Rapid SmI2-mediated reductions of alkyl halides and electrochemical properties of SmI2/H2O/amine

Mixtures of SmI2/H2O/amine have been found to reduce alkyl halides more efficiently than SmI2/HMPA/alcohol mixtures at room temperature. Alkyl and aryl iodides were quantitatively reduced in <1 min and alkyl bromides in 10 min, while alkyl and aryl chlorides required more than 5 h for completion. Determination of the reaction order of Et3N in the reduction of 1-chlorodecane showed that the reaction order is one. Water was shown not to participate in the rate-determining step of this reduction. There was a significant change of the UV-vis spectrum and color Of SMI2 upon addition of either PMDTA or water, while no effect was observed with the addition of Et3N or TMEDA. Although the combination Of SMI2, water, and amines produces a very efficient reducing system, cyclic voltammetric experiments showed that the redox potential is nearly identical with that Of SMI2 alone. These results are consistent with precipitation providing the driving force for reduction. Taken together, the results of these experiments show that the combination of SmI2/H2O/amine provides a fundamentally novel and useful approach to enhance the reactivity Of SMI2.