Zinc, bromo reaction with alkynes

Similarly, l-bromo-l,l-difluoro-2-alkynes, which were prepared by the reaction of lithium acetylides with CF2ClBr [284] or CF2Br2 [285], also reacted with carbonyl compounds in the presence of zinc to afford the corresponding a,a-difluoropropargyl alcohol [285]. This reaction has been utilized for the preparation of 3-fluoro-2,5-disubstituted furans [286] and other fluorinated biologically active compounds [285,287] (Scheme 99). 

Polyfunctional zinc-copper reagents react efficiently with 1-bromo- or I-iodoaUcynes furnishing functionalized alkynes in good yields. The reaction proceeds at low temperature (—65 °C to —55 °C) and has been applied to the preparation of pheromones (Scheme 9-23 [53]) and polyfunctional acetylenic ethers [54]. 

Ohgofunctional zinc-copper reagents such as 110 react efficiently with 1-bromo-and l-iodoalkynes to furnish functionahzed aUcynes such as 111 in good yields (Scheme 4.25). Presumably, the reaction mechanism consists of a two-step sequence involving carbocupration of the alkyne followed by fS-elimination of copper hahde [115]. Regardless of this, the transformation is of synthetic utility... 

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