Fuchs Alkyne Synthesis

CBr4 (2 equiv) / PhsP (2 equiv) Zn dust (2 equiv) CH2CI2/O °C, 1-2h 80-90% 

The mechanism of dibromoolefin formation from the aldehyde is similar to the mechanism of the Wittig reaction. However, there is very little known about the formation of the alkyne from the dibromoolefin. The mechanism below is one possible pathway to the observed product. 

In the laboratory of J.H. van Boom, the synthesis of highly functionalized c/s- and frans-fused polycyclic ethers of various ring sizes via radical cyclization of carbohydrate-derived p-(alkynyloxy)acrylates was developed/ The radical cyclization precursors were prepared iteratively and the terminal alkyne moieties were installed using the Corey-Fuchs procedure. 

The total synthesis of Galubulimima alkaloid 4,4a-didehydrohimandravine, using an intramolecular Diels-Alder reaction and a Stille coupling as the key steps, was accomplished in the laboratory of M.S. Sherburn. The required vinylstannane intermediate for the Stille coupling was prepared via the one-pot Corey-Fuchs reaction, followed by radical hydrostannylation. 

Kerr and co-workers carried out the total synthesis of (+)-taylorione starting from readily available (+)-2-carene and using a modified Pauson-Khand annulation with ethylene gas as the key step. The key terminal alkyne intermediate was prepared by the Corey-Fuchs reaction. Interestingly, the ketal protecting group was sensitive to the excess of CBr4, so the addition of this reagent had to be monitored carefully to cleanly transform the aldehyde to the desired dibromoolefin. 

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W. Oppolzer et al. utilized the Corey-Fuchs alkyne synthesis for the preparation of a key acyclic enynyl carbonate during the total synthesis of (+)-hirsutene. ... 

The stereoselective synthesis of the C5-C20 subunit of the aplyronine family of polyketide marine macrolides was accomplished by J.A. Marshall and co-workers. The C15-C20 moiety was prepared using the original Seyferth-Gilbert homologation conditions. The diazophosphonate was deprotonated with potassium fert-butoxide at low temperature, and then the solution of the aldehyde was added slowly also at low temperature. Interestingly, the alternative Corey-Fuchs alkyne synthesis was unsuccessful on this substrate, since extensive decomposition was observed. 

Corey-Fuchs alkyne synthesis One-carbon homologation of aldehydes to form the corresponding terminal alkynes. 104... 

Related reactions Corey-Fuchs alkyne synthesis ... 

Corey-Fuchs alkyne synthesis can be seen as a cousin of the Wittig olefin synthesis. 

Intermediate 143 having secured, the synthesis was carried on by deprotection to form the primary alcohol 144 (Scheme 25) which was oxidized to the aldehyde 145 and converted into the envisaged alkyne (corresponding to 139) via a Corey Fuchs chain elongation via dibromide 146. 

The presence of halogen atoms in a molecule is compatible with formation of an ylid and subsequent Wittig reaction. Carbon tetrabromide and triphenylphosphine have been used to give vinyl dibromide products, which are rapidly converted to the corresponding alkyne. Indeed, this is an important synthetic route to alkynes called the Corey-Fuchs procedure. The reaction of 511 with this reagent gave vinyl dibromide 512 in 77% yield as part of Marshall s synthesis of callystatin When 512 was treated with butyllithium... 

A general one-pot procedure for the synthesis of alkynes from aldehydes (Corey-Fuchs reaction) that involves the synthesis of the triphenylphosphonium dibromomethane reagent has been explored by Michel and coworkers. In general, the base of choice is f-BuOK, but in case of the N-Boc piperidine, use of BuLi in order to avoid unwanted side reactions between the carbamate and the acetylide function provides a cleaner reaction at low temperature (eq 64). 

Ene-yne metathesis has been employed in an elegant synthesis of stemoamide 8.415 (Scheme 8.112). The starting lactam 8.407, available itself from glutamic acid, was iV-alkylated, then subjected to deprotection, Swern oxidation and application of the Corey-Fuchs method for installation of an alkyne by Wittig... 

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