Aluminum derivatives incorporating 4,4′-methylenebis(cyclohexyl) linked dehydroacetic acid-imine ligands: structural aspects, CO2/styrene oxide coupling reaction

A series of methylene-bis-cyclohexyl amine ligands, LMeH2, LPhH2 and L(DA)H(2 )are generated from the reaction of 4,4'-methylenebis(cyclohexylamine) with 2,4-pentanedione, benzoylacetone, and dehydroacetic acid, respectively in methanol. Later, the combination of LMeH2, LPhH2, and LDAH2 with two equivalents of AlMe3 in methylene chloride initiate the di-aluminum compounds, L-Me[AlMe2](2), L-Ph[AlMe2](2) and L-DA[AlMe2](2). As supporting catalysts, the Al-derivatives are effective in the coupling of CO2 with epoxide to form cyclic carbonates. Interestingly, the optimized catalyst system displays > 90% conversion of the epoxides in solvent free condition while employing TBAI (tetra-n-butylammonium iodide) and TBAB (tetra butyl ammonium bromide) as co-catalyst. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

A series of methylene-bis-cyclohexyl amine ligands were synthesized and reacted with AlMe3 to form di-aluminum compounds, which acted as effective catalysts for the coupling reaction of CO2 with epoxide. The optimized catalyst system exhibited high conversion rates of epoxides under solvent-free conditions, using TBAI and TBAB as co-catalysts.