Protodeboronation

[4][5] One of the earliest reports of protodeboronation was made by Ainley and Challenger, who were the first researchers to explore the reactivity of boronic acids with common chemical reagents.

In particular, boronic acids have become increasingly important reagents for the facile construction of carbon-carbon and carbon-heteroatom bonds via metal-catalysed cross-coupling reactions.

The mechanism of protodeboronation was initially investigated by Kuivila in the 1960s, long before the discovery of the Suzuki reaction and the popularisation of boronic acids.

Substrates that display only these two modes of protodeboronation (typically simple aromatic and alkyl boronic acids) are generally very stable in neutral pH solution, where both acid- and base-catalysed processes are minimised.

For aromatic boronic acids bearing electron-withdrawing substituents, there is a competing dissociative mechanism involving generation of a transient aryl anion.

For the 2-pyridine boronic acid, the zwitterionic compound is responsible for its rapid protodeboronation under neutral pH, through a unimolecular fragmentation of the C-B bond.