Alternative Solvents and Recycle of the Catalyst

Abstract In the search for more environmentally benign alternatives to common organic solvents water, ionic liquids and perfluorinated solvents display valuable features, being able in some cases to influence the outcome of asymmetric reactions and offering additional gain for the catalyst recycle by liquid-liquid extraction. Although some classical catalysts have been used in their native form in these non-conventional reaction media, in most cases a suitable structural modification of the ligands or organocatalysts is required in order to increase their phase affinity and recyclability. In a complementary approach, catalysts have been immobilized on a variety of unsoluble materials to be recovered from organic solutions by simple liquid/solid-phase separation. Since some limits in the catalytic performances could stem from the heterogeneous reaction conditions, there is an increased interest in the development of catalysts covalently bonded to soluble macromolecular supports and easily recyclable after selective precipitation or ultrafiltration.

Keywords Non-conventional solvents • Water-compatible catalysts • Catalyst recycle • Self-supported catalysts • Soluble macromolecular supports • Magnetic nanoparticles

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