What Are the Two Starting Materials for a Robinson Annulation?

Answer

A Robinson annulation combines a carbon nucleophile derived from an enolizable carbonyl compound with an α,β-unsaturated ketone (an enone).

The first partner is the Michael donor: commonly an enolate from a β-keto ester or a β-diketone. The second is the Michael acceptor, such as methyl vinyl ketone. An enamine can also serve as the donor in an appropriate variant.

Why these two partners work

1. The donor attacks the enone's β-carbon in a Michael addition, creating a carbon–carbon bond.
2. The resulting carbonyl arrangement permits an intramolecular aldol reaction that closes a six-membered ring.
3. Dehydration gives a substituted cyclohexenone.

For example, ethyl acetoacetate can supply the donor enolate and methyl vinyl ketone can supply the acceptor. The base enables enolate formation; it is not one of the two carbon-building partners.

Without a specified target structure, the answer identifies the two reactant classes rather than a unique pair of molecules.