Dmitry Tsvelikhovsky - Cerium(IV)-Promoted Ethylation of Schiff Bases by Triethylaluminum

Version 1

      Publication Details (including relevant citation   information):

      Synthesis 2006, 11, 1819–1822

      Dmitry  Tsvelikhovsky, Herbert Schumann, Jochanan Blum*

     

      a Department of Organic Chemistry, The Hebrew University,   Jerusalem 91904, Israel

      Fax +972(2)6513832; E-mail: jblum@chem.ch.huji.ac.il

      b Institut für Chemie, Technische Universität, 10623 Berlin,   Germany

      Fax +49(30)31422168; E-mail: schumann@chem.tu-berlin.de

     

      Received 12 January 2006; revised 10 February 2006

      Abstract:

      Schiff bases Ar1CH=NAr2 that are refractory towards

      Et3Al are activated at room temperature by cerium(IV) compounds.

      The ethylation takes place selectively at the methine moiety of   the

      imine. The process is strongly influenced by steric hindrance and

      depends on the electronic nature of the substrate:   electron-donating

      substituents promote the reaction while electron-withdrawing

      groups cause it to slow down. Application of cerium(IV) ammonium

      nitrate as promoter gives the best results. In the absence of   excess

      Et3Al it causes, however, transformation of the Schiff base to

      the corresponding aldehydes and amines.

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