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<p>The novel catalyst PEN[MIM]₄[OH]₄ was designed and successfully synthesized, exhibiting outstanding catalytic efficiency in the synthesis of tetrahydrobenzo[b]pyrans, achieving a high yield of 96% under optimized conditions. Its remarkable thermal stability allowed it to endure elevated temperatures without degradation, ensuring consistent performance across multiple cycles. As a heterogeneous catalyst, it was easily separated and reused, significantly minimizing waste and lowering overall costs. The presence of four catalytic units contributed to enhanced reaction kinetics compared to monodentate counterparts, facilitating faster conversions and improved selectivity. Mechanistic investigations revealed a dual activation pathway: the hydroxide anion promoted deprotonation of malonitrile. At the same time, hydrogen bonding between the imidazolium cation and the aldehyde’s carbonyl group stabilized the transition state, effectively reducing activation energy. Computational studies utilizing Density Functional Theory provided critical insights into the catalyst’s electronic properties, with molecular electrostatic potential mapping, reactivity indices (electronegativity, electrophilic index, softness, and hardness), and frontier molecular orbital (HOMO–LUMO) analysis confirming its superior reactivity compared to [DMIM][OH]. These findings establish PEN[MIM]<sub>4</sub>[OH]<sub>4</sub> as a highly efficient and reusable catalyst with promising applications in diverse organic syntheses.</p>

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Synthesis of pentaerythrityl tetramethyl imidazolium hydroxide: catalytic activity in tetrahydrobenzo[b]pyran formation and density functional theory analysis

  • 期刊论文

  • 发表日期：

    2025年6月9日

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  • Fariba Heidarizadeh,
  • Bahareh Kheirollah

摘要

The novel catalyst PEN[MIM]₄[OH]₄ was designed and successfully synthesized, exhibiting outstanding catalytic efficiency in the synthesis of tetrahydrobenzo[b]pyrans, achieving a high yield of 96% under optimized conditions. Its remarkable thermal stability allowed it to endure elevated temperatures without degradation, ensuring consistent performance across multiple cycles. As a heterogeneous catalyst, it was easily separated and reused, significantly minimizing waste and lowering overall costs. The presence of four catalytic units contributed to enhanced reaction kinetics compared to monodentate counterparts, facilitating faster conversions and improved selectivity. Mechanistic investigations revealed a dual activation pathway: the hydroxide anion promoted deprotonation of malonitrile. At the same time, hydrogen bonding between the imidazolium cation and the aldehyde’s carbonyl group stabilized the transition state, effectively reducing activation energy. Computational studies utilizing Density Functional Theory provided critical insights into the catalyst’s electronic properties, with molecular electrostatic potential mapping, reactivity indices (electronegativity, electrophilic index, softness, and hardness), and frontier molecular orbital (HOMO–LUMO) analysis confirming its superior reactivity compared to [DMIM][OH]. These findings establish PEN[MIM]4[OH]4 as a highly efficient and reusable catalyst with promising applications in diverse organic syntheses.