"Haliranium Ion"-Induced Intermolecular Friedel-Crafts Alkylation in HFIP: Synthesis of β,β-Diaryl α-Halo carbonyl Compounds

Here reports a highly regio- and diastereoselective haliranium ion-induced intermolecular Friedel-Crafts reaction of alpha,beta-unsaturated carbonyl compounds in HFIP. The operationally simple and mild method affords the synthetically useful beta,beta-diarylated alpha-halo carbonyl compounds in good yields after a very short reaction time. As an application, a few examples of beta,beta-diarylated olefins are prepared in excellent yields. Based on the experimental results and a qualitative study of 1D-NMR-experiments, a plausible reaction mechanism is proposed.