Doering-LaFlamme-Allen synthesis
The Doering-LaFlamme-Allen synthesis is a name reaction from organic chemistry . The reaction is named after the American chemist W. von E. Doering and PM LaFlamme and was published in 1958. The Doering-LaFlamme-Allen synthesis enables the synthesis of allenes from olefins in two steps.
Overview reaction
In the first step, a trihalomethane is added to the olefin via a reactive intermediate in the form of a carbene . In the second step, the allene is synthesized using a metal or a metal compound.
Reaction mechanism
The following mechanism is described in the literature.
An unstable carbanion 2 is initially formed from tribromomethane ( 1 ) by deprotonation with a strong base . By eliminating a bromide ion, the reactive dibromocarbene 3 is formed :
The dibromocarbene 3 then attaches to the double bond of the olefin 4 , so that the dibromocyclopropane 5 is formed. Via a metal-halogen exchange, e.g. B. with an alkyllithium, the allene 6 is finally formed .
further reading
- Efthimios Chinoporos: Carbenes. Reactive Intermediates Containing Divalent Carbon. In: Chem. Rev. 63, 1963, pp. 235-255, doi: 10.1021 / cr60223a002 .
- Christian E. Janßen and Norbert Krause: Studies on the Synthesis of Macrocyclic Allenes by Ring Closing Metathesis and Doering – Moore – Skattebøl Reaction. In: Eur. J. Org. Chem. 2005, pp. 2322-2329, doi: 10.1002 / ejoc.200500096 .
- Kay M. Brummond and Jolie E. DeForrest: Synthesizing Allenes Today (1982-2006). In: Synthesis . 2007, pp. 795-818, doi: 10.1055 / s-2007-965963 .
Individual evidence
- ^ W. von E. Doering and PM LaFlamme: A two-step of synthesis of allees from olefins In: Tetrahedron . 2, 1958, pp. 75-79, doi: 10.1016 / 0040-4020 (58) 88025-4 .
- ^ W. von E. Doering and A. Kentaro Hoffmann: The Addition of Dichlorocarbene to Olefins In: J. Am. Chem. Soc. 76, 1954, pp. 6162-6165, doi: 10.1021 / ja01652a087 .
- ↑ László Kürti and Barbara Czako: Strategic Applications of Named Reactions in Organic Synthesis , Elsevier, 2005, ISBN 9780080575414 , pp. 146–147.