Phosphine functionalized polyphosphazenes: soluble and re-usable polymeric reagents for highly efficient halogenations under Appel conditions

摘要

In this paper we present the preparation and application of a novel soluble phosphine functionalized polyphosphazene (poly[3-(diphenylphosphino)propylamino]phosphazene) and investigate its application as a polymeric reagent. Upon chlorination of the pendant phosphine groups, the polymer was found to facilitate the rapid and efficient transformation of alcohols to the corresponding chlorides and bromides under Appel-type conditions. Reaction times followed by P-31 NMR spectroscopy are shown to be rapid (several minutes) and the yields for the transformation of alcohols to the corresponding halides are in the range 80-99 %. The facile recovery of the oxidized polymeric agent by precipitation is also described, offering a significant advantage over notoriously difficult to remove small molecule phosphine oxide by-products. Furthermore the regeneration of the reactive phosphine chloride pendant groups is demonstrated, which could be efficiently re-used in a further chlorination reaction.