Polymer-Supported Organotin Hydrides as Immobilized Reagents for Free Radical Synthesis
17 September 2002 (online)
Two immobilized tin hydrides have been developed as reagents for free radical organic syntheses, for both batch or column procedures. Separation of the reaction product from the reagent, which has been problematic in many cases with monomer tin hydrides so far, is easily effected now by simple filtration or elution. In both reactive polymers, the stannyl group is separated from the phenyl ring of a polystyrene by two methylene units, hence is stable towards splitoff. The first is prepared by uniform monohydrostannation of commercial m-/p-divinylbenzene by dibutyltin chloride hydride, polymerization of the product, and reduction by means of dibutylaluminum hydride. It contains 1.5 mmol active Sn-H/g polymer, and has been recycled after use at least five times without noticeable loss of activity. The second one is obtained by vinylation of a given polystyrene, subsequent hydrostannation and reduction (active Sn-H: 0.9 mmol/g).