Nucleophilic Fluoroalkylation of α,β-Unsaturated Carbonyl Compounds with α-Fluorinated Sulfones: Investigation of the Reversibility of 1,2-Additions and the Formation of 1,4-Adducts

A detailed investigation of the reactions of PhSO2CF2H and PhSO2CH2F with (E)-chalcone (=(E)-1,3-diphenylprop-2-en-1-one) at low temperatures revealed that these two reactions were kinetically controlled, and the ratios of 1,2- vs. 1,4-adducts, which did not change much over time at these temperatures, reflect the relative rates of the two reaction pathways. The controlled experiments of converting the PhSO2CF2- and PhSO2CHF-substituted 1,2-adducts to 1,4-adducts showed that these isomerizations are not favored due to the low stability and hard-soft nature of PhSO2CF(2)(1) and PhSO2CHF- anions. Moreover, taking advantage of the remarkable stability and softness of (PhSO2)2CF- anion, an efficient thermodynamically controlled isomerization of (PhSO2)2CF-substituted 1,2-adduct to 1,4-adduct was achieved for the first time.