Imination of Sulfides and Sulfoxides with Sulfonylimino‐λ 3 ‐Bromane under Mild, Metal‐Free Conditions

Exposure of sulfides and sulfoxides to trifluoromethanesulfonylimino(aryl)‐λ 3 ‐bromane in dichloromethane at 0 °C results in a facile transfer of the sulfonylimino group to sulfur atoms and affords N ‐triflylsulfilimines and ‐ sulfoximines in high yields under transition‐metal‐free conditions. Imination of ( R )‐methyl p ‐tolyl sulfoxide proceeded with predominant retention of configuration at the stereogenic sulfur center. The Hammett plot afforded ρ values of −0.58 for para ‐substituted thioanisoles and −0.49 for their equivalent sulfoxides, which suggests a buildup of positive charge on the sulfur atoms of sulfides and sulfoxides in the transition state. Calculations suggest a bimolecular nucleophilic‐substitution mechanism on the negatively charged nitrogen atom of the sulfonylimino‐λ 3 ‐bromane, which involves the attack of a sulfide from the opposite side to bromine(III).