Chemistry of 2,4,6-tri-tert-butylanilides possessing isolable rotational isomer

Nobutaka Ototake, Osamu Kitagawa

研究成果: Review article

抄録

Amide C-N bond in 2,6-di-tert-butylanilides has a high rotational barrier and the individual amide rotational isomers can be isolated at ambient temperature. These anilides have been reported by Chupp et al. in 1967, but no systematic study with anilide substrates other than a - haloacetoanilides, or the stereoselective synthesis of anilide rotamers have been reported. In addition, the structural properties of these anilides have not been investigated in detail. We succeeded in the highly selective stereodivergent synthesis of Z- and E-rotamers of various N-allyl-2,4,6-tri-tert-butylanilides through Pd(0) and Pd (II) catalyzed N-allylation of O-allyl-N-(2,4,6-tri-tert-butylphenyl) imidates. Moreover, the relative thermodynamic stabilities of the obtained anilide rotamers were clarified. Specific reactivity of 2,4,6-tri-tert-butylanilide derivatives was also found. For examples, in intramolecular Diels-Alder reaction of N-ally 2-furoyl amides, 2,4,6-tri-tert-butylphenyl group on the nitrogen atom remarkably accelerated the reaction. Although the reaction of ordinal anilide anion with alkyl halide gives N-alkylation product, the alkylation with 2,4,6-tri-tert-butylanilide anion preferentially proceeded on the oxygen atom to give O-alkyl imidate. O-Benzyl imidate, which was obtained by the reaction with benzyl bromide, was used as bezylation reagent of alcohols and carboxylic acids. In contrast to rotational rigidity of 2,4,6-tri-tert-butylanilide, in the anilide enolates, interconversion between the rotamers readily occurs at ambient temperature, and their reaction with electrophiles gave rotamer mixtures of the products in a ratio that depends on the reactivity of the electrophiles. Furthermore, as an application of this isomerization reaction, switching between the anilide rotamers was achieved.

元の言語English
ページ(範囲)575-583
ページ数9
ジャーナルYuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry
76
発行部数6
DOI
出版物ステータスPublished - 2018 1 1

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Anilides
Isomers
Imidoesters
Amides
Alkylation
Anions
Allylation
Atoms
2,4,6-tri-tert-butylanilide
Isomerization
Carboxylic Acids
Rigidity
Structural properties
Thermodynamic stability
Nitrogen
Alcohols
Oxygen
Derivatives
Temperature

ASJC Scopus subject areas

  • Organic Chemistry

これを引用

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title = "Chemistry of 2,4,6-tri-tert-butylanilides possessing isolable rotational isomer",
abstract = "Amide C-N bond in 2,6-di-tert-butylanilides has a high rotational barrier and the individual amide rotational isomers can be isolated at ambient temperature. These anilides have been reported by Chupp et al. in 1967, but no systematic study with anilide substrates other than a - haloacetoanilides, or the stereoselective synthesis of anilide rotamers have been reported. In addition, the structural properties of these anilides have not been investigated in detail. We succeeded in the highly selective stereodivergent synthesis of Z- and E-rotamers of various N-allyl-2,4,6-tri-tert-butylanilides through Pd(0) and Pd (II) catalyzed N-allylation of O-allyl-N-(2,4,6-tri-tert-butylphenyl) imidates. Moreover, the relative thermodynamic stabilities of the obtained anilide rotamers were clarified. Specific reactivity of 2,4,6-tri-tert-butylanilide derivatives was also found. For examples, in intramolecular Diels-Alder reaction of N-ally 2-furoyl amides, 2,4,6-tri-tert-butylphenyl group on the nitrogen atom remarkably accelerated the reaction. Although the reaction of ordinal anilide anion with alkyl halide gives N-alkylation product, the alkylation with 2,4,6-tri-tert-butylanilide anion preferentially proceeded on the oxygen atom to give O-alkyl imidate. O-Benzyl imidate, which was obtained by the reaction with benzyl bromide, was used as bezylation reagent of alcohols and carboxylic acids. In contrast to rotational rigidity of 2,4,6-tri-tert-butylanilide, in the anilide enolates, interconversion between the rotamers readily occurs at ambient temperature, and their reaction with electrophiles gave rotamer mixtures of the products in a ratio that depends on the reactivity of the electrophiles. Furthermore, as an application of this isomerization reaction, switching between the anilide rotamers was achieved.",
keywords = "Allylation, Anilides, Benzylation, Enolates, Imidates, Isolable rotamers, Isomerization, Palladium, Switching",
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T1 - Chemistry of 2,4,6-tri-tert-butylanilides possessing isolable rotational isomer

AU - Ototake, Nobutaka

AU - Kitagawa, Osamu

PY - 2018/1/1

Y1 - 2018/1/1

N2 - Amide C-N bond in 2,6-di-tert-butylanilides has a high rotational barrier and the individual amide rotational isomers can be isolated at ambient temperature. These anilides have been reported by Chupp et al. in 1967, but no systematic study with anilide substrates other than a - haloacetoanilides, or the stereoselective synthesis of anilide rotamers have been reported. In addition, the structural properties of these anilides have not been investigated in detail. We succeeded in the highly selective stereodivergent synthesis of Z- and E-rotamers of various N-allyl-2,4,6-tri-tert-butylanilides through Pd(0) and Pd (II) catalyzed N-allylation of O-allyl-N-(2,4,6-tri-tert-butylphenyl) imidates. Moreover, the relative thermodynamic stabilities of the obtained anilide rotamers were clarified. Specific reactivity of 2,4,6-tri-tert-butylanilide derivatives was also found. For examples, in intramolecular Diels-Alder reaction of N-ally 2-furoyl amides, 2,4,6-tri-tert-butylphenyl group on the nitrogen atom remarkably accelerated the reaction. Although the reaction of ordinal anilide anion with alkyl halide gives N-alkylation product, the alkylation with 2,4,6-tri-tert-butylanilide anion preferentially proceeded on the oxygen atom to give O-alkyl imidate. O-Benzyl imidate, which was obtained by the reaction with benzyl bromide, was used as bezylation reagent of alcohols and carboxylic acids. In contrast to rotational rigidity of 2,4,6-tri-tert-butylanilide, in the anilide enolates, interconversion between the rotamers readily occurs at ambient temperature, and their reaction with electrophiles gave rotamer mixtures of the products in a ratio that depends on the reactivity of the electrophiles. Furthermore, as an application of this isomerization reaction, switching between the anilide rotamers was achieved.

AB - Amide C-N bond in 2,6-di-tert-butylanilides has a high rotational barrier and the individual amide rotational isomers can be isolated at ambient temperature. These anilides have been reported by Chupp et al. in 1967, but no systematic study with anilide substrates other than a - haloacetoanilides, or the stereoselective synthesis of anilide rotamers have been reported. In addition, the structural properties of these anilides have not been investigated in detail. We succeeded in the highly selective stereodivergent synthesis of Z- and E-rotamers of various N-allyl-2,4,6-tri-tert-butylanilides through Pd(0) and Pd (II) catalyzed N-allylation of O-allyl-N-(2,4,6-tri-tert-butylphenyl) imidates. Moreover, the relative thermodynamic stabilities of the obtained anilide rotamers were clarified. Specific reactivity of 2,4,6-tri-tert-butylanilide derivatives was also found. For examples, in intramolecular Diels-Alder reaction of N-ally 2-furoyl amides, 2,4,6-tri-tert-butylphenyl group on the nitrogen atom remarkably accelerated the reaction. Although the reaction of ordinal anilide anion with alkyl halide gives N-alkylation product, the alkylation with 2,4,6-tri-tert-butylanilide anion preferentially proceeded on the oxygen atom to give O-alkyl imidate. O-Benzyl imidate, which was obtained by the reaction with benzyl bromide, was used as bezylation reagent of alcohols and carboxylic acids. In contrast to rotational rigidity of 2,4,6-tri-tert-butylanilide, in the anilide enolates, interconversion between the rotamers readily occurs at ambient temperature, and their reaction with electrophiles gave rotamer mixtures of the products in a ratio that depends on the reactivity of the electrophiles. Furthermore, as an application of this isomerization reaction, switching between the anilide rotamers was achieved.

KW - Allylation

KW - Anilides

KW - Benzylation

KW - Enolates

KW - Imidates

KW - Isolable rotamers

KW - Isomerization

KW - Palladium

KW - Switching

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