Acid-promoted direct electrophilic trifluoromethylthiolation of phenols

Abstract

The electrophilic aromatic ring trifluoromethylthiolation of various substituted phenols was accomplished using PhNHSCF₃ (N-trifluoromethylsulfanyl)aniline, (1) in the presence of BF₃·Et₂O (2) or triflic acid as the promoter. The functionalization was exclusively para-selective; phenols unsubstituted in both the ortho- and para positions solely gave the para-substituted SCF₃-products in all cases, while para-substituted phenols gave the ortho-substituted SCF₃-products. 3,4-Dialkyl substituted phenols yielded the corresponding products according to the Mills-Nixon effect, and estrone and estradiol furnished biologically interesting SCF₃-analogues. The highly reactive catechol and pyrogallol substrates gave the expected products smoothly in the presence of BF₃·Et₂O, whereas less reactive phenols required triflic acid. 2-Allylphenol gave the expected p-SCF₃ analogue, which underwent an addition/cyclization sequence and furnished a new di-trifluoromethylthio substituted 2,3-dihydrobenzofuran derivative. Some additional transformations of 4-(trifluoromethylthio)phenol with NBS, NIS, HNO₃, HNO₃/H₂SO₄ and 4-bromobenzyl bromide were performed giving bromo-, iodo-, nitro- and benzyl substituted products. The latter derivative underwent Suzuki–Miyaura coupling with phenylboronic acid.

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Introduction

The introduction of a fluorine atom or a fluorine-containing substituent into an organic molecule often favorably modulates the compounds’ properties, thus making new functional and advanced materials.^1–6 Fluorinated organic molecules frequently possess enhanced stability, binding affinity and biological activity in comparison with their non-fluorinated precursors.^7,8 The trifluoromethyl group shares an exceedingly important part in biologically relevant molecules, and the number of newly introduced trifluoromethylated substances in the pharmaceutical and medicinal chemistry industries has been growing considerably.^9–11 Consequently, there has been a strong interest in the direct introduction of CF₃ groups into organic molecules regardless of the approach, via radical, nucleophilic or electrophilic modes, thus making trifluoromethylation a current topic of great interest.^12–19

An interesting variety of the CF₃ group is the trifluoromethylthiol group SCF₃, which considerably contributes to enhanced lipophilicity, and is an indispensable moiety in the agrochemistry and medicinal chemistry industries;²⁰ however its introduction has received considerably less attention than the CF₃ group. A 2′-SCF₃ substituted uridine derivative was found to be a powerful label for probing the structure and function of RNA using ¹⁹F NMR spectroscopy.²¹

Recently, significant progress in the introduction of a SCF₃ moiety has been achieved.²² The introduction of the SCF₃ group could occur directly with CF₃SCl²³ or (CF₃)₂S,²⁴ (extremely noxious and hazardous gases that are not suitable for non-specialized laboratories) or indirectly i.e. by interconversion of functional groups.²⁵ Nucleophilic and radical sources of the SCF₃ group are often copper-²⁶ or silver-based²⁷ metallic reagents, or [NH₄][SCF₃];²⁸ furthermore, trifluoromethylthiolation can also be realized with a combination of two different sources for the sulfur functionality and CF₃ group.²⁹ In particular, the popularity of electrophilic trifluoromethylthiolation has grown remarkably in recent years; the new period of interest began with the work of Billard, Langlois and coworkers.³⁰ They prepared PhNHSCF₃ and its derivatives: easy-to-handle electrophilic SCF₃-transfer reagents for use with alkenes and alkynes,³¹ indoles,³² tryptamines,³³ organometallic species,³⁴ amines,³⁵ and allyl silanes.³⁶ In addition, terminal alkynes were trifluoromethylthiolated in the presence of a catalytic amount of base.³⁷ Internal alkynes reacted with PhNHSCF₃, yielding the corresponding 3-(trifluoromethyl)thio derivatives of indoles,³⁸ benzofurans, benzothiophenes³⁹ and 1H-isochromen-1-ones.⁴⁰ Similarly, 4-((trifluoromethyl)thio)-2H-benzo[e][1,2]thiazine 1,1-dioxides were efficiently prepared in the presence of BiCl₃ in dichloroethane.⁴¹ An interesting trifluoromethanesulfonyl hypervalent iodonium ylide able to deliver the trifluoromethylthiol group was developed recently.⁴²N-(Trifluoromethylthio)succinimide was utilized in the Pd-catalyzed trifluoromethylthiolation of arenes,⁴³ while an in situ formed reagent from AgSCF₃ and NCS was employed in the functionalization of alkynes.⁴⁴ A new thioperoxide^45,46 type of electrophilic trifluoromethylthiolating reagent was able to react with β-ketoesters, boronic acids,⁴⁷ alkynes and aliphatic carboxylic acids,⁴⁸ giving the corresponding SCF₃-substituted products. This thioperoxide reagent in combination with TMSOTf was also found to be a powerful activating agent of different thioglycosides.⁴⁹ Additionally, the thioperoxide reagent was used in enantioselective catalytic trifluoromethylthiolations,⁵⁰ as well as N-trifluoromethylthiophthalimide⁵¹ and an AgSCF₃/trichloroisocyanuric acid system.⁵² The latter system was also utilized in the synthesis of 3-((trifluoromethyl)thio)-4H-chromen-4-ones.⁵³ Electrophilic trifluoromethylthiolation of various carbonyl compounds⁵⁴ and aromatics⁵⁵ was accomplished using a new N-((trifluoromethyl)thio)benzenesulfonamide type of reagent. N-Trifluoromethylthiosaccharin was developed recently and utilized in the trifluoromethylation of alcohols, amines, thiols, electron-rich aromatics, aldehydes, ketones, acyclic β-ketoesters and alkynes.⁵⁶

PhNHSCF₃ (N-trifluoromethylsulfanyl)aniline, (1) is a simple and easy-to-handle electrophilic reagent for the direct introduction of a SCF₃ group into organic molecules. Its electrophilic power usually requires activation with an appropriate promoter of the Lewis or Brønsted type. Its reactivity is mostly unexplored, and we decided to test it on phenols, since there are many biologically relevant phenols i.e. steroids of estrone type, epinephrine, thymol, and others. We report on a direct and remarkably highly regioselective trifluoromethylthiolation of phenols using PhNHSCF₃ in combination with a boron trifluoride etherate complex or triflic acid.

Results and discussion

Initially, the reaction conditions were examined using phenol (3a) as a model substrate; the results are summarized in Table 1. Initially 3a was subjected to 1 without an activator, and remained unreacted (Table 1, entry 1). BF₃·Et₂O and p-TsOH·H₂O were found to be rather unpromising promoters for this reaction (entries 2–5).

Table 1 Optimization of the reaction conditions^a

Entry	Activator	Amount (equiv.)	Conversion^b (%)
a Conditions: 3a (1 mmol), PhNHSCF3 (1, 1.2–1.3 mmol), activator, DCM (10 mL), 14 h, rt. b Conversion determined by ^1H NMR. c Isolated yield.
1	—	—	0
2	BF3·Et2O	2.5	0
3		5	0
4	p-TsOH·H2O	2.5	0
5		5	0
6	CH3SO3H	1.5	0
7		2	30
8	TfOH	1.2	91
9		1.3	100 (77)^c

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We decided to examine the effect of considerably stronger activators, i.e. CH₃SO₃H (MSA) and triflic acid (TfOH). MSA was found to be a somewhat better activator (entries 6 and 7), while TfOH was the promoter of choice (entries 8 and 9). In all cases, 4-trifluoromethylthiophenol (4a) was obtained, and no ortho substitution was noted. Results from the functionalization of different phenols are presented in Table 2. 2-Methylphenol (3b) and 3-methylphenol (3c) both yielded the 4-SCF₃-substituted products 4b and 4c exclusively (Table 2, entries 1 and 2). 4-Methylphenol (3d) and 4-i-propylphenol (3e) yielded the corresponding 2-SCF₃-substituted products 4d and 4e as the sole products. In the cases of 2-t-butylphenol (3f) and 4-t-butylphenol (3g), ipso substitution could have been observed; however, the 4-SCF₃-substituted 4f and 2-SCF₃-substituted product 4g were formed as the sole products (entries 5 and 6). Similarly, 2-benzylphenol (3h) yielded the 4-SCF₃-substituted product 4h, while no ipso substitution was observed. 4-Phenylphenol (3i) was regioselectively transformed into its 2-SCF₃-substituted product 4i. The reactions of 2,5-dimethylphenol (3j) and 2,6-dimethylphenol (3k) cleanly furnished their 4-SCF₃-substituted derivatives 4j and 4k (entries 9 and 10). 2,3,5-Trimethylphenol (3l) and 2,3,6-trimethylphenol (3m) gave their 4-SCF₃-substituted derivatives 4l and 4m as the sole products (entries 11 and 12).

Table 2 Acid-promoted trifluoromethylthiolation of phenols^a

Entry	Reactant	Product	Yield^b (%)
a Conditions: 3 (1 mmol), PhNHSCF3 (1, 1.2–1.3 mmol), TfOH (1.2–5 mmol), DCM (10 mL), 14 h, rt. b Isolated yield.
1	o-Cresol 3b		81
2	m-Cresol 3c		79
3	p-Cresol 3d		80
4	4-i-Propylphenol 3e		82
5	2-t-Butylphenol 3f		64
6	4-t-Butylphenol 3g		87
7	2-Benzylphenol 3h		86
8	4-Phenylphenol 3i		48
9	2,5-Dimethylphenol 3j		90
10	2,6-Dimethylphenol 3k		91
11	2,3,5-Trimethylphenol 3l		84
12	2,3,6-Trimethylphenol 3m		93
13	2,4,6-Trimethylphenol 3n		83

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2,4,6-Trimethylphenol (3n) was an interesting substrate, because all potentially reactive positions were substituted. None of the possible ipso adducts were observed, but 2,4,6-trimethyl-3-trifluoromethylthiophenol (4n) was isolated as the sole product (entry 13).

Next, we examined the reactivity of 3,4-dimethylphenol (5a), 5-indanol (5b) and 5,6,7,8-tetrahydro-2-naphthol (5c) (Scheme 1). Such compounds possess unequally reactive ortho positions; this phenomenon is known as the Mills–Nixon effect.⁵⁷5a furnished the expected 6a as the major product, while no 6aa was detected. Instead, double functionalization took place, yielding 6a′ as a minor product. The relative distribution ratio of 6a/6a′ was 94 : 6. 5b yielded only one expected product 6b; whereas no 6bb was detected. 5c reacted in accordance with the anticipated reactivity giving 6c and 6cc in a relative ratio of 56 : 44. The regioselectivity of trifluoromethylthiolation for 3,4-dimethylphenol and 5-indanol is similar to that of their bromination reactions,⁵⁸ while bromination of 5,6,7,8-tetrahydro-2-naphthol was more selective (78 : 22) than its trifluoromethylthiolation. Nitration of 3,4-dimethylphenol (57 : 43) and 5-indanol (58 : 42) with NaNO₂/H₂O₂/H₂SO₄ was less regioselective than trifluoromethylthiolation, while nitration was more selective in the case of 5,6,7,8-tetrahydro-2-naphthol (63 : 37).⁵⁹

Scheme 1 The effect of the structure of 3,4-dialkyl substituted phenols on trifluoromethylthiolation.

It is known that PhNHSCF₃ reacts with alkenes,³¹ and so we examined the reactivity of 2-allylphenol (7) due to the two diverse potential reaction sites (Scheme 2). We established that 7 reacted with 1 in the presence of TfOH as both phenol and alkene, thus proposed a secondary carbocation intermediate 8. The reaction proceeded in dichloromethane in the absence of a good nucleophile, and the phenolic oxygen atom took part in an intramolecular cyclization thus producing five-membered product 9 as a novel type of trifluoromethylthiolated product. It appears that the stability of 8 was of crucial importance for the reaction selectivity. The other possible product, a six-membered isomeric product originating from a reversed addition of PhNHSCF₃ to the double bond that would have generated a primary carbocation, was not observed. The structure of 9 was confirmed using NMR spectroscopy, and the key experiment was DEPT 135. The carbon atom attached to the SCF₃ group appeared as a quartet in the same phase with the second aliphatic signal, whereas the third aliphatic signal was in the opposite phase. This was a clear indication that the SCF₃ group was attached to the CH₂, and not to a CH group.

Scheme 2 The double functionalization of 2-allylphenol with PhNHSCF₃.

The reactivity of highly reactive bicyclic-, alkoxy- and hydroxyphenols with PhNHSCF₃ is summarized in Table 3.

Table 3 Reactivity of highly electron-rich phenols with PhNHSCF₃ ^a,b

Entry	Reactant	Product	Yield^c (%)
a Conditions: 10 (1 mmol), PhNHSCF3 (1, 1.2–1.3 mmol), TfOH (1.3–4 mmol) or BF3·Et2O (2, 2–3 mmol), DCM (10 mL), 14 h, rt. b TfOH was used in entries 1, 2, 5, 6 and 7. BF3·Et2O was used in rest of the entries. c Isolated yield.
1	2-Methoxy-4-methylphenol 10a		97
2	2,6-Dimethoxyphenol 10b		84
3	5,6,7,8-Tetrahydronaphth-1-ol 10c		93
4	1-Naphthol 10d		95
5	2-Naphthol 10e		82
6	2,7-Dihidroxynaphthalene 10f		86
7	2′,6′-Dihydroxyacetophenone 10g		79
8	Catechol 10h		70
9	4-Methylcatechol 10i		88
10	Resorcinol 10j		80
11	Pyrogallol 10k		60

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2-Methoxy-4-methylphenol (10a) produced 6-SCF₃ analogue 11a as the sole product, while 2,6-dimethoxyphenol (10b) selectively yielded its 3-SCF₃ derivative 11b (Table 3, entries 1 and 2). 5,6,7,8-Tetrahydro-1-naphthol (10c) was regioselectively transformed into its 4-SCF₃ analogue 11c in good yield. The transformations of 1-naphthol (10d) and 2-naphthol (10e) were completely selective in both cases. The former led to its 4-SCF₃ derivative 11d, whereas the latter led to its 1-SCF₃ analogue 11e (entries 4 and 5). Additionally, 2,7-dihydroxynaphthalene (10f) was tested due to the possibility of double functionalization. Indeed, 1,8-diSCF₃ derivative 11f was isolated as a single product in good yield. 2′,6′-dihydroxyacetophenone (10g) was smoothly converted into its 3-SCF₃ derivative 11g (entry 7). In continuation, some naturally occurring phenols were successfully transformed into their trifluoromethylthio analogues. Catechol (10h) selectively produced its 4-SCF₃ derivative 11h, and 4-methylcatechol (10i) yielded its 5-SCF₃ derivative 11i exclusively (entries 8 and 9). Functionalization of resorcinol (10j) smoothly afforded its 4-SCF₃ analogue 11j in a good yield. The highly oxidation-prone pyrogallol (10k) was also efficiently transformed into its 3-SCF₃ derivative 11k (entry 11). It could be concluded that the reaction system of PhNHSCF₃/activator is compatible with highly electron-rich phenols and that introduction of the SCF₃ group took place efficiently without a noticeable amount of oxidation.

In addition, we tested some biologically relevant molecules possessing a phenolic functionality (Scheme 3). 3,4-(Methylenedioxy)phenol (12a) as a highly reactive substance afforded the corresponding 6-SCF₃ derivative 13a as the sole product. The reaction was complete within 20 minutes, and the product, 13a, was obtained in good yield. 6-Hydroxy-1,3-benzoxathiol-2-one (12b) was successfully converted into its 5-SCF₃ derivative 13b in spite of the acid-sensitive oxathiolone functional group. This is a good demonstration that the acidic reaction system is also compatible with sensitive functionalities. Thymol (12c) was effectively transformed into its 4-SCF₃ derivative 13c in high yield. Estrone (12d) and estradiol (12e) are important steroid hormones bearing a phenolic functionality. Both were regioselectively transformed into the corresponding o-SCF₃ analogues (13d, 13dd, and 13e, 13ee; Scheme 4). The regioselectivity of functionalization of estrone was similar to that of the nitration reaction;⁵⁹ however, the selectivity of trifluoromethylthiolation was higher in the case of estradiol.

Scheme 3 The reactivity of some biologically active phenols with PhNHSCF₃.

Scheme 4 Electrophilic trifluoromethylthiolation of estrogenic hormones with PhNHSCF₃.

In addition, some further functionalizations of 4-(trifluoromethylthio)phenol (4a) were studied (Scheme 5). The strong electron-withdrawing nature of the trifluoromethylthio group significantly influences the reactivity of such compounds. 4a was nitrated with 65% HNO₃ under solvent-free reaction conditions for 14 hours at 30–40 °C, selectively yielding mono-nitrated product 14, and no over-nitration took place. The reason for the perfect selectivity is that dinitration required considerably more rigorous reaction conditions to occur: 70–80° C and the presence of concentrated sulfuric acid. The dinitrophenol derivative 15 was isolated in a 78% yield. The introduction of halogens is highly significant because of the possibility for additional reactions, particularly various cross-couplings. Bromination of 4a with NBS in 1-methyl-3-butylimidazolium tetrafluoroborate ([Bmim]BF₄) and in the presence of a small amount of water⁶⁰ afforded dibromo analogue 16 in 94% yield. Iodination was performed using the same reaction medium, producing diiodo derivative 17. Preparation of diphenyl ether derivative 18 was accomplished using t-BuOK and diphenyliodonium triflate⁶¹ in THF. Finally, 4a was converted into its 4-bromobenzyl ether 19, which reacted with phenyl boronic acid in the presence of Pd(OAc)₂ and PPh₃ to yield a cross-coupled derivative 20 in good yield.

Scheme 5 The reactivity of 4-(trifluoromethylthio)phenol (4a) with different reagents.

The detailed reaction mechanism is not known; however, the most likely reaction pathway is an electrophilic one. The reaction selectivity for para- and ortho- positions is one of the strong arguments in favor of an electrophilic pathway. The reagent PhNHSCF₃ (1) is principally an amine and a relatively weak electrophilic reagent. The strong Brønsted acid TfOH seemingly protonates 1, thus forming a corresponding salt with considerably more pronounced polarization between the nitrogen and sulfur atoms. The strong electron deficiency of the nitrogen atom presumably tends to attract electron density; thus resulting in a weaker C–S bond and a stronger sulfur electrophile able to react with phenols (Scheme 6).

Scheme 6 A plausible reaction mechanism.

Trifluoromethylthiolation of m-cresol in the presence of the free radical TEMPO^62,63 took place in the same manner as without TEMPO. This is another indication that a radical pathway is not very likely to be the chief reaction course.

Conclusions

In summary, we have developed a new highly regioselelective and efficient method for the trifluoromethylthiolation of phenols. The reaction pathway is most likely to be an electrophilic substitution pathway. The method is suitable for non-specialized laboratories because the transformation was accomplished with PhNHSCF₃ and without the extremely noxious CF₃SCl or (CF₃)₂S. An additional advantage was operational simplicity; specifically, the reactions were performed with non-dried dichloromethane in an air atmosphere at room temperature. The reaction selectivity was remarkably high; when both the para- and ortho- sites were unsubstituted, only para- functionalization took place. When the para- position was already substituted, functionalization of the ortho- site took place, and no ipso-substitution was noted. The reaction conditions were also demonstrated to be compatible with acid sensitive groups i.e. the thioxolone moiety.

Experimental section

General information

All transformations were carried out in untreated dichloromethane under an air atmosphere with stirring at room temperature. The starting phenols and other chemicals were obtained from commercial sources; PhNHSCF₃1 was prepared using the literature procedure.³⁰ The crude products were purified by column chromatography on silica gel (63–200 μm, 70–230 mesh ASTM; Fluka). TLC was performed on Merck-60-F₂₅₄ plates using mixtures of hexane and diethyl ether. The melting points were determined in open-capillaries on Büchi 535 apparatus and are uncorrected. All products were characterized using ¹H, ¹³C and ¹⁹F NMR spectra, IR, HRMS and/or elemental analysis, and also using the melting points when solid. The ¹H and ¹³C NMR spectra were recorded on Bruker Avance 300 DPX and Bruker Avance III 500 instruments, while the ¹⁹F NMR spectra were only recorded on the latter instrument. Chemical shifts are reported in δ (ppm), values are relative to δ = 7.26 ppm in CDCl₃ or δ = 2.05 ppm in acetone-d₆ for ¹H NMR, and to the central peak of CDCl₃ (δ = 77.00 ppm) or the central peak of acetone-d₆ (δ = 30.83 ppm) for ¹³C NMR. ¹⁹F NMR spectra are referenced to CFCl₃ (δ = 0.00 ppm).

Representative procedure for the acid-promoted trifluoromethylthiolaton of phenols

To a solution of phenol (1 mmol, or 0.5 mmol in the case of the steroids) in dichloromethane (10 mL), PhNHSCF₃ (1.2–1.3 equiv.) was added along with a corresponding amount of triflic acid (1.2–5 equiv.) or BF₃·Et₂O (2–3 equiv.). The resulting mixture was stirred at room temperature for up to 16 h. In most cases, the starting phenol was fully consumed, as determined by TLC. The reaction mixture was diluted with 10 ml of dichloromethane, washed with a 10% solution of NaHCO₃, then water and then dried over anhydrous Na₂SO_4. The crude reaction mixture was subjected to column chromatography after removal of the solvent. In numerous cases, this was only a ‘filtration’ over silica gel, because of the excellent reaction selectivity.

Reactivity of 4a with different reagents

Reaction with HNO₃. To 4-(trifluoromethylthio)phenol (4a) (0.4 mmol, 77 mg), HNO₃ (65%, 1.6 mmol, 156 mg) was added and the resulting reaction mixture was stirred at 30–40 °C overnight. TLC revealed the full consumption of 4a. The reaction mixture was cooled to room temperature, and the product was extracted three times using 5 mL of dichloromethane, washed two times with water, and then dried over anhydrous Na₂SO₄. Pure product 14 (84 mg, 87%) was obtained as a yellow solid after column chromatography (hexane–diethyl ether).

Reaction with HNO₃/H₂SO₄. HNO₃ (65%, 1.6 mmol, 156 mg) was added to 4a (0.4 mmol, 77 mg) and the resulting reaction mixture was stirred at 30–40 °C overnight. TLC revealed the full consumption of 4a. HNO₃ (65%, 1.6 mmol, 156 mg) and concentrated H₂SO₄ (98%, 0.8 mmol, 80 mg) were then added and reaction mixture was stirred at 70–80 °C overnight. TLC showed the disappearance of the mononitro product. The reaction mixture was cooled to room temperature, and the product was extracted three times using 5 mL of dichloromethane and brine. The organic phase was dried over anhydrous Na₂SO₄, and the solvent evaporated. After column chromatography (hexane–diethyl ether), pure product 15 (88 mg, 77%) was obtained as a yellow solid.

Reaction with NBS in [Bmim]BF₄. The reaction was performed according to the reported procedure.⁶⁰4a (0.3 mmol, 58 mg) reacted with N-bromosuccinimide (0.72 mmol, 128 mg) in 20 minutes. The crude reaction mixture was purified by chromatography (hexane–diethyl ether), and a yellowish solid product, 16 (98 mg, 94%), was obtained.

Reaction⁶⁰ with NIS in [Bmim]BF₄. The same reaction procedure and reagent amounts were used as in the case of NBS. From 4a (0.3 mmol, 58 mg), after column chromatography 17 (120 mg, 90%) was obtained as a grey solid.

Reaction with Ph₂IOTf/t-BuOK. The transformation was performed according to the literature.⁶¹ A solution of 4a (0.4 mmol, 77 mg) in dry THF (1 mL) under an argon atmosphere was cooled to 0 °C and t-BuOK (0.5 mmol, 56 mg) was added, and then the mixture was stirred for 15 minutes at 0 °C. The reaction mixture was warmed to 40 °C, diphenyliodonium triflate (0.6 mmol, 258 mg) was added, and the mixture was stirred for three hours at 40 °C. The crude product was purified by chromatography (hexane–diethyl ether) and a colorless oily product, 18 (69 mg, 64%), was obtained.

Reaction with 4-bromobenzyl bromide/K₂CO₃. A mixture of 4a (0.4 mmol, 77 mg), 4-bromobenzyl bromide (0.4 mmol, 100 mg) and K₂CO₃ (0.48 mmol, 66 mg) was stirred for one hour at 80 °C in acetonitrile. TLC showed consumption of the starting phenol 4a. The reaction mixture was cooled to room temperature, and the solvent was removed under vacuum. The product was extracted three times using 5 mL of dichloromethane and water, and then dried over anhydrous Na₂SO₄. The solvent was removed and the product purified by chromatography (hexane–diethyl ether), thus giving a bright yellow product, 19 (137 mg, 95%).

Suzuki–Miyaura coupling. Phenylboronic acid (0.275 mmol, 33 mg) was added to a solution of 18 (0.25 mmol, 90 mg) in isopropanol (5 mL) and the mixture was purged with argon for 10 minutes. Pd(OAc)₂ (0.022 mmol, 5 mg), triphenylphosphine (0.095 mmol, 25 mg), a degassed solution of K₂CO₃ (1.5 mL, 2 M) and deionized water (1 mL) were added consecutively. The resulting mixture was stirred for 1 hour at reflux temperature, and TLC showed consumption of 18. The mixture was cooled, concentrated under vacuum, and diluted with dichloromethane (10 mL) and water (10 mL). After separation of the phases, the aqueous phase was additionally extracted three times with 5 mL of dichloromethane. The combined organic phase was dried over anhydrous Na₂SO₄, filtered and the solvent removed. The crude product was purified by chromatography (hexane–diethyl ether), thus yielding a white solid, 20 (66 mg, 73%).

Spectroscopic and analytical data

4-(Trifluoromethylthio)phenol 4a. ⁵⁶ Colorless solid; mp 52.9–53.5 °C; (1 mmol 3a, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 5.23 (br s, 1H), 6.84–6.90 (m, 2H), 7.51–7.57 (m, 2H); ¹³C NMR (125 MHz, CDCl₃): δ 115.2 (q, J = 2.0 Hz), 116.5, 129.5 (q, J = 308.1 Hz), 138.6, 158.0; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.4 (s, SCF₃); IR: 3221, 1670, 1584, 1493, 1436, 1364, 1346, 1226, 1083, 826, 754, 650 cm⁻¹; ESI-HRMS: m/z calcd for C₇H₄F₃OS (M − H)⁻ 192.9935, found 192.9945.

2-Methyl-4-(trifluoromethylthio)phenol 4b. Yellow, viscous liquid; (1 mmol 3b, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 2.26 (s, 3H), 5.07 (br s, 1H), 6.79 (d, J = 8.3 Hz, 1H), 7.38 (dd, J = 8.3, 1.8 Hz, 1H), 7.42 (d, J = 1.8 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 15.6, 114.7 (q, J = 1.7 Hz), 115.9, 125.3, 129.6 (q, J = 308.1 Hz), 136.0, 139.4, 156.3; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.4 (s, SCF₃); IR: 3409, 1588, 1495, 1401, 1261, 1087, 891, 814, 755 cm⁻¹; ESI-HRMS: m/z calcd for C₈H₆F₃OS (M − H)⁻ 207.0097, found 207.0095.

3-Methyl-4-(trifluoromethylthio)phenol 4c. Orange, viscous liquid; (1 mmol 3c, 1.3 mmol PhNHSCF₃, 1.2 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 2.49 (s, 3H), 5.13 (br s, 1H), 6.70 (dd, J = 8.4, 2.7 Hz, 1H), 6.80 (d, J = 2.7 Hz, 1H), 7.53 (d, J = 8.4 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 21.3, 114.1, 114.8 (q, J = 1.5 Hz), 117.8, 129.8 (q, J = 308.6 Hz), 140.3, 146.4, 158.1; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.0 (s, SCF₃); IR: 3348, 1594, 1575, 1480, 1453, 1294, 1240, 1098, 1046, 947, 857, 812, 754, 731 cm⁻¹; ESI-HRMS: m/z calcd for C₈H₆F₃OS (M − H)⁻ 207.0097, found 207.0095.

4-Methyl-2-(trifluoromethylthio)phenol 4d. Light yellow solid; mp 42.5–43.1 °C; (1 mmol 3d, 1.3 mmol PhNHSCF₃, 2 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 2.30 (s, 3H), 6.14 (s, 1H), 6.97 (d, J = 8.4 Hz, 1H), 7.24 (dd, J = 8.4, 1.7 Hz, 1H), 7.36 (d, J = 1.7 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 20.2, 107.7 (q, J = 1.2 Hz), 115.9, 128.7 (q, J = 310.5 Hz), 130.9, 135.1, 138.0, 155.9; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.4 (s, SCF₃); IR: 3417, 1489, 1136, 1097, 1055, 825 cm⁻¹; ESI-HRMS: m/z calcd for C₈H₆F₃OS (M − H)⁻ 207.0097, found 207.0094.

4-Isopropyl-2-(trifluoromethylthio)phenol 4e. White solid; mp 36.8–37.4 °C; (1 mmol 3e, 1.3 mmol PhNHSCF₃, 2.0 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 1.23 (d, J = 6.9 Hz, 6H), 2.87 (septet, J = 6.9 Hz, 1H), 6.15 (br s, 1H), 7.00 (d, J = 8.5 Hz, 1H), 7.30 (dd, J = 8.5, 2.1 Hz, 1H), 7.40 (d, J = 2.1 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 24.0, 33.1, 107.7 (q, J = 1.2 Hz), 115.9, 128.8 (q, J = 310.5 Hz), 132.5, 135.6, 142.0, 156.0; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.4 (s, SCF₃); IR: 3429, 3410, 1487, 1467, 1456, 1283, 1183, 1103, 832, 728 cm⁻¹; ESI-HRMS: m/z calcd for C₁₀H₁₀F₃OS (M − H)⁻ 235.0410, found 235.0409.

2-tert-Butyl-4-(trifluoromethylthio)phenol 4f. Yellow, viscous liquid; (1 mmol 3f, 1.3 mmol PhNHSCF₃, 1.2 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 1.41 (s, 9H), 5.15 (br s, 1H), 6.69 (d, J = 8.2 Hz, 1H), 7.37 (dd, J = 8.2, 2.2 Hz, 1H), 7.53 (d, J = 2.2 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 29.3, 34.7, 114.8 (d, J = 1.8 Hz), 117.5, 129.7 (q, J = 308.1 Hz), 135.7, 136.0, 137.6, 156.7; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.4 (s, SCF₃); IR: 3408, 2962, 1587, 1494, 1260, 1113, 1097, 1080, 815, 755 cm⁻¹; ESI-HRMS: m/z calcd for C₁₁H₁₂F₃OS (M − H)⁻ 249.0566, found 249.0566.

4-tert-Butyl-2-(trifluoromethylthio)phenol 4g. Yellow, viscous liquid; (1 mmol 3g, 1.3 mmol PhNHSCF₃, 2 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 1.30 (s, 9H), 6.14 (br s, 1H), 7.00 (d, J = 8.6 Hz, 1H), 7.47 (dd, J = 8.6, 2.4, Hz, 1H), 7.54 (d, J = 2.4 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 31.3, 34.2, 107.5 (q, J = 1.1 Hz), 115.6, 128.8 (q, J = 310.5 Hz), 131.6, 134.7, 144.5, 155.8; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.4 (s, SCF₃); IR: 3507, 1490, 1365, 1103, 822, 755 cm⁻¹; ESI-HRMS: m/z calcd for C₁₁H₁₂F₃OS (M − H)⁻ 249.0561, found 249.0566.

2-Benzyl-4-(trifluoromethylthio)phenol 4h. Yellow, viscous liquid; (1 mmol 3h, 1.3 mmol PhNHSCF₃, 1.5 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 3.98 (s, 2H), 5.12 (br s, 1H), 6.77–6.81 (m, 1H), 7.18–7.26 (m, 3H), 7.28–7.33 (m, 2H), 7.39–7.44 (m, 2H); ¹³C NMR (125 MHz, CDCl₃): δ 36.2, 115.1 (q, J = 1.9 Hz), 116.8, 126.7, 128.5, 128.6, 128.8, 129.6 (q, J = 308.1 Hz), 136.6, 138.8, 139.4, 156.3; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.4 (s, SCF₃); IR: 3523, 1587, 1494, 1453, 1411, 1091, 823, 729, 697 cm⁻¹; ESI-HRMS: m/z calcd for C₁₄H₁₀F₃OS (M − H)⁻ 283.0410, found 283.0410.

3-(Trifluoromethylthio)biphenyl-4-ol 4i. White solid; mp 101.6–101.9 °C; (1 mmol 3i, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 6.32 (br s, 1H), 7.16 (d, J = 8.5 Hz, 1H), 7.32–7.40 (m, 1H), 7.40–7.49 (m, 2H), 7.50–7.58 (m, 2H), 7.68 (dd, J = 8.5, 2.2 Hz, 1H), 7.81 (d, J = 2.2 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 108.7 (q, J = 1.2 Hz), 116.6, 126.7, 127.4, 128.7 (q, J = 310.7 Hz), 128.9, 133.0, 134.9, 136.5, 139.2, 157.4; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.2 (s, SCF₃); IR: 3408, 1602, 1473, 1334, 1194, 1155, 1132, 1100, 1055, 895, 860, 763, 738, 700 cm⁻¹; ESI-HRMS: m/z calcd for C₁₃H₈F₃OS (M − H)⁻ 269.0253, found 269.0253.

2,5-Dimethyl-4-(trifluoromethylthio)phenol 4j. Yellow, viscous liquid; (1 mmol 3j, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 2.22 (s, 3H), 2.45 (s, 3H), 4.91 (br s, 1H), 6.73 (s, 1H), 7.41 (s, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 15.0, 20.8, 114.3 (q, J = 1.6 Hz), 117.3, 122.6, 129.9 (q, J = 308.7 Hz), 141.1, 143.6, 156.4; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.0 (s, SCF₃); IR: 3602, 3412, 2866, 1395, 1377, 1256, 1222, 1094, 1017, 892, 852, 754, 625 cm⁻¹; ESI-HRMS: m/z calcd for C₉H₈F₃OS (M − H)⁻ 221.0253, found 221.0255.

2,6-Dimethyl-4-(trifluoromethylthio)phenol 4k. Yellow solid; mp 40.4–42.7 °C; (1 mmol 3k, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 2.26 (s, 6H), 4.91 (br s, 1H), 7.28 (s, 2H); ¹³C NMR (125 MHz, CDCl₃): δ 15.7, 113.9 (q, J = 1.8 Hz), 124.3, 129.7 (q, J = 308.0 Hz), 137.0, 154.7; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.4 (s, SCF₃); IR: 3613, 3449, 1586, 1473, 1330, 1153, 1093, 876, 754, 730 cm⁻¹; ESI-HRMS: m/z calcd for C₉H₈F₃OS (M − H)⁻ 221.0253, found 221.0253.

2,3,5-Trimethyl-4-(trifluoromethylthio)phenol 4l. White solid; mp 82.1–82.4 °C; (1 mmol 3l, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 2.19 (s, 3H), 2.50 (s, 3H), 2.55 (s, 3H), 5.02 (br s, 1H), 6.64 (s, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 12.5, 19.1, 22.3, 115.0 (q, J = 1.2 Hz), 115.1, 121.7, 130.1 (q, J = 309.5 Hz), 144.0, 145.8, 155.5; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.5 (s, SCF₃); IR: 3321, 1690, 1575, 1446, 1298, 1097, 1076, 858, 846, 753 cm⁻¹; ESI-HRMS: m/z calcd for C₁₀H₁₀F₃OS (M − H)⁻ 235.0410, found 235.0411.

2,3,6-Trimethyl-4-(trifluoromethylthio)phenol 4m. Yellow solid; mp 51.6–54.2 °C (1 mmol 3m, 1.3 mmol PhNHSCF₃, 1.2 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 2.22 (s, 3H), 2.23 (s, 3H), 2.48 (s, 3H), 4.89 (br s, 1H), 7.35 (s, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 12.7, 15.5, 18.2, 114.2 (q, J = 1.5 Hz), 121.1, 123.4, 129.9 (q, J = 308.6 Hz), 138.0, 142.0, 154.6; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.3 (s, SCF₃); IR: 3477, 1465, 1400, 1213, 1184, 1144, 1100, 1020, 909, 754 cm⁻¹; ESI-HRMS: m/z calcd for C₁₀H₁₀F₃OS (M − H)⁻ 235.0410, found 235.0412.

2,4,6-Trimethyl-3-(trifluoromethylthio)phenol 4n. Light yellow solid; mp 75.5–76.4 °C; (1 mmol 3n, 1.3 mmol PhNHSCF₃, 5 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 2.25 (s, 3H), 2.48 (s, 3H), 2.51 (s, 3H), 4.62 (br s, 1H), 6.99 (s, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 14.9, 16.1, 21.6, 121.3 (q, J = 1.4 Hz), 126.9, 130.1, 130.1 (q, J = 309.4 Hz), 130.2, 137.0, 150.8; ¹⁹F NMR (470 MHz, CDCl₃): δ −42.8 (s, SCF₃); IR: 3365, 1470, 1378, 1299, 1151, 1096, 998, 871, 801, 753 cm⁻¹; ESI-HRMS: m/z calcd for C₁₀H₁₀F₃OS (M − H)⁻ 235.0410, found 235.0408.

4,5-Dimethyl-2-(trifluoromethylthio)phenol 6a. White solid; mp 65.6–65.8 °C; (1 mmol 5a, 1.3 mmol PhNHSCF₃, 1.2 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 2.20 (s, 3H), 2.26 (s, 3H), 6.06 (s, 1H), 6.88 (s, 1H), 7.30 (s, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 18.6, 20.1, 104.5 (q, J = 1.2 Hz), 117.0, 128.8 (q, J = 310.6 Hz), 129.9, 138.2, 144.0, 156.0; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.8 (s, SCF₃); IR: 3398, 3372, 1480, 1313, 1210, 1145, 1101, 1022, 871 cm⁻¹; ESI-HRMS: m/z calcd for C₉H₈F₃OS (M − H)⁻ 221.0253, found 221.0250.

3,4-Dimethyl-2,6-bis(trifluoromethylthio)phenol 6a′. White solid; mp 48.5–48.9 °C; (1 mmol 5a, 1.3 mmol PhNHSCF₃, 1.2 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 2.28 (s, 3H), 2.53 (s, 3H), 6.86 (s, 1H), 7.53 (s, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 19.0, 20.1, 107.0 (q, J = 1.7 Hz), 110.9 (q, J = 1.3 Hz), 128.9 (q, J = 311.3 Hz), 129.1 (q, J = 310.1 Hz), 130.6, 142.7, 149.1, 158.7; ¹⁹F NMR (470 MHz, CDCl₃): δ −42.6 (s, SCF₃), −43.2 (s, SCF₃); IR: 3455, 1440, 1391, 1271, 1092, 904, 755, 671 cm⁻¹; Anal Calcd for C₁₀H₈F₆OS₂: C, 37.27; H, 2.50. Found: C, 37.41; H, 2.48.

6-(Trifluoromethylthio)-2,3-dihydro-1H-inden-5-ol 6b. White solid; mp 73.7–74.5 °C; (1 mmol 5b, 1.3 mmol PhNHSCF₃, 3 mmol BF₃·Et₂O); ¹H NMR (500 MHz, CDCl₃): δ 2.09 (quintet, J = 7.4 Hz, 2H), 2.85 (t, J = 7.4 Hz, 2H), 2.90 (t, J = 7.4 Hz, 2H), 6.19 (br s, 1H), 6.94 (s, 1H), 7.37 (s, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 25.7, 31.7, 33.3, 105.1 (q, J = 1.2 Hz), 111.8, 128.8 (q, J = 310.7 Hz), 133.0, 137.3, 152.0, 156.6; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.9 (s, SCF₃); IR: 3418, 3401, 1471, 1440, 1430, 1330, 1129, 1103, 897, 879 cm⁻¹; ESI-HRMS: m/z calcd for C₁₀H₈F₃OS (M − H)⁻ 233.0248, found 233.0253.

3-(Trifluoromethylthio)-5,6,7,8-tetrahydronaphthalen-2-ol 6c. White solid; mp 52.8–53.0 °C; (1 mmol 5c, 1.3 mmol PhNHSCF₃, 3 mmol BF₃·Et₂O); ¹H NMR (500 MHz, CDCl₃): δ 1.74–1.81 (m, 4H), 2.67–2.73 (m, 2H), 2.73–2.79 (m, 2H), 6.03 (br s, 1H), 6.78 (s, 1H), 7.25 (s, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 22.6, 22.9, 28.3, 29.6, 105.0 (q, J = 1.1 Hz), 115.8, 128.8 (q, J = 310.5 Hz), 130.6, 138.2, 144.4, 155.4; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.7 (s, SCF₃); IR: 3411, 2941, 2857, 1612, 1564, 1476, 1210, 1129, 1099, 1031, 863, 754 cm⁻¹; ESI-HRMS: m/z calcd for C₁₁H₁₀F₃OS (M − H)⁻ 247.0410, found 247.0411.

1-(Trifluoromethylthio)-5,6,7,8-tetrahydronaphthalen-2-ol 6cc. White solid; mp 49.3–49.5 °C; (1 mmol 5c, 1.3 mmol PhNHSCF₃, 3 mmol BF₃·Et₂O); ¹H NMR (500 MHz, CDCl₃): δ 1.72–1.85 (m, 4H), 2.69–2.74 (m, 2H), 2.92–2.97 (m, 2H), 6.39 (s, 1H), 6.87 (d, J = 8.4 Hz, 1H), 7.15 (d, J = 8.4 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 22.5, 22.9, 28.8, 29.1, 107.8, 113.1, 128.9 (q, J = 311.7 Hz), 130.6, 134.9, 143.2, 156.6; ¹⁹F NMR (470 MHz, CDCl₃): δ −42.2 (s, SCF₃); IR: 3422, 2938, 1592, 1579, 1471, 1430, 1303, 1204, 1146, 1128, 1094, 832, 818, 752, 734 cm⁻¹; ESI-HRMS: m/z calcd for C₁₁H₁₀F₃OS (M − H)⁻ 247.0410, found 247.0410.

5-(Trifluoromethylthio)-2-((trifluoromethylthio)methyl)-2,3-dihydrobenzofuran 9. Yellow, viscous liquid; (1 mmol 7, 2.5 mmol PhNHSCF₃, 4 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 3.08 (dd, J = 16.1, 6.6 Hz, 1H), 3.16 (dd, J = 14.0, 6.3 Hz, 1H), 3.28 (dd, J = 14.0, 6.3 Hz, 1H), 3.46 (dd, J = 16.1, 9.2 Hz, 1H), 5.05–5.13 (m, 1H), 6.82 (d, J = 8.1 Hz, 1H), 7.42–7.47 (m, 2H); ¹³C NMR (125 MHz, CDCl₃): δ 34.2, 81.6, 110.7, 115.2 (d, J = 1.9 Hz), 127.4, 129.6 (q, J = 308.2 Hz), 130.7 (q, J = 306.4 Hz), 133.6, 137.9, 161.3; ¹⁹F NMR (470 MHz, CDCl₃): δ −41.4 (s, SCF₃), −44.5 (s, SCF₃); IR: 1604, 1589, 1474, 1237, 1092, 974, 819, 755 cm⁻¹; Anal Calcd for C₁₁H₈F₆OS₂: C, 39.52; H: 2.41. Found: C, 39.30; H, 2.34.

2-Methoxy-4-methyl-5-(trifluoromethylthio)phenol 11a. Light yellow solid; mp 51.9–52.1 °C; (1 mmol 10a, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 2.47 (s, 3H), 3.91 (s, 3H), 5.49 (br s, 1H), 6.79 (s, 1H), 7.21 (s, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 20.8, 55.9, 112.6, 114.4 (q, J = 1.5 Hz), 123.6, 129.8 (q, J = 308.8 Hz), 136.7, 143.8, 148.9; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.7 (s, SCF₃); IR: 3343, 1580, 1266, 1135, 1100, 1043, 872, 850, 817, 753 cm⁻¹; ESI-HRMS: m/z calcd for C₉H₈F₃O₂S (M − H)⁻ 237.0203, found 237.0200.

2,6-Dimethoxy-3-(trifluoromethylthio)phenol 11b. Brown solid; mp 44.7–46.5 °C; (1 mmol 10b, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 3.93 (s, 3H), 3.97 (s, 3H), 5.66 (br s, 1H), 6.69 (d, J = 8.7 Hz, 1H), 7.16 (d, J = 8.7 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 56.3, 61.2, 106.7, 109.5 (d, J = 1.8 Hz), 129.0, 129.4 (q, J = 308.7 Hz), 139.2, 148.9, 150.5; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.6 (s, SCF₃); IR: 3523, 3371, 1594, 1489, 1469, 1439, 1294, 1219, 1083, 892, 796 cm⁻¹; ESI-HRMS: m/z calcd for C₉H₈F₃O₃S (M − H)⁻ 253.0152, found 253.0151.

4-(Trifluoromethylthio)-5,6,7,8-tetrahydronaphthalen-1-ol 11c. Grey solid; mp 65.2–67.5 °C; (1 mmol 10c, 1.3 mmol PhNHSCF₃, 3 mmol BF₃·Et₂O); ¹H NMR (500 MHz, CDCl₃): δ 1.76–1.86 (m, 4H), 2.61–2.67 (m, 2H), 2.93–2.99 (m, 2H), 5.04 (br s, 1H), 6.66 (d, J = 8.3 Hz, 1H), 7.42 (d, J = 8.3 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 22.0, 22.5, 23.2, 28.9, 112.8, 114.7 (q, J = 1.5 Hz), 125.3, 129.8 (q, J = 308.7 Hz), 137.1, 144.7, 156.1; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.8 (s, SCF₃); IR: 3590, 3461, 1573, 1456, 1440, 1416, 1073, 1029, 819, 805, 750 cm⁻¹; ESI-HRMS: m/z calcd for C₁₁H₁₀F₃OS (M − H)⁻ 247.0410, found 247.0411.

4-(Trifluoromethylthio)naphthalen-1-ol 11d. Gray solid; mp 64.8–67.2 °C; (1 mmol 10d, 1.3 mmol PhNHSCF₃, 3 mmol BF₃·Et₂O); ¹H NMR (300 MHz, CDCl₃): δ 6.84 (d, J = 7.9 Hz, 1H), 7.54–7.61 (m, 1H), 7.64–7.71 (m, 1H), 7.82 (d, J = 7.9 Hz, 1H), 8.23–8.29 (dd, J = 8.3, 0.5 Hz, 1H), 8.47–8.53 (m, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 108.6, 112.5 (q, J = 1.5 Hz), 122.3, 125.1, 125.9, 126.0, 128.2, 129.6 (q, J = 309.5 Hz), 136.7, 138.7, 155.0; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.8 (s, SCF₃); IR: 3346, 1591, 1569, 1510, 1348, 1158, 1092, 1047, 830, 763, 753 cm⁻¹; ESI-HRMS: m/z calcd for C₁₁H₆F₃OS (M − H)⁻ 243.0097, found 243.0096.

1-(Trifluoromethylthio)naphthalen-2-ol 11e. Light yellow solid; mp 91.8–92.2 °C (lit.⁵⁶ 88.8–90.7 °C); (1 mmol 10e, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 6.92 (br s, 1H), 7.30 (d, J = 9.0 Hz, 1H), 7.39–7.47 (m, 1H), 7.58–7.67 (m, 1H), 7.77–7.85 (m, 1H), 7.95 (d, J = 9.0 Hz, 1H), 8.30–8.36 (d, J = 8.4 Hz, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 100.8 (q, J = 0.6 Hz), 117.1, 124.3, 124.4, 128.4, 128.5, 128.8 (q, J = 312.8 Hz), 129.4, 134.9, 135.8, 158.4; ¹⁹F NMR (470 MHz, CDCl₃): δ −42.3 (s, SCF₃); IR: 3415, 1618, 1591, 1569, 1462, 1384, 1196, 1146, 1125, 1101, 1029, 867, 772, 655 cm⁻¹; ESI-HRMS: m/z calcd for C₁₁H₆F₃OS (M − H)⁻ 243.0097, found 243.0097.

1,8-Bis(trifluoromethylthio)naphthalene-2,7-diol 11f. Light orange solid; mp 90.3–91.4 °C; (1 mmol 10f, 2.4 PhNHSCF₃, 4.0 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 7.25 (d, J = 8.8 Hz, 2H), 7.71 (s, 2H), 7.87 (d, J = 8.8 Hz, 2H); ¹³C NMR (125 MHz, CDCl₃): δ 99.9, 115.0, 125.9, 128.5 (q, J = 312.8 Hz), 136.5, 137.2, 161.7; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.5 (s, SCF₃); IR: 3411, 1607, 1514, 1430, 1355, 1155, 1084, 841, 752 cm⁻¹; ESI-HRMS: m/z calcd for C₁₂H₅F₆O₂S₂ (M − H)⁻ 358.9641, found 358.9650.

1-(2,6-Dihydroxy-3-(trifluoromethylthio)phenyl)ethanone 11g. Yellow solid; mp 114.7–117.5 °C; (1 mmol 10g, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 2.77 (s, 3H), 6.60 (d, J = 8.8 Hz, 1H), 7.58 (br s, 1H), 7.61 (d, J = 8.8 Hz, 1H), 13.40 (br s, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 33.5, 98.2 (q, J = 1.5 Hz), 110.0, 111.9, 128.4 (q, J = 311.7 Hz), 144.1, 160.7, 168.1, 204.9; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.4 (s, SCF₃); IR: 3343, 1622, 1581, 1472, 1440, 1373, 1245, 1235, 1158, 1120, 1097, 1042, 963, 903, 819, 656 cm⁻¹; ESI-HRMS: m/z calcd for C₉H₆F₃O₃S (M − H)⁻ 250.9995, found 250.9994.

4-(Trifluoromethylthio)benzene-1,2-diol 11h. White solid; mp 67.8–69.0 °C; (1 mmol 10h, 1.3 mmol PhNHSCF₃, 2.0 mmol BF₃·Et₂O); ¹H NMR (500 MHz, CDCl₃): δ 5.60 (br s, 1H), 5.78 (br s, 1H), 6.90 (d, J = 8.2 Hz, 1H), 7.14 (dd, J = 8.2, 1.8 Hz, 1H), 7.18 (d, J = 1.8 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 115.1 (q, J = 2.0 Hz), 116.0, 123.3, 129.5 (q, J = 308.2 Hz), 130.5, 143.6, 146.4; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.3 (s, SCF₃); IR: 3533, 3486, 3349, 1593, 1507, 1276, 1245, 1124, 1100, 811, 782 cm⁻¹; ESI-HRMS: m/z calcd for C₇H₄F₃O₂S (M − H)⁻ 208.9890, found 208.9889.

4-Methyl-5-(trifluoromethylthio)benzene-1,2-diol 11i. White solid; mp 71.1–71.5 °C; (1 mmol 10i, 1.3 mmol PhNHSCF₃, 2.0 mmol BF₃·Et₂O); ¹H NMR (500 MHz, CDCl₃): δ 2.42 (s, 1H), 5.25 (br s, 1H), 5.61 (br s, 1H), 6.84 (s, 1H), 7.17 (s, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 20.4, 113.9 (q, J = 1.6 Hz), 117.5, 124.8, 129.8 (q, J = 308.8 Hz), 138.1, 141.3, 146.6; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.9 (s, SCF₃); IR: 3284, 1593, 1508, 1447, 1272, 1094, 875, 866, 816 cm⁻¹; ESI-HRMS: m/z calcd for C₈H₆F₃O₂S (M − H)⁻ 223.0046, found 223.0045.

4-(Trifluoromethylthio)benzene-1,3-diol 11j. White solid; mp 48.5–49.7 °C; (1 mmol 10j, 1.3 mmol PhNHSCF₃, 3.0 mmol BF₃·Et₂O); ¹H NMR (300 MHz, CDCl₃): δ 5.16 (br s, 1H), 6.30 (br s, 1H), 6.47 (dd, J = 8.5, 2.7 Hz, 1H), 6.54 (d, J = 2.7 Hz, 1H), 7.43 (d, J = 8.5 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 99.6 (q, J = 1.1 Hz), 102.9, 109.6, 128.6 (q, J = 310.9 Hz), 139.4, 159.4, 160.8; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.5 (s, SCF₃); IR: 3645, 3492, 3338, 1592, 1473, 1324, 1134, 1094, 1057, 968, 843, 809 cm⁻¹; ESI-HRMS: m/z calcd for C₇H₄F₃O₂S (M − H)⁻ 208.9890, found 208.9889.

4-(Trifluoromethylthio)benzene-1,2,3-triol 11k. Brown solid; mp 82.0–84.9 °C; (1 mmol 10k, 1.3 mmol PhNHSCF₃, 2.0 mmol BF₃·Et₂O); ¹H NMR (300 MHz, CDCl₃/acetone-d₆): δ 6.47 (d, J = 8.6 Hz, 1H), 6.92 (d, J = 8.6 Hz, 1H); ¹³C NMR (75 MHz, CDCl₃/acetone-d₆): δ 99.2 (q, J = 1.7 Hz), 108.4, 128.9 (q, J = 310.2 Hz), 129.4, 131.9, 147.0, 148.5; ¹⁹F NMR (470 MHz, CDCl₃/acetone-d₆): δ −44.3 (s, SCF₃); IR: 3507, 3484, 3397, 3218, 1601, 1503, 1460, 1291, 1267, 1090, 1007, 888, 800, 754, 657 cm⁻¹; ESI-HRMS: m/z calcd for C₇H₄F₃O₃S (M − H)⁻ 224.9839, found 224.9838.

6-(Trifluoromethylthio)benzo[d][1,3]dioxol-5-ol 13a. Light yellow solid; mp 82.2–82.7 °C; (1 mmol 12a, 1.3 mmol PhNHSCF₃, 1.3 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 5.99 (s, 2H), 6.18 (br s, 1H), 6.59 (s, 1H), 6.94 (s, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 97.7, 102.0, 115.0, 128.6 (q, J = 311.5 Hz), 142.0, 152.7, 154.9; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.5 (s, SCF₃); IR: 3433, 1614, 1496, 1470, 1160, 1099, 1030, 930, 871, 830, 754, 713 cm⁻¹; ESI-HRMS: m/z calcd for C₈H₄F₃O₃S (M − H)⁻ 236.9839, found 236.9840.

6-Hydroxy-5-(trifluoromethylthio)benzo[d][1,3]oxathiol-2-one 13b. Light yellow solid; mp 128.9–131.7 °C; (1 mmol 12b, 1.3 mmol PhNHSCF₃, 4.0 mmol TfOH); ¹H NMR (500 MHz, acetone-d₆): δ 7.12 (s, 1H), 7.96 (s, 1H), 9.93 (br s, 1H); ¹³C NMR (125 MHz, acetone-d₆): δ 102.4, 108.6 (q, J = 1.5 Hz), 115.7, 131.5 (q, J = 308.4 Hz), 134.3, 153.7, 161.7, 170.6; ¹⁹F NMR (470 MHz, acetone-d₆): δ −43.0 (s, SCF₃); IR: 3416, 1732, 1603, 1454, 1428, 1327, 1145, 1090, 1032, 1013, 881, 865 cm⁻¹; ESI-HRMS: m/z calcd for C₈H₂F₃O₃S₂ (M − H)⁻ 266.9403, found 266.9404.

2-Isopropyl-5-methyl-4-(trifluoromethylthio)phenol 13c. Colorless, viscous liquid; (1.0 mmol 12c, 1.3 mmol PhNHSCF₃, 2.0 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 1.25 (d, J = 6.9 Hz, 6H), 2.44 (s, 3H), 3.14 (septet, J = 6.9 Hz, 1H), 4.95 (br s, 1H), 6.70 (s, 1H), 7.44 (s, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 20.7, 22.4, 26.8, 114.7 (q, J = 1.7 Hz), 117.7, 129.9 (q, J = 308.7 Hz), 133.4, 137.1, 143.1, 155.4; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.0 (s, SCF₃); IR: 3422, 1397, 1256, 1152, 1095, 1070, 736 cm⁻¹; ESI-HRMS: m/z calcd for C₁₁H₁₂F₃OS (M − H)⁻ 249.0566, found 249.0567.

(13S)-13-Methyl-2-(trifluoromethylthio)-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclopenta[a]phenanthrene-3,17-diol 13d. White solid; mp 96.1–98.9 °C; (0.5 mmol 12d; 0.65 mmol PhNHSCF₃, 0.65 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 0.79 (s, 3H), 1.10–1.60 (m, 8H), 1.63–1.77 (m, 1H), 1.83–2.02 (m, 2H), 2.06–2.22 (m, 2H), 2.24–2.35 (m, 1H), 2.81–2.91 (m, 2H), 3.74 (t, J = 8.4 Hz, 1H), 6.04 (br s, 1H), 6.79 (s, 1H), 7.44 (s, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 11.0, 23.1, 26.2, 26.8, 29.6, 30.5, 36.5, 38.4, 43.2, 43.6, 49.9, 81.8, 105.1 (q, J = 0.9 Hz), 115.8, 128.8 (q, J = 310.6 Hz), 134.1, 135.0, 144.2, 155.6; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.7 (s, SCF₃); IR: 3318, 2921, 2867, 1560, 1447, 1102, 1055, 1011, 797 cm⁻¹; ESI-HRMS: m/z calcd for C₁₉H₂₂F₃O₂S (M − H)⁻ 371.1298, found 371.1303.

(13S)-13-Methyl-4-(trifluoromethylthio)-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclopenta[a]phenanthrene-3,17-diol 13dd. White solid; mp 84.8–87.5 °C; (0.5 mmol 12d; 0.65 mmol PhNHSCF₃, 0.65 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 0.78 (s, 3H), 1.14–1.22 (m, 1H), 1.23–1.43 (m, 5H), 1.43–1.55 (m, 2H), 1.67–1.76 (m, 1H), 1.92–2.00 (m, 2H), 2.08–2.22 (m, 2H), 2.25–2.33 (m, 1H), 2.84–2.95 (m, 1H), 3.14–3.22 (m, 1H), 3.74 (t, J = 8.5 Hz, 1H), 6.43 (br s, 1H), 6.91 (d, J = 8.6 Hz, 1H), 7.40 (d, J = 8.6 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 11.0, 23.0, 26.4, 27.0, 29.2, 30.6, 36.6, 38.0, 43.2, 44.1, 49.9, 81.8, 108.0, 113.0, 128.9 (q, J = 311.8 Hz), 131.1, 134.0, 143.2, 156.5; ¹⁹F NMR (470 MHz, CDCl₃): δ −42.0 (s, SCF₃); IR: 3645, 3455, 2938, 2857, 1572, 1352, 1156, 1114, 1098, 1009, 821, 802, 755 cm⁻¹; ESI-HRMS: m/z calcd for C₁₉H₂₂F₃O₂S (M − H)⁻ 371.1298, found 371.1307.

(13S)-3-Hydroxy-13-methyl-2-(trifluoromethylthio)-7,8,9,11,12,13,15,16-octahydro-6H-cyclopenta[a]phenanthren-17(14H)-one 13e. White solid; mp 160.4–160.9 °C; (0.5 mmol 12e, 0.65 mmol PhNHSCF₃, 0.65 mmol TfOH); ¹H NMR (300 MHz, CDCl₃): δ 0.92 (s, 3H), 1.34–1.74 (m, 6H), 1.90–2.30 (m, 5H), 2.34–2.43 (m, 1H), 2.45–2.58 (m, 1H), 2.85–2.97 (m, 2H), 6.09 (br s, 1H), 6.81 (s, 1H), 7.44 (s, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 13.8, 21.5, 25.8, 26.2, 29.5, 31.4, 35.8, 37.9, 43.6, 47.9, 50.4, 105.4 (q, J = 1.2 Hz), 115.9, 128.8 (q, J = 310.6 Hz), 133.5, 135.0, 143.9, 155.8, 220.5; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.7 (s, SCF₃); IR: 3323, 1723, 1601, 1502, 1410, 1103, 895, 877, 674 cm⁻¹; ESI-HRMS: m/z calcd for C₁₉H₂₀F₃O₂S (M − H)⁻ 369.1142, found 369.1141.

(13S)-3-Hydroxy-13-methyl-4-(trifluoromethylthio)-7,8,9,11,12,13,15,16-octahydro-6H-cyclopenta[a]phenanthren-17(14H)-one 13ee. White solid; mp 171.7–172.7 °C; (0.5 mmol 12e, 0.65 mmol PhNHSCF₃, 0.65 mmol TfOH); ¹H NMR (500 MHz, CDCl₃): δ 0.92 (s, 3H), 1.37–1.58 (m, 5H), 1.59–1.70 (m, 1H), 1.93–2.00 (m, 1H), 2.02–2.11 (m, 2H), 2.11–2.20 (m, 1H), 2.21–2.29 (m, 1H), 2.34–2.42 (m, 1H), 2.48–2.66 (m, 1H), 2.89–3.00 (m, 1H), 3.21–3.28 (m, 1H), 6.44 (br s, 1H), 6.92 (d, J = 8.7 Hz, 1H), 7.40 (d, J = 8.7 Hz, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 13.8, 21.5, 26.0, 26.3, 29.0, 31.5, 35.8, 37.5, 44.1, 47.9, 50.3, 108.0, 113.2, 128.9 (q, J = 311.8 Hz), 131.1, 133.4, 143.0, 156.7, 220.7; ¹⁹F NMR (470 MHz, CDCl₃): δ −41.9 (s, SCF₃); IR: 3396, 1732, 1471, 1154, 1118, 1092, 824, 754 cm⁻¹; ESI-HRMS: m/z calcd for C₁₉H₂₀F₃O₂S (M − H)⁻ 369.1142, found 369.1143.

2-Nitro-4-(trifluoromethylthio)phenol 14. Yellow solid; mp 51.6–52.9 °C; ¹H NMR (300 MHz, CDCl₃): δ 7.25 (d, J = 8.8 Hz, 1H), 7.84 (dd, J = 8.8, 2.2 Hz, 1H), 8.45 (d, J = 2.2 Hz, 1H), 10.77 (s, 1H); ¹³C NMR (75 MHz, CDCl₃): δ 115.7 (q, J = 2.3 Hz), 121.5, 129.1 (q, J = 308.8 Hz), 133.6, 133.7, 144.8, 156.9; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.7 (s, SCF₃); IR: 3256, 1614, 1519, 1474, 1413, 1316, 1243, 1150, 1108, 1088, 1072, 848, 672 cm⁻¹; ESI-HRMS: m/z calcd for C₇H₃F₃NO₃S (M − H)⁻ 237.9791, found 237.9792.

2,6-Dinitro-4-(trifluoromethylthio)phenol 15. Yellow solid; decomp., 170 °C; ¹H NMR (500 MHz, acetone-d₆): δ 8.38 (s, 2H); ¹³C NMR (125 MHz, acetone-d₆): δ 106.8, 131.3 (q, J = 308.0 Hz), 140.1, 143.5, 158.4; ¹⁹F NMR (470 MHz, acetone-d₆): δ −44.0 (s, SCF₃); IR: 3438, 3091, 1624, 1527, 1338, 1252, 1136, 1090, 913, 776, 724, 683 cm⁻¹; ESI-HRMS: m/z calcd for C₇H₂F₃N₂O₅S (M − H)⁻ 282.9642, found 282.9643.

2,6-Dibromo-4-(trifluoromethylthio)phenol 16. Yellow solid; mp 51.3–53.4 °C; ¹H NMR (500 MHz, CDCl₃): δ 6.23 (br s, 1H), 7.77 (s, 2H); ¹³C NMR (125 MHz, CDCl₃): δ 110.2, 117.2 (q, J = 2.2 Hz), 129.1 (q, J = 308.9 Hz), 139.7, 152.1; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.8 (s, SCF₃); IR: 3459, 1452, 1383, 1325, 1159, 1094, 877, 735, 709 cm⁻¹; ESI-HRMS: m/z calcd for C₇H₂Br₂F₃OS (M − H)⁻ 348.8151, found 348.8152.

2,6-Diiodo-4-(trifluoromethylthio)phenol 17. Gray solid; mp 86.0–87.6 °C; ¹H NMR (300 MHz, CDCl₃): δ 6.05 (br s, 1H), 7.97 (s, 2H); ¹³C NMR (125 MHz, CDCl₃): δ 82.2, 118.3 (q, J = 2.0 Hz), 129.1 (q, J = 308.9 Hz), 146.7, 156.1; ¹⁹F NMR (470 MHz, CDCl₃): δ −43.8 (s, SCF₃); IR: 3439, 1440, 1375, 1302, 1105, 895, 753, 699 cm⁻¹; ESI-HRMS: m/z calcd for C₇H₂F₃I₂OS (M − H)⁻ 444.7873, found 444.7883.

(4-Phenoxyphenyl)(trifluoromethyl)sulfane 18. Colorless, viscous liquid; ¹H NMR (300 MHz, CDCl₃): δ 6.96–7.03 (m, 2H), 7.04–7.10 (m, 2H), 7.16–7.23 (m, 1H), 7.35–7.44 (m, 2H), 7.56–7.63 (m, 2H); ¹³C NMR (125 MHz, CDCl₃): δ 117.2 (q, J = 1.9 Hz), 118.6, 120.1, 124.6, 129.5 (q, J = 308.2 Hz), 130.0, 138.3, 155.5, 160.4; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.1 (s, SCF₃); IR: 1581, 1485, 1240, 1110, 1081, 869, 834, 754, 692 cm⁻¹; Anal Calcd for C₁₃H₉F₃OS: C, 57.77; H, 3.36. Found: C, 57.73; H, 3.09.

(4-(4-Bromobenzyloxy)phenyl)(trifluoromethyl)sulfane 19. Light yellow solid; mp 54.8–55.5 °C; ¹H NMR (500 MHz, CDCl₃): δ 5.04 (s, 2H), 6.96–7.00 (m, 2H), 7.30 (d, J = 8.3 Hz, 2H), 7.53 (d, J = 8.3 Hz, 2H), 7.56–7.60 (m, 2H); ¹³C NMR (125 MHz, CDCl₃): δ 69.4, 115.4 (q, J = 1.9 Hz), 115.8, 122.2, 129.1, 129.6 (q, J = 308.2 Hz), 131.8, 135.2, 138.3, 160.7; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.3 (s, SCF₃); IR: 1590, 1494, 1453, 1411, 1377, 1251, 1107, 1088, 1042, 1012, 831, 809, 799, cm⁻¹; ESI-HRMS: m/z calcd for C₁₄H₉BrF₃OS (M − H)⁻ 360.9515, found 360.9522.

(4-(Biphenyl-4-ylmethoxy)phenyl)(trifluoromethyl)sulfane 20. White solid; mp 107.0–108.4 °C; ¹H NMR (300 MHz, CDCl₃): δ 5.14 (s, 2H), 7.01–7.07 (m, 2H), 7.33–7.41 (m, 1H), 7.42–7.54 (m, 4H), 7.57–7. 67 (m, 6H); ¹³C NMR (125 MHz, CDCl₃): δ 69.9, 115.2 (q, J = 1.9 Hz), 115.8, 127.1, 127.5, 128.0, 128.8, 129.6 (q, J = 308.2 Hz), 135.1, 138.3, 140.6, 141.3, 161.0; ¹⁹F NMR (470 MHz, CDCl₃): δ −44.3 (s, SCF₃); IR: 1589, 1491, 1380, 1247, 1106, 1083, 1028, 1005, 826, 763, 700 cm⁻¹; ESI-HRMS: m/z calcd for C₂₀H₁₄F₃OS (M − H)⁻ 359.0723, found 359.0720.

Acknowledgements

Mrs T. Stipanovič and Prof. B. Stanovnik for elemental combustion analyses, Dr D. Urankar and Prof. J. Košmrlj for HRMS, and the Ministry of Higher Education, Science and Technology (P1-0134) for financial support are gratefully acknowledged.

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Footnote

† Electronic supplementary information (ESI) available: Copies of the ¹H, ¹³C and ¹⁹F NMR spectra for all products. See DOI: 10.1039/c4ob02633k

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