Aim:
To synthesize chromeno-pyrazolo[1,2-b]phthalazine-6,9,14(7H)-trione analogs with the help of silica-supported bismuth
nitrate catalyst.
Background:
Nitrogen-containing heterocyclic compounds are widespread, and their applications to pharmaceuticals, agrochemicals, and
functional materials are becoming more and more important. Pyrazoles are an important class of compounds for new drug development, as
they are the core structure of numerous biologically active compounds, including blockbuster drugs such as celecoxib, viagra, pyrazofurine,
and many others. Similarly, heterocycles containing a phthalazine moiety are of current interest due to their pharmacological and biological
activities, for example, pyrazolo[1,2-b]phthalazinedione is described as an anti-inflammatory, analgesic, antihypoxic, and antipyretic agent.
Objective:
In continuation of our ongoing investigation for the construction of efficient and simple approaches for the preparation of
heterogeneous catalysts herein we wish to disclose a highly efficient, simple, and one-pot synthesis of chromeno-pyrazolo-phthalazine
derivatives via a one-pot multi-component reaction between 4-hydroxycoumarin, aromatic/heterocyclic aldehydes and 2,3-dihydro-1,4-
phthalazinedione using silica-supported bismuth nitrate as an inexpensive, environmentally friendly and reusable catalysts under solvent-free
conditions.
Materials and Methods:
Microanalytical data (C, H, and N) were collected on Carlo Erba analyzer model 1108. The microwave synthesis
was performed in Anton Paar, Monowave 300 microwave synthesizer. Melting points were measured in open glass capillaries in the Kofler
apparatus and may be uncorrected. Spectroscopic data were obtained using the following instruments: Fourier transform infrared spectra (KBr
discs, 4000-400 cm-1
) by Shimadzu IR-408 Perkin-Elmer 1800 instrument; 1H NMR and 13C NMR spectra by Bruker Avance-II 400 MHz using
DMSO-d6 as a solvent containing TMS as the internal standard. Mass spectra were set down on a JEOL D-300 mass spectrometer.
Results:
To continue our ongoing studies to synthesize heterocyclic and pharmaceutical compounds by mild, facile, and efficient protocols,
herein we wish to report our experimental results on the synthesis of chromeno-pyrazolo-phthalazine derivatives under solvent-free condition
derivatives, using various aromatic/heterocyclic aldehydes in the presence of silica-supported bismuth nitrate catalyst. The prepared catalyst
was characterized by various physical and chemical techniques.
Conclusion:
We have demonstrated an efficient reaction path for the synthesis of new aryl and heteroaryl chromeno-pyrazolo[1,2-
b]phthalazine-6,9,14(7H)-trione by one-pot three-component condensation of aryl/heteroaryl aldehydes, 2,3-dihydro-1,4-phthalazinedione
and 4-hydroxy coumarin using silica-supported bismuth nitrate (SSBN) under microwave irradiation. The scheme not only offers the use of microwave at low temperatures and significant yield of products but also affords mild reaction conditions, without harmful solvent, shorter
reaction times, high purity, operational simplicity, and easy workup.
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