A modular dehomologation strategy, which skeletally remodels cyclic α-substituted eneformamides to one-carbon shorter α-ketonyl saturated cyclic amines is described. The approach hinges on N-iodosuccinimide-assisted C–halogen bond formation followed by C–N bond cleavage to arrive at α-iodo ketones, which undergo base-mediated cyclization. An intramolecular C(sp³)–H amination of in situ-generated N-iodo tethered ketones also affords the desired α-ketonyl cyclic amines. The transformation is applicable to an array of α-functionalized eneformamides, but some chemoselective challenges were encountered with a few substrates.