WORK UP SCAVENGER SELECTION
Resin Selection
Solvent Compatibility
Lightly cross-linked polystyrene resins typically require the use of solvents that will swell the resin to allow reagents from the bulk solution to gain access to the resin-bound functional groups. If the reaction solvent does not swell the resin, it may be necessary to add a co-solvent that is compatible with the resin. In this catalog, the names of lightly cross-linked polystyrene resins have a “PS-” prefix.
The resin-bound functional groups of the more highly cross-linked macroporous resins come in contact with
reagents by diffusion through the pore network and do not require the use of a solvent that will swell the resin. Macroporous resins are effective in any solvent that is not reactive with the resin functionality and do not swell
or undergo significant volume changes in the presence of solvents that swell PS resins, such as DCM and THF. In this catalog, the names of macroporous resins have an “MP-’’ prefix. Electrophile Scavengers
Nucleophile Scavengers
Metal Scavengers
MP-Trisamine
MP-Isocyanate
PS-DEAM
PS-Trisamine
PS-Tosyl hydrazide
PS-Isocyanate
PS-Benzaldehyde
PS-Thiophenol
PS-TsCl(HL)
MP-Carbonate
PS-Triphenylphosphine
MP-TsOH
MP-TMT PS-TBD
MP-Trisamine
PS-Triphenylphosphine
Table 1. Scavenger resin applications require an excess of scavenger resin, ca. 3-5 equivalents relative to the excess reagent or by-product to be scavenged. Scavenging of less reactive substrates can be accelerated by using two sequential treatments with scavenger resin. Acids
MP-TsOH
Bases
MP-Carbonate PS-DIEA PS-NMM PS-TBD
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Table 2. MP-Carbonate is effective for neutralization and for reactions requiring a mild inorganic base. Bound tertiary amines PS-DIEA and PS-NMM are used as acid acceptors which can be removed by filtration and are useful analogs to small molecule amines. Typical reactions include esterifications, amidation, mesylate, and sulfonamide formation. For reactions requiring stronger bases than tertiary amines, the bound guanidine base PS-TBD is available. PS-TBD is sufficiently basic to deprotonate moderately acidic hydrogens, such as phenolic and activated methylenes.