Optically active amines. 31. Spectral observations on the substituted benzene chromophore

Smith, Howard E.; Neergaard, Jon R.; Chen, Fu Ming

doi:10.1021/ja00344a026

Cited by 29 publications

(52 citation statements)

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“…The ECD of the 1 L b band of benzene derivatives is usually interpreted on the grounds of qualitative rules like the sector and benzene chirality ones 2,3,40 . They successfully predict the ECD sign and therefore the absolute configuration of a number of related molecules, 21,22,41–47 but some exceptions have been documented like ( R )‐methylmandelate, 48 ( R )‐1‐indancarboxylate, 49 and ( R )‐α‐isopropylphenylethane 20 …”

Section: Resultsmentioning

confidence: 99%

“…The ECD of the 1 L b band of benzene derivatives is usually interpreted on the grounds of qualitative rules like the sector and benzene chirality ones. 2,3,40 They successfully predict the ECD sign and therefore the absolute configuration of a number of related molecules, 21,22,[41][42][43][44][45][46][47] but some exceptions have been documented like (R)methylmandelate, 48 (R)-1-indancarboxylate, 49 and (R)α-isopropylphenylethane. 20 Sector rule predicts that the ECD of R enantiomer of PhEtOH is dominated by HT effects and is negative, according to the preferred position of the benzylic hydrogen and the sectors where the OH and CH 3 groups are located.…”

Section: Effect Of the Chlorinementioning

confidence: 99%

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The role of chlorine position in the electronic circular dichroism of chlorophenyl‐ethanol investigated by vibronic calculations

Aranda

Santoro

2020

Chirality

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(R)‐1‐phenyl‐ethanol (PhEtOH) and the different isomers of (R)‐1‐(chlorophenyl)ethanol (ClPhEtOH) exhibit very interesting electronic circular dichroism (ECD) in methanol. In all cases, the spectrum shows clear vibronic features, but it is monosignated and negative for PhEtOH and meta‐ClPhEtOH, positive for the ortho isomer and bisignated for the para isomer. We used computational chemistry to rationalise this behaviour adopting CAM‐B3LYP/def2‐TZVP, describing the bulk solvent effects with polarizable continuum models and solute–solvent specific interactions with clusters comprising the solute and two solvent molecules. We adopted harmonic vibronic models to compute the ECD spectral shapes of all stable conformers, and we obtained the room‐temperature spectra by Boltzmann average. Simulated spectra are in very good agreement with experiment and allow us to rationalise their difference in terms of the relevance of Franck–Condon (FC) and Herzberg–Teller (HT) intensity‐borrowing contributions, modulated by the substituent effect. The bisignated shape of the spectrum of para‐ClPhEtOH arises from the competition of opposite‐sign FC and HT bands, promoted by different vibrational modes. Due to the challenges we document in computing its ECD spectrum, para‐ClPhEtOH represents a good test case to help the development of novel methodologies for an improved description of weak vibronic ECD spectra of flexible systems in explicit solvents.

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Section: Resultsmentioning

confidence: 99%

Section: Effect Of the Chlorinementioning

confidence: 99%

The role of chlorine position in the electronic circular dichroism of chlorophenyl‐ethanol investigated by vibronic calculations

Aranda

Santoro

2020

Chirality

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“…The appropriate shape is present, and while the amplitudes are somewhat diminished compared to similar complexes, 36,37 they are still strong compared to the amines from which they are derived. 40,41 Ideally, the wavelength of the null in the bisignate CD spectrum should correspond to the max of a peak in the UV-vis spectrum, centered between the two Cotton effects with opposite signs. , 238 nm shoulder, 1 B b ).…”

Section: Resultsmentioning

confidence: 99%

Derivatization, complexation, and absolute configurational assignment of chiral primary amines: Application of exciton‐coupled circular dichroism

et al. 2003

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We report here a sensitive method for the determination of the absolute configurations of primary amines using exciton-coupled circular dichroism (ECCD). The method works on a microgram scale by derivatization of chiral amines with quinoline chromophores. Complexation of the chiral ligands with metal ion fixes the geometry of the chromophores, resulting in a twist that is governed by the asymmetric carbon configuration and steric environment of the amine. The absolute configurations of the primary amines can be interpreted from the couplets of the ECCD spectra of the derivatized complexes. Crystal structures, 2D NMR studies, and semiempirical calculations provide structural evidence for our model.

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“…Absolute configuration determined by comparison with literature. 2,3 Supelco gama Dex TM 225 column (30 m ×0.25 mm × 0.25 µm), He 1.0 mL/min, column temperature: 160 o C; t R = 24.1min (minor), t R = 24.6 min (major).…”

Section: General Procedures For Asymmetric Hydrogenationmentioning

confidence: 99%

Rhodium-Catalyzed Enantioselective Hydrogenation of Oxime Acetates

2013

Synfacts

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Optically active amines. 31. Spectral observations on the substituted benzene chromophore

Cited by 29 publications

References 0 publications

The role of chlorine position in the electronic circular dichroism of chlorophenyl‐ethanol investigated by vibronic calculations

The role of chlorine position in the electronic circular dichroism of chlorophenyl‐ethanol investigated by vibronic calculations

Derivatization, complexation, and absolute configurational assignment of chiral primary amines: Application of exciton‐coupled circular dichroism

Rhodium-Catalyzed Enantioselective Hydrogenation of Oxime Acetates

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