Diversity-oriented pyrazol-3-one synthesis based on hydrazinodipeptide-like units prepared via the Ugi reaction

N-Cyanoacetyl-N′-trifluoroacetyl-N′-alkylhydrazines, prepared via hydrazino-Ugi reaction, provided different pyrazol-3-ones when exposed to mildly acidic and mildly basic conditions at 60 °C. These approaches offer a facile access to two different pyrazol-3-one-containing chemotypes in a diversity-oriented fashion, in only two chemical operations from simple precursors.