General Conditions for Use
Removal of excess carbonyls from solution generally requires upto a three-fold excess of PS-TsNHNH2. Addition of a catalytic amount of HOAc (5–10%) may be required for ketones and hindered aldehydes. HOAc is also required for sequestering aldehydes in DMF. Complete removal of common aldehydes occurs in 0.5 to 3 h and removal of a ketone takes from 2 to 16 h. Elevated temperatures were required for hindered ketones (e.g. 2,6-dimethylcyclohexanone). Upon completion of the scavenging, the resin is rinsed with a suitable solvent (i.e. those which swell polystyrene), and the product is isolated by concentration.
Application to Grignard Reactions
PS-TsNHNH2 was successfully used to work up the synthesis of alcohols by addition of a Grignard reagent to aldehydes. PS-TsNHNH2 is also potentially useful as a polymer-supported reagent. Supported sulfonyl hydrazones, formed by condensation with carbonyl compounds, can be utilized in further synthetic transformations. The high accessibility of tosyl hydrazide functional groups in PS-TsNHNH2 afford high synthetic fidelity relative to reported systems.
This scavenger can be applied to the rapid clean-up of tertiary amines prepared through reductive amination using MP-Triacetoxyborohydride and microwave irradiation.