Enhanced CO<sub>2</sub>/Epoxide Cycloaddition Catalyzed by Pyridine-Substituted Triazole-Quaternary Ammonium Bromide
A series of ionic quaternary ammonium bromides featuring triazole moieties, <b>QAS-trzBn</b> <sub><b>4</b></sub> , <b>QAS-trzPic</b> <sub><b>4</b></sub> , and <b>QAS-trzBn</b> <sub><b>2</b></sub> <b>Pic</b> <sub><b>2</b></sub> , were synthesized via Cu-catalyzed azide-alkyne cycloaddition (CuAAC) between propargyl-based ammonium bromide and benzyl- or 2-picolylazide. X-ray crystallographic analyses of <b>QAS-trzBn</b> <sub><b>4</b></sub> and <b>QAS-trzBn</b> <sub><b>2</b></sub> <b>Pic</b> <sub><b>2</b></sub> revealed strong interactions between Br<sup>-</sup> ions and both triazolyl H and methylene H atoms (<sup>+</sup>NCH<sub>2</sub>), as evidenced by short Br<sup>-</sup>···H contacts ranging from 2.68 to 3.00 Å. The catalytic activities of these compounds as bifunctional, single-component catalysts for the CO<sub>2</sub>/epoxide cycloaddition were evaluated under both atmospheric and elevated CO<sub>2</sub> pressures. Notably, catalysts containing pyridyl-triazole groups exhibited superior catalytic performances compared with the benzyl-triazole-based catalyst, <b>QAS-trzBn</b> <sub><b>4</b></sub> . A substrate scope study using <b>QAS-trzPic</b> <sub><b>4</b></sub> under 20 atm of CO<sub>2</sub> at 100 °C revealed that electron-deficient epoxide substrates were more active, yielding good to excellent conversions (88-100%) to cyclic carbonates within 6 h. Computational studies identified key binding modes in pyridine-substituted systems that position both the epoxide and CO<sub>2</sub> in close proximity. In particular, the <b>QAS-trzPic</b> <sub><b>4</b></sub> <b>-CO</b> <sub><b>2</b></sub> <b>-epoxide</b> complex is more stabilized than its benzyl derivative, <b>QAS-trzBn</b> <sub><b>4</b></sub> <b>-CO</b> <sub><b>2</b></sub> <b>-epoxide</b>, due to favorable interactions of CO<sub>2</sub> with the pyridyl substituents.
Authors
- Preeyanuch Sangtrirutnugul (ORCID: https://orcid.org/0000-0001-6201-2814)
- Vasut Nakarajouyphon
- Thanthapatra Bunchuay (ORCID: https://orcid.org/0000-0001-5665-0254)
- Khetpakorn Chakarawet (ORCID: https://orcid.org/0000-0001-5905-3578)
- Panida Surawatanawong (ORCID: https://orcid.org/0000-0002-0300-4205)
- Khamphee Phomphrai (ORCID: https://orcid.org/0000-0002-3132-680X)
- Natchayatorn Keawkla
- David J. Harding (ORCID: https://orcid.org/0000-0001-8866-2401)
- Wanida Krisanakaset
- Pawares Pornchaiprasartkul
Institutions
- Mahidol University (TH)
- Shanghai Institute for Science of Science (CN)
- Center for Innovation (US)
- Vidyasirimedhi Institute of Science and Technology (TH)
- Suranaree University of Technology (TH)
Publication Details
- Journal
- ACS Omega
- Published
- 2025-10-01
- DOI
- https://doi.org/10.1021/acsomega.5c04751
- Primary Topic
- Carbon dioxide utilization in catalysis
- Type
- article
- Field-Weighted Citation Impact
- 0.00