Lithium diethyl amide, structure

Pridefine (80) is a somewhat structurally related antidepressant. It is a centrally active neurotransmitter blocking agent. It blocks norepinephrine in the hypothalamus but does not affect dopamine or 5-hydroxytryptamine. Its synthesis be-(jins by lithium amide-promoted condensation of diethyl succinate and benzophenone followed by saponification to 78. Heating in the presence of ethylamine gives N-ethylsuccinimide 79. Lithium aluminum hydride reduction completes the synthesis of pridefine (80)... 

Unhindered aliphatic ketones selectively yield E-enolates if they are deprotonated by a lithium amide via a transition state structure of type A of Figure 13.15. This occurs, for example, when the B-type transition state is destabilized because of the use of a base that is even more sterically demanding than LDA such as, for example, LTMP (for structure, see Figure 4.18). For example, diethyl ketone and LTMP form the if-enolate with ds = 87 13. 

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