Novel spiro[fluorene-9,3′-[1,2,4]triazoles were obtained in excellent yields from the reaction of N3-substituted benzamidrazones and (2,4,7-trinitro-9 H-fluoren- 9-ylidene)propanedinitrile in ethyl acetate solution at ambient temperature. The react ion mechanism is discussed.
Reaction of amidrazones 1a-1i with (1,5-dihydro-3-methyl-5-oxo-1-phenyl-4H-pyrazol-4-ylidene)propanedinitrile (2) in ethyl acetate solution in one-step reaction led to the formation of unprecedented pyrazolo[4,3-c][1,2,4]triazino[4,5-a]quinolin-4(5H)-ones 3a-3g along with pyrazolo[4,3-c][1,2,4]triazino[4,5-a]quinolin-12b-oles 3h-3m in moderate to excellent yields. These novel heterocycles were formed via a Michael addition reaction followed by intramolecular cyclization via a dearomatization process.
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 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.
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