Saturated heterocycles are privileged scaffolds in bioactive molecules1. Despite the availability of numerous de novo routes to various heterocyclic compounds, accessing diverse heterocycles from a unified, readily available carbocycle would offer a strategic alternative for constructing challenging heterocyclic structures from unconventional precursors2. Here we report a modular approach that transforms a single cyclic ketone into various saturated heterocycles through formal carbonyl replacement with heteroatoms, by a scarcely explored bis(aroylperoxy) ketal intermediate. Through electronically guided peroxy cleavage, this intermediate enables double C–C bond scission of cyclic ketones, generating alkyl dichlorides as versatile handles for modular N/O/S/Se/Te incorporation using simple nucleophiles. This method exhibits broad substrate scope and functional-group tolerance, enabling both accelerated target synthesis and late-stage diversification of bioactive molecules. Its utility is also extended through ‘ring construction–carbonyl replacement’ and ‘ring functionalization–carbonyl replacement’ strategies, in which cyclic ketones prepared by well-established methods are converted into challenging-to-access heterocycles for which analogous methods remain underdeveloped. By combining C–H oxidation with carbonyl replacement, a proof-of-concept formal ‘CH2-to-heteroatom’ conversion is further demonstrated.
