text: After the deprotonation, the hydrazone turns into an azaenolate with lithium cation chelating both the nitrogen and oxygen. There are two possible options for lithium chelation. One is that lithium is antiperiplanar to the C=C bond (blue colored), leading to the conformation of Z; the other one is that lithium and the C=C bond are at the same side of the C-N bond (red colored), leading to the E conformer. There are also two available orientations for the chelating nitrogen and R group, being either E or Z. This leads to four possible azaenolate intermediates (A, B, C and D) for the Enders' SAMP/RAMP hydrazone alkylation reaction.
  Experiments and calculations show that one specific stereoisomer of the azaenolate is favored over the other three possible candidates. Therefore, although four isomers are possible for the azaenolate, only the one (azaenolate A) with the stereochemistry of its C=C double bonds being E and that of its C-N bond being Z stereochemistry is dominant (EZ) for both cyclic and acyclic ketones.