The addition of diethyl malonate to benzaldehyde in the presence of the basic amine piperi...

The addition of diethyl malonate to benzaldehyde in the presence of the basic amine piperidine gives the unsaturated diester, diethyl 2-benzylidenemalonate. This is an example of the Knoevenagel reaction, a synthetically useful carbonyl condensation reaction, which is related to the aldol condensation.

(a) What is the nucleophile in the Knoevenagel reaction?

(b) The unsaturated diester A in part (c) was prepared by a Knoevenagel reaction and used to synthesize the anticonvulsant drug gabapentin. From which two reactants is the diester synthesized?

(c) Fill in the missing reagents in the reaction scheme.