Atroposelective Electrophilic Sulfenylation of N-Aryl Aminoquinone Derivatives Catalyzed by Chiral SPINOL-Derived Sulfide.

Atroposelective electrophilic sulfenylation of N-aryl aminoquinone derivatives has been achieved for the first time. This transformation is enabled by a new chiral 6,6'-disubstituted SPINOL-derived sulfide catalyst, which was first synthesized and then successfully explored for catalyzing enantioselective reactions. Various axially chiral sulfur-containing diarylamine derivatives were readily obtained in moderate to excellent yields with moderate to excellent enantioselectivities. A class of relatively flexible stereogenic C-N axes was easily constructed. The experimental results and a computational study suggested that an intramolecular N-H⋅⋅⋅S hydrogen bond is important for the stability of the C-N axis, which is consistent with our hypothesis. Density functional theory calculations revealed the origin of atroposelectivity and underscored the importance of catalyst rigidity in this sulfenylation reaction.