Halides, alkyl reaction with hydrazone anions

Until about 30 years ago, hydrazones derived from carbonyl compounds were not used in organic synthesis. They were used only for analytical purposes , and as protecting groups of aldehydes and ketones ". Corey investigated dimethylhydrazones of ketones and aldehydes with a-hydrogens, and found that they undergo deprotonation with LDA or BuLi in THF at the a-carbons to the hydrazonic moiety in 90-100% yield. The formed lithium compounds, used as enolate anion equivalents, create new carbon-carbon bonds in their reaction with different electrophiles such as alkyl halides or oxiranes, ketones and aldehydes (equation 21). 

Aqueous work-up of the vinyllithium leads to protonation of the anion and an alkene with the same carbon skeleton as the original carbonyl compound (or hydrazone). On the other hand, quenching with electrophiles such as alkyl halides and aldehydes leads to alkenes with extended carbon skeletons (see reaction 5A.47). 

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