Divergent Preparation of Fluoroalkylated Sulfilimine and Sulfilimino Iminium Salts

We have successfully extended our previously described methodology for the preparation of trifluoromethyl N-acyl sulfilimines to the case of bromodifluoro- and dichlorofluoromethyl derivatives. Attempts to convert such N-acyl sulfilimines to free NH-sulfilimines failed. However, a strategy based on the reaction of their direct ditriflyl ketal precursor with amines allows the isolation of either original sulfilimino iminium salts using secondary amines or of free NH-sulfilimines using primary amines. The latter were further easily N-functionalized with electron-withdrawing groups giving structures close to those of efficient perfluoroalkylating agents. Preliminary experiments showed that these new sulfilimine-based compounds have poor perfluoroalkylating abilities, demonstrating that the sulfilimine function is not sufficiently activating for that purpose, contrary to sulfur(VI) reagents.