Synthesis of Novel 3  <i>a</i> ‐Substituted Tetrahydro‐1 <i>H</i> ‐1λ ⁶ ‐pyrrolo[1,2‐ <i>b</i> ]isothiazole‐1,1,3(2 <i>H</i> )‐triones through the CSIC Reaction

Abstract We report a strategy for the construction of tetrahydro‐1 H ‐1λ 6 ‐pyrrolo[1,2‐ b ]isothiazole‐1,1,3(2 H )‐triones bearing the substituents at the 5‐ and/or 3a‐positions. To this purpose, a range of 2‐substituted and 2,4‐disubstituted methyl 2‐pyrrolidinecarboxylates were sulfonylated with methanesulfonyl chloride and the resulting sulfonamides were subjected to sulfa‐Dieckmann condensation through the CSIC (Carbanion mediated Sulfonate (Sulfonamido) Intramolecular Cyclization) reaction to give the desired 1λ 6 ‐isothiazolidine‐1,1,4‐triones. All the precursors, as well as target compounds, could be synthesized in a multigram scale following the general protocols.