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Intensive Cycloalkyl-Fused Pyridines for Aminopyridyl–Zinc–Heteroimidazoles Achieving High Efficiency toward the Ring-Opening Polymerization of Lactides
- Source :
- Molecules, Vol 29, Iss 17, p 4150 (2024)
- Publication Year :
- 2024
- Publisher :
- MDPI AG, 2024.
-
Abstract
- The model precatalyst sp3- and sp2-N dinitrogen-coordinated zinc–heteroimidazole has been used as an efficient catalyst for the ring-opening polymerization of cyclic esters. Subsequent to our exceptional active 5,6,7-trihydroquinolin-8-amine-zinc catalysts for the ring-opening polymerization (ROP) of ε-caprolactone, various pyridine-fused cycloalkanones (ring size from five to eight) are developed for the correspondent fused amine–pyridine derivatives and their zinc–heteroimidazole chloride complexes Zn1–Zn8 (LZnCl2) bearing N-diphenylphosphinoethyl pendants. Activated with two equivalents of LiN(SiMe3)2, the title zinc complexes efficiently promote the ROP of L-lactide (L-LA) in situ; among them, Zn4/2Li(NSiMe3)2 catalyzed 500 equivalent L-LA at 80 °C with 92% conversion in 5 min (TOF: 5520 h−1). Under the same conditions, the catalytic efficiency for the ROP of rac-LA by Zn1–Zn8/2Li(NSiMe3)2 was slightly lower than that for L-LA (highest TOF: 4440 h−1). In both cases, cyclooctyl-fused pyridyl–zinc complexes exhibited higher activity than others, while the cycloheptyl-fused zinc complexes showed the lowest activity. The microstructure analysis of the polymers showed they possessed a linear structure capped with CH3O as major and cyclic structure as minor. In this work, all the ligands and zinc complexes were well characterized by 1H/13C/31P NMR, FT-IR spectroscopy as well as elemental analysis.
- Subjects :
- zinc complexes
ring-opening polymerization
polylactides
Organic chemistry
QD241-441
Subjects
Details
- Language :
- English
- ISSN :
- 14203049
- Volume :
- 29
- Issue :
- 17
- Database :
- Directory of Open Access Journals
- Journal :
- Molecules
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.9daddded93c4062a7642ecb898a17fe
- Document Type :
- article
- Full Text :
- https://doi.org/10.3390/molecules29174150