Copper Compounds Vinylcopper reagents

The preparation of a,p-unsaturated ketones by direct acylation of vinylcopper reagents has proven more problematic, since lithium cuprates do add to the product enones. Better results are obtained with the less reactive monovinyl copper compounds in the presence of a palladium catalyst. Alkynic ketones have been prepared by a variation of the Stephens-Castro coupling. ... 

Vinylic bromides. Reaction of vinylcopper reagents (2) with bromine leads to products of oxidation (dienes). However, vinylic bromides can be prepared from (2) by a two-step procedure. For example, (3) undergoes copper-mercury exchange with retention of configuration on treatment with mercuric bromide (0.5 eq.) to give (4) in 74% yield. This compound is converted by bromine in... 

Alkylcoppers, arylcoppers, allylcoppers and vinylcoppers, besides acetylene-coppers, are also able to be used as organocopper reagents. The reactions with organocopper compounds, besides acetylene coppers, are not called the Castro reaction. However, recently these reactions are noted as being highly selective [43-b9]. 

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