Tropos Aminoalcohol Mediated Enantioselective Aryl Transfer Reactions to Aromatic Aldehydes

The preparation of new chiral amino alcohols that possess a flexible biphenylazepine moiety and can work as tropos catalysts, is presented. In these compounds, the sign of the induced axial chirality depends on the nature of stereogenic centers near the flexible fragment and can determine the stereochemical outcome in asymmetric reactions mediated by them. The efficiency of these new ligands has been explored in the asymmetric addition of arylzinc species prepared in situ to aromatic aldehydes. Among them, amino alcohol (1R,2S)-4 gave the best results and afforded optically active diarymethanols, which are precursors of well-known chiral drugs, in high yields and with enantioselectivity up to 96%.