S-(Trifluoromethyl)dibenzothiophenium Triflate1

[129946-88-9]  · C14H8F6O3S2  · S-(Trifluoromethyl)dibenzothiophenium Triflate  · (MW 402.36)

(trifluoromethylating agent for many nucleophilic substrates)

Physical Data: mp 155 °C.

Solubility: sol MeCN, DMF, DMSO; slightly sol THF, CH2Cl2; insol Et2O.

Form Supplied in: white crystals; commercially available.

Analysis of Reagent Purity: 1H and 19F NMR, IR.

Purification: recrystallization from CH3CN/Et2O at rt.

Handling, Storage, and Precautions: nonhygroscopic and thermally stable crystals; should be stored in a dry atmosphere protected from light.


S-(Trifluoromethyl)dibenzothiophenium triflate (1) is an electrophilic trifluoromethylating agent. Other related useful trifluoromethylating agents are S-(trifluoromethyl)-3,7-dinitrodibenzothiophenium triflate (2) and Se-(trifluoromethyl)dibenzoselenophenium triflate (3). The trifluoromethylating power order of these compounds varies as (3) < (1) < (2). The strongest reagent (2) smoothly fluorinates less reactive nucleophiles, while the mildest reagent (3) satisfactorily reacts with the more reactive nucleophiles. The title reagent (1) trifluoromethylates nucleophiles of intermediate reactivity. Thus (1) can trifluoromethylate metal salts of active methylene compounds (eq 1), acetylides (eq 2), enamines, enol silyl ethers (eq 3), reactive aromatics, heteroaromatics (eq 4), arenethiolates, and iodide anions in good yields. Enolate anions are trifluoromethylated in high yields by (1) in the presence of an equivalent amount of 2-phenylbenzo-1,3-dioxa-2-borole (eq 5).3

While (1) cannot trifluoromethylate triphenylphosphine, the more powerful reagent (2) provides access to (trifluoromethyl)triphenylphosphonium triflate in 78% yield. While (1) reacts with an alkanethiolate to give a trifluoromethyl alkyl sulfide in 47% yield along with 30% of a dialkyl disulfide as a byproduct, (3) produces a trifluoromethyl alkyl sulfide in 87% yield. The powerful trifluoromethylating agent (2) readily reacts with activated aromatics and heteroaromatics to yield trifluoromethylated compounds in good yields. Triflates (1)-(3) are all commercially available. The corresponding perfluoroalkyl analogs, S-(perfluoroethyl)-, -(perfluorobutyl)-, and -(perfluorooctyl)dibenzothiophenium triflates, are also available. Similar perfluoroalkylations are expected.1 Since (3) is much more reactive than (1), the stability decreases, and (3) should be stored in a refrigerator.

1.Umemoto, T.; Ishihara, S. JACS 1993, 115, 2156.
2.Umemoto, T.; Ishihara, S. TL 1990, 31, 3579.
3.Umemoto, T.; Adachi, K. JOC 1994, 59, 5692.

Teruo Umemoto

Daikin MEC Laboratory, Tsukuba, Japan

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