Lithium dialkyl cuprates R2CuLi

A different outcome is observed when a lithium dialkyl cuprate (R2CuLi) is employed. 

What if the ketone is the desired product We have a problem here, because the Grignard reagent will attack twice. We can t stop it from attacking twice. If we just try to use exactly one equivalent of the Grignard reagent, we will observe a mess of products (some molecules of the acid halide will get attacked twice, and others will not get attacked at all). In order to prepare the ketone, we need a carbon nucleophile that will only react with an acid halide, but will not react with a ketone. And we are in luck, because there is a class of compounds that will do exactly that. They are called lithium dialkyl cuprates (R2CuLi). 

R2CuLi /C=C lithium dialkyl cuprate (Gilman reagents) enamine O II H2C=CH —C —H O II H2C=CH—C—R conjugated aldehyde conjugated ketone... 

R2CuLi 2) HsO Michael reaction A lithium dialkyl cuprate is a weak nucleophile and can serve as a Michael donor. It will react with a suitable Michael acceptor (see Table 22.2). 

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