Selective Electrochemical Hydrocarboxylation of Vinyl Phosphonates with CO ₂ Enabled by Alternating Polarity

Electrochemical hydrocarboxylation of vinyl phosphonates with CO 2 to form carboxylic‐substituted phosphonates is developed. The alternating polarity affords a boost in Faraday efficiency and enables generalizable catalytic control to provide high product yields over a broad substrate scope by maintaining electrode activity through the regeneration of its surface. The disclosed method provides high selectivity of the target hydrocarboxylation without side transformations of vinyl phosphonates in an undivided cell affording a short way to valuable carboxylic acids featuring a phosphonate fragment. The high selectivity of hydrocarboxylation is achieved through the integration of an alternating polarity strategy with an efficient sequence of one‐electron reduction, followed by CC bond formation, subsequent second one‐electron reduction, and protonation. These results establish the utility of the alternating polarity technique and provide a foundation for its adaptation to other electrochemical reactions.