Dinuclear Aluminum Poly(phenolate) Complexes as Efficient Catalysts for Cyclic Carbonate Synthesis

A series of dinuclear aluminum complexes 1–4 stabilized by amine-bridged poly­(phenolato) ligands have been synthesized, which are highly active in catalyzing the cycloaddition of epoxides and CO2. In the presence of 0.3 mol % complex 3 and 0.9 mol % NBu4Br at 1 bar CO2 pressure, terminal epoxides bearing different functional groups were converted to cyclic carbonates in 60–97% yields. Complex 3 is one of the rare examples of Al-based catalysts capable of promoting the cycloaddition at 1 bar pressure of CO2. Moreover, reactions of more challenging disubstituted epoxides also proceeded at an elevated pressure of 10 bar and afforded cyclic carbonates in 52–90% yields.