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Hyperconjugative Antiaromaticity Activates 4H-Pyrazoles as Inverse-Electron-Demand Diels-Alder Dienes.

ABSTRACT: The Diels-Alder reactivity of 4,4-difluoro-3,5-diphenyl-4H-pyrazole was investigated experimentally and computationally with endo-bicyclo[6.1.0]non-4-yne. The computationally predicted rate enhancement from hyperconjugative antiaromaticity induced by fluorination of cyclopentadienes at the 5-position extends to five-membered heterocyclic dienes containing a saturated center. 4,4-Difluoro-4H-pyrazoles are new electron-deficient dienes with rapid reactivities toward strained alkynes.

SUBMITTER: Levandowski BJ

PROVIDER: S-EPMC7015664 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Hyperconjugative Antiaromaticity Activates 4H-Pyrazoles as Inverse-Electron-Demand Diels-Alder Dienes.

Levandowski Brian J BJ Abularrage Nile S NS Houk K N KN Raines Ronald T RT

Organic letters 20191007 20

The Diels-Alder reactivity of 4,4-difluoro-3,5-diphenyl-4H-pyrazole was investigated experimentally and computationally with endo-bicyclo[6.1.0]non-4-yne. The computationally predicted rate enhancement from hyperconjugative antiaromaticity induced by fluorination of cyclopentadienes at the 5-position extends to five-membered heterocyclic dienes containing a saturated center. 4,4-Difluoro-4H-pyrazoles are new electron-deficient dienes with rapid reactivities toward strained a ...[more]

PMID: 31589054

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