It has been widely used in combinatorial chemistry and organic chemistry. It can provide homogeneous reaction conditions and has the advantages of easy purification and easy analysis. Therefore, using PEG as a solvent and/or catalyst has been increasingly applied in laboratory research and industrial production.

PEG as A Solvent

As a solvent, research in recent years tends to be "green" of PEG. With the excellent viscosity, low toxicity, thermal stability, low price, non-volatility, biodegradability, and environmentally friendly characteristics at both room temperature and high temperature, PEG has received more and more attention in synthetic chemistry and heterogeneous catalysis, such as Heck reaction, Suzuki coupling reaction, oxidation reaction, reduction reaction, addition reaction and asymmetric Aldo reaction.

Heck reaction refers to the reaction of halogenated hydrocarbons and activated unsaturated hydrocarbons to produce trans products under palladium catalysis. Using poly(ethylene glycol) (PEG) with molecular weight 2000 (or lower) as an efficient reaction medium for Pd-catalyzed C-C bond formation is more rapid and high yielding, and the catalyst is easily recycled with high efficiency.

Suzuki reaction (also known as Suzuki–Miyaura reaction) is a palladium catalyzed carbon–carbon bond formation between organoboron compounds with aromatic halides. The research reported in 2001 shown that this reaction was preceded in high yield in PEG400 as an inexpensive and non-toxic reaction medium.

Pd-catalyst carbon–carbon bond formation between a terminal alkyne and an aryl or vinyl halide is known as Sonogashira coupling reaction. The first study of this reaction was performed in PEG 6000 as reaction medium and a polymeric PEG-PdL catalyst with high catalytic reusability potential for ten times in the Sonogashira reaction of 4-bromoacetophenone and phenylacetylene.

The Hiyama-coupling is a palladium-catalyzed cross-coupling reaction of organosilanes with organic halides discovered by Hiyama and Hatanaka in 1988. In 2007, researchers first developed a fluoride-free catalyst system employing Pd(OAc)2 in a mixture containing 3 mL of H2O and 3 g of PEG2000 as solvent.