Abstract
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•Use of plant based benzoates as sustainable green anions for ionic liquids.•Benzoates anions induce supramolecular polymeric aggregation.•These short alkyl chain ionic liquids can serve as catalyst in aqueous medium.•Benzoate containing ILs are excellent substitutesfor base catalyzed organic reactions.
Naturally occurring benzoic acid (BA) derived anions have been used to prepare halogen free hydrophilic ionic liquids (ILs 1–4). The supramolecular polymeric aggregation behaviour of these ILs has been studied through high-resolution electron spray ionization mass spectrometry (HR-ESI-MS). Furthermore, these ILs were applied as catalyst/phase transfer catalyst in the synthesis of tetrahydrobenzo[b]pyran and its derivatives. These reactions were conducted in aqueous medium under ultrasound assistance. The results suggested that 1-ethyl-3-methylimidazolium 2-hydroxybenzoate (IL-1) was a highly efficient catalyst yielding 86.9% product in 30 min. In addition, the impact of aggregation behaviour of ILs on their catalytic activity was also investigated.