Unsaturated carbonyl compounds reaction with organocopper reagents

In reactions with a,(3-unsaturated carbonyl compounds, the organocopper reagents prefer 1,4-over 1,2-addition. 

Addition to a, -unsaturated carbonyl compounds is characteristic of organocopper and cuprate compounds, as alkyllithium and Grignard reagents react only with the carbonyl group of enones to give the 1,2-addition products. This synthetically useful reaction has been reviewed by Posner (1972). 

Hahdes of transition metals react with methyllithium to give methyl compounds. This reaction is alternatively afforded by organocopper compounds hke hthiumdialkylcuprates which are also known as Gilman reagents. These reagents are widely used for nucleophilic substitutions of epoxides, alkyl hahdes and for conjugate additions to a,p-unsaturated carbonyl compounds by methyl anion. 

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