Organocopper reagents reactions with enones

In many cases a Lewis acid has been added to a cuprate to enhance its reactivity with an enone, but there are also examples for which the Lewis acid-organocopper reagents do not work well, (Scheme 10). Reaction of the bicyclic enonate (24) with Me2CuLi led to smooth conjugate addition,71 but the use of either Me2CuLiBF3 or MeCuBFj resulted in formation of a dark resinous material. It is often difficult to predict when the reaction will go astray, but it should be recognized that a Lewis acid-cuprate complex is not always an effective solution to a reactivity problem. 

Patterson and Fried [139] inserted the a-side chain by alkylation of a cyclo-pentatone enol ether. Intermediate (127) was first obtained by reaction of cyclopent-2-enone with an organocopper reagent followed by formation of the silyl enol ether and the a-chain then added by alkylation of 127 with c/s-7-bromooct-5-enoate, thus leading to ( )-l l-deoxy-PGE2 methyl ester. 

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