TESOTf

TESOTf, or triethylsilyl triflate, is a reactive organosilicon reagent used in organic synthesis as a silylating agent and Lewis acid promoter. It consists of the triethylsilyl group bound to a non-nucleophilic triflate counterion (Et3SiOTf). The reagent is typically a moisture-sensitive liquid or low-boiling solvent. In common practice, alcohols or other nucleophiles react with Et3SiOTf to form silyl ethers (RO–SiEt3), with triflic acid generated as a byproduct.

Applications of TESOTf include rapid silylation of alcohols to protect them as triethylsilyl ethers, enabling selective sequence control in multi-step syntheses. Beyond protection, Et3SiOTf acts as a strong Lewis acid, activating carbonyl groups, acetals, and glycosyl donors in various transformations, including glycosylation and acetalization reactions. Its high electrophilicity and compatibility with many solvents allow reactions to proceed under relatively mild conditions, often at low temperatures. TESOTf is frequently used in catalytic or stoichiometric roles, sometimes together with other promoters to fine-tune selectivity.

Preparation and availability are straightforward: TESOTf is commercially available and can also be prepared by metathesis of Et3SiCl with AgOTf, or by in situ generation from reactive silicon-oxygen species and triflate sources in moisture-free media. Safety considerations include its moisture sensitivity and corrosive, irritant nature; it should be handled under inert atmosphere with appropriate personal protective equipment and stored away from water and air.