One‐Component Aluminum(heteroscorpionate) Catalysts for the Formation of Cyclic Carbonates from Epoxides and Carbon Dioxide

• Published in: ChemSusChem 2017-03, Vol.10 (6), p.1175-1185
• Main Authors: Martínez, Javier, Castro‐Osma, José A., Alonso‐Moreno, Carlos, Rodríguez‐Diéguez, Antonio, North, Michael, Otero, Antonio, Lara‐Sánchez, Agustín
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum - chemistry; Bimetals; Carbon dioxide; Carbon Dioxide - chemistry; carbon dioxide fixation; Carbonates; Carbonates - chemical synthesis; Carbonates - chemistry; Catalysis; Catalysts; Cationic; cyclic carbonates; epoxides; Epoxy Compounds - chemistry; Hydrocarbons, Chlorinated - chemistry; Models, Molecular; Molecular Conformation; Stereoisomerism; sustainable chemistry; Synthesis (chemistry)
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201601370

New neutral and zwitterionic chiral NNO‐donor scorpionate ligands 1 and 2 were designed to obtain new mononuclear and dinuclear NNO‐heteroscorpionate aluminum complexes. Reaction of 1 with [AlR3] (R=Me, Et) in a 1:1 or 1:2 molar ratio afforded the neutral mononuclear alkyl complexes [AlR2(κ2‐bpzappe)] {R=Me (3), Et (4); bpzappeH=2,2‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1‐[4‐(dimethylamino)phenyl]‐1‐phenylethanol} and bimetallic complexes [{AlR2(κ2‐bpzappe)}(μ‐O){AlR3}] [R=Me (5), Et (6)]. By reaction of complexes 3–6 with PhCH2Br, mononuclear and dinuclear cationic aluminum complexes [AlR2(κ2‐bbpzappe)]Br {R=Me (7), Et (8); bbpzappeH=N‐benzyl‐4‐[2,2‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐1‐hydroxy‐1‐phenylethyl]‐N,N‐dimethylbenzenaminium bromide} and [{AlR2(κ2‐bbpzappe)}(μ‐O){AlR3}]Br [R=Me (9), Et (10)] were synthesized. Both neutral aluminum complexes in the presence of Bu4NBr and cationic aluminum complexes were investigated as catalysts for cyclic carbonate formation from epoxides and carbon dioxide. Amongst them, complex 10 was found to be an efficient one‐component catalyst for the synthesis of cyclic carbonates from both monosubstituted and internal epoxides and was shown to have broad substrate scope. Fixation sensation: The synthesis and structural characterization of one‐component (scorpionate)Al complexes are reported. An investigation of these complexes as catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide has led to the development of a bimetallic one‐component aluminum complex that acts as an efficient catalyst for the production of cyclic carbonates from a broad range of epoxides in good to excellent yields.