Alkylation of hydrazones

The l//-l,2,4-triazolo[4,3-a]pyrimidinium betaine was prepared by the alkylation of hydrazone (403) followed by hydrolysis to hydrazine (404)... 

Alkylations of hydrazone anions derived from aldehydes and ketones are closely related to imine anion alkylations. Lithiated hydrazones are particularly powerful nucleophiles for alkylation reactions. The alkylated hydrazones may be cleaved with periodate, as shown below.The choice of solvent and base is critical to the success of hydrazone alkylations hexane-free medium is essential for complete metalation. °... 

In the light of highly successful results with the alkylation of hydrazones, attention has been focussed upon the potential of chiral enamines. Excellent yields of chiral -[2-(trimethylsilyl-... 

Alpha alkylation of hydrazones and Shapiro reaction in a one-pot process provides a versatile route to tetrasubstituted alkenes. The addition of 2 equiv of butyllithium to a trisyUiydrazone generates a dianion, which may be trapped at low temperature with different electrophiles such as methyl iodide. An additional equivalent of butyllithium generates a dianion species that decomposes at room temperature to yield the vinyllithium intermediate of the Shapiro reaction. This t)q)e of compound can react with different electrophiles as commented before. In this example, the final addition of paraformaldehyde gave rise to the tetrasubstituted alkene represented in eq 22. ... 

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