Taken together, these observations suggest that the reactivity of amines in boronic acid-catalysed amidation reactions is affected not only by the nucleophilicity of the amine, but also its ability to stabilise off-cycle inactive species derived from the catalyst. This latter effect becomes particularly important when the amine has low reactivity in the desired amidation reaction and leads to 'negative feedback' as significant quantities of catalyst are sequestered in the off-cycle complex, further suppressing the amidation rate. Although benzylamine is capable of forming a relatively stable off-cycle species, its high nucleophilicity means that amidation still readily occurs. In contrast, whilst aniline has relatively low nucleophilicity it is less able to form a stable off-cycle complex with the catalyst so direct amidation reactions of anilines are usually straightforward. With borate ester catalysts, the formation of stable off-cycle complexes with the amine is less-favourable, so catalyst deactivation is less problematic and amides can be prepared from these challenging amines.