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<p>The design of recyclable polymer-supported catalysts represents an effective strategy for integrating activity, durability, and environmental sustainability in homogeneous-to-heterogeneous transformations. In this work, a new polystyrene-anchored mixed-valent [V<sup>IV</sup>O(L)V<sup>V</sup>O<sub>2</sub>]-catalyst, [(V<sup>V</sup>O<sub>2</sub>){V<sup>IV</sup>O(MeOH)<sub>2</sub>}L]@PS (<b>PS-1</b>), has been prepared by first assembling a binuclear vanadium complex [(V<sup>V</sup>O<sub>2</sub>){V<sup>IV</sup>O(MeOH)<sub>2</sub>}L] (<b>1</b>) from 1,3-bis(2-hydroxy-3,5-di-<i>t</i>-butylphenylmethylideneamino)guanidine (<b>H</b><sub><b>3</b></sub><b>L</b>) and [VO(acac)<sub>2</sub>], followed by its covalent grafting onto the polymer backbone. Crystallographic studies of an oxidized analogue of <b>1</b> provided direct evidence of a binuclear V<sup>IV</sup>O/V<sup>V</sup>O<sub>2</sub> structural core and confirmed the presence of accessible -NH groups, thereby establishing a structural basis for covalent immobilization on the polystyrene support. Anchoring onto polystyrene was validated by FT-IR, UV–vis, EPR, MP-AES, FE-SEM, and AFM studies, demonstrating both successful grafting and retention of structural integrity. The resulting catalyst efficiently mediated the one-pot, three-component synthesis of zwitterionic benzylpyrazolyl pyrazolates under green reaction protocols, delivering excellent yields and selectivity. Notably, <b>PS-1</b> could be recycled for at least five runs without measurable vanadium leaching or loss of efficiency. Mechanistic investigations, supported by the isolation of pyrazol-5-ol as a key intermediate, establish the essential role of the V(IV/V) redox centres in facilitating the multicomponent sequence. These findings highlight <b>PS-1</b> as a robust and reusable catalytic platform, underscoring the promise of polymer-anchored vanadium systems for sustainable synthetic methodologies.</p> Graphical Abstract <p></p>

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Merrifield Resin-Immobilized Binuclear Mixed-Valent Vanadium Catalyst for Efficient Multicomponent Synthesis of Zwitterionic Benzylpyrazolyl Pyrazolates

  • 期刊论文

  • 发表日期：

    2025年12月23日

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  • Mannar R. Maurya,
  • Naveen Kumar,
  • Monojit Nandi

摘要

The design of recyclable polymer-supported catalysts represents an effective strategy for integrating activity, durability, and environmental sustainability in homogeneous-to-heterogeneous transformations. In this work, a new polystyrene-anchored mixed-valent [VIVO(L)VVO2]-catalyst, [(VVO2){VIVO(MeOH)2}L]@PS (PS-1), has been prepared by first assembling a binuclear vanadium complex [(VVO2){VIVO(MeOH)2}L] (1) from 1,3-bis(2-hydroxy-3,5-di-t-butylphenylmethylideneamino)guanidine (H3L) and [VO(acac)2], followed by its covalent grafting onto the polymer backbone. Crystallographic studies of an oxidized analogue of 1 provided direct evidence of a binuclear VIVO/VVO2 structural core and confirmed the presence of accessible -NH groups, thereby establishing a structural basis for covalent immobilization on the polystyrene support. Anchoring onto polystyrene was validated by FT-IR, UV–vis, EPR, MP-AES, FE-SEM, and AFM studies, demonstrating both successful grafting and retention of structural integrity. The resulting catalyst efficiently mediated the one-pot, three-component synthesis of zwitterionic benzylpyrazolyl pyrazolates under green reaction protocols, delivering excellent yields and selectivity. Notably, PS-1 could be recycled for at least five runs without measurable vanadium leaching or loss of efficiency. Mechanistic investigations, supported by the isolation of pyrazol-5-ol as a key intermediate, establish the essential role of the V(IV/V) redox centres in facilitating the multicomponent sequence. These findings highlight PS-1 as a robust and reusable catalytic platform, underscoring the promise of polymer-anchored vanadium systems for sustainable synthetic methodologies.

Graphical Abstract