Sustainable and Reusable Sulfonic Acid-Functionalized Task-Specific Ionic Liquid Catalysts for Multicomponent Reactions. A Review

Abstract

Improvements in Sustainable Organic Synthesis are usually related to the investigation of less hazardous, non-corrosive and renewable materials, as well as waste prevention, energy efficiency, solvent-free reactions, and the development of efficient reusable catalysts. In this context, multicomponent reactions emerged as important strategies for the rapid and more sustainable synthesis of organic molecules. In addition, the use of task-specific ionic liquids as non-conventional solvents and/or catalysts in multicomponent reactions has recently received great attention, contributing to the development of greener synthetic methodologies. This review describes the studies on the use of structurally diverse homogeneous and heterogeneous sulfonic acid-functionalized task-specific ionic liquids as acidic catalysts for multicomponent reactions applied to the synthesis of nitrogen- and oxygen-based heterocycles, as well as related compounds. The combination of the green credentials of multicomponent reactions and acidic ionic liquids are able to improve process sustainability and green metrics, contributing to sustainable chemical development and, ultimately, to economic growth and cleaner industrial production.

Groebke‐Blackburn‐Bienaymé Multicomponent Reaction Catalysed by Reusable Brønsted‐Acidic Ionic Liquids

“…[58] Also, BAILs have been recently reported as catalysts for the multicomponent synthesis of dihydropyrido [2,3-d]pyrimidines, [59] 5-dihydro-2H-pyrrol-2ones, [60] and dihydropyrano [2,3-c]pyrazoles, [61] among several other important heterocyclic scaffolds. [57] The combination of the synthetic advantages of multicomponent reactions (i. e. atom-efficiency, high molecular diversity and complexity, waste reduction, and operational simplicity) with the fine-tuned properties of ionic liquids can offer many possibilities for the development of eco-friendly heterocyclic synthetic approaches. [62] Nevertheless, the use of ionic liquids in GBB reactions, either as reaction media or catalyst, is relatively rare and only few examples describing the use of guanidinium ionic liquids and ordinary 1-butyl-3-methylimidazolium bromide are reported in the literature.…”

“…[56] Recently, we reviewed the use of sulfonic acid-functionalized TSILs as homogeneous and heterogeneous catalysts for MCRs. [57] For example, enantioselective Biginelli MCR for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones can be efficiently catalysed by chiral TSIL composed by a functionalized dialkyl imidazolium cation and a chiral phosphoric acid anion, in a very efficient asymmetric counter anion-directed catalytic approach. [58] Also, BAILs have been recently reported as catalysts for the multicomponent synthesis of dihydropyrido [2,3-d]pyrimidines, [59] 5-dihydro-2H-pyrrol-2ones, [60] and dihydropyrano [2,3-c]pyrazoles, [61] among several other important heterocyclic scaffolds.…”