Draw the structures of the nucleophilic B-keto ester and the aB-unsaturated ketone acceptor that were combined in a Robinson annulation to give the following product: Ph ČO,Et

I H H3C NOC XT :0: MET H₂C base H3C The aldol reaction is a carbonyl condensation reaction between two carbonyl partners and involves a combination of nucleophilic addition and a-substitution steps. One partner is converted into an enolate ion nucleophile and adds to the electrophilic carbonyl group of the second partner. In the classic aldol reaction, the carbonyl partners are aldehydes or ketones, although aldehydes are more reactive. The product is a ß-hydroxy carbonyl compound. H OH q H3C H₂C H Under reaction conditions slightly more vigorous than those employed for the aldol reaction, the ß-hydroxyl group is eliminated in an E1cB dehydration to give an a,ß-unsaturated carbonyl compound. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions heat H H + H₂O

2 H3C H3C H C→XT OH H3C The aldol reaction is a carbonyl condensation reaction between two carbonyl partners and involves a combination of nucleophilic addition and a-substitution steps. One partner is converted into an enolate ion nucleophile and adds to the electrophilic carbonyl group of the second partner. In the classic aldol reaction, the carbonyl partners are aldehydes or ketones, although aldehydes are more reactive. The product is a ß-hydroxy carbonyl compound. base :0: OH H H Under reaction conditions slightly more vigorous than those employed for the aldol reaction, the ß-hydroxyl group is eliminated in an E1cB dehydration to give an a,ß-unsaturated carbonyl compound. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instruct ns H3C heat OH H3C :0: H + H₂O H

The Robinson annulation is a combination of two carbonyl coupling reactions, the Michael reaction and the intramolecular aldol condensation. The most common partners in the reaction are a nucleophilic donor (such as a cyclic ketone, a ß-keto ester, an enamine, or a ß-diketone) and an a,ß-unsaturated ketone acceptor. The product is a substituted 2-cyclohexenone derivative. il The above reaction between a ß-keto ester and an a,ß-unsaturated ketone yields a product containing a 2- cyclohexenone ring. One of the steps of this reaction follows. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions AC↔XT я OEt -I H OEt CO₂Et Eto: يز OEt EtOH