Mechanistic insight into the thermal activation of Togni's trifluoromethylation reagents

Abstract

Herein we investigate the propensity of hypervalent iodine based electrophilic trifluoromethylating agents to undergo thermally induced fragmentation of the F₃C–I–O motif. For the first time we are able to observe a dissociative electron transfer mechanism using mass spectroscopy techniques to generate and trap CF₃ radicals. Consistent with this mechanism, alkyl radical elimination from these reagents is in full support of an intermediate cyclic iodanyl radical and a reagent-specific temperature of maximum radical production was found to correlate with reported solution phase reactivity.