Stereoselective control by face-to-face versus edge-to-face aromatic interactions: the case of C(3)-Ti(IV) amino trialkolate sulfoxidation catalysts.

The stereoselective oxidation of differently functionalised benzyl phenyl sulfides has been examined by using enantiopure Ti(IV) trialkanolamine complexes. These complexes efficiently catalyse the sulfoxidation with good stereoselectivities. The data highlight the contribution to the stereoselectivity of steric effects and non-covalent pi-pi interactions between the aromatic rings of the Ti(IV) complex and those pertaining to the substrates. Enantiomeric excesses have been correlated with the electrostatic potential surfaces (EPS) of the reacting sulfides. The overall study leads to a mechanistic interpretation that explains the stereoselectivity of the system and dissects the role of aromatic and steric interactions in the stereoselective process.