Electrophilic compounds umpolung reduction

From the retrosynthetic point of view, electrochemical redox reactions are an easy way to accomplish the principle of redox-umpolung (polarity reversal) [2]. As can be seen in Scheme 22.1, oxidation of an electron-rich neutral compound will lead to an electrophilic cation radical, or starting with a nucleophilic anion, anodic oxidation may lead to an electrophilic cation. In the mirror image reductions, an electron-poor neutral compound is transformed to a nucleophilic anion radical, or an electrophilic cation will end up as a nucleophilic anion. 

A carbonylation reaction with Ni(CO)4 generating 1,4,7-tricarbonyl compounds has also been published Synthesis of 1,6-dicarbonyl systems via mercury(II) intermediates and radical chain additions to electrophilic olefins has been achieved (equation 70). This sequence constitutes an umpolung if one considers that the carbonyl moiety is masked in siloxycyclopropanes TTireo-juvabione has been synthesized from a methoxycyclo-propane via a mercury(II) salt cleavage/reduction sequence ... 

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