Organic copper compounds, characterized by carbon-copper bonds, play a pivotal role in organometallic chemistry. As one of the oldest transition metals used in synthetic organic chemistry, copper remains a staple in the synthesis of natural products. The unique properties of organocopper compounds make them indispensable for conjugate additions and various critical reactions. Learn more：organic copper.

Applications
Cross-Coupling Reactions:
Copper has been a longstanding choice for catalyzing cross-coupling reactions, predating the development of palladium catalysts by nearly a century. While palladium offers faster and more selective reactions, copper has regained popularity due to its environmental friendliness and cost-effectiveness. The cross-coupling reaction mechanism involves the oxidative addition of alkyl halides to Cu (I), forming planar Cu (III) intermediates, followed by reductive elimination, with nucleophilic attack as the rate-determining step.

Coupling Reactions:

Oxidative Coupling: Includes the coupling of copper acetylides to conjugated alkynes in the Glaser coupling or to aryl halides in the Castro-Stephens Coupling.
Reductive Coupling: Involves the coupling of aryl halides with copper metal in the Ullmann reaction.
Decarboxylation Coupling: Utilizes a catalytic amount of Cu (I) to displace the carboxyl group, forming an aryl copper (ArCu) intermediate. Concurrently, palladium catalysts convert aryl bromides into organic palladium intermediates, leading to the formation of ArPdAr’.
The Sonogashira cross-coupling reaction is a prominent example using organocopper compounds as catalysts. This reaction, crucial for carbon-carbon bond formation in organic synthesis, is valued for its mild conditions—conducted at room temperature, in aqueous media, or with a mild base—making it suitable for complex molecule synthesis. Its applications span the production of natural products, organic materials, pharmaceuticals, and nanomaterials.

Conjugate Addition:
When Grignard reagents are added to cyclohexenone in the presence of Cu (I), it results in a 1,4-addition rather than a 1,2-addition, prompting extensive research on conjugate additions to enones with organocuprates. With Grignard reagents, the reaction with enones proceeds via 1,2-addition. The mechanism involves copper (II) 1,4-addition forming Cu (III) intermediates through the nucleophilic addition of Cu (I) species at the β-carbon of the alkene, followed by reduction and elimination of Cu (I).