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

Dmitry Tsvelikhovsky; Herbert Schumann; Jochanan Blum

doi:10.1055/s-2006-942379

PAPER

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

Dmitry Tsvelikhovsky^a, Herbert Schumann^b, Jochanan Blum*^a
^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;

Abstract

All articles of this category

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.

Key words

cerium(IV) compounds - C-ethylation - lanthanides, Schiff bases - triethylaluminum

Full Text

References

1 Eisch JJ. In Comprehensive Organometallic Chemistry Vol. 1: Wilkinson G. Stone FGA. Abel EN. Pergamon Press; Oxford UK: 1982. Chap. 6. and references therein

2a Alberola A. Cermeño FA. Anton A. An. Quim. 1977, 73: 886

2b Schumann H. Kaufmann J. Dechert S. Schmalz H.-G. Tetrahedron Lett. 2002, 43: 3507

3 Denhez C. Vasse J.-L. Szymoniak J. Synthesis 2005, 2075

4 Tsvelikhovsky D. Gelman D. Molander GA. Blum J. Org. Lett. 2004, 6: 1995

5 Shenglof M. Gelman D. Molander GA. Blum J. Tetrahedron Lett. 2003, 44: 8593

6 Blum J. Rosenfeld A. Gelman F. Schumann H. Avnir D. J. Mol. Catal. A: Chem. 1999, 146: 117

7 Kim S.-J. Yang N. Kim D.-H. Kang SO. Ko J. Organometallics 2000, 19: 4036

8 Reinheckel H. Haage K. Jahnke D. Organomet. Chem. Rev., Sect. A 1969, 4: 47

9 Baciocchi E. Del Giacco T. Murgia SM. Sebastiani GV. Tetrahedron 1988, 44: 6651

10 Friestad GK. Tetrahedron 2001, 57: 5461 ;and references therein.

11 Vázquez M. Landa M. Reyes L. Miranda R. Tamariz J. Delgado F. Synth. Commun. 2004, 34: 2705

12 Csaszar J. Acta Phys. Chem. 1986, 32: 17

13 Thomas J. Henry-Bash E. Fréon P. Bull. Soc. Chim. Fr. 1969, 109

14 Csaszar J. Bizony M. Magy. Kem. Foly. 1997, 103: 29

15 Aitken RA. Thomas AW. Arkivoc 2002, (iii): 71

16 Koslo NG. Basalaeva LI. Russ. J. Gen. Chem. (Engl. Transl.) 2001, 71: 250