Dual Catalyst System for Asymmetric Alternating Copolymerization of Carbon Dioxide and Cyclohexene Oxide with Chiral Aluminum Complexes: Lewis Base as Catalyst Activator and Lewis Acid as Monomer Activator

Citations Over TimeTop 10% of 2012 papers

Abstract

Optically active aluminum complexes such as Schiff base, binuclear β-ketoiminate, and bisprolinol complexes were found to promote asymmetric alternating copolymerizations of carbon dioxide and cyclohexene oxide. The aluminum Schiff base complexes–tetraethylammonium acetate afforded isotactic poly(cyclohexene carbonate)s with low enantioselectivities. Lewis bases having two coordinating sites were utilized to enhance activity and selectivity based on the binuclear structure of the aluminum β-ketoiminate clarified by X-ray crystallography. [2gAlMe]2–bulky bisimidazole produced the alternating copolymer with high enantioselectivity (62% ee). The polymerization is considered to preferentially proceed at more crowded, enantioselective site owing to coordination of bulky Lewis bases to aluminums in less enantioselective sites. 32AlMe–2-picoline also exhibited a high enantioselectivity (67% ee). Methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) was applied to perform faster and more enantioselective copolymerizations at low temperature (82% ee). The asymmetric copolymerizations were found to be significantly dependent on size of epoxide, temperature, and kind/amount of activators.

Related Papers

• → Efficient allylic oxidation of cyclohexene with oxygen catalyzed by chloromethylated polystyrene supported tridentate Schiff-base complexes(2010)52 cited
• → Chemical transformations of captured CO2 into cyclic and polymeric carbonates(2019)26 cited
• → Complexes of poly(2-N,N-dimethylaminoethyl) methacrylate with heavy metals II. Oxidation of cyclohexene with tert-butylhydroperoxide(2007)5 cited
• → Alumina‐Catalyzed Alcoholysis of Cyclohexene Oxide(1979)2 cited
• → Asymmetric Opening of the Epoxide Ring in Cyclohexene Oxide by Thiophenol Using Homochiral Phosphinamide Catalysts(2007)1 cited