SO2CF3

SO2CF3 denotes the trifluoromethylsulfonyl group, also known as the triflyl group. Structurally, it consists of a sulfur atom bonded to two oxygens (a sulfonyl unit) and to a trifluoromethyl substituent (CF3). In SMILES notation, the fragment is often represented as O=S(=O)CF3. The group is most commonly encountered in organic chemistry as CF3SO2−, the basis of the triflate leaving group.

In practice, the SO2CF3 fragment appears in reagents such as trifluoromethanesulfonyl chloride (often called triflyl chloride, CF3SO2Cl) and trifluoromethanesulfonic anhydride (CF3SO2)2O. The corresponding acid, triflic acid (CF3SO3H), is a superacid widely used as a catalyst and dehydrating agent. The triflate group derived from this fragment, RO–SO2–CF3 (ROTf), is an exceptionally good leaving group, making triflate esters among the most versatile activated substrates in organic synthesis.

Preparation and reactions commonly involve transforming alcohols or other nucleophiles into triflate esters. Alcohols react with triflyl chloride or triflic anhydride in the presence of base to form ROTf, which then undergoes rapid substitution or cross-coupling. Consequently, triflate esters are extensively used to enable nucleophilic substitutions, cross-coupling reactions (e.g., Suzuki, Negishi), and other transformations that require a superior leaving group. The SO2CF3 fragment thus serves as a key activating motif for challenging substitutions and for enabling diverse synthetic strategies.

Safety and handling notes: reagents containing CF3SO2Cl, (CF3SO2)2O, or CF3SO3H are highly reactive and moisture-sensitive, requiring appropriate protective equipment and precautions.