Titanium-promoted enantioselective diethylzinc addition to benzaldehyde in the presence of C2-symmetrical bis(camphorsulfonamide) ligands

The synthesis of several C2-symmetric bissulfonamides is described, starting from camphorsulfonyl chloride and various aromatic as well as aliphatic diamines. These compounds have been used as ligands for titanium tetraisopropoxide promoted diethylzinc addition to benzaldehyde. The best enantiomeric excess obtained in this study was 67%. The stereochemical outcome of the reaction is highly influenced both by the structure of ligand and the reaction parameters.