triflyl

Triflyl is a functional group in organic chemistry represented by the sulfonyl substituent -SO2CF3. It is the sulfonyl fragment derived from triflic acid (trifluoromethanesulfonic acid) and is commonly encountered attached to a carbon or other atom within a molecule. The term emphasizes the presence of the CF3SO2 moiety bonded through sulfur.

Structure and properties: The triflyl group features a sulfur center double-bonded to two oxygens and bound to a trifluoromethylsulfonyl fragment. Its attachment to the rest of the molecule occurs via the sulfur atom, forming a sulfonyl linkage. The group is highly electron-withdrawing, which stabilizes sulfonyl derivatives and strongly influences reactivity at adjacent sites.

Relationship to triflate and triflic acid: Triflic acid (TfOH) is the parent sulfonic acid. The corresponding anion CF3SO3− is known as triflate. When the triflyl group is bonded to oxygen, as in RO-SO2-CF3, the product is a triflate ester (R-OTf), a widely used leaving group in organic synthesis. The triflyl fragment also appears in reagents such as triflic anhydride and triflic chloride, which are used to install the group onto substrates.

Preparation and installation: The triflyl group is typically introduced by treating alcohols or other nucleophiles with triflic anhydride (Tf2O) or triflyl chloride under appropriate conditions, yielding triflate esters or related sulfonyl derivatives.

Reactivity and applications: Triflate esters are among the best leaving groups for SN1 and SN2 reactions and are widely employed to enable cross-coupling, nucleophilic substitutions, and formation of C–C and C–heteroatom bonds. Aryl and alkyl triflates serve as versatile intermediates in pharmaceuticals and materials science.

Safety and handling: Reagents bearing the triflyl group are generally moisture-sensitive and strongly electrophilic. Triflic anhydride, triflic chloride, and triflate esters should be handled in a fume hood with appropriate personal protective equipment.