Abstract
A series of chelated dehydroacetic acid–imine-based ligands L1H~L4H was synthesized by reacting dehydroacetic acid with 2-t-butylaniline, (S)-1-phenyl-ethylamine, 4-methoxylbenzylamine, and 2-(aminoethyl)pyridine, respectively, in moderate yields. Ligands L1H~L4H reacted with AlMe3 in toluene to afford corresponding compounds AlMe2L1 (1), AlMe2L2 (2), AlMe2L3 (3), and AlMe2L4 (4). All the ligands and aluminum compounds were characterized by IR spectra, 1H and 13C NMR spectroscopy. Additionally, the ligands L1H~L4H and corresponding aluminum derivatives 1, 3, and 4 were characterized by single-crystal X-ray diffractometry. The catalytic activities using these aluminum compounds as catalysts for the ε-caprolactone ring-opening polymerization (ROP) and styrene oxide-CO2 coupling reactions were studied. The results show that increases in the reaction temperature and selective solvent intensify the conversions of ε-caprolactone to polycaprolactone. Regarding the coupling reactions of styrene oxide and CO2, the conversion rate is over 90% for a period of 12 h at 90 °C. This strategy dispenses the origination of cyclic styrene carbonates, which is an appealing concern because of the transformation of CO2 into an inexpensive, renewable and easy excess carbon feedstock.
Highlights
Published: 28 December 2021Many issues regarding the environmental situation have increased the attention being paid to it among the scientific community
We are interested in synthesizing poly ε-caprolactone and cyclic carbonate
1–4 ligands were obtained from the reactions of dehydroacetic acid and amines in ethanol via imine condensaA series of bidentate and tridentate dehydroacetic acid–imine ligands were obtained tion [28] with a small amount of formic acid as catalyst
Summary
Many issues regarding the environmental situation have increased the attention being paid to it among the scientific community. Many chemists are trying to address these issues, and many strategies have been developed as solutions to solve these problems Among these issues, we are interested in synthesizing poly ε-caprolactone and cyclic carbonate. Ring-opening polymerization of ε-caprolactone using metal catalysts is considering to be an efficient method. Many metal catalysts have been studied and developed for catalyzing ε-caprolactone ring-opening polymerization [5,6,7]. The methods for synsynthesizing cyclic carbonates include epoxide–CO or urea–polyol coupling reactions [8–. Thesetypes typesofofligands ligandsare areconsidered considered totobe bedistinctly distinctlyinteresting interestingand anddesirable desirablematerials materialsowing owingtototheir theirunusual unusualcharacteristics, characteristics, which whichnotably notablyinclude includeresource-rich resource-richstructures, structures,easy easysynthetic syntheticprocedures, procedures,and anddiverse diverse chemical applications We selected these ligands to determine their catalytic acchemical applications. Coupling in epoxide–CO coupling reactions andring-opening the ring-opening polymerization of ε-caprolactone
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