Preparation of Imines as Precursors for the Synthesis of Chiral Amines and Hydroxylamines
Titanium coordination compounds with chiral ligands feature prominently in many asymmetric organic transformations requiring a Lewis acid. Asymmetric addition reactions to carbonyl compounds such as benzaldehyde are a well-known example. However, much less is known about titanium mediated asymmetric addition reactions to imine substrates to produce amines and hydroxylamines. Given the significance of these functional groups biologically and in pharmaceutical applications, the synthesis of resolved amines and hydroxylamines is an important area of research. We have been investigating the alkylation of novel prochiral aldimine and ketoimine substrates containing an O-diphenylphosphoryl oxime group in order to directly and asymmetrically produce chiral amines and hydroxylamines. Several imine substrates have been prepared. Catalysis results show that alkylation of the O-diphenylphosphoryl oximes with dialkyl zinc and a titanium Lewis acid catalysts are not as effective as in the alkylation of benzaldehyde, the related N-phosphinoylimine, or the simple imine substrate N-benzylidene aniline.
Bufan Zhang, Vassar College ’17, Mary-Margaret McElduff, Vassar College ’17 and Prof. Joseph M. Tanski