Corey-Fuchs reaction

The Corey-Fuchs reaction is a chemical reaction that is used to prepare alkynes 5 from aldehydes 3 . It is named after its discoverers Elias James Corey and Philip L. Fuchs . The following scheme shows an overview of the reaction without the leaving groups:

mechanism

The Corey-Fuchs reaction is a two-step synthesis . In the first stage, a doubly brominated phosphor ylide is produced in situ from triphenylphosphine 1 , tetrabromomethane 2 and zinc . The ylid reacts with the aldehyde 3 in a Wittig reaction to form a 1,1-dibromo alkene 4 .

n -butyllithium (BuLi) abstracted from the geminal dibromo alkene 4 a bromide to give stereoselectively forms a Vinylcarbenoid intermediate. The Vinylcarbenoid goes down migration of a hydrogen atom into an alkyne, with the second equivalent of n reacts immediately butyllithium to lithium acetylide. In the case of aqueous work-up, reprotonation produces the terminal alkyne 5  :

For the implementation of the dibromo alkene 4 to the alkyne 5 , different mechanistic descriptions can also be found in the literature.

Individual evidence

1. ↑ EJ Corey, PL Fuchs: A synthetic method for formyl → ethynyl conversion (RCHO → RC – CH or RC – CR ′). In: Tetrahedron Letters. 13, No. 36, 1972, pp. 3769-3772, doi : 10.1016 / S0040-4039 (01) 94157-7 .
2. ↑ Reinhard Brückner: reaction mechanisms . 3rd edition, Spektrum Akademischer Verlag, Munich 2004, ISBN 3-8274-1579-9 , pp. 615–616.
3. ↑ Bradford P. Mundy, Michael G. Ellerd, Frank G. Favaloro, Jr .: Name Reactions and Reagents in Organic Synthesis , John Wiley & Sons, 2nd Edition (2005) pp. 176-177, ISBN 0-471-22854 -0 .