CF3SO2Cl

CF3SO2Cl, commonly called triflyl chloride, is a reactive sulfonyl chloride used widely in organic synthesis. It is the acid chloride derivative of triflic acid (CF3SO3H) and functions as a strong electrophile that converts nucleophiles into sulfonyl or triflate-containing products.

Physically, triflyl chloride is a colorless to pale yellow liquid or solution with a sharp, acrid odor. It is highly moisture sensitive and reacts violently with water, alcohols, and amines, releasing hydrochloric acid and triflic acid. It must be handled under strictly anhydrous, inert conditions and stored in tightly closed containers to minimize hydrolysis and decomposition.

In synthetic applications, triflyl chloride is most notable for generating triflate esters. In the presence of a base, an alcohol or phenol reacts with CF3SO2Cl to form the corresponding alkyl or aryl triflate (R–OTf), a superb leaving group that facilitates a range of nucleophilic substitutions and cross-coupling reactions. Triflyl chloride can also sulfonylate amines to form triflylamides (R–SO2–NR2–CF3), expanding its utility beyond simple ester formation.

Preparation and availability vary by supplier, but CF3SO2Cl is a common commercial reagent used in laboratories and industry. It is typically used under anhydrous conditions, often in inert solvents such as dichloromethane or acetonitrile, with appropriate bases to scavenge HCl produced during reactions.

Safety considerations are paramount. Triflyl chloride is highly corrosive and a respiratory and skin irritant. It reacts exothermically with water and protic substances, releasing toxic fumes. Standard laboratory precautions include use in a fume hood, protective eyewear, gloves, and meticulous moisture exclusion.