Dynamic Amide Formation by Reversible Nitrone Exchange of Potassium Acyltrifluoroborates (KATs) and Hydroxylamines in Aqueous Conditions

The condensation of potassium acyltrifluoroborates (KATs) and hydroxylamines occurs under ambient, aqueous conditions to form KAT nitrones in a reversible manner. The KAT nitrones exchange rapidly under aqueous acidic conditions, resulting in a dynamic covalent library that can be converted to the corresponding static amides by treatment with strong acid. Extensive studies on the conditions and kinetics show that – counterintuitively – KAT nitrone formation is accelerated by water. The overall process serves as a dynamic system operating at room temperature under aqueous conditions with the rare ability of trapping the mixture into stable secondary amides.