Intensive Cycloalkyl-Fused Pyridines for Aminopyridyl–Zinc–Heteroimidazoles Achieving High Efficiency toward the Ring-Opening Polymerization of Lactides
Yun Wang,
Wenjuan Zhang,
Pengjiang Zhu,
Wei You,
Xiaopan Xue,
Rui Wang,
Yanping Ma,
Wen-Hua Sun
Affiliations
Yun Wang
Beijing Key Laboratory of Clothing Materials R&D and Assessment, Beijing Engineering Research Center of Textile Nanofiber, School of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing 100029, China
Wenjuan Zhang
Beijing Key Laboratory of Clothing Materials R&D and Assessment, Beijing Engineering Research Center of Textile Nanofiber, School of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing 100029, China
Pengjiang Zhu
Beijing Key Laboratory of Clothing Materials R&D and Assessment, Beijing Engineering Research Center of Textile Nanofiber, School of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing 100029, China
Wei You
Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
Xiaopan Xue
Beijing Key Laboratory of Clothing Materials R&D and Assessment, Beijing Engineering Research Center of Textile Nanofiber, School of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing 100029, China
Rui Wang
Beijing Key Laboratory of Clothing Materials R&D and Assessment, Beijing Engineering Research Center of Textile Nanofiber, School of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing 100029, China
Yanping Ma
Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
Wen-Hua Sun
Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
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.
