The 1,3-dipolar cycloaddition of four hydrazonoyl chloride derivatives with the sodium salt of unsymmetrical β-diketones (benzoylacetone) offers a versatile method for the regioselective synthesis of 2H-pyrazoles in a similar fashion to the cycloaddition of the nitrilimides with α,β-unsaturated ketones and esters; the structures of the prepared isomeric pyrazole and pyrazoline derivatives are established by spectroscopic and chemical methods.
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