Lawesson's reagent

Other names: 2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide

C₁₄H₁₄O₂P₂S₄

6/50 common

Lawesson’s reagent is a powerful thiation agent used to convert C=O carbonyl groups into C=S thiocarbonyl derivatives. Its four-membered phosphorus-sulfur heterocycle readily decomposes to generate reactive phosphorus sulfide species, enabling the synthesis of thioketones, thioamides, and phosphorothioates. First developed in the 1950s, it has become a staple in organic synthesis. In its pure form, it is a yellow crystalline solid with an intensely pungent, sulfurous odor, often compared to rotting cabbage. Despite its smell, its reactivity and efficiency make it invaluable in sulfur chemistry.