Polyethylene-Bound Tin Halide as a Catalyst for Reductions of Alkyl Halides Using NaBH4

Abstract

The synthesis, characterization and use of polyethylene-bound dibutyltin chloride as a catalyst for the reduction of alkyl halides using a suspension of sodium borohydride in toluene and a crown ether as a phase transfer catalyst is described. This tin-containing soluble macromolecule was synthesized by anionic oligomerization of ethylene followed by electrophilic substitution of the resulting “living” oligomer with dibutyltin dichloride. The resulting polyethylene-bound tin reagent was characterized by NMR and IR spectroscopy. It was used as a cocatalyst (5–10%) along with 10–20% of a phase transfer catalyst (usually a crown ether) in reductions of alkyl halides using a suspension of sodium borohydride in hot toluene at 110 °C. Preliminary kinetic studies imply that the reaction rate is dependent on the rate of transport of sodium borohyride into the toluene phase by the crown cocatalyst. Yields of reduced products are typically >90%.