The dynamic chemistry of the boron–nitrogen bond

Here we report that fully reversible B←N bond formation/cleavage is a promising tool for the achievement of dynamic libraries (DLs) of rapidly interconverting compounds. The composition of a number of minimal DLs of adducts between phenylboronic acid catechol ester 1 and a series of nitrogen-based aromatic heterocycles (<i>N</i>ArHets) is demonstrated to be predictable taking into account the association constants related to the formation processes of the single adducts involved. Furthermore, such composition can be controlled over time by the use of activated carboxylic acids (ACAs). Depending on the amount of added ACA, a B←N based DL can be either overturned in terms of composition, transiently overexpressing an adduct initially under-expressed, or transiently fully disassembled into its building blocks.