Abstract In this contribution, we describe a straightforward and efficient synthesis of oxazolidin‐2‐ones through a Cu(I)‐catalyzed four‐component coupling of amines, aldehydes, terminal alkynes, and CO 2 via carboxylative cyclization of propargylamine intermediates. This strategy enables the selective synthesis of a variety of ( Z )‐5‐alkylidene‐oxazolidin‐2‐ones substituted in positions 3, 4 and 5 of the heterocyclic core with a variety of functional groups, well‐tolerated in terms of scope. A mechanistic study was carried out monitoring the process in solution by different techniques (operando FTIR, multi‐nuclear NMR), with the aim of identifying the intermediates, both organic compounds and Cu(I) coordination complexes, which showed the plausible multi‐metallic nature of the catalytic intermediates (identified by X‐ray diffraction analyses on monocrystal).