13C and 19F NMR Spectra of substituted ethyl α-fluorocinnamates. Application of the DSP-NLR equation

Robinson, Charles N.; Stablein, Gregory E.; Slater, Carl

doi:10.1016/s0040-4020(01)85418-1

Cited by 9 publications

(6 citation statements)

References 21 publications

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“…The inverse correlations observed for the β‐Cs in 5 – 8 , are striking contrasts to the normal correlations (ρ = 174.82 – 268.96 ppm) in the cases of 1 – 4 , as shown in Table . The inverse substituent effect was reported for the α‐Cs of m ‐ and p ‐substituted styrene and for the α‐Cs of the substituted cinnamate esters …”

Section: Resultssupporting

confidence: 86%

Studies of NMR Chemical Shifts of Chalcone Derivatives of Five‐membered Monoheterocycles and Determination of Aromaticity Indices

Jeong

Lee

2019

Bulletin Korean Chem Soc

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A series of the chalcone derivatives of the five‐membered monoheterocyclic compounds, (E)‐1‐aryl‐3‐heteroarylpropen‐1‐ones, were prepared by aldol condensation of the corresponding aldehydes of thiophene, pyrrole, and furan with m‐ and p‐substituted acetophenones. Similar condensation of the acetyl compounds of the heterocycles with m‐ and p‐substituted benzaldehydes gave another series of the chalcone derivatives, (E)‐1‐heteroaryl‐3‐arylpropen‐1‐ones. The 13C chemical shift values (δC) of the chalcone derivatives were determined in order to find if they correlated with the Hammett σ values. A good correlation, especially for the β‐C for both series, was found for the 13C chemical shift values (δC) of the chalcone derivatives with the Hammett σ values. The chemical shift values of the β‐C of the heterocyclic compounds were plotted against those of the benzene derivatives. The resulting slopes were found to be close to the values of the aromaticity indices.

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Section: Resultssupporting

confidence: 86%

Studies of NMR Chemical Shifts of Chalcone Derivatives of Five‐membered Monoheterocycles and Determination of Aromaticity Indices

Jeong

Lee

2019

Bulletin Korean Chem Soc

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“…The inverse correlation of 2‐C in 2 may be explained by the transmission of the electronic effect alternating like a wave . The alternation of substituent‐induced charges was suggested as a general phenomenon for carbon atoms in π systems . Apparently, such a phenomenon also seems to take place through the sp 3 ‐hybridized carbon skeleton, as shown by a negative ρ and the best r (0.984) value observed in the present system.…”

Section: Resultsmentioning

confidence: 92%

Effects of Substituents on NMR Chemical Shifts and Mass Fragmentation Patterns of 1‐Aryl‐3‐phenylpropanes

Jeong

Lee

2016

Bulletin Korean Chem Soc

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The 1 H and 13 C chemical shifts and the mass spectral fragmentation patterns of 1-aryl-3-phenylpropanes with m-or p-substituents (H, NO 2 , Br, Cl, OCH 3 , CH 3 ) were studied. The electronic effects of the substituents seemed to be transmitted by the through-space as well as by a through-bond mechanism, resulting in an inverse correlation in the plot of the chemical shift values of i-C vs. the Hammett σ values. The mass spectra showed the substituted benzyl fragments as the base peaks when the substituents were electron donating, whereas the benzyl fragment was observed as the base peaks with the electron-withdrawing substituents.

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“…The 13 C=O shows a trend of a negative slope with poor, but similar, correlation coefficients (r = 0.739-0.819) for 1-4. The inverse correlation of 1 3 C=O vs σ has been reported for various benzoyl series, Z-C 6 H 4 -C(=O)X (X = NH 2 , F, OEt, OH, Me, H) [7], m-and p-substituted phenyl esters R-C(=O)-O-C 6 H 4 -Z [4], m-and p-s u b s t i t u t e d anilides R-C(=O)-NH-C 6 H 4 -Z [5,15], and ethyl m-and psubstituted cinnamates, Z-C 6 H 4 -C H = C H -C ( = O ) -O -C 2 H 5 [16]. The correlations were much better for the series of esters (r = 0.989) [4].…”

Section: Resultsmentioning

confidence: 99%

Infrared and nuclear magnetic resonance properties of benzoyl derivatives of five‐membered monoheterocycles and determination of aromaticity indices

Jeon

Jun

et al. 2003

Journal of Heterocyclic Chem

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Benzophenones, 2-benzoylthiophenes, 2-benzoylpyrroles, and 2-benzoylfurans, which have substituents at m-and p-positions of the benzoyl ring were prepared and their ir and nmr spectra were obtained in 0.1 M chloroform-d solution. The chemical shift values of each series were plotted against the Hammett substituent parameters to give good correlation, with the exception of the ortho-Hs and -Cs. The slopes as well as the differences in chemical shift gave sets of meaningful values for the indices of aromaticy.J. Heterocyclic Chem., 40, 763(2003).There are a variety of methods for estimating the aromaticity of five-membered monoheterocyclic compounds, namely thiophene, furan, and pyrrole. The degree of aromaticity is typically compared to that of benzene whose aromaticity index is set as 1 [1]. A set of aromaticity indices of 1.00, 0.75, 0.59, and 0.46 were reported for benzene, thiophene, pyrrole, and furan, respectively, by comparison of the ring currents measured by the chemical shifts of the protons [2]. Consideration of bond length and the number of π electrons in the ring gives a different set of the indices: benzene 1, thiophene 0.93, pyrrole 0.91, and furan 0.87 [3]. There are a number of sets of the indices reported in the literature [1][2][3].We have reported a method of estimating the aromaticity index by comparing the chemical shifts of the carbonyl carbon atoms of m-and p-substituted phenyl esters of the five-membered heterocyclic carboxylic acids to those of benzoic acids [4]. The results were: benzene 1.00, thiophene 0.85, and furan 0.75 in dimethyl sulfoxide-d 6 ; and benzene 1.00, thiophene 0.90, and furan 0.78 in chlorof o r m -d. A similar approach with m-and p-s u b s t i t u t e d anilides gave a slightly different set of the indices: benzene 1.00, thiophene 0.79, and furan 0.52 in dimethyl sulfoxided 6 [5]. The poor solubilities of the anilides in chloroformd did not allow determination of a set of indices in that solvent. Our effort to estimate the index of aromaticity of pyrrole by similar method was not successful because of the difficulty of preparing the ester, m-and p-substituted phenyl 2-pyrrolecarboxylates and the 2-pyrrolylanilides. These esters and amides were very difficult to purify because they hydrolyze readily.In order to complete the estimation of the aromaticity indices of the five-membered monoheterocyclic compounds under the same conditions we needed to have sets of substituted phenyl derivatives of the heterocycles for thiophene, pyrrole and furan. Therefore, we prepared the benzoyl derivatives of the heterocycles and obtained their NMR spectra. This paper reports the results of our attempts to obtain the indices of aromaticity. Results and Discussions.The m-and p-substituted benzoyl compounds 1-4 were prepared by Friedel-Crafts benzoylation of benzene, thiophene, pyrrole, and furan in 30-85% yields. The ketones were purified by either recrystallization or column chromatography. Their ir, nmr, and mass spectra were consistent with the desired structures. Positions 3-, 4-, an...

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13C and 19F NMR Spectra of substituted ethyl α-fluorocinnamates. Application of the DSP-NLR equation

Cited by 9 publications

References 21 publications

Studies of NMR Chemical Shifts of Chalcone Derivatives of Five‐membered Monoheterocycles and Determination of Aromaticity Indices

Studies of NMR Chemical Shifts of Chalcone Derivatives of Five‐membered Monoheterocycles and Determination of Aromaticity Indices

Effects of Substituents on NMR Chemical Shifts and Mass Fragmentation Patterns of 1‐Aryl‐3‐phenylpropanes

Infrared and nuclear magnetic resonance properties of benzoyl derivatives of five‐membered monoheterocycles and determination of aromaticity indices

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