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

Exposure of sulfides and sulfoxides to trifluoromethanesulfonylimino(aryl)‐λ³‐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‐λ³‐bromane, which involves the attack of a sulfide from the opposite side to bromine(III).     

Carbene‐Stabilized Phosphenium Oxides and Sulfides

Carbene→chalcogenophosphenium adducts, which correspond to an intermolecular stabilization mode of the so far elusive, free oxo‐ and thiooxophosphenium species [R₂P⁺ = X] (X=O, S) by imidazolylidene (NHC) and diaminocyclopropenylidene (BAC) donors, have been isolated and fully characterized. The dative character of the R₂C:→P⁺(X)Ph₂ bond was confirmed experimentally by nucleophilic displacement of the carbene donor with a chloride ion and by an exchange reaction of the NHC ligand of the NHC:→P⁺(O)Ph₂ adduct with an independently prepared BAC ligand, thereby giving the BAC:→P⁺(O)Ph₂ adduct. This dative character was further characterized by the DFT‐calculated preference of carbene→chalcogenophosphenium systems for a heterolytic dissociation mode over a homolytic one.