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Zwitterionic Hydrobromic Acid Carriers for the Synthesis of 2-Bromopropionic Acid From Lactide

Matthias Kehrer, Julian Mehler, Nicola Taccardi, Jens Nagengast, Julian Kadar, Dimitris Collias, Peter Dziezok, Peter Wasserscheid, Jakob Albert

ChemSusChem. 2018 Mar 22;11(6):1063-1072.

PMID: 29389081

Abstract:

A convenient and highly efficient way of synthesizing 2-bromopropionic acid (2-BrPA) from lactide is presented. The procedure uses ionic liquids obtained from the addition of HBr to ammonium-based zwitterions as the solvent and bromination agent. The buffered HBr acidity, high polarity, and charge stabilizing character of the ionic liquid (IL) enable the synthesis of 2-BrPA with excellent selectivity. The best results are obtained with an imidazolium-based IL, that is, 1-(4-butanesulfonic acid)-3-methylimidazolium bromide ([MIMBS]Br). The HBr loading and water content of the IL are crucial parameters for the bromination reaction. The formed 2-BrPA product can be selectively isolated by extraction from the IL, and the unconverted substrate remains in the [MIMBS]Br IL for the next run. Successful recycling of the IL over four cycles is demonstrated.

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