We have been investigating titanium(III)-catalyzed reductive couplings for the synthesis of small synthetic building blocks. One of these reactions is a ketonitrile cyclization that leads to valuable hydroxyketones and has been subject to intensive mechanistic studies by my group. Recently, we have been developing a diastereoselective variant that employs substituted precursors and leads to extraordinary selectivity. In order to understand the origin of the diastereoselectivity, a computational investigation of the reaction path will be carried out.