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

• Main Authors: Levandowski, Brian (Author), Abularrage, Nile S (Author), Houk, KN (Author), Raines, Ronald T (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Chemistry (Contributor)
• Format: Article
• Language: English
• Published: American Chemical Society (ACS), 2020-11-20T18:37:43Z.
• Subjects: Article
• Online Access: Get fulltext

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.
National Institutes of Health (Grant R01-GM044783)
National Science Foundation (Grant CHE-1764328)