Monolithic polymer supports and scavengers were prepared via nucleophilic displacement of chlorine in poly(4-vinylbenzyl chloride-codivinylbenzene) PolyHIPE materials. Reactions of monolithic PolyHIPE with tris(2-aminoethyl)amine, 4-aminobutanol, tris(hydroxymethyl)aminomethane, morpholine, and hexamethylenetetramine led to functionalized polymers with amino and hydroxy functionalities with high degrees of conversion. 4-Chlorobenzoyl chloride was efficiently and rapidly scavenged from solution by the tris(2-aminoethyl)amine derivative of monolithic poly(4-vinylbenzyl chloride-co-divinylbenzene) PolyHIPE at ambient temperature.
As part of ongoing research efforts to discover alternative support materials to polymer beads
for use in polymer-supported synthesis, particularly under flow-through conditions, this work
involves the synthesis of PolyHIPE (High Internal Phase Emulsion) polymer monoliths.
PolyHIPEs containing high loadings of chloromethyl groups were efficiently prepared by the
direct copolymerization of 4-vinylbenzyl chloride and divinylbenzene monomers. The ‘Merrifield'
PolyHIPE proved to be an excellent support for batch and flow-through Suzuki cross-coupling
reactions. A remarkably high yield of pure biaryl product was obtained using the PolyHIPE
support in cubic form and utilizing an electron-rich boronic acid. In comparison to polymer beads,
this material was found to be a much more efficient support in both batch and continuous flow
modes. PolyHIPE converted a greater amount of chloromethyl groups into biaryl product under
identical reaction conditions. It is suggested that the absence of channelling with PolyHIPE
monoliths gives better performance under flow-through conditions than permanently porous
beads.
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