triflate

Triflate refers to the trifluoromethanesulfonate group, CF3SO3−, and to the corresponding esters derived from it. In organic chemistry, triflate esters (R-OTf or Ar-OTf) are widely used as leaving groups. The term encompasses both the triflate anion and the alkyl or aryl triflate derivatives formed from alcohols or phenols.

The triflate anion is highly resonance-stabilized, extremely non-nucleophilic, and only very weakly basic. Its conjugate acid, triflic acid (CF3SO3H), is one of the strongest known acids (pKa around -14). As a leaving group, the triflate moiety imparts high reactivity, enabling various substitution and coupling reactions, and triflate esters are generally more robust to base than many other sulfonate esters.

Preparation and common reagents: Alkyl and aryl triflates are typically prepared by treating alcohols or phenols with triflic anhydride (Tf2O) in the presence of a base (such as pyridine or lutidine). This converts ROH or ArOH into ROtf or ArOTf, releasingHOTf. Methyl triflate (CH3OTf) is a representative alkyl triflate and is a widely used, highly reactive methylating agent; it and other triflate reagents are commercially available.

Applications: Aryl and alkyl triflates serve as versatile substrates in modern organic synthesis. They are prominent in palladium-catalyzed cross-coupling reactions (such as Suzuki, Negishi, and related processes) as alternatives to traditional aryl halides. They are also employed for selective methylation and in various carbon–carbon and carbon–heteroatom bond-forming transformations.

Safety: Handling triflic acid, triflic anhydride, and triflate esters requires appropriate precautions due to their corrosivity and reactivity. Methyl triflate is particularly hazardous and should be handled under stringent safety protocols with inert atmosphere and proper PPE.