2-Cyanoethyl N,N,N′,N′-tetraisopropylphosphorodiamidite is a colorless viscous liquid, which is soluble in most organic solvents. It is a widely used phosphitylating reagent for the preparation of various phosphorylated biomolecules, such as nucleoside carbohydrate conjugates, phospholipids and glycopeptides. In particular, this reagent is highly effective for automated solid-phase DNA/RNA oligonucleotide synthesis. 2-Cyanoethyl N,N,N′,N′-tetraisopropylphosphorodiamidite has shown great utility in the coupling of nucleobases or carbohydrates via their phosphotriesters in the presence of activators such as 1H-tetrazole, in moderate yields under mild conditions. Additionally, 2-cyanoethyl N,N,N′,N′-tetraisopropylphosphorodiamidite is cheaper and more stable than 2- cyanoethyl N,N-diisopropylchlorophosphorodiamidite, the other commonly used phosphinylating reagent. 2-Cyanoethyl N,N,N′,N′-tetraisopropylphosphorodiamidite is commercially available but can also be prepared in an inexpensive manner using a two-step, one-pot procedure and purified by vacuum distillation (Scheme ).