A new method for the mild sulfurization of phosphorus(III) compounds with thiiranes catalyzed by ReOCl3(PPh3)(2) (I) or ReOCl3(SMe2)OPPh3) (II) is reported. The novel catalytic sulfur transfer reactions are rapid and occur efficiently under ambient conditions in organic solvents. This methodology enabled propylene sulfide to be used as a sulfurizing agent for the synthesis of a protected nucleotide phosphorothioate ester. (C) 1997 Elsevier Science Ltd.