The Chemistry of 4-(dicyanomethylene)-3-methyl-l-phenyl-2-pyrazoline-5-ones as a Privileged Scaffold in the Synthesis of Heterocycles

Background: The reactivity of 4-(dicyanomethylene)-3-methyl-l-phenyl-2-pyrazoline-5-one DCNP 1 and its derivatives makes it valuable as a building block for the synthesis of heterocyclic compounds like pyrazolo- imidazoles, -thiazoles, spiropyridines, spiropyrroles, spiropyrans, and others. As a number of publications have reported on the reactivity of DCNP and its derivatives, we compiled some features of this interesting molecule. Objective: This article aims to review the preparation of DCNP, its reactivity, and application in heterocyclic and dyes synthesis. Conclusion: In this review, we have provided an overview of recent progress in the chemistry of DCNP and its significance in the synthesis of various classes of heterocyclic compounds and dyes. The unique reactivity of DCNP offers unprecedentedly mild reaction conditions for the generation of versatile cynomethylene dyes from a wide range of precursors, including amines, α-aminocarboxylic acids, their esters, phenols, malononitriles, and azacrown ethers. We anticipate that more innovative transformations involving DCNP will continue to emerge in the near future.