Solid-Bound Reagents

Polymer-bound reagents are functional polymers designed to perform synthetic transformations in same way as their solution counterparts. Excess reagent and by-products remain attached to the resin, while the end product is purified by simple filtration.

In addition to simplifying purification, bound reagents also offer other unique capabilities. Functionalities that would react with each other when present as small molecules can be used simultaneously when they are resin-bound. In some circumstances resin-bound active intermediates are sufficiently stable that they can be stored for future use. Polymer-bound reagents are also used in "Catch and Release" strategies in which a small molecule is "caught" on the resin as an activated polymer intermediate and is then "released" by a subsequent transformation.

Biotage uses two different resin types for its scavengers, 1% crosslinked poly(styrene-co-divinylbenzene) and highly crosslinked, macroporous polystyrene. The 1% crosslinked polystyrene is designated by PS-. MP- designates highly crosslinked, macroporous resin.

Lightly crosslinked polystyrenes typically require the use of solvents that will swell the resin to allow reagents access to the resin-bound functional groups. In cases where the solvent does not swell the resin, it may be necessary to add a co-solvent that is compatible with resin swelling, e.g. THF. Swelling data can be found in the specification documents for the individual resins.

Highly crosslinked macroporous resins swell significantly less in solvent and they are not dependent on swelling to be effective. Instead, reagents diffuse through the pore structure to reach reactive sites. For this reason, MP- resins can be used in confined volumes where swelling would be a problem. They can also be used with a much wider variety of solvents.