Meglumine-Promoted Eco-Compatible Pseudo-Three-Component Reaction for the Synthesis of 1,1-Dihomoarylmethane Scaffolds and Their Green Credentials

A simple, straightforward, and energy-efficient greener route for the synthesis of a series of biologically interesting functionalized 1,1-dihomoarylmethane scaffolds has been developed in the presence of meglumine as an efficient and eco-friendly organo-catalyst via one-pot pseudo-three-component reaction at room temperature. Following this protocol, it is possible to synthesize 1,1-dihomoarylmethane scaffolds of an assortment of C-H activated acids such as dimedone, 1,3-cyclohexadione, 4-hydroxy-6-methyl-2-pyrone, 4-hydroxycoumarin, and 1-phenyl-3-methyl-pyrazolone. The salient features of the present green protocol are mild reaction conditions, good to excellent yields, operational simplicity, easy isolation of products, no cumbersome post treatment, high atom economy, and low E-factor. In addition, this chemistry portrays several green advantages including the reusability of reaction media and product scalability, which makes protocol sustainably efficient. Additionally, several control experiments such as protection of catalyst reactive site, D₂O exchange, and ¹H NMR studies revealed possible pathways for meglumine-promoted reactions. Inspired by the natural physiological environment of 1,1-dihomoarylmethane scaffolds, we reconnoitered the biological profile of our compounds and synthesized compounds that were promising for their antiproliferative and antibacterial activities.

Grinding Synthesis of Pyrazolyl-Bis Coumarinyl Methanes Using Potassium 2-Oxoimidazolidine-1,3-diide

AIM AND OBJECTIVE

Potassium 2-oxoimidazolidine-1,3-diide (POImD) as a novel and reusable catalyst was used for the synthesis of pyrazolyl-bis coumarinyl methanes by a nucleophilic addition reaction of synthetized pyrazolecarbaldehyde and two equivalents of 4-hydroxycoumarin under grinding. The catalyst can be reused and recovered several times without loss of activity. This method provides several advantages such as eco-friendliness, simple work-up and shorter reaction time as well as excellent yields. All of the synthesized compounds were characterized by IR, 1H and 13C NMR spectroscopy and elemental analyses.

MATERIAL AND METHOD

Synthetized pyrazole carbaldehyde 1a (1 mmol), 4-hydroxycoumarin 2 (2 mmol), 1 mmol of POImD and 10mL of H2O were ground in a mortar by a pestle for 30-90 minutes. After the completion of the reaction, as monitored by TLC on silica gel using ethyl acetate/n-hexane (1:2), the mixture was allowed to cool to room temperature. After completion of the reaction, we extracted the product with CH2Cl2/H2O. This was followed by separation of phases, evaporation of the organic phase and recrystallization of the residue with 50 mL of ethanol/H2O (1:1). The pure product was then obtained in 87 to 96% yield. The aqueous phase was concentrated under reduced pressure to recover the catalyst for subsequent use.

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 pyrazolylbis coumarinyl methanes, using various synthetized pyrazole carbaldehydes and 4-hydroxycoumarin in the presence of POImD in aqueous media at room temperature.

CONCLUSION

Finally, we developed an efficient, fast and convenient procedure for the three-component synthesis of pyrazolyl-bis coumarinyl methanes through the reaction of pyrazole carbaldehydes and 4- hydroxycoumarin, using POImD as a novel and reusable catalyst. The remarkable advantage offered by this method is that the catalyst is non-toxic, inexpensive, easy to handle and reusable. A short reaction time, simple work-up procedure, high yields of product with better purity and the green aspect by avoiding a hazardous solvent and a toxic catalyst are the other advantages. To the best of our knowledge, this is the first report on the synthesis of pyrazolyl-bis coumarinylmethane derivatives using potassium 2-oxoimidazolidine-1,3-diide (POImD).

A novel pyrazole biscoumarin based chemosensors for the selective detection of Cu(2+) and Zn(2+) ions

A novel chemosensor based on pyrazole biscoumarin molecule "4-hydroxy-3-((4-hydroxy-2-oxo-2H-chromen-3-yl)(1,3-diphenyl-1H-pyrazol-4-yl)methyl)-2H-chromen-2-one" (PBC) was synthesized by a simple method. The chemosensing properties of PBC towards transition metal ions like Cu(2+) and Zn(2+) by naked eye, UV-Visible and fluorescence spectroscopic methods were described. The PBC solution with Cu(2+) and Zn(2+) ion showed brown and blue colour respectively. The UV-Visible spectra of PBC with Cu(2+) and Zn(2+) ions exposed their corresponding absorption maxima. Further, the Job's plot method confirmed the 1:1 and 2:1 stoichiometry of the complex formation between the PBC with Cu(2+) and Zn(2+) ions respectively. The fluorescence enhancement of PBC on binding with Cu(2+) and Zn(2+) is due to the inhibition of photo induced electron transfer mechanism.

Synthesis of pyrazolylbisindoles over mesoporous Lewis acidic ZrTUD-1: Potential application in selective Cu(2+) colorimetric detection

A series of pyrazolylbisindole (PBI) derivatives were prepared by simple condensation of indole and pyrazole aldehyde utilizing amorphous mesoporous ZrTUD-1 having predominant Lewis acid sites. The applicability of pyrazolylbisindolyl derivate as a colorimetric chemosensor with high selectivity toward Cu(2+) over other cations were tested. Among heavy and transition metal (HTM) ions in CH3CN solution, the probe only sensed Cu(2+) detectable by naked eye. The sensor exhibited a new absorption band at 488 nm (a red shift of 206 nm from 282 nm) with a large colorimetric response and affinity to Cu(2+) over other cations tested (Al(3+), Pb(2+), Cd(2+), Mg(2+), Mn(2+), Zn(2+), K(+), Fe(2+), Ca(2+), Cu(2+) and Hg(2+)).

Direct glycol assisted synthesis of an amorphous mesoporous silicate with framework incorporated Co2+: characterization and catalytic application in ethylbenzene oxidation

Exclusive Co²⁺ incorporation into the framework of a TUD-1 type silicate was obtained using tetraethylene glycol (TEG) as a non-surfactant structure directing agent which was shown to be active for ethylbenzene oxidation.