Diethyl trimethylsilyl phosphite is primarily used as a reagent in organic synthesis, particularly in the phosphorylation of various compounds. It plays a significant role in the preparation of phosphonates and phosphates, which are essential intermediates in the production of pharmaceuticals, agrochemicals, and flame retardants. Additionally, it is utilized in the modification of nucleosides and nucleotides, aiding in the development of antiviral and anticancer drugs. Its ability to act as a protecting group for phosphorus-containing compounds makes it valuable in complex synthetic pathways. Furthermore, it is employed in the synthesis of organophosphorus ligands, which are crucial in catalysis and material science applications.