A convenient synthesis of functionalized pyrazolones bearing a highly twisted 1,3-butadiene moiety with skew geometry

<p>The four-component reaction among arylhydrazine, alkyl acetoacetate derivatives, alkyl isocyanides, and dialkyl acetylenedicarboxylates, leading to the formation of dialkyl 2-[(<i>Z</i>)-(alkylamino)(3-alkyl-5-oxo-1-phenyl-1,5-dihydro-4<i>H</i>-pyrazol-4-ylidene)methyl] fumarates is described. The structure of target compounds was confirmed using X-ray diffraction study. These pyrazolone derivatives contain a highly twisted exocyclic 1,3-butadiene moiety with skew (<i>ϕ</i> = 87°) geometry.</p>