Corey-Fuchs rearrangement

Scientists at DuPont Merck Pharmaceuticals [31] had also developed a new process to prepare 37, based on a modification of the Corey-Fuchs method, from cyclopropylaldehyde, prepared by thermal rearrangement of butadiene monoxide. 

The one-step Seyferth procedure offers an alternative to the Corey -Fuchs sequence. After a Horner-Wadsworth-Emmons olefmation of an aldehyde 37 to an unsaturated diazo compound 38. elimination of nitrogen and [1,2]-rearrangement of the resulting vinylcarbene 39 leads here as well to a Cy-extended terminal alkyne 40.19... 

Fig. 14.32. Aldehyde alkyne chain elongation via [l,2]-rearrangement of a vinyl carbenoid (Corey—Fuchs procedure). The aldehyde and phosphonium ylide A generated in situ undergo a Wittig olefina-tion and form the 1,1-dibro-moalkene (B). In the second stage, the dibromoalkene is reacted with two equivalents of n-BuLi and the vinyl carbenoid D is formed stereoselectively. The carbenoid undergoes H migration to form the alkyne C. The alkyne C reacts immediately with the second equivalent of n-BuLi to give the lithium acetylide and is reconstituted by reprotonation during aqueous workup.

Alkyne 13 was prepared from aldehyde 9 by Corey-Fuchs reaction (10), alkylation (11), 1,2-Wittig rearrangement (12) and silylation reaction. The reaction of alkyne 13 and BuaSnH afforded compound 14 via a 5-exo-dig cyclization and the cleavage of Si-0 bond by MeLi. ... 

Such dibromomethylenation/Br,Li exchange/rearrangement sequences, possibly followed by a C-alkylation in situ—like toward our P-lipomycin candidates—were introduced by Corey, E. J. Fuchs, P. L. Tetrahedron Lett. 1972, 36, 3769-3772. 

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