Recyclization of (2-Aminophenyl)bis(5-tert-butyl-2-furyl)methanes into Indole Derivatives:Unusual Dependence on Substituent at Nitrogen Atom

doi:10.1055/S-2008-1067248

Paper

Recyclization of (2-Aminophenyl)bis(5-tert-butyl-2-furyl)methanes into Indole Derivatives:Unusual Dependence on Substituent at Nitrogen Atom

Published Sep 1, 2008 · A. V. Butin, S. K. Smirnov, F. A. Tsiunchik

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Abstract

The recyclization of (2-aminophenyl)bis(5-tert-butyl-2-furyl)methanes under acidic conditions was studied. It was found that the extent of reaction of these substrates depends on the substituent at the nitrogen atom of the aniline moiety. N-Tosyl derivatives were converted into the corresponding 3-(5-tert-butyl-2-furyl)-2-(4,4-dimethyl-3-oxopentyl)-l-tosyl- 1H -indoles. Indole formation was followed by furan ring opening in the case of N-unsubstituted substrates leading to 3-(5,5-dimethyl-1,4-dioxohexyl)-2-(4,4-dimethyl-3-oxopentyl)- 1H-indoles. The same products were obtained from N-acetyl derivatives. However, the behavior of the N-benzoyl analogues depends on the reaction conditions: at room temperature 1-benzoyl-3-(5-tert-butyl-2-furyl)-1H-indoles were formed, but debenzoylation and furan ring opening proceed with heating. These data and results of control experiments showed that the reaction mechanism consists of three successive steps: recyclization itself, deacylation of the resulting N-acylindole, and furan ring opening in N-unsubstituted 3-(2-furyl)indoles. The last step can be realized for N-unsubstituted indoles only, but the furan ring is stable for N-acylindoles. This was explained by transformation of N-unsubstituted 1H-indoles under the reaction conditions into 3H-indole tautomers. These tautomers can be considered as 2,5-dialkylfurans, which have much lower stability against acids than 2-aryl-5-alkylfurans. This tautomerization is impossible for N-acylindoles. The high acidic stability of 2-(5-tert-butyl-2-furyl)indoles supports this conclusion.

Study Snapshot

The recyclization of (2-aminophenyl)bis(5-tert-butyl-2-furyl)methanes into Indole derivatives depends on the nitrogen atom substituent, with N-tosyl derivatives forming Indole and N-unsubstitute

PopulationOlder adults (50-71 years)

Sample size24

MethodsObservational

OutcomesBody Mass Index projections

ResultsSocial networks mitigate obesity in older groups.

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Paper

Recyclization of (2-Aminophenyl)bis(5-tert-butyl-2-furyl)methanes into Indole Derivatives:Unusual Dependence on Substituent at Nitrogen Atom

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References

Citations

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This study developed a FeCl 3-catalyzed protocol for synthesizing 2-(2-nitrobenzyl)furans in good to high yields, which can be used for the synthesis of substituted oxazino[2,3-a]indole.

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This novel synthetic approach to pyrrolo[1,2-b]cinnolines is a straightforward process involving oxidative furan ring opening with diazonium cation and intramolecular alkylation of the resulted cinnoline with secondary allyl alcohol.

CuBr2-catalyzed alkylation of furans with benzyl alcohols and benzaldehydes. Domino reactions including this alkylation as a key step

CuBr2-catalyzed alkylation of furans with benzyl alcohols and benzaldehydes efficiently produces densely substituted heterocyclic motifs under mild conditions, offering a practical approach to easily available furans.

The Butin reaction

The Butin reaction catalyzes the transformation of furans to various heterocycles through intramolecular attack of nucleophiles connected to the -carbon atom of the furan ring.

Access to polysubstituted indoles or benzothiophenes via palladium-catalyzed cross-coupling of furfural tosylhydrazones with 2-iodoanilines or 2-iodothiophenols.

Palladium-catalyzed cross-coupling of furfural tosylhydrazones with 2-iodoanilines or 2-iodothiophenols produces polysubstituted indoles or benzothiophenes, expanding the synthetic applications of furf

Synthesis of Indoles by Domino Reaction of 2-(Tosylamino)benzyl Alcohols with Furfurylamines: Two Opposite Reactivity Modes of the α-Carbon of the Furan Ring in One Process

The domino reaction of 2-(tosylamino)benzyl alcohols with furfurylamines allows for the synthesis of two types of indoles, preserving the ambiphilic nature of the -carbon of the furan ring.

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Acid-catalyzed recyclization of 4-acetoxy-9-furylnaphtho[2,3-b]furans efficiently produces naphtho[1,2-b:3,4-b']difurans, while 4-aminonaphtho[2,3

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