Condensation

Introducing reactions of condensation.

Robinson cyclization of acetone and methyl vinyl ketone:

Steps:

1. α-H of the carbonyl group is abstracted, followed by Michael addition to α,β-unsaturated ketone;
2. Carbonyl α-H in the formed methyl ketone is abstracted, followed by intramolecular nucleophilic attack to the intramolecular carbonyl group;
3. Water is eliminated from the intermediate, forming the bicyclic product.

Ethyl acetate condenses into ethyl acetoacetate:

Steps:

1. Carbonyl α-H in ethyl acetate is abstracted, then the enolate attacks another ethyl acetate molecule;
2. Tetrahedral intermediate eliminates ethoxy anion, generating ethyl acetoacetate;
3. Ethyl acetoacetate is then deprotonated to form its anions as the final product.