Transition Metal-free gem-difluorocyclopropanation of Alkenes with CF3SiMe3-NaI System: a Recipe for Electron-deficient Substrates

Reaction of various electron-deficient alkenes, as well as functionalized styrene derivatives with CF3SiMe3-NaI system is studied. Relative reactivity of the substrates is established. It is shown that many alpha,beta-unsaturated esters can be difluorocyclopropanated efficiently under slow addition protocol conditions, which provides access to mono- and spirocyclic gem-difluorocyclopropyl-substituted carboxylic acids with good yields (36-79% for two steps) on up to 100 g scale.