Conformational and Stereodynamic Behavior of Five- to Seven-Membered 1-Aryl-2-iminoazacycloalkanes

Díaz, Jimena Estela; Mazzanti, Andrea; Orelli, Liliana R.; Mancinelli, Michele

doi:10.1021/acsomega.9b00192

Cited by 9 publications

(7 citation statements)

References 37 publications

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“…Since then, steric congestion along with strain effects have been claimed to be the driving force of a wide variety of phenomena ranging from classic textbook examples of reactivity [8][9][10] to state-of-the-art developments in supra-molecular chemistry. [11][12][13] Some phenomena where SH has been invoked to play a major role include: the origin of the rotational barriers of alkanes and other derivatives, [14][15][16][17] the stability of conformers of cycloalkanes and macrocycles, [18,19] the ligand ability towards metal centers, [20,21] the trends in the reactivity of nucleophilic substitution and elimination reactions, [22,23] the torsional barriers of biphenyls and their optically active derivatives, [24] the reactions between tertiary amines and boron derivatives, [25] the geometrical features of methyl like radicals, [26] the stability of cis-trans isomers, [27] the competition between the basicity and nucleophilicity of nucleophiles and the stereopreference and the selectivity of the active site of enzymes or organic catalysts, [28] among others.…”

Section: Introduction Chemical Intuition and Steric Hindrancementioning

confidence: 99%

Energetic Descriptors of Steric Hindrance in Real Space: An Improved IQA Picture**

2021

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Steric hindrance (SH) plays a central role in the modern chemical narrative, lying at the core of chemical intuition. As it however happens with many successful chemical concepts, SH lacks an underlying physically sound root, and multiple mutually inconsistent approximations have been devised to relate this fuzzy concept to computationally derivable descriptors. We here argue that being SH related to spatial as well as energetic features of interacting systems, SH can be properly handled if we chose a real space energetic stance like the Interacting Quantum Atoms (IQA) approach. Drawing on previous work by Popelier and coworkers (ChemistryOpen 8, 560, 2019) we build an energetic estimator of SH, referred to as E ST . We show that the rise in the self-energy of a fragment that accompanies steric congestion is a faithful proxy for the chemist's SH concept if we remove the effect of charge transfer. This can be done rigorously, and the E ST here defined provides correct sterics even for hydrogen atoms, where the plain use of deformation energies leads to non-chemical results. The applicability of E ST is validated in several chemical scenarios, going from atomic compressions to archetypal S N2 reactions. E ST is shown to be a robust steric hindrance descriptor.

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Section: Introduction Chemical Intuition and Steric Hindrancementioning

confidence: 99%

Energetic Descriptors of Steric Hindrance in Real Space: An Improved IQA Picture**

2021

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“…A subsequent study where 1‐aryl‐2‐iminoazacycloalkanes were used as the chemical scaffold confirmed this trend …”

Section: Steric Factorsmentioning

confidence: 71%

Stereochemistry and Recent Applications of Axially Chiral Organic Molecules

et al. 2020

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This minireview covers the literature of the last decade related to the stereochemistry of axially chiral molecules. The first section reviews the use of dynamic NMR and dynamic HPLC for the ranking of the steric size of common organic moieties. The second and third sections describe the recent advances in the preparation of new atropisomeric scaffolds, and in the asymmetric synthesis of stereogenic axes by means of atroposelective organocatalysis.

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“…Interestingly, NMR‐spectroscopic observations provided evidence that the novel BODIPY Ugi adducts participate in dynamic conformational processes that were deemed to deserve further attention, especially in view of several recent conformational studies with related aniline‐derived compounds [23–25] . Interestingly, a series of Ugi adducts reported previously by our research group did not show this dynamic effect [21] .…”

Section: Introductionmentioning

confidence: 80%

Structure and Conformation of Novel BODIPY Ugi Adducts

et al. 2022

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Two novel BODIPY‐Ugi (boron dipyrromethene) adducts exhibit peculiar room temperature (T=20 °C) H‐1 NMR spectra in that several protons located at the aromatic aniline‐type ring are lost in the baseline. This observation revealed the existence of a dynamic conformational process where rotation around the C−N bond is hindered. Variable‐temperature H‐1 and C‐13 NMR spectroscopic analysis confirmed this conclusion; that is, low‐temperature spectra show distinct signals for all four aromatic protons below coalescence, whereas average signals are recorded above coalescence (T=+120 °C). Particularly interesting was the rather large difference in chemical shifts for the ortho protons below coalescence, Δδ=1.45 ppm, which was explained based on DFT computational analysis. Indeed, the calculated lowest‐energy gas‐phase conformation of the BODIPY Ugi adducts locates one half of the aniline‐type ring in the shielding anisotropic cone of the bridge phenyl ring in the BODIPY segment. This is in contrast to the solid‐state conformation established by X‐ray diffraction analysis that shows a nearly parallel arrangement of the aromatic rings, probably induced by crystal packing forces.

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Conformational and Stereodynamic Behavior of Five- to Seven-Membered 1-Aryl-2-iminoazacycloalkanes

Cited by 9 publications

References 37 publications

Energetic Descriptors of Steric Hindrance in Real Space: An Improved IQA Picture**

Energetic Descriptors of Steric Hindrance in Real Space: An Improved IQA Picture**

Stereochemistry and Recent Applications of Axially Chiral Organic Molecules

Structure and Conformation of Novel BODIPY Ugi Adducts

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