolinol ethers [16] and MacMillian's imidazolidone catalysts were investigated as examples for covalent organocatalysts [17] …”

Section: Methodsmentioning

confidence: 99%

Structure Elucidation of In Situ Generated Chiral Hypervalent Iodine Complexes via Vibrational Circular Dichroism (VCD)

et al. 2022

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The structure of in situ generated chiral arylλ 3 -iodanes obtained under oxidative reaction conditions was not yet observable with experimental techniques and their proposed structures are purely based on DFT calculations. Herein, we establish vibrational circular dichroism (VCD) spectroscopy as an experimental technique to verify DFT-calculated chiral iodane structures. Based on a chiral triazole-substituted iodoarene catalyst, we were able to elucidate a yet undescribed cationic chiral iodane as the most populated intermediate under oxidative conditions with a significant intramolecular NÀ I-interaction and no significant interactions with tosylate or m-chlorobenzoic acid as potential anionic ligands. Instead, aggregation of these substrates was found, which resulted in the formation of a noncoordinating anionic hydrogen bonded complex. The importance of VCD as a crucial experimental observable is further highlighted by the fact that our initial structural proposal, that was purely based on DFT calculations, could be falsified.

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Section: Methodsmentioning

confidence: 99%

Structure Elucidation of In Situ Generated Chiral Hypervalent Iodine Complexes via Vibrational Circular Dichroism (VCD)

et al. 2022

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“…Für chirale Thioharnstoff‐Katalysatoren nutzten wir die VCD‐Spektroskopie, um deren Bindungsmodus und die relative Ausrichtung von Katalysator und Substrat in wasserstoffgebundenen Komplexen aufzudecken [15] . Prolinolether vom Jørgensen‐Hayashi‐Typ [16] und der Imidazolidon‐Katalysator von MacMillian wurden als Beispiele für kovalente Organokatalysatoren untersucht [17] …”

Section: Methodsunclassified

Strukturaufklärung eines chiralen in situ erzeugten hypervalenten Iod‐Komplexes mittels VCD‐Spektroskopie

et al. 2022

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Die Struktur von in situ erzeugten chiralen Aryl-λ 3 -iodanen, die unter oxidativen Reaktionsbedingungen erhalten wurden, konnte bisher nicht mit experimentellen Techniken beobachtet werden. Deren vorgeschlagene Strukturen beruhen nahezu ausschließlich auf DFT-Berechnungen. In diesem Beitrag etablieren wir die Schwingungszirkulardichroismus-Spektroskopie (VCD) als eine experimentelle Technik zur Verifizierung von DFT-berechneten chiralen Iodanstrukturen. Für einen chiralen Triazol-substituierten Iodoaren-Katalysator wird ein bisher unbeschriebenes kationisches chirales Iodan identifiziert, dass eine intramolekulare N-I-Wechselwirkung aber keine signifikanten Wechselwirkungen mit Tosylat oder m-Chlorbenzoesäure als potenzielle anionische Liganden aufweist. Stattdessen wurde eine Aggregation dieser Substrate festgestellt, die zur Bildung eines nicht-koordinierenden anionischen wasserstoffgebundenen Komplexes führte. Die Bedeutung der VCD-Spektroskopie als entscheidende experimentelle Methode zum Nachweis der kationischen Spezies wird auch durch die Tatsache unterstrichen, dass unser ursprünglicher Strukturvorschlag, der rein auf DFT-Berechnungen basierte, widerlegt werden konnte.

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“…This sensitivity has been utilized to characterize solute-solvent interactions, biomolecular interactions [28][29][30][31] or asymmetric catalysts. [32][33][34][35][36][37][38] The key to the analysis of a VCD spectrum and the only route to derive detailed information on the level of conformational preferences from it is the comparison with computed spectra obtained at density functional theory (DFT) level. 1,4 This may also be the main reason why one of the main fields of application for ECD spectroscopy, the characterization of supramolecular structures, has not yet been widely explored using VCD spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

“…This sensitivity has been utilized to characterize solute–solvent interactions, 6–27 biomolecular interactions 28–31 or asymmetric catalysts. 32–38…”

Section: Introductionmentioning

confidence: 99%

VCD spectroscopy reveals conformational changes of chiral crown ethers upon complexation of potassium and ammonium cations

Weirich

Tusha

Engelage

et al. 2022

Phys. Chem. Chem. Phys.

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Vibrational CD study on the solution phase structures of the MacMillan catalyst and its corresponding iminium ion

Abstract: We demonstrate that VCD spectroscopy can reveal insights into the conformational preferences of iminium ion obtained from MacMillan’s imidazolidinone catalyst. For both, the isolated and in-situ generated iminium ion, the...

Cited by 11 publications

References 53 publications

Structure Elucidation of In Situ Generated Chiral Hypervalent Iodine Complexes via Vibrational Circular Dichroism (VCD)

Structure Elucidation of In Situ Generated Chiral Hypervalent Iodine Complexes via Vibrational Circular Dichroism (VCD)

Strukturaufklärung eines chiralen in situ erzeugten hypervalenten Iod‐Komplexes mittels VCD‐Spektroskopie

VCD spectroscopy reveals conformational changes of chiral crown ethers upon complexation of potassium and ammonium cations

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