Soluble Polyethylene- and Polystyrene-Bound Tin Halides as Catalysts for Reductions of Alkyl and Aryl Bromides and Iodides by Sodium Borohydride

Article abstract of DOI:10.1021/jo00282a034

The synthesis, characterization, and use of soluble polyethylene- and polystyrene-bound tin chlorides as catalysts for the reduction of alkyl halides using a suspension of sodium borohydride in toluene and a crown ether as a phase-transfer catalyst are described.These tin-containing soluble macromolecules were synthesized by anionic oligomerization of ethylene or styrene followed by electrophilic substitution of the resulting "living" oligomer with various organic tin halides including tin tetrachloride, n-butyltin trichloride, di-n-butyltin dichloride, and diphenyltin dichloride.The resulting oligomer-bound tin reagents were characterized by 1H and 119Sn NMR spectroscopy, and the tin content of the oligomers was analyzed by ICP analysis.Typically the tin reagents were used as cocatalysts (ca. 10percent) along with 10-20percent of a crown ether as a phase-transfer catalyst in reductions of primary, secondary, and aryl halides using a suspension of sodium borohydride in hot toluene at 110 deg C.Kinetic studies showed that the reaction rate was dependent on the concentration of the tin catalyst and the secondary halides reacted slightly faster than primary halides.