Preparation of pyrazoles from the C(α)NN-trianion of hydrazones having an α-hydrogen atom

Certain hydrazones having an α-hydrogen atom were treated with 3 mol. equiv. of n-butyl-lithium to give (presumably) the C(α)NN-trianions. These trianions were aroylated with esters at the α-carbanionic centre and cyclized with acid to give pyrazoles.