Ch18: Organocopper reagents

Chapter 18: Enols and Enolates

Conjugate Addition with Organocopper reagents

conjugate addition of organocopper reagents

Reaction type : Nucleophilic Addition

Summary

Organolithium cuprates, R₂CuLi are particularly useful for conjugate or 1,4-addition to α,β-unsaturated aldehydes and ketones.
Lithium dialkylcuprates are formed from organolithium compounds (review)

Other organometallic reagents such as alkyl lithiums tend to undergo direct or 1,2-addition, while Grignard reagents may give mixtures of 1,2- and 1,4-addition depending on the system.

STUDY TIPS:

Remember that like enolates, organometallic compounds are a source of nucleophilic C systems e.g. RMgX is equivalent to R^-
So it is "useful" to impose ionic character on organometallics e.g. RMgX is equivalent to R^-Mg2+ X^-or R₂CuLi is equivalent to (R^-)₂Cu+ Li+

Related reactions

MECHANISM OF THE ORGANOCUPRATE ADDITION*
Step 1: The nucleophilic C in the cuprate attacks the conjugated ketone at the electrophilic alkene C in a nucleophilic addition type process with the electrons being pushed through to the electronegative O, giving an intermediate enolate.
Step 2: On acidic work-up, the enolate is protonated at the α-C creating the more favourable carbonyl group.

* This is a simplified representation of the mechanism

© Dr. Ian Hunt, Department of Chemistry