Kauffmann olefination

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).

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. It is remarkable that the organometallic catalyst tolerates the inorganic reaction products.

References

References

1. (1992). "Organomolybdän- und Organowolfram-Reagenzien, II. über den carbonylolefinierenden μ-Methylenkomplex aus Mo₂Cl₁₀ und vier äquivalenten Methyllithium". Chem. Ber..
2. (1993). "Organomolybdän- und Organowolfram-;Reagenzien, III. Chemoselektive, nichtbasische Carbonylmethylenierungs-;Reagenzien aus MoOCl₃(THF)₂ und MoOCl₄: Bildung, Thermolabilität, Struktur". Chem. Ber..
3. (1993). "Organomolybdän- und Organowolfram-;Reagenzien, IV. über die Chemoselektivität des carbonylmethylenierenden Reagenzes aus 2 MoOCl₃(THF)₂ und 4 CH₃Li". Chem. Ber..
4. T. Kauffmann. (1997). "Neue Reaktionen molybdän- und wolframorganischer Verbindungen: Additiv-reduktive Carbonyldimerisierung, spontane Umwandlung von Methyl- in μ-Methylenliganden und selektive Carbonylmethylenierung". Angew. Chem..
5. (2002). "'One-pot' Reactions: Total Synthesis of the Spirocyclic Marine Sesquiterpene, (+)-Axenol". Synlett.