Acetylene Corey-Fuchs reaction

Steps 1-2 Conversion of a ketone to a terminal alkyne (compare with Corey-Fuchs reaction where an aldehyde is converted to a terminal alkyne). Step 4 Me2CuLi adds to the acetylenic ester in a conjugate manner to provide (Z)-olefin. 

In their total synthesis of 6,7-dehydrostipiamide, Negishi prepared acetylene 8 (Cs-Cis subunit) by the Corey-Fuchs reaction. 

Corey-Fuchs reaction has also been employed to make pharmaceutically interesting compounds. The treatment of bromo-acetylene 20 with /-BuLi and the quench of resulting lithium alkylanide with phenyl isocyanate produced amide 21. After SEM removal, NMDA receptor antagonist 22 for stoke therapy was obtained. ... 

There are also wide spread application of the Corey-Fuchs reaction in the material science, since dibromoalkenes and terminal acetylenes are well suited for Pd-catalyzed reactions to make highly conjugated linear and branch compounds. For example, acetylene 27 was made by the Corey-... 

The reaction sequence in steps two and three is known as the Corey-Fuchs method to create an alkyne from an aldehyde 10 Reaction of triphenylphosphane with carbontetrabromide gives phenylphosphane-dibromomethylene. This reagent then transforms aldehyde 19 into the corresponding dibromoalkene 20 thereby extending the chain by one carbon. Reaction of the bromo compound with two equivalents of n-butyllithium in THF at -78 °C results in the rapid formation of the acetylenic lithio derivative which forms the terminal acetylene 21 upon aqueous work-up. 

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