Acrylate dimerisation under ionic liquid–supercritical carbon dioxide conditions

Abstract

Ionic liquid 1-n-butyl-3-methylimidazolium tetrafluoroborate and supercritical CO₂ have been used for the biphasic palladium-catalysed dimerisation of methyl acrylate. Substrate and product distribution between the two phases and extraction capability of scCO₂ are evaluated. The effect of the biphasic medium on the catalyst performance is also addressed. The selectivity for the tail-to-tail dimers is >98%, as high as under monophasic conditions. The same trend stands for turnover number and frequency although there is a lower substrate to palladium ratio in the IL phase. The CO₂-rich phase acts as a substrate and product reservoir, a suitable case for studying the reaction under continuous feed and extraction regime.