Used in the synthesis of oligonucleotides, particularly in the preparation of modified DNA or RNA strands for research and therapeutic applications. Acts as a phosphitylating agent to introduce phosphoramidite linkages during solid-phase oligonucleotide synthesis. The chlorosaligenyl group enhances stability and reactivity, making it suitable for automated synthesis platforms. Commonly employed in the development of antisense oligonucleotides, siRNA, and other nucleic acid-based drugs where precise chemical modifications are required to improve nuclease resistance and binding affinity.