Recent advances in polyethylene glycol as a dual-functional agent in heterocycle synthesis: Solvent and catalyst

Abstract

Reactant solubility, which dictates achievable concentrations, and the stability of reaction intermediates (excited states), solvents modulate the potential energy landscape and influence reaction rates. Consequently, solvent selection is pivotal in optimizing process productivity, economic feasibility, and environmental footprint. At present, organic synthesis pivots around the idea of sustainability. In particular, PEG-400, a popular solvent and phase transfer catalyst, is considered greener as it can be reused several times without significant loss in its catalytic activity, which checks the box regarding sustainability. This review highlights the emerging potential of Polyethylene Glycol 400 (PEG-400) as a dual-threat agent in sustainable organic synthesis. We explore its efficacy as a catalyst, promoting various reactions under mild conditions and often eliminating the need for traditional metal catalysts. Additionally, PEG-400's role as a green solvent is addressed, emphasizing its biodegradability, low toxicity, and ability to facilitate reactions without hazardous Volatile Organic Compounds (VOCs). The review examines recent research on PEG-400 mediated reactions, showcasing its effectiveness in diverse transformations, thus exploring the potential of PEG 400 as a facilitator for heterocycle synthesis in both multicomponent reactions and stepwise approaches. It identifies exciting research directions that promise to expand the boundaries of polymer-based solvents in heterocyclic chemistry.