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Intensive Cycloalkyl-Fused Pyridines for Aminopyridyl–Zinc–Heteroimidazoles Achieving High Efficiency toward the Ring-Opening Polymerization of Lactides

Authors :
Yun Wang
Wenjuan Zhang
Pengjiang Zhu
Wei You
Xiaopan Xue
Rui Wang
Yanping Ma
Wen-Hua Sun
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.

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