Substituent and temperature controlled tautomerism: multinuclear magnetic resonance, X-ray, and theoretical studies on 2-phenacylquinolines

Kolehmainen, Erkki; Ośmiałowski, Borys; Krygowski, Tadeusz M.; Kauppinen, Reijo; Nissinen, Maija; Gawinecki, Ryszard

doi:10.1039/a908874a

Cited by 75 publications

(127 citation statements)

References 44 publications

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“…[11] Diesters, such as oxalate, may react with two molecules of the lithium derivative. This should result in formation of the respective a-diketone, 1,4-di(quinolin-2-yl)butane-2,3-dione, 2 KK (Scheme 1).…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, the position of the latter signal is different from the typical chemical shift of the carbonyl carbon atom in the enaminone form. [11] It is also noteworthy that the value of 177.21 ppm is not a result of the vicinity of the two carbonyl groups in a-diketones. [17] The 15 N chemical shift (À 209.3) is also different from that of enaminones.…”

Section: Discussionmentioning

confidence: 99%

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Identity Double‐Proton Transfer in (3Z)‐3‐Hydroxy‐1,4‐di(quinolin‐2‐yl)but‐3‐en‐2‐one

Ośmiałowski¹,

Kolehmainen²,

Gawinecki³

2003

Chemistry A European J

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Although there is a very fast (on the NMR timescale) double-proton transfer in (1Z,3Z)-3-hydroxy-4-quinolin-2-yl-1-quinolin-2(1H)-ylidenbut-3-en-2-one (the product of the condensation of ethyl oxalate with 2lithiomethylquinoline), it is the only species present in chloroform solution. Comparison of the product of condensation of ethyl oxalate with 2lithiomethyl derivatives of pyridine (recent studies) and quinoline (present studies) shows that benzoannulation considerably affects the tautomeric equilibrium. The observed changes are not only quantitative but also qualitative. Moreover, contrary to the proton transfer in the pyridine tautomers, this process is fast in the quinoline tautomers. Comparison of the experimental and ab initio/DFT GIAO-calculated (13)C and (15)N chemical shifts for the transition states in the proton-transfer reactions between (1Z,3Z)- 3-hydroxy-4-quinolin-2-yl-1-quinolin-2(1H)-ylidenbut-3-en-2-one and its tautomers support the theory that a concerted identity reaction takes place between the enolimine-enaminone and enaminone-enolimine tautomeric forms. As a consequence, the most stable tautomeric form, (1Z,3Z)-1,4-di(quinolin-2-yl)buta-1,3-diene-2,3-diol, is not present in the tautomeric mixture.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Identity Double‐Proton Transfer in (3Z)‐3‐Hydroxy‐1,4‐di(quinolin‐2‐yl)but‐3‐en‐2‐one

Ośmiałowski¹,

Kolehmainen²,

Gawinecki³

2003

Chemistry A European J

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“…37,[40][41][42][43] Presumably, the properties of BF 2 -carrying molecules may also be tuned in this way. This is due to the fact that proton involved in the intramolecular hydrogen bonding 40,41 can be easily replaced by another acid such as BF 2 + cation. The proton-to-BF 2 exchange thus creates an opportunity to synthesize a number of new dyes.…”

Section: Introductionmentioning

confidence: 99%

Influence of Substituent and Benzoannulation on Photophysical Properties of 1-Benzoylmethyleneisoquinoline Difluoroborates

et al. 2015

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A series of 1-benzoylmethyleneisoquinoline difluoroborates were synthesized and their photophysical properties were determined. The effect of the substituent and 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 benzoannulation on their properties was investigated to make a comparison with recently published results focused on related quinolines. The photophysical properties of isoquinoline derivatives differ from those of quinolines and most pronounced differences are found for the fluorescence quantum yields. Both, experimental and theoretical approaches were used to explain the observed photophysical properties.

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“…Their 1 H NMR spectra display two closely overlapping sets of signals and their proton-decoupled 13 C NMR spectra generally show two sets of lines. By comparison of the magnitudes of the enolic and ketonic shifts to values from the literature, 30 they were identified as the ketone and enol forms K and O; enaminone tautomers E were not observed (Scheme 3). The integrated intensities of the side-chain methylene and vinyl protons in the 1 H NMR spectra of CDCl 3 solutions of 10a−k indicated a predominance of the O forms in 10c,e,g,j 62−92% while K forms predominated in 10a,d,f,h,i 58−95%.…”

Section: Methodsmentioning

confidence: 95%

A convenient access to 1-substituted-2-azinyl-1-ethanones via acylation of alkylated azines with N-acylbenzotriazoles

Katritzky

Abdel‐Fattah²,

Akhmedova³

2005

Arkivoc

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Substituent and temperature controlled tautomerism: multinuclear magnetic resonance, X-ray, and theoretical studies on 2-phenacylquinolines

Cited by 75 publications

References 44 publications

Identity Double‐Proton Transfer in (3Z)‐3‐Hydroxy‐1,4‐di(quinolin‐2‐yl)but‐3‐en‐2‐one

Identity Double‐Proton Transfer in (3Z)‐3‐Hydroxy‐1,4‐di(quinolin‐2‐yl)but‐3‐en‐2‐one

Influence of Substituent and Benzoannulation on Photophysical Properties of 1-Benzoylmethyleneisoquinoline Difluoroborates

A convenient access to 1-substituted-2-azinyl-1-ethanones via acylation of alkylated azines with N-acylbenzotriazoles

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