Introduction of an amino group into a carbon framework constitutes amine synthesis in organic chemistry. The new C–N bond may be formed by nucleophilic substitution of an alkyl electrophile by ammonia or an amine, by reductive amination of a carbonyl, by hydroamination of an unsaturated hydrocarbon, or by addition of a carbon nucleophile to an imine or iminium ion. Biocatalytic variants, including transaminases and related enzymes, produce enantioenriched amines by transferring an amino group to a prochiral ketone ^[1]. Carbonyl alkylative amination combines a carbonyl, an amine, and an alkyl fragment in one operation to generate a tertiary amine without prior isolation of an imine ^[2]. The conceptual boundary is construction of the C–N linkage that defines the amine, not subsequent N-functionalization of an already formed amine (acylation, sulfonylation) and not biosynthetic decarboxylation of amino acids except insofar as those processes also create an amine. Primary, secondary, and tertiary amines differ by the number of carbon substituents on nitrogen, and synthetic design is classified by which of those substitution patterns is generated in the key C–N-forming step.