Esters deprotonation

Cyclization gives a five-membered ring /3-keto ester deprotonated under reaction conditions this is the observed product (C12H1805). 

Notice that one molecule of the ester (deprotonated, reacting as the enolate) serves as the nucleophile to attack another molecule of the ester, which serves as the acylating reagent in this nucleophilic acyl substitution. 

Enones—see Futoenones 17,6-Estradiol fatty acid esters, deprotonation... 

By substituting (S)-(-)-l-amino-2-(dimethylmethoxymethyl)pyrrolidine (S)-(83) for (S)-(4), Enders has developed an efficient and enantioselective Hantzsch synthesis (Scheme 4). In this synthesis, the more-hindered hydrazone formed from (83) was condensed with an acetoacetic acid ester. Deprotonation of the hydrazone so-formed (the major tautomer present was an enehydrazine) followed by addition of an arylidene malonate derivative yielded (85), which could be closed with mild acid to yield optically active... 

For esters, deprotonation is effected with triethyl amine (which favors E2), while El ionization is disfavored because it requires moving the bulky terr-butyl group into planarity. For thioesters, Ei reaction is facilitated by the thiophenyl group, while E2 reaction is slowed by use of the bulky diisopropyl ethyl amine. ... 

Possible transition states for general base-catalyzed hydrolysis of an ester deprotonation of water (left) or protonation of the departing alkoxide ion (right). 

Mechanistic Details Treatment of a SAMP/RAMP hydra-zone with LDA at — 110°C typically results in kinetic removal of the least sterically hindered proton. However, the opposite regioselectivity results for hydrazones having electronically activating groups (e.g., phenyl and ester)." Deprotonation is followed by equilibration of the azaeno-late to a species having the -configuration at the C C bond and the Z-configuration at the C N bond. 

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