The Diels-Alder reactivity of 4,4-difluoro-3,5-diphenyl-4-pyrazole was investigated experimentally and computationally with -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-4-pyrazoles are new electron-deficient dienes with rapid reactivities toward strained alkynes.