Lewis Acid-Assisted Formal C═S Insertion of Thioindolinones to Bicyclobutanes: Diastereoselective Access to Trisubstituted Cyclobutanethiols

Although a variety of nucleophilic approaches have been utilized to access substituted cyclobutanes, the synthesis of cyclobutanethiols remains underexplored within the realm of bicyclo[1.1.0]butane (BCB) chemistry. Herein, we report a Lewis acid-assisted C═S insertion of thioindolinones into BCBs, enabling efficient access to a diverse range of 1,3,3-trisubstituted cyclobutanethiols in high diastereoselectivity. The transformation proceeds via a Lewis acid-promoted cascade comprising the (3 + 2) annulation of BCBs with the C═S moiety of thioindolinones followed by the aromaticity-driven ring-opening sequence.