PEG as a Reaction Solvent

PPG 425 has been used in the preparation of a range of benzaldehydes that were subsequently used in the solvent free synthesis of calix[4]resorcinarenes. The aldehydes are isolated in near quantitative yields by distillation from the PPG, which can be recycled. PPG has also been used in the indium metal mediated allylation of imines and sulfonylimines. Ultrasound was used for two reasons to clean the metal surface and to increase the solubility of the imine in PPG. The solvent was recycled three times, but a desire to develop an easier drying and recycling method was indicated. 

Polyethylene glycol in aqueous biphasic reactive extraction. Aqueous biphasic reactive extraction (ABRE) is used to describe the use of ABS in biphasic reaction chemistry. When it is used effectively, it can aid in separating reactants, products and catalysts, and increase yields and selectivities. Although, PEG and ABS have been used in bio-separations since the 1950s, it is only during the last 10 years that they have been explored as green reaction media. The three main characteristics offered by ABRE in this area are  

Phase separation of reactants and products that can act to drive the reaction forward. 

A PEG-rich top phase in PEG-salt ABS, which has organic solvent type properties and can act as a reaction medium. 

Catalytic PEG and metal complexes can be used and separated after the reaction. 

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