# Ionic Liquids in the Aza-Michael Reaction: From Early Imidazolium Salts to Bio-Based Catalytic Media

## TL;DR

This paper reviews how ionic liquids have evolved as effective media and catalysts for the aza-Michael reaction, a key method for forming carbon-nitrogen bonds in organic chemistry.

## Contribution

The paper provides a comprehensive and critical overview of the development and application of ionic liquids in aza-Michael reactions, emphasizing recent advances in sustainable and efficient C–N bond formation.

## Key findings

- Ionic liquids have been shown to stabilize intermediates and enhance electrophilicity in aza-Michael reactions.
- Task-specific ionic liquids with Brønsted acidic or basic motifs improve activity and selectivity.
- Supported and polymeric ionic liquids combine reactivity with recyclability and operational simplicity.

## Abstract

The aza-Michael reaction is a fundamental transformation for carbon–nitrogen bond formation, providing efficient access to β-amino carbonyl compounds, nitriles, and related nitrogen-containing building blocks of broad importance in medicinal chemistry and organic synthesis. Over the past two decades, ionic liquids (ILs) have attracted considerable attention as alternative reaction media, promoters, and catalysts for aza-Michael reactions, owing to their distinctive physicochemical properties and tunable structures. This review presents a comprehensive and critical overview of ionic-liquid-mediated aza-Michael reactions, emphasizing the evolution of IL design from early imidazolium-based systems to modern task-specific, supported, and bio-derived ionic liquids. Conventional room-temperature ionic liquids are discussed as non-innocent solvents capable of stabilizing charged intermediates and enhancing electrophilicity, thereby enabling catalyst-free or metal-assisted aza-Michael additions. Subsequent sections focus on task-specific ionic liquids incorporating Brønsted acidic, basic, hydrogen-bond-donating, or bifunctional motifs, highlighting how rational structural design translates into improved activity, selectivity, and substrate scope. Particular attention is devoted to guanidine-, DABCO-, and DBU-based ionic liquids, where mechanistic studies reveal cooperative activation modes rather than simple acid–base catalysis. Recent advances in supported and polymeric ionic liquids are also reviewed, demonstrating effective strategies to combine IL-like reactivity with enhanced recyclability and operational simplicity. Overall, this review clarifies the diverse roles of ionic liquids in aza-Michael chemistry and outlines current challenges and future perspectives toward more sustainable and efficient C–N bond-forming methodologies.