TESCl

TESCl, or triethylsilyl chloride, is an organosilicon reagent widely used as a protecting group in organic synthesis. The compound has the formula (C2H5)3SiCl and a molecular weight of about 150.5 g/mol. It is typically a colorless to pale yellow liquid that is highly moisture sensitive and reacts with water and oxygen to form triethylsilanol and HCl, so it must be handled under strictly dry conditions.

TESCl is commercially available but can be prepared by chlorination of triethylsilane or by reaction of triethylsilanol with HCl. In practice, TESCl is used to convert alcohols into triethylsilyl ethers: ROH + (Et)3SiCl → RO-SiEt3 + HCl, often in the presence of a base such as imidazole or DIPEA in an aprotic solvent (e.g., dichloromethane).

Triethylsilyl ethers are relatively stable to base and many reaction conditions but can be removed selectively with fluoride sources (e.g., TBAF or HF-pyridine). TESCl is less bulky than TIPSCl or TBDPSCl, providing a balance between protection efficiency and deprotection ease. It is typically stored in a dry, inert atmosphere away from moisture.