Palladium-Catalyzed Asymmetric Trifluoromethylated Allylic Alkylation of Pyrazolones Enabled by α‑(Trifluoromethyl)alkenyl Acetates

The first asymmetric trifluoromethylated allylic alkylation of pyrazolones using α-(trifluoromethyl)­alkenyl acetates as a novel trifluoromethylated allylation reagent is described, affording various functionalized chiral pyrazolones containing a trifluoromethylated allyl substituent in high yields with excellent regio-/enantio-/diastereoselectivities. Mechanistically, the double-bond migration of α-(trifluoromethyl)­alkenyl acetates in the presence of 1,8-diazabicyclo[5.4.0]­undec-7-ene is initial and interesting step. More importantly, this study is of significance in providing a novel and widely applicable trifluoromethyl-containing allylation reagent.