KOtBu as a Single Electron Donor? Revisiting the Halogenation of Alkanes with CBr4 and CCl4

Abstract

The search for reactions where KO<i>^t</i>Bu and other <i>tert</i>-alkoxides might behave as single electron donors led us to explore their reactions with tetrahalomethanes, CX₄, in the presence of adamantane. We recently reported the halogenation of adamantane under these conditions. These reactions appeared to mirror the analogous known reaction of NaOH with CBr₄ under phase-transfer conditions, where initiation features single electron transfer from a hydroxide ion to CBr₄. We now report evidence from experimental and computational studies that KO<i>^t</i>Bu and other alkoxide reagents do not go through an analogous electron transfer. Rather, the alkoxides form hypohalites upon reacting with CBr₄ or CCl₄, and homolytic decomposition of appropriate hypohalites initiates the halogenation of adamantane.