24623-65-2Relevant articles and documents
Robust bifunctional aluminium-salen catalysts for the preparation of cyclic carbonates from carbon dioxide and epoxides
Rulev, Yuri A.,Gugkaeva, Zalina,Maleev, Victor I.,North, Michael,Belokon, Yuri N.
, p. 1614 - 1623 (2015)
Two new one-component aluminium-based catalysts for the reaction between epoxides and carbon dioxide have been prepared. The catalysts are composed of aluminium-salen chloride complexes with trialkylammonium groups directly attached to the aromatic rings of the salen ligand. With terminal epoxides, the catalysts induced the formation of cyclic carbonates under mild reaction conditions (25-35 °C; 1-10 bar carbon dioxide pressure). However, with cyclohexene oxide under the same reaction conditions, the same catalysts induced the formation of polycarbonate. The catalysts could be recovered from the reaction mixture and reused.
Electronic Effects of Aluminum Complexes in the Copolymerization of Propylene Oxide with Tricyclic Anhydrides: Access to Well-Defined, Functionalizable Aliphatic Polyesters
Van Zee, Nathan J.,Sanford, Maria J.,Coates, Geoffrey W.
, p. 2755 - 2761 (2016)
The synthesis of well-defined and functionalizable aliphatic polyesters remains a key challenge in the advancement of emerging drug delivery and self-assembly technologies. Herein, we investigate the factors that influence the rates of undesirable transesterification and epimerization side reactions at high conversion in the copolymerization of tricyclic anhydrides with excess propylene oxide using aluminum salen catalysts. The structure of the tricyclic anhydride, the molar ratio of the aluminum catalyst to the nucleophilic cocatalyst, and the Lewis acidity of the aluminum catalyst all influence the rates of these side reactions. Optimal catalytic activity and selectivity against these side reactions requires a careful balance of all these factors. Effective suppression of undesirable transesterification and epimerization was achieved even with sterically unhindered monomers using a fluorinated aluminum salph complex with a substoichiometric amount of a nucleophilic cocatalyst. This process can be used to synthesize well-defined block copolymers via a sequential addition strategy.
Asymmetric bis-salicylaldiminato binuclear titanium complexes for ethylene polymerization and copolymerization
Qin, Yawen,Li, Tingcheng,Chen, Xiong,Li, Jian,Meng, Xiang,You, Qingliang,Xie, Guangyong
, p. 11390 - 11398 (2021/07/06)
Polyolefins with high molecular weight and broad molecular weight distribution have attracted great attention due to their ease of processing and wide applications. In this paper, methylene-bridged asymmetric disalicylaldimine ligands bearing phenylthio and alkylthio sidearms (4a-4c) were synthesized from methylene-bridged disalicylaldehyde that reacted successively with 2-phenylthio and 2-alkylthio anilines, which then directly coordinated with TiCl4to afford asymmetric bis-salicylaldiminato binuclear titanium complexes5a-5cin one step. The asymmetric complexes were detailedly characterized by FTIR,1H NMR,13C NMR, and elemental analysis. Under the activation of modified methylaluminoxane (MMAO), these asymmetric complexes displayed high activity over 106g mol(Ti)?1h?1atm?1for ethylene polymerization and copolymerization with 1-hexene or norbornene. Compared with the corresponding mononuclear complexes, the asymmetric binuclear catalysts showed higher catalytic activity (up to 2.29 × 106g mol(Ti)?1h?1atm?1) for ethylene polymerization to produce higher molecular weight polyethylenes with much wider molecular weight distribution due to the presence of two different active centers. For ethylene polymerization and copolymerization with 1-hexene, the catalytic activity of binuclear5awhich carries phenylthio and methylthio sidearms and the properties of the obtained polyolefins were more similar to those of mononuclear6bwhich bears a phenylthio sidearm, indicating that the phenylthio group exerted major influences. However, for ethylene/norbornene copolymerization,5ashowed an activity significantly higher than that of6b, yet similar to that of mononuclear6awhich bears a methylthio sidearm, indicating that the methylthio sidearm in5aplayed a major role in this case. A smaller sidearm in the ligand was more conducive to the polymerization reaction when large comonomers were involved, and a balance of the steric hindrance between the ligand and the comonomer might be needed for achieving high catalytic performance.
Vanadium-Catalyzed Oxidative Intramolecular Coupling of Tethered Phenols: Formation of Phenol-Dienone Products
Gilmartin, Philip H.,Kozlowski, Marisa C.
supporting information, p. 2914 - 2919 (2020/04/10)
A mild and efficient method for the vanadium-catalyzed intramolecular coupling of tethered free phenols is described. The corresponding phenol-dienone products are prepared directly in good yields with low catalyst loadings. Electronically diverse tethered phenol precursors are well tolerated, and the catalytic method was effectively applied as the key step in syntheses of three natural products and a synthetically useful morphinan alkaloid precursor.
