Synthesis of cyclic carbonates catalysed by aluminium heteroscorpionate complexes

Abstract

Parallel catalyst screening was used to develop new aluminium scorpionate based catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide. Nineteen complexes were included in the catalyst screening, which resulted in the development of trimetallic complex 27 which had the same catalytic activity at one bar carbon dioxide pressure that the initial lead complex (8) had at ten bar carbon dioxide pressure. The combination of complex 27 and tetrabutylammonium bromide could be used to form cyclic carbonates from a range of terminal epoxides and kinetic studies showed that the reactions were first order in epoxide, complex 27 and tetrabutylammonium bromide concentrations. Based on this data a catalytic cycle has been proposed which accounts for all of features of the catalyst system.