CF3SO2

CF3SO2 denotes the trifluoromethanesulfonyl moiety, a sulfonyl group bearing a trifluoromethyl substituent. It is a core fragment in triflate chemistry and is present in a variety of reagents and reagents used in organic synthesis. The related acid, triflic acid (CF3SO3H), contains the same sulfonyl framework and is among the strongest known Brønsted superacids. The conjugate base of triflic acid is the triflate anion, CF3SO3−, while the neutral CF3SO2 fragment is common in neutral sulfonylated species such as triflyl groups.

Structure and properties: The CF3SO2 fragment centers on sulfur in the +6 oxidation state, bonded to two oxygens and to a trifluoromethyl group. In triflate esters, this group is bound to an alkyl or aryl oxygen (ROSO2CF3), whereas in sulfonyl chlorides and related reagents the group is bonded to chlorine (e.g., CF3SO2Cl). The sulfonyl group is highly electron-withdrawing, and compounds containing it are typically moisture- and air-sensitive, with pronounced reactivity toward nucleophiles and bases.

Applications: CF3SO2 is a defining feature of triflate chemistry. Triflate esters are among the most effective leaving groups in organic synthesis, enabling SN1/SN2 substitutions and cross-coupling reactions. Reagents such as triflyl chloride and triflic anhydride are employed to activate alcohols, sulfonylate substrates, and to introduce the CF3SO2 group in various transformations. The resulting triflate salts or esters are widely used in catalysis, polymer chemistry, and medicinal chemistry.

Safety and handling: Compounds bearing the CF3SO2 moiety are typically moisture-sensitive and corrosive. They require appropriate protective equipment and handling under controlled conditions to minimize exposure and moisture-related degradation.