Kauffmann olefination

The Kauffmann olefination is a chemical reaction to convert aldehydes and ketones to methylene-olefins. This reaction was discovered by the German chemist Thomas Kauffmann and is related to the better known Tebbe olefination or Wittig reaction.

Contents

Formation of the reagent

The reagent was in situ-generated by conversion of different Molybdenum- or Tungsten-halogenides with methyllithium at low temperatures (-78°C).[1][2][3][4]

During the warm-up process the formation of the active reagent occurs. nmr-experiments has shown that the active reagent is not a Schrock carbene (e.g. Tebbe-reagent).

Mechanism

Mechanism experiments shows that the olifination process is a sequence of cycloaddition and cycloelemination steps.

Application

For a long time there wasn't any usage of this reaction in the synthetic organic chemistry. In the year 2002 it was used in a total synthesis of the terpene gleenol as a mild and non-basic reagent.[5] An one-pot-protokol with an olefinmetathese-step with Grubbs catalyst is also available.[6] Remarkable is that the metallorganic catalyst tolerates the inorganic reaction products.

References

  1. ^ T. Kauffmann, M. Papenberg, R. Wieschollek, J. Sander: In Chem. Ber. 1992, 125, 143-148
  2. ^ T. Kauffmann, P. Fiegenbaum, M. Papenberg, R. Wieschollek, D. Wingbermühl: In Chem. Ber. 1993, 126, 79-87
  3. ^ T. Kauffmann, J. Braune, P. Fiegenbaum, U. Hansmersmann, C. Neiteler, M. Papenberg, R. Wiescholleck: In Chem. Ber. 1993, 126, 89-96
  4. ^ T. Kauffmann: In Angew. Chem. 1997, 109, 1312-1329
  5. ^ K. Oesterreich, D. Spitzner: In Tetrahedron 2002, 58, 4331-4334
  6. ^ K. Oesterreich, I. Klein, D. Spitzner: In Synlett 2002, 1712-1714