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A strategy for the construction of spiro[cycloalkane-1,3′-1′λ⁶-isothiazolidine]-1′,1′,4′-triones through the sulfonylation of 1-aminocyclopropane- and 1-aminocyclobutanecarboxylates with methanesulfonyl chloride followed by alkylation with methyl iodide and subsequent cyclization in the presence of potassium tert-butoxide in N,N-dimethylformamide is reported. An efficient synthesis of starting 1-aminocyclopropane- and 1-aminocyclobutanecarboxylic acids was developed. The reaction of spiro[cycloalkane-1,3′-1′λ⁶-isothiazolidine]-1′,1′,4′-triones with N,N-dimethylformamide dimethyl acetal (DMFDMA) gives 5′-[(Z)-(dimethylamino)methylene]spiro[cycloalkane-1,3′-1′λ⁶-isothiazolidine]-1′,1′,4′-triones, the structure of which was confirmed by X-ray diffraction study.