Aluminum chelates supported by β-quinolyl enolate ligands: synthesis and ROP of ε-CL

Abstract

Treatment of tautomers of β-quinolyl ketone-enaminones with AlMe3 afforded β-quinolyl enolato dialkylaluminium complexes LAlMe2 (L = [(2-C9H6N)-CH[double bond, length as m-dash]C(R)-O-], R = CH3 (), (t)Bu (), Ph (), o-tolyl (), p-tolyl (), p-OMePh ()), respectively. reacted with benzyl alcohol to generate the corresponding LAl(OBn)2 complex . Complexes and were characterized by (1)H and (13)C NMR spectroscopy, elemental analyses and single crystal X-ray diffraction analyses. All complexes were tested as catalyst precursors for ring-opening polymerization of ε-caprolactone (ε-CL). The results indicated that LAlMe2 () exhibited good activity towards the ROP of ε-CL in the presence of benzyl alcohol at 80 °C, and LAl(OBn)2 exhibited higher catalytic activity in the absence of alcohol than for the ROP of ε-CL. However, both polymerizations were less controlled. Kinetic studies showed that the polymerization reaction catalyzed by and proceeded with first-order dependence on the monomer and took place through coordination-insertion.

Collaboration between Trinuclear Aluminum Complexes Bearing Bipyrazoles in the Ring-Opening Polymerization of ε-Caprolactone

“…A survey of recent literature of CL polymerization using Al complexes as catalysts at 0–30 °C is illustrated in Figure . An Al complex bearing a Salen ligand revealed the greatest catalytic activity in CL polymerization at 0 °C. Other Al complexes, including an Al complex bearing aminophenolate, a low-valent Al­(II)–Al­(II) complex bearing 1,2-bis­(2,6-iPr 2 -C 6 H 3 )-iminoacenaphthene, an Al complex bearing (oxybis­(2,1-phenylene))­bis­(cyclohexylamide), a five-membered Al complex bearing a thiol-Schiff base, and an Al complex bearing benzofurazan, as well as D Bu 2 Al 3 Me 5 could polymerize CL in 15 min at room temperature.…”

The Facile Synthesis of Lithium 2‐R‐Hydroquinolinide Complexes and Their High Activity toward ROP of ε‐Caprolactone

“…Recently, our group reported the Al complexes bearing β‐quinolyl enolate ligands as catalysts for the ROP of ε ‐CL . As an extension to this work, we report the synthesis and characterization of metallic lithium complexes based on quinoline derivatives and their catalytic activities toward the ROP of ε ‐CL in the presence and absence of benzyl alcohol.…”

Controlled and effective ring-opening (co)polymerization of rac-lactide, ε-caprolactone and ε-decalactone by β-pyrimidyl enolate aluminum complexes

“…Recently, Chen and co-workers reported the synthesis of alumi-num complexes supported by various types of N-heteroatomic enolate/enamine ligands (B-E). [41][42][43][44] β-Quinolyl enolate aluminum complexes (B) were active initiators of the ROP of ε-CL but could not initiate the ROP of rac-LA. 41 Furthermore, β-quinolyl enamino aluminum complexes (C), where the quinoline ring can be perceived as the electron-withdrawing group of β-diketiminate aluminum complexes (A), were reported to be more active than β-quinolyl enolate aluminum complexes (B) in the ROP of ε-CL in the presence of BnOH.…”