Beitrag zum Problem der Decarboxylierung. 3. Mitteilung. Theoretische Betrachtungen zum Problem der Decarboxylierungsreaktion

Schenkel, H.; Schenkel‐Rudin, M.

doi:10.1002/hlca.19480310231

Cited by 41 publications

(10 citation statements)

References 28 publications

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“…No further spectral change was observed for the cations of either 9-ACA or 9−MCA in concentrated acid solutions, although aromatic carboxylic acids and esters are known to undergo protonation at the carbonyl oxygen near H 0 −8 . The absorption spectrum of 9-AA also does not show any change in the above acidity region, except in concentrated HClO 4 ( H 0 −7.7) where it is reported to undergo decarboxylation to produce anthracene 5 Absorption spectra (long-wavelength band) of the prototropic species of 9-ACA and 9-MCA (insert).…”

Section: Resultsmentioning

confidence: 97%

Fluorescence Spectral Study of 9-Acridinecarboxylic Acid and Its Methyl Ester. Understanding the Unusual Fluorescence Behavior of 9-Anthroic Acid

et al. 1997

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The absorption and fluorescence spectral characteristics of 9-acridinecarboxylic acid (9-ACA) and 9-(methoxycarbonyl)acridine (9-MCA) were studied in a series of organic solvents and in aqueous solutions. Fluorescence quantum yields (Φf) and lifetimes (τf) of the compounds were measured in these solvents. Unlike 9-anthroic acid (9-AA), as reported in the literature, no large Stokes-shifted fluorescence emission band was observed for 9-ACA and 9-MCA in neutral organic solvents or water. The absence of large Stokes-shifted emission in the case of 9-ACA and 9-MCA suggests the existence of a charge-transfer emitting state in 9-AA in which the carboxyl group is nearly coplanar with the aromatic ring. The Φf values for both compounds increase as a function of hydrogen-bonding capacity of the solvents. In near neutral to slightly acidic solutions, 9-ACA exists mainly in the zwitterionic form. Both 9-ACA and 9-MCA form monoprotonated species in moderately concentrated acid solutions. The acidium cation of 9-AA formed in the excited state in moderately concentrated acid solution reorganizes to produce a carbocation centered at the carbon atom of the carboxyl group. However, there was no indication of the formation of such acidium cations in the case of 9-ACA and 9-MCA even in concentrated perchloric acid medium. The pK as of various prototropic equilibria involved in the ground electronic state of the compounds were estimated. Semiempirical AM1 calculations were performed to obtain the energies of the various configurations of 9-AA and 9-ACA in the ground (S0) as well as in the lowest excited singlet (S1) electronic state. The results suggest that the COOH group is oriented at an angle of ∼55° with respect to the aromatic ring in the S0 state in both the molecules. However, in the S1 state, it approaches coplanarity with the aromatic ring. The calculated bond lengths, charge densities, and dipole moments suggest that the resonance charge transfer from the aromatic ring to the COOH group increases in the S1 state of 9-AA. However, despite the decrease of twist angle of the COOH group, no significant charge transfer was observed in 9-ACA. The charge density data indicate that the ring nitrogen and the carbonyl oxygen of the COOH group become more basic upon electronic excitation.

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Section: Resultsmentioning

confidence: 97%

Fluorescence Spectral Study of 9-Acridinecarboxylic Acid and Its Methyl Ester. Understanding the Unusual Fluorescence Behavior of 9-Anthroic Acid

et al. 1997

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“…In 1948, Schenkel and Schenkel-Rudin (9) suggested that some organic acids are decarboxylated by a bimolecular electrophilic substitution mechanism (S,2). Since then, several exanlples of S,2 mechanisms have been found (4,6,10).…”

Section: Discussionmentioning

confidence: 99%

The Decarboxylation of Anthranilic Acid

Stevens¹,

Pepper²,

Lounsbury³

1952

Can. J. Chem.

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Anthranilic acid is known to decarboxylate on being heated above its melting point, v r on being boiled in water. We have found that the aqueous decomposition can be acid catalyzed, but that, after the concentration of added mineral acid approximates that of the anthranilic acid, the reaction rate decreases with increasing mineral acid concentration. A mass specirometer study of the carbon dioxide produced in the decomposition has shown that C12-carboxyl anthranilic acid decomposes a t the same rate as C13-carboxyl anthranilic acid. Thus, unlilie all other organic acid decarbox~lations in which an "isotope effect" has been searched for thus far, the decarboxylation of anthranilic acid cloes not show an "isotope effect". From the experimental facts available, it appears that the mechanism of the decarboxylatioli is best explained as billlolecular electrophilic substitution, with the attack of a proton being the rate determining step. While other possibilities are not entirely excluded, a proton attack on t h e a carbon of the zwitterion is the detailed mechanism suggested as being most probable.

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“…Polyenoic acids could serve as a concealed form of polyenes if mild methods existed for their protodecarboxylation. The existing acid-catalyzed protodecarboxylation methods are not typically compatible with polyenes due to possible polymerization issues . In recent years, metal-catalyzed protodecarboxylations and decarboxylative coupling reactions have received much attention .…”

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confidence: 99%

Palladium-Catalyzed Chemoselective Protodecarboxylation of Polyenoic Acids

et al. 2018

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Conditions for the first palladium-catalyzed chemoselective protodecarboxylation of polyenoic acids to give the desired polyenes in good yields are presented. The reactions proceed under mild conditions using either a Pd(0) or Pd(II) catalyst and tolerate a variety of aryl and aliphatic substitutions. Unique aspects of the reaction include the requirement of phosphines, water, and a polyene adjacent to the carboxylic acid.

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Beitrag zum Problem der Decarboxylierung. 3. Mitteilung. Theoretische Betrachtungen zum Problem der Decarboxylierungsreaktion

Cited by 41 publications

References 28 publications

Fluorescence Spectral Study of 9-Acridinecarboxylic Acid and Its Methyl Ester. Understanding the Unusual Fluorescence Behavior of 9-Anthroic Acid

Fluorescence Spectral Study of 9-Acridinecarboxylic Acid and Its Methyl Ester. Understanding the Unusual Fluorescence Behavior of 9-Anthroic Acid

The Decarboxylation of Anthranilic Acid

Palladium-Catalyzed Chemoselective Protodecarboxylation of Polyenoic Acids

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