A wide selection of phosphine activators has been screened to improve the selection process in the asym- metric Appel reaction. Of the activators screened, hexachloroacetone (HCA) gave the highest selectivity with excellent yield, but at least one of its by-products, pentachloroacetone (PCA), can become involved in the selection process. In addressing this, a new reaction of phosphines with oxalyl chloride was discov- ered that can also generate the key intermediate chlorophosphonium salt (CPS), gives better enantiose- lectivity and possesses significant advantages over other phosphine activators.