Nucleophilic catalysis is a mode of catalysis in which a nucleophilic species adds reversibly to an electrophilic functional group, generating a covalently activated intermediate that undergoes subsequent transformation more rapidly than the uncatalyzed substrate ^[1][2]. In asymmetric synthesis and catalysis the concept is bounded by turnover: the nucleophilic catalyst must be released after the bond-forming event so that it is not consumed as a stoichiometric reagent. Essential features include a nucleophilic atom (commonly nitrogen, phosphorus, or carbon in an N-heterocyclic carbene or related heterocycle), a defined addition–elimination or addition–transfer sequence, and, in enantioselective variants, a chiral catalyst architecture that differentiates the faces of the activated intermediate ^[3]. Typical electrophiles are acyl donors, aldehydes, and imine-type carbonyl analogues. Anilinium and related nucleophiles accelerate oxime ligation and hydrazone formation by forming a more reactive iminium or Schiff-base intermediate that then undergoes transimination ^[1][2]. 4-(Dialkylamino)pyridines operate by nucleophilic addition to acylating agents to give an N-acylpyridinium ion whose reactivity and selectivity depend on the substitution pattern of the pyridine ^[4]. The concept is distinguished from general-base catalysis, in which the catalyst only abstracts a proton, and from Lewis-acid catalysis, in which activation occurs by coordination rather than by covalent addition.