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.