Acetylenes Sonogashira reactions, copper® iodide

Cacchi- and Sonogashira-Hagihara couplings occur only if a primary, secondary, or tertiary amine is present, and it is best to have the amine present in large excess. Under these conditions the acetylene will at least form a small equilibrium concentration of the corresponding ammonium acetylide or copper complex thereof. The copper iodide serves to trap this species as a copper acetylide. The copper acetylide represents a substantially improved nucleophile in comparison to the free acetylene. Without the Cul addition, the acetylide content of the reaction mixture is so small that a reaction occurs only at higher temperatures. 

In 2008 Bhanage s team reported on a copper-catalyzed carbonylative Sonogashira reaction of aryl iodides [68]. In this procedure, copper bis(2,2,6,6-tetra-methyl-3,5-heptanedionate) [Cu(TMHD)2] was used as the catalyst for this transformation and using NEta as a base. Alkynones were produced in good yields (Scheme 5.33). A nickel-catalyzed carbonylation of allyl halides and acetylenes was reported on by Moreto and colleagues [69]. Cyclopentane skeletons were produced in high yields and with controlled stereochemistry. 

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