Kauffmann olefination explained

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

Formation of the reagent

The reagent was generated in situ by conversion of different halogenides of molybdenum or tungsten 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 have shown that the active reagent is not a Schrock carbene (e.g. Tebbe-reagent).

Mechanism

Mechanism experiments shows that the olefination process is a sequence of cycloaddition and cycloelimination steps.

Applications

For a long time this reaction had no applications in synthetic organic chemistry. In 2002 it was used in a total synthesis of the terpene gleenol as a mild and non-basic reagent in a one-pot-protocol with an olefin metathesis step with Grubbs catalyst.^[5] It is remarkable that the organometallic catalyst tolerates the inorganic reaction products.

Notes and References

1. T. Kauffmann . M. Papenberg . R. Wieschollek . J. Sander . Chem. Ber.. 1992. 125. 143–148. 10.1002/cber.19921250123. Organomolybdän- und Organowolfram-Reagenzien, II. über den carbonylolefinierenden μ-Methylenkomplex aus Mo₂Cl₁₀ und vier äquivalenten Methyllithium.
2. T. Kauffmann . P. Fiegenbaum . M. Papenberg . R. Wieschollek . D. Wingbermühl . Chem. Ber.. 1993. 126. 79–87. 10.1002/cber.19931260114. Organomolybdän- und Organowolfram-;Reagenzien, III. Chemoselektive, nichtbasische Carbonylmethylenierungs-;Reagenzien aus MoOCl₃(THF)₂ und MoOCl₄: Bildung, Thermolabilität, Struktur.
3. T. Kauffmann . J. Baune . P. Fiegenbaum . U. Hansmersmann . C. Neiteler . M. Papenberg . R. Wiescholleck . Chem. Ber.. 1993. 126. 89–96. 10.1002/cber.19931260115. Organomolybdän- und Organowolfram-;Reagenzien, IV. über die Chemoselektivität des carbonylmethylenierenden Reagenzes aus 2 MoOCl₃(THF)₂ und 4 CH₃Li.
4. T. Kauffmann. Angew. Chem.. 1997. 109. 1312–1329. 10.1002/ange.19971091205. Neue Reaktionen molybdän- und wolframorganischer Verbindungen: Additiv-reduktive Carbonyldimerisierung, spontane Umwandlung von Methyl- in μ-Methylenliganden und selektive Carbonylmethylenierung. 12. 1997AngCh.109.1312K.
5. K. Oesterreich . I. Klein . D. Spitzner . Synlett. 2002. 1712–1714. 'One-pot' Reactions: Total Synthesis of the Spirocyclic Marine Sesquiterpene, (+)-Axenol . 10 . 10.1055/s-2002-34211 .