Imination of Sulfides and Sulfoxides with Sulfonylimino‐λ3‐Bromane under Mild, Metal‐Free Conditions

Abstract

Exposure of sulfides and sulfoxides to trifluoromethanesulfonylimino(aryl)-lambda(3)-bromane in dichloromethane at 0 degrees 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 rho 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-lambda(3)-bromane, which involves the attack of a sulfide from the opposite side to bromine(III).