Organocatalytic Applications of Sulfonyl Squaramides in Anion‐Recognition Strategies

Abstract A modular, 3‐steps protocol for the synthesis of N ‐sulfonyl squaramides has been developed. The strategic installation of a tetrahedral, electron‐withdrawing sulfonyl group into the squaramido core allowed the prevention of undesired self‐aggregations, therefore upgrading the solubility in common organic solvents, and moreover, enhancing their H‐bond donor abilities for molecular recognition. These unique features have been efficiently exploited in two different ion‐pairing reactions: ( i ) the challenging C4‐selective dearomatization of 2‐picoline with silyl ketene acetals and ( ii ) the tritylation of N ‐methylindole. Furthermore, their catalytic activities have been directly compared with other common and well‐established (thio)urea analogues and related H‐bond donors, revealing that highly acidic designs are essential to reach optimal catalytic performances.