Synthesis of functionalised pyrazolones and imidazolines/imidazoles through divergent cyclisation reactions

The base-promoted reactions of easily accessible α-aminohydrazones represent a simple and efficient method for the preparation of both 1-substituted and 1-unsubstituted-4-aminocarbonyl-1H-pyrazol-5(2H)-ones, whereas the copper promoted reactions provide a divergent facile regiocontrolled synthesis of the imidazoline/imidazole ring system. The copper-promoted reaction of the α-benzylaminohydrazone produces a 2-oxo-1,4-diazadiene derivative. Finally, the imidazolines can be easily hydrolyzed to α-ketohydrazones.