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

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  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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