Rotational Behavior of <i>N</i>-(5-Substituted-pyrimidin-2-yl)anilines: Relayed Electronic Effect in Two N–Ar Bond Rotations

Homma, Daiki; Taketani, Shuhei; Shirai, Takeshi; Caytan, Elsa; Roussel, Christian; Elguero, José; Alkorta, Ibón; Kitagawa, Osamu

doi:10.1021/acs.joc.2c00845

Cited by 6 publications

(5 citation statements)

References 32 publications

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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 , 24 , 25 ] Interestingly, a series of Ugi adducts reported previously by our research group did not show this dynamic effect. [21] By the same token, the work reported by Ogawa and coworkers, which describes structurally related derivatives not containing the BODIPY core (Figure 1 ), did not exhibit such dynamic behavior.…”

Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 80%

“…The dynamic behavior described above for the H‐1 and C‐13 NMR signals corresponding to the nuclei in the aniline‐type aromatic ring can be easily explained in terms of hindered rotation around the C−N bond leading to atropisomerism[ 23 , 24 , 25 ] (Scheme 4 ).…”

Section: Resultsmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 80%

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Structure and Conformation of Novel BODIPY Ugi Adducts

et al. 2022

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“…Unfortunately, the rotational barriers about the N–C 1′ bond in anilines 9 were difficult to evaluate because the barrier values were too low. To elucidate the correlation between two N–Ar bond rotations and the electronic effect, we designed N -methyl-2-methoxymethylanilines 10a – g bearing various 5-substituted-pyrimidyl groups, while anilines 10a – g do not possess a stable atropisomeric structure . The rotational barriers about the two N–Ar bonds in 10a – g were evaluated through a VT-NMR experiment of pyrimidine hydrogens Ha and ortho -methylene hydrogens Hb followed by a line-shape simulation (Ha and Hb showed a nonequivalency by rotational restriction around N–Ar bonds at the NMR time scale).…”

Section: Electronic Effect and Rotational Barriers: Application To Pr...mentioning

confidence: 99%

Structural Chemistry of C–N Axially Chiral Compounds

Kitagawa

2024

J. Org. Chem.

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In the last several years, atropisomers owing to the rotational restriction around a C−N single bond (C−N axially chiral compounds) have attracted significant attention in the field of synthetic organic chemistry. In particular, the highly enantioselective synthesis of various C− N axially chiral compounds and their application to asymmetric reactions have been reported by many groups. On the other hand, studies on the structural chemistry of C−N axially chiral compounds have attracted scant attention in comparison with synthetic studies. For over 25 years, our group has explored asymmetric synthesis of C−N axially chiral compounds and their synthetic application. In the course of these synthetic studies, we found several notable structural properties in relation to the C−N bond rotation and an association of enantiomers (the relationship between the rotational stability and the structure or electronic effect, the chiralitydependent halogen bond, and the self-disproportionation of enantiomers). Furthermore, on the basis of these structural properties, the development of acid-mediated molecular rotors and the synthesis of isotopic atropisomers possessing high stereochemical purity and rotational stability were achieved. Through this Perspective, I wish to make the chemistry community aware that C−N axially chiral compounds are attractive molecules from the viewpoints of both synthetic organic chemistry and structural chemistry.

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“…In 2020, Gustafson and co-workers reported the enantioselective halogenation of N -aryl quinoid atropisomers which were chosen as more configurationally stable analogues to diarylanilines ,, due to the intramolecular hydrogen bonding interaction between the aniline N–H and the quinone carbonyl in the favored configuration (Figure ). Additionally, the authors hypothesized that this hydrogen bonding interaction would reduce the two-axis system, as seen for diaryl anilines, to a single axis system and reduce the extent of racemization through geared rotation pathway, where the barrier to atropisomerization is reduced through the simultaneous rotation about a two-axis system.…”

Section: Dynamic Kinetic Reactions Of Atropisomersmentioning

confidence: 99%

Stereodynamic Strategies to Induce and Enrich Chirality of Atropisomers at a Late Stage

Roos,

Chiang,

Murray

et al. 2023

Chem. Rev.

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Rotational Behavior of N-(5-Substituted-pyrimidin-2-yl)anilines: Relayed Electronic Effect in Two N–Ar Bond Rotations

Cited by 6 publications

References 32 publications

Structure and Conformation of Novel BODIPY Ugi Adducts

Structure and Conformation of Novel BODIPY Ugi Adducts

Structural Chemistry of C–N Axially Chiral Compounds

Stereodynamic Strategies to Induce and Enrich Chirality of Atropisomers at a Late Stage

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