sc9b05682_si_003.cif (423.2 kB)
Catalyst-Free One-Pot Three-Component Synthesis of 4‑Hydroxy-3-pyrazolylcoumarins in Ethanol at Room Temperature: Enolisable Aroylhydrazones as Efficient Ambident Nucleophile
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posted on 2019-12-13, 20:06 authored by Sayan Mukherjee, Animesh PramanikA sustainable and atom economic synthesis of biologically
important
4-hydroxy-3-pyrazolylcoumarin derivatives via a catalyst-free one-pot
three-component reaction of arylglyoxals, 4-hydroxycoumarins, and
aroylhydrazones has been successfully achieved. Significantly, this
green protocol embraces ethanol as a green solvent, a catalyst-free
room temperature reaction, column chromatography/recrystallization
free product isolation, high atom economy (up to 91.65%), low E-factor (up to 0.29 g/g), and gram scale product formation.
Remarkably, this method has been successfully utilized for synthesis
of polyheterocyclic 4-hydroxy-3-pyrazolylcoumarin derivatives containing
up to five different heterocycles. Additionally, employment of arylhydrazones
instead of aroylhydrazones in the above reaction produces a new class
of biologically and pharmacologically important hydrazones bearing
4-hydroxycoumarin along with different aryls and heterocycles. Unlike
arylhydrazones, aroylhydrazones exhibit keto–enol tautomerism,
and the enolic form promotes efficient ambidentate nucleophilic attack
which leads to facile formation of 4-hydroxy-3-pyrazolylcoumarin derivatives
in mild and eco-friendly reaction conditions.
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Keywords
product isolationaroylhydrazone4- hydroxycoumarinCatalyst-Free One-Pot Three-Component Synthesis4- hydroxycoumarinsEnolisable AroylhydrazonesEfficient Ambident Nucleophilecatalyst-free room temperature reactionarylhydrazone4- hydroxy -3-pyrazolylcoumarin derivativescatalyst-free one-pot three-component reactionsynthesisheterocycleambidentate nucleophilic attackatom economygram scale product formationenolic formeco-friendly reaction conditionspolyheterocyclic 4- hydroxy -3-pyrazolylcoumarin derivativesRoom Temperature
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