Novel and practical preparation of α-fluoro-functionalized esters from fluoroiodoacetates

Abstract

The addition reaction of fluoroiodoacetates 2 to various electron-rich alkenes 3 initiated by iron powder in dry THF at 70–80 °C gave 1 : 1 adducts 4 in good yields. A variety of functionalities in the alkenes such as trimethylsilyl, alkoxy, acetoxy, hydroxy and ester could be tolerated under the reaction conditions. Reduction of the adducts 4 with Zn–AcOH in ethanol or Zn–NiCl₂·6H₂O in moist THF was readily accomplished, and the overall procedure was amenable to a convenient one-flask procedure. Treatment of fluoroiodoacetates 2 with electron-deficient alkenes 7 in the presence of an Fe–CrCl₃·6H₂O– bpy bimetal redox system in ethanol at 70–80 °C resulted in the formation of iodine-free 1:1 adducts 8 in moderate to good yields. It is proposed that the addition reactions of fluoroiodoacetates 2 to electron-rich and electron-deficient alkenes proceeded through a single-electron-transfer mechanism.