Aldol reaction

The aldol reaction forms a carbon-carbon bond when an enol or enolate adds to an aldehyde or ketone. The initial addition product is a beta-hydroxy carbonyl compound, containing the combined carbon frameworks.

For example, acetaldehyde can add to another acetaldehyde molecule to give 3-hydroxybutanal. Subsequent loss of water gives an alpha,beta-unsaturated carbonyl compound, the condensation product. Keeping addition and dehydration distinct explains why an aldol reaction need not itself eliminate water. The reaction is useful for constructing longer carbon skeletons with predictable functional groups.

Addition of an enolate or enol to an aldehyde or ketone, giving a beta-hydroxy carbonyl compound. Subsequent dehydration is a distinct step and gives an aldol condensation.

Aldol-type carbonyl addition at a more remote carbon of a conjugated enolate.

conjugate addition generates an enolate that is intercepted by an aldehyde or ketone.

An aldol reaction between two reactive sites of the same molecule. A tethered enol or enolate attacks a carbonyl group to close a ring; the tether, conformation and competing chemical reactions influence the product.

An aldol addition organized through a boron enolate and a coordinated carbonyl partner. Enolate geometry and auxiliary-controlled facial selection jointly determine product stereochemistry.

A six-membered chair-like organization of a metal enolate and carbonyl compound used to rationalize aldol stereoselectivity.

A six-membered chair-like transition-state model for an aldol-type bond-forming step. It predicts relative stereochemistry by comparing substituent placement and nonbonded interactions, but must be adapted to the actual enamine or metal-enolate catalyst.

An enamine formed reversibly between proline and an enolizable carbonyl compound attacks an electrophilic carbonyl. The carboxylic acid group can orient and activate the electrophile; hydrolysis releases the aldol product and regenerates proline.

An aldol addition followed by water elimination, commonly producing a conjugated carbonyl compound. Identifying which carbonyl supplies the enolate distinguishes constitutional products.