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Bifunctional Aluminum Catalysts for the Chemical Fixation of Carbon Dioxide into Cyclic Carbonates

2018; American Chemical Society; Volume: 6; Issue: 4 Linguagem: Inglês

10.1021/acssuschemeng.8b00102

2168-0485

Felipe de la Cruz‐Martínez, Javier Martı́nez, Miguel A. Gaona, Juan Fernández‐Baeza, Luis F. Sánchez‐Barba, Ana M. Rodrı́guez, José A. Castro‐Osma, Antonío Otero, Agustín Lara‐Sánchez,

Asymmetric Hydrogenation and Catalysis

Bifunctional aluminum complexes supported by novel zwitterionic NNO-donor scorpionate ligands were found to be efficient bifunctional catalysts for cyclic carbonate synthesis from terminal and internal epoxides in good yields and with broad substrate scope. Neutral scorpionate ligands (1–2) were designed and used as precursors to obtain two novel zwitterionic NNO-heteroscorpionate ligands (3–4). Reaction of 3 or 4 with [AlX3] (X = Me, Et) in a 1:1 or 1:2 molar ratio afforded the mononuclear and dinuclear cationic aluminum complexes [AlX2{κ2-mbpzbdmape}]I2 (X = Me (5), Et (6)), [AlX2{κ2-mbpzbdeape}]I2 (X = Me (7), Et (8)), [{AlX2(κ2-mbpzbdmape)}(μ-O){AlX3}]I2 (X = Me (9), Et (10)), and [{AlX2(κ2-mbpzbdeape)}(μ-O){AlX3}]I2 (X = Me (11), Et (12)) with elimination of the corresponding alkane. These complexes were investigated as catalysts for cyclic carbonate formation from epoxides and carbon dioxide in the absence of a co-catalyst. Complex 7 was found to be the most active catalyst for cyclic carbonate formation from various epoxides and carbon dioxide.