Lawson reagent, also known as Lloyd's reagent, is a chemical reagent commonly used in the preparation of organosulfur compounds, which is a yellowish solid powder at room temperature and pressure, with a strong unpleasant rotting odor. In 1956, it was first prepared by the reaction of aromatic hydrocarbons with tetraphosphorus decasulfide. Swedish chemist Sven-Olov Lawesson carefully studied its reaction with organic compounds, making its application greatly popular, hence the name. The molecules of Lawson's reagent contain a four-membered ring structure composed of alternating sulfur and phosphorus. Depolymerization occurs upon heating to form two unstable phosphorus thiophyllide (RChemicalbook-PS2), which are the main reactive intermediates. WHEN THE LAWSON REAGENT REACTED WITH TWO DIFFERENT SUBSTITUENTS, MOLECULES WITH INTERSTITUENTS WERE OBSERVED IN THE 31NMR SPECTRUM OF THE PRODUCT, THUS CONFIRMING THE EXISTENCE OF THE INTERMEDIATE R-PS2. Lawson reagent is an oxygen-sulfur exchange reagent, the most common application is the preparation of thioamide, the conversion of carbonyl compounds into thiocarbonyl compounds, the substrates that can be reacted include ketones, esters, lactones, amides, lactams, quinones, etc. Electron-rich carbonyl groups are more reactive. When reacting with α, β-unsaturated aldehyde ketones, the double bond is not affected.