Deoxygenative trifluoromethylthiolation of carboxylic acids

A deoxygenative trifluoromethylthiolation method produces trifluoromethyl thioesters from readily available carboxylic acids.


S-(trifluoromethyl) 4-bromobenzothioate (3i)
Following the General Procedure with the corresponding carboxylic acid (0.3 mmol). The crude product purified by flash column chromatography, using n-pentane/diethyl ether = 30/1 (v/v) as an eluent, to yield the title compound 3i (68 mg) in 80%. The spectra were consistent with the spectrum reported in the literature. 2

S-(trifluoromethyl) 2-chlorobenzothioate (3k)
Following the General Procedure with the corresponding carboxylic acid (0.3 mmol). The crude product purified by flash column chromatography, using n-pentane/diethyl ether = 30/1 (v/v) as an eluent, to yield the title compound 3k (44 mg) in 61%. The spectra were consistent with the spectrum reported in the literature. 3

S-(trifluoromethyl) 4-(trifluoromethyl)benzothioate (3n)
Following the General Procedure with the corresponding carboxylic acid (0.3 mmol). The crude product purified by flash column chromatography, using hexanes/EA = 30/1 (v/v) as an eluent, to yield the title compound 3n (53 mg) in 65%. The spectra were consistent with the spectrum reported in the literature. 3 S11

4-((trifluoromethylthio)carbonyl)benzoate (3o)
Following the General Procedure with the corresponding carboxylic acid (0.3 mmol). The crude product purified by flash column chromatography, using hexanes/EA = 20/1 (v/v) as an eluent, to yield the title compound 3o (54 mg) in 68%. The spectra were consistent with the spectrum reported in the literature. 2

Figure S51. 31 P NMR study of reaction
To probe the presence of different P species during the reaction, 31 P spectra of various species and the reaction mixture were collected. Addition of N-(Trifluoromethylthio)phthalimide (2a) to a solution of PPh3 in THF-d8 at room temperature led to the formation of a species with a 31 P signal at δ = 21.8. This peak was tentatively assigned to trifluoromethylthiophosphonium ion II. When 2a was added to a mixture of PPh3 and 4-Phenylbenzoic acid (1a), new signals appeared at δ = 33.3, 42.2 and 23.3 (triphenylphosphine oxide) while the 31 P signal at δ 21.8 decayed. The peaks at δ = 33.3 and 42.2 are tentatively assigned to the acyloxyphosphonium intermediates including III.