Conjugate Reactions

• Only one of the reactants can form an enolate in this reaction.

• The other reactant must have no alpha-hydrogen atoms.

• One reactant must be more electrophilic than the other, acting as the carbonyl component.

• Aldehydes are more effective as electrophiles than ketones.

Intramolecular aldols can be part of this reaction process with the necessity that there needs to be a dicarbonyl compound so that the carbonyl component and the enolate component come from the same molecule. This molecule must also be sizeable enough to create a stable cyclic aldol product. By necessity there needs to be four carbon atoms “between” the two carbonyl groups so that a stable five-membered ring can be created in this type of reaction. Remember, too, that the aldehydes will be more electrophilic than ketones so the reaction will proceed with the aldehyde being the electrophile and the ketone being the nucleophile.

CONJUGATE REACTIONS

In the case of enone or enol, there can be reaction of the carbon atom on the far side of the double bond, called conjugate reactions. The reaction involves a nucleophile that attacks the conjugate or beta carbon atom, resulting in the addition of the nucleophile. What this looks like is seen in figure 88:

Figure 87.

This can involve the use of organocopper reagents under acidic circumstances. Organolithium cuprates or R2CuLi can result in the addition of the R chain to the beta carbon atom in an enone or enal molecular situation. There are two R groups associated