A Convenient Synthesis of Functionalized Pyrazolones Bearing a Highly Twisted 1,3-Butadiene Moiety with Skew Geometry

Pyrazolones are important heterocycles, which have been used in many fields, since they exhibitbiological and pharmacological properties [1]. In recent years, much effort has devotedto designing new isocyanide-based multicomponent reactions toward the synthesis of variouscompounds [2]. The four-component reaction among arylhydrazine, alkyl acetoacetatederivatives,alkyl isocyanides, and dialkyl acetylenedicarboxylates, leading to the formation of dialkyl2-[(Z)-(alkylamino) (3-alkyl-5-oxo-1-phenyl-1,5-dihydro-4H-pyrazol-4-ylidene) methyl]fumarates isdescribed. The structure of target compounds was confirmed usingX-ray diffractionstudy. These pyrazolone derivatives contain a highlytwisted exocyclic 1,3-butadienemoiety with highly twisted skew (ϕ=87º) geometry. Various features of these reactions will bepresented and discussed.