Palladium-mediated organic synthesis using porous polymer monolith formed in situ as a continuous catalyst support structure for application in microfluidic devices

Abstract

The development and advantages of in situ synthesis of organic polymer monolith supports for metal pre-catalysts in narrow bore fused silica capillary microreactors are described. Catalyst immobilisation involves the covalent attachment of ligand binding sites to the porous polymer monolith, followed by coordination to metal centres. Flow-through microreactors using poly(chloromethylstyrene-co-divinylbenzene) monolith in capillaries of internal diameter 250 micrometers were used successfully for Suzuki– Miyaura and Sonogashira reactions, utilising both 1,10-phenanthroline and imidazole/carbene binding to palladium and with very low palladium leaching, illustrating the potential of flow-through technology at the microscale level using organic monolith support for transition metal catalysed reactions. Polymer monoliths, present as a continuous phase filling capillaries and bonded to the internal surface, are promising new materials for solid supported catalysis in microreactors. The performance of the flow-through microreactors included quantitative yields for the conversion of iodobenzene in the Suzuki–Miyaura reaction, and quantitative yields for Sonagashira coupling of p-iodoacetophenone with phenylacetylene.