Choosing the Product in Carbonyl Addition

Alpha,beta-unsaturated carbonyl compounds can react at two electrophilic sites. The carbonyl carbon and the beta carbon can both attract a nucleophile. This gives two possible outcomes: conjugate addition, also called 1,4-addition, and direct addition, also called 1,2-addition.

Conjugate addition...

α,β-unsaturated carbonyl compounds undergo nucleophilic attack via two possible modes—conjugate or 1,4-addition and direct or 1,2-addition.

Conjugate-addition products are thermodynamically controlled. They form slowly as the β carbon is less electrophilic, and they are more stable since the stronger carbonyl bond is retained while the we...