Solvent-free one-pot synthesis of 4-aryl-3,5-dimethyl-1, 4,7,8-tetra hydrodipyrazolo[3,4-b:4′,3′-e]pyridines using Fe3O4@SiO2@(BuSO3H)3 catalytic Fe3+ system as selective colorimetric

The synthesis of 4-Aryl-(3,5-dimethyl-1,4,7,8-tetrahydro-dipyrazolo[3,4b:4',3'e] pyridine derivatives was accomplished using Fe3O4@SiO2@(BuSO3H)(3) catalyst through the reaction of various aldehydes, 2-methyl pyrazolo-5-one, and ammonium acetate reactants in one pot under the mild conditions with an appropriate time, high efficiency, and yields in comparison of the other catalysts. 3,5-dimethyl(1,4,7,8-tetrahydro pyrazolo pyridine)phenol was applied as Fe3+ ions colorimetric sensor with a detection limit of 8.1 x 10(-9) M. The DFT results of this compound was indicated that HOMO and LUMO orbitals are localized on the pyrazolo, pyridine, and phenol rings, respectively. The 3D mapped molecular electrostatic potential and 2D contour plot on the electrostatic surface showed two significant valence-shell charge depletion near NH bonds of five-membered rings, which were appropriated to accept transition metals. Based on NBO analysis, stability of the considered complexes can be attributed to the donation of electron density from lone pairs of nitrogen atoms or of bonding orbitals C-N bond (as a donor moieties) to the empty LP* of transition metals (as an acceptor). [GRAPHICS] .

Automated summary

The synthesis of 4-Aryl-(3,5-dimethyl-1,4,7,8-tetrahydro-dipyrazolo[3,4b:4',3'e] pyridine derivatives was successfully achieved using a specific catalyst, Fe3O4@SiO2@(BuSO3H)(3). The resulting compound, 3,5-dimethyl(1,4,7,8-tetrahydro pyrazolo pyridine)phenol, was used as a colorimetric sensor for Fe3+ ions. The study also explored the molecular electrostatic potential and charge distribution of the compound, shedding light on its potential interactions with transition metals.