Evidence for a strong enaminic character of 3,4-diaminothiophene: a fast carbon-carbon coupling with 4,6-dinitrobenzofuroxan

Terrier, François; Pouet, Marie Jose; Kizilian, Elyane; Hallé, Jean-Claude; Outurquin, Françis; Paulmier, Claude

doi:10.1021/jo00069a037

Cited by 34 publications

(17 citation statements)

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“…As to the origin of the KIE, from the first observation by Zollinger and co-workers 8,9,10 of such a finding, steric hindrance in the arenonium ion intermediate has been considered to be the primary source, although electronic effects governing the intrinsic acidity of the departing proton may also be contributing. 2,5,30,31,48 Here it is noteworthy that the situation contrasts with that previously observed in the analogous coupling of DNBF at the unsubstituted 3-carbon of various indoles, which does not exhibit a KIE. 30,31 A reasonable explanation for this was provided by Illuminati and co-workers, 49,50 who noted that addition reactions at a substituted or unsubstituted aor b-position of a pyrrole or thiophene ring are not subject to significant steric hindrance, even when there is a substituent in the adjacent position.…”

Section: Discussioncontrasting

confidence: 72%

“…172°C (lit. 172-174.5°C [20][21][22][23][24][25][26][27][28][29][30][31]48,58 ). All the hydroxy-and methoxysubstituted benzenes (1a-1e) were commercial products (Aldrich or Acros) which were purified prior to use.…”

Section: Discussionmentioning

confidence: 99%

“…39 Reactions depicted in Scheme 1 afforded the adducts 3 in their acid form, which is not very stable in air. Based on previous observations that exchanging the H counterion for a K or Na cation often allows a facile isolation of DNBF s-adducts as crystalline alkali salts, 30,31,41,48,58 the same procedure as that used in the pyrrole or indole series was employed here to isolate 3a-3e as alkali salts. Using potassium fluoride or sodium acetate as the added salt, the method was actually successful in the case of the 1,3,5-trimethoxybenzene adduct 3b, the 1,3-dihydroxybenzene adduct 3d and the 1,3-dimethoxybenzene adduct 3e.…”

Section: Discussionmentioning

confidence: 99%

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Electrophilic aromatic substitutions: reactions of hydroxy- and methoxy‐substituted benzenes with 4,6-dinitrobenzofuroxan: kinetics and mechanism

Terrier

Pouet

Hallé

et al. 1998

J. Phys. Org. Chem.

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Rate constants have been determined in aqueous Me 2 SO mixtures for the reaction of super-electrophilic 4,6-dinitrobenzofuroxan (DNBF) with a series of hydroxy-and methoxy-substituted benzenes whose pK a values range between -3 and -9. The study extends the reactivity range of weakly basic aromatics with DNBF, from the family of indoles previously studied with pK a values ranging from -1 to -6. The overall rate constants for the reactions of DNBF as the electrophile are at least one order of magnitude greater than for the reactions of H 3 O with the same series of aromatics. This lends further credence to the notion that DNBF possesses super-electrophilic properties. An LFER is observed between logk DNBF 50%Me 2 SO and pK H 2 O a with slope 0.54. In the case of 1,3,5-trimethoxybenzene a significant kinetic isotope effect (KIE) is observed (k H /k D = 3.71 in 50% Me 2 SO). This system hence affords one of the few instances in which a KIE has been observed in S E Ar reactions. It follows from the observed KIE that the addition of DNBF to the aromatic is not rate-limiting and that reversion to reactants and proton loss from the arenonium intermediate occur at comparable rates. Structures of the products of electrophilic substitution have been confirmed by 1 H NMR. In all cases the regiochemistry of the reactions was identical to that observed in protonation studies of the starting aromatics.

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Section: Discussioncontrasting

confidence: 72%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Electrophilic aromatic substitutions: reactions of hydroxy- and methoxy‐substituted benzenes with 4,6-dinitrobenzofuroxan: kinetics and mechanism

Terrier

Pouet

Hallé

et al. 1998

J. Phys. Org. Chem.

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“…Such a situation is not unprecedented, however, as exclusive preferences for a CC rather than a CN coupling has been recently found in different systems. These include not only the reaction of DNBF with 8 a ,3d, 10 but also the reactions of this electrophile with 3‐aminothiophenes and 2‐aminothiazoles 3f. 7c…”

Section: Resultsmentioning

confidence: 99%

Superelectrophilicity of the Nitroolefinic Fragment of 4‐Nitrobenzodifuroxan in Michael‐Type Reactions with Indoles: A Kinetic Study in Acetonitrile

Lakhdar

Goumont

Berionni

et al. 2007

Chemistry A European J

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The kinetics of the coupling of 4-nitrobenzodifuroxan (NBDF) with a series of indoles 8 a-e to give the expected Michael-type adducts 9 a-e have been investigated in acetonitrile solution. No significant influence of the nature of the isotopic substitution at C-3 of the indole ring has been found, indicating that the NBDF addition step is the rate limiting step of the SEAr substitution of the indole moiety. This implies that the measured second-order rate constants (k) for the reactions are identical to the second order rate constants (k1NBDF) associated to the C--C coupling step. By using the known N and s parameters characterizing the nucleophilicity of indoles, the k1NBDF rate constants are found to fit nicely to the three parameters equation logk1=s(N+E) introduced by Mayr to describe the feasibility of nucleophilic-electrophilic combinations. Based on this, the electrophilicity parameter E of NBDF could be determined as E=-6.15. This corresponds to a positioning of the reactivity of the nitroactivated double bond of NBDF in the domain of superelectrophilicity previously defined for nitrobenzofuroxans, in accord with the finding that the rates of coupling of 8 a-e with NBDF are only one order of magnitude lower than those for the coupling of these indoles with 4,6-dinitrobenzofuroxan (DNBF). The theoretical scale of electrophilicity introduced by Domingo et al. on the basis of the global electrophilicity index omega defined by Parr is also a very useful tool to discuss the relative reactivities of NBDF, DNBF, and a number of differently activated C==C double bonds.

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“…Referring meanly to the readily accessible prototype substrates, namely 4,6-dinitrobenzofuroxan (DNBF, A), this review will highlight this behaviour which has proved to be very useful to assess the nucleophilic reactivity of extremely weak carbon base. In the same context, some remarkable reactivity sequences deriving from an aza substitution of the carbocyclic ring or a change in the nature of the annelated ring will be also emphasized with a particular focus on the behaviour of this extremely electrophilic substrates, namely 6-nitro [2,1,3] oxadiazolo [4, 5- i.e. the 4-aza-6-nitro analogue of DNBF (ANBF, H).…”

Section: Introductionmentioning

confidence: 99%

NMR Spectroscopy: A Useful Tool in the Determination of the Electrophilic Character of Benzofuroxans - Case Examples of the Reactions of Nitrobenzofuroxans with Dienes and Nucleophiles

Sebban¹,

Sepulcri²,

Jovene³

et al. 2012

Magnetic Resonance Spectroscopy

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Evidence for a strong enaminic character of 3,4-diaminothiophene: a fast carbon-carbon coupling with 4,6-dinitrobenzofuroxan

Cited by 34 publications

References 0 publications

Electrophilic aromatic substitutions: reactions of hydroxy- and methoxy‐substituted benzenes with 4,6-dinitrobenzofuroxan: kinetics and mechanism

Electrophilic aromatic substitutions: reactions of hydroxy- and methoxy‐substituted benzenes with 4,6-dinitrobenzofuroxan: kinetics and mechanism

Superelectrophilicity of the Nitroolefinic Fragment of 4‐Nitrobenzodifuroxan in Michael‐Type Reactions with Indoles: A Kinetic Study in Acetonitrile

NMR Spectroscopy: A Useful Tool in the Determination of the Electrophilic Character of Benzofuroxans - Case Examples of the Reactions of Nitrobenzofuroxans with Dienes and Nucleophiles

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