Synthesis of β-Fluorovinyliodonium Salts by the Reaction of Alkynes

Feb 12, 2018 - ... should be prepared beforehand by the electrochemical fluorination of p-TolI ... (11) The latter method using the Michael addition o...
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Article Cite This: J. Org. Chem. 2018, 83, 2773−2778

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Synthesis of β‑Fluorovinyliodonium Salts by the Reaction of Alkynes with Hypervalent Iodine/HF Reagents Tsugio Kitamura,* Shota Mizuno, Kensuke Muta, and Juzo Oyamada Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Hojo-machi Saga 840-8502, Japan S Supporting Information *

ABSTRACT: The reaction of alkynes with PhIO and Py·HF followed by treatment with BF3·OEt2 gave β-fluorovinyliodonium tetrafluoroborates in good to high yields. More conveniently, the reaction using PhI and Py·HF in the presence of m-CPBA also afforded β-fluorovinyliodonium tetrafluoroborates in good yields. These methods have the advantages that β-fluorovinyliodonium salts can be prepared without ArIF2.

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Scheme 2. Synthetic Methods for β-Fluorovinyliodonium Salts

INTRODUCTION Organofluorine compounds have attracted much attention in the fields of biology and material science because of their unique chemical and physical properties. Among the organofluorine compounds, it is known that fluoroalkenes have the similarity in chemical and structural properties to amide groups and serve as an isopolar and isosteric mimic of the amide moiety in peptides, as shown in Scheme 1.1 Therefore, the Scheme 1. β-Fluorovinyliodonium Salts as a Building Block for Fluoroalkene Isosteres

the former method (Scheme 2, (i), however, p-TolIF2 should be prepared beforehand by the electrochemical fluorination of p-TolI with Et3N·5HF,7 the reaction of p-TolIO with hydrofluoric acid,8 or the direct fluorination of p-TolI with F2,9 XeF2,10 or Selectfluor.11 The latter method using the Michael addition of HF (Scheme 2, (ii)) also requires the synthesis of alkynyliodonium salts before the fluorination. To reduce the complicatedness of the previous procedures, we envisioned facile methods for the synthesis of βfluorovinyliodonium salts. Since we have developed a simple fluorinating reagent composed of PhIO and HF,3 we considered to use this reagent for the synthesis of βfluorovinyliodonium salts (Scheme 2, (iii)). Furthermore, the method would be more convenient if β-fluorovinyliodonium salts could be prepared without PhIO. Thus, we developed the

synthesis of fluoroalkenes is significant in the field of medicinal chemistry. As for the fluoroalkenes, many applications to material sciences are also found.2 Thus, in the course of our study on hypervalent iodine-mediated fluorination reactions,3 we considered that β-fluorovinyliodonium salts are an excellent candidate for constructing such fluoroalkenes. The βfluorovinyliodonium salts are suitable as the building block of fluoroalkenes because phenyliodonio group may be readily replaceable with many functional groups under mild conditions due to its superleaving ability.4 A shown in Scheme 2, two methods have been developed for synthesis of β-fluorovinyliodonium salts so far. One method includes the reaction of p-(difluoroiodo)toluene (p-TolIF2) with 1-alkynes (Scheme 2, (i)).5 Another one is the Michael addition of HF to 1-alkynyliodonium salts (Scheme 2, (ii)).6 In © 2018 American Chemical Society

Received: December 21, 2017 Published: February 12, 2018 2773

DOI: 10.1021/acs.joc.7b03223 J. Org. Chem. 2018, 83, 2773−2778

Article

The Journal of Organic Chemistry

Therefore, we determined the stereochemistry of 2a as the (E) isomer.

procedure using iodoarenes which were oxidized to iodosylarenes and converted into difluoroiodoarenes (Scheme 2, (iv)). Using these methods, the synthesis of β-fluorovinyliodonium salts were much improved. Here, we report these convenient and facile methods for the synthesis of β-fluorovinyliodonium salts.

Scheme 3. Stereochemistry of β-Fluorovinyliodonium Salts

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RESULTS AND DISCUSSION First, we chose 1-octyne (1a) as the substrate and initiated our study by examining several hypervalent iodine reagents and HF reagents for the fluorination. The results are given Table 1. The

Using the optimized conditions in hand, we examined the reaction of several alkynes to determine the scope of the substrates. The results are given in Table 2. Fluorination of

Table 1. Reaction of 1-Octyne (1a) with Hypervalent Iodine/HF Reagentsa

entry

hypervalent iodine reagent

HF reagent

yieldb (%)

1 2 3 4 5 6 7 8c 9d 10d,e

PhI(OAc)2 PhIO PhI(OH)OTs PhI(OCOCF3)2 PhIO PhIO PhIO PhIO PhIO PhIO

Py·HF Py·HF Py·HF Py·HF 55% HF TEA·3HF TEA·5HF Py·HF Py·HF Py·HF

58 81 38 55 66 25 52 85 87

Table 2. Synthesis of β-Fluorovinyliodonium Salts 2a

a Conditions: 1a (0.5 mmol), iodine reagent (0.6 mmol), HF reagent (2.5 mmol HF), CH2Cl2 (2 mL); BF3·OEt2 (2 mmol). bYields were determined by 19F NMR. cPy·HF (5 mmol HF) was used. dPhIO (0.75 mmol) and Py·HF (5 mmol HF) were used. eWithout BF3·OEt2.

reaction of 1a with a fluorinating reagent of PhI(OAc)2 (1.2 equiv) and pyridine HF complex (Py·HF) (5 equiv) was conducted at room temperature, and then the reaction mixture was treated with BF3·OEt2 (4 equiv) at −78 °C. Workup of the reaction mixture gave 2-fluoro-1-octenyl(phenyl)iodonium tetrafluoroborate (2a) in 58% yield (entry 1). We screened several hypervalent iodine reagents. Use of PhIO improved the yield of 2a to 81% (entry 2). However, Koser’s salt [PhI(OH)OTs] and PhI(OCOCF3)2 resulted in decrease of the yield (entries 3 and 4). In the reaction using PhIO as the hypervalent iodine reagent, HF reagents such as 55% HF, TEA· 3HF, and TEA·5HF were examined, but none of them gave a better result (entries 5−7). Furthermore, we tuned the amount of Py·HF or PhIO to optimize the conditions. A slight increase of the yield was observed when 10 equiv of Py·HF was used (entry 8). Further, the yield of 2a was increased to 87% using 1.5 equiv of PhIO (entry 9). To confirm the effect of BF3·OEt2, the same reaction under the conditions described in entry 9 was conducted without addition of BF3·OEt2. However, the corresponding 2-fluoro-1-octenyl(phenyl)iodonium fluoride was not obtained, but 1a was recovered. This result suggests that activation of PhIF2 by Py·HF is not enough to react with 1a and needs a stronger activating agent such as BF3·OEt2. The stereochemistry of β-vinyliodonium salt 2a could be readily determined by 1H NMR. The vinylic proton was appeared at 6.70 ppm and coupled with fluorine atom. The coupling constant 3JH−F was 14.8 Hz. This value was in good agreement with the reported data,6a,b as shown in Scheme 3.

a Conditions: 1 (0.5 mmol), PhIO (0.75 mmol), Py cdt•HF (5 mmol HF), CH2Cl2 (2 mL), and BF3·OEt2 (2 mmol).

terminal alkynes gave the corresponding β-fluorovinyliodonium salts 2a−e in 71−83% yields (entries 1−5). Even in the case of internal alkynes 3-hexyne (1f) and 6-dodecyne (1g), βfluorovinyliodonium tetrafluoroborates 2f and 2g were obtained in 60 and 78% yields, respectively (entries 6 and 7). Functionalized alkynes bearing phenyl (1h), methyl ester (1i), 2774

DOI: 10.1021/acs.joc.7b03223 J. Org. Chem. 2018, 83, 2773−2778

Article

The Journal of Organic Chemistry

Table 4. Synthesis of β-Fluorovinyliodonium Salts Using PhI and m-CPBAa

tosylate (1j), and phthalimide (1k) also underwent the fluorination reaction to afford the corresponding β-fluorovinyliodonium salts 2h−k in 73−78% yields (entries 8−11). It is clear from the above result that the present reagent using PhIO and Py·HF is useful as synthesis of β-fluorovinyliodonium salts 2. On the other hand, hypervalent iodine compounds are readily prepared by oxidation of the corresponding iodoarenes with some oxidants.12 For example, diaryliodonium salts can be conveniently prepared by the reaction of iodoarenes with arenes in the presence of m-CPBA as oxidant.13 This method does not need the synthesis of hypervalent iodine reagents such as iodosylarenes or (diacetoxyiodo)arenes. We then examined a direct method for the synthesis of β-fluorovinyliodonium salts from iodoarenes. We chose 1-octyne (1a) as the substrate again and reacted with iodoarenes in the presence of m-CPBA as the oxidant. The results are given in Table 3. When the reaction of 1a with PhI Table 3. Fluorination of 1a Using PhI and m-CPBAa

entry

PhI (mmol)

m-CPBA (mmol)

HF reagent (HF, mmol)

yieldb (%)

1 2 3 4 5 6 7 8

0.75 0.75 0.75 0.75 1 0.75 1 0.75

0.75 0.75 0.75 0.75 0.75 1 1 0.75

Py·HF (5) 55% HF (5) TEA·3HF (5) TEA·5HF (5) Py·HF (5) Py·HF (5) Py·HF (5) Py·HF (10)

73 64 31 60 66 51 46 80

a

Conditions: 1a (0.5 mmol), PhI, HF reagent, m-CPBA, CH2Cl2 (2 mL); BF3•OEt2 (2 mmol). bYields were determined by19F NMR.

(1.5 equiv) was conducted in the presence of Py·HF (HF, 10 equiv) and m-CPBA (1.5 equiv) followed by treatment with BF3·OEt2 (4 equiv), β-fluorovinyliodonium tetrafluoroborate 2a was obtained in 73% yield (entry 1). Replacement of the HF reagent with 55% HF, TEA·3HF, or TEA·5HF reagent did not improve the yield (entries 2−4). Even if the amount of PhI and/or m-CPBA increased, the yield of 2a did not improve (entries 5−7). Finally, use of 20 equiv of HF gave the best result of 80% (entry 8). With the optimized conditions in hand, we further examined the substrate scope in the one-pot synthesis of β-fluorovinyliodonium salts 2 using PhI. As shown in Table 4, the one-pot fluorination reaction of terminal alkynes 1a−e proceeded efficiently to give the corresponding β-fluorovinyliodonium salts 2a−e in 63−79% yields (entries 1−5). Internal alkynes 1f and 1g afforded the corresponding β-fluorovinyliodonium salts 2f and 2g in 52 and 76% yields, respectively (entries 6 and 7). Similarly, the reaction of functionalized alkynes 1h−k furnished β-fluorovinyliodonium salts 2h−k in 66−76% yields (entries 8−11). To expand the scope of the reaction, we examined the reaction using iodoarenes. Although p-iodoanisole and piodonitrobenzene could not be applied to this reaction, piodotoluene, p-chloroiodobenzene, p-bromoiodobenzene, and o-iodotoluene were good substrates as the iodoarene. The

a

Conditions: 1 (0.5 mmol), PhI (0.75 mmol), Py·HF (10 mmol HF), m-CPBA (0.75 mmol), CH2Cl2 (2 mL); BF3·OEt2 (2 mmol).

corresponding β-fluorovinyliodonium salts 3a−e were obtained in 66−79% yields, respectively (Scheme 4). Addition of PhIF2 to alkynes 1 takes place stereoselectively to give (E)-β-fluorovinyliodonium salts 2. The stereoselective formation of 2 can be explained as follows. As shown in Scheme 5, PhIF2 is generated in situ by the reaction of PhIO with HF reagent.14 Similarly, the oxidation reaction of PhI with m-CPBA in the presence of HF is considered to furnish PhIF2 since the catalytic fluorination proceeds under the same conditions.15 Addition of BF3·Et2O in the reaction mixture leads to the formation of HBF4 due to the presence of excess HF. Moreover, it is known that HBF4 activates p-TolIF2 to promote the fluorination reaction of alkynes.5b Accordingly, the in situ generated PhIF2 is activated by HBF4 and undergoes electrophilic addition to alkynes 1 to form bridged iodonium species, which are subject to the nucleophilic attack of fluoride ion to form (E)-β-vinyliodonium fluorides. The ligand exchange with HBF4 provides the final product 2. The 2775

DOI: 10.1021/acs.joc.7b03223 J. Org. Chem. 2018, 83, 2773−2778

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The Journal of Organic Chemistry

(100 MHz, CDCl3): δ 17.8, 22.4, 28.0, 28.2, 28.5, 28.6, 28.7, 33.4, 50.9, 67.9, 83.9, 173.5. Synthesis of 9-Decynyl Tosylate (1j).17 To a solution of 9decyn-1-ol (1.5 g, 10 mmol), Et3N (3 mL, 20 mmol), and (dimethylamino)pyridine (0.12 g, 1 mmol) in CH2Cl2 (20 mL) was added dropwise a solution of TsCl (2.3 g, 12 mmol) in CH2Cl2 (10 mL) at 0 °C, and the mixture was stirred at room temperature for 17 h. After evaporation of the solvent, the product was extracted with CH2Cl2 (20 mL × 3), and the organic phase was washed with brine and dried over anhydrous Na2SO4. After evaporation of the solvent, the residue was submitted to column chromatography on silica gel. Elution with hexane/EtOAc (10:1) gave 9-decynyl tosylate (1j), 2.28 g (74%), as a colorless oil. 1H NMR (400 MHz, CDCl3): δ 1.24−1.37 (m, 8H), 1.45−1.53 (m, 2H), 1.59−1.66 (m, 2H), 1.95 (s, 1H), 2.14− 2.18 (m, 2H), 2.45 (s, 3H), 4.0 (t, J = 6.4 Hz, 2H), 7.34 (d, J = 8 Hz, 2H), 7.79 (d, J = 8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ 18.0, 21.3, 24.9, 28.0, 28.2, 28.3, 28.4, 28.5, 68.0, 70.4, 84.3, 127.5, 129.5, 132.5, 144.4. Synthesis of N-9-Decyn-1-ylphthalimide (1k). To a mixture of phthalimide (1.47 g, 10 mmol), 9-decyn-1-ol (1.85 g, 12 mmol), and PPh3 (3.15 g, 12 mmol) in THF (30 mL) was added diethyl azodicarboxylate (2.61 g, 15 mmol) over 10 min at 0 °C. The mixture was stirred at room temperature for 17 h. After evaporation of the solvent, a mixed solvent of EtOAc and hexane (1:4) was added to the residue, and the precipitates were filtered off. The product was extracted with CH2Cl2 (20 mL × 3), and the organic phase was dried over anhydrous Na2SO4. The solvent was evaporated, and the residue was submitted to column chromatography on silica gel. Elution with EtOAc/hexane (1:9) gave N-decynylphthalimide 1k, 2.61 g (92%), as white solids. Mp: 53−54 °C. 1H NMR (400 MHz, CDCl3): δ 1.25− 1.40 (m, 8H), 1.45−1.55 (m, 2H), 1.60−1.70 (m, 2H), 1.93 (s, 1H), 2.15−2.19 (m, 2H), 3.68 (t, J = 7.4 Hz, 2H), 7.70−7.85 (m, 4H). 13 C{1H} NMR (100 MHz, CDCl3): δ 17.7, 26.2, 27.8, 27.96, 28.03, 28.35, 28.44, 37.3, 68.0, 83.8, 122.4, 131.5, 133.2, 167.5. HRMS (FAB, double focusing): m/z [M + H]+ calcd for C18H22NO2 284.1645, found 284.1650. Synthesis of β-Fluorovinyliodonium Salts 2 Using Iodosylbenzene. In a Teflon tube were placed PhIO (0.165 g, 0.75 mmol), Py·HF (0.143 g, 5.0 mmol), and CH2Cl2 (2 mL). The mixture was stirred at room temperature for 15 min, and then alkyne 1 (0.5 mmol) was added at this temperature. After the mixture was cooled to −78 °C, BF3·Et2O (0.25 mL, 2.0 mmol) was added and the mixture stirred for 10 min. The reaction mixture was warmed to room temperature and stirred for 20 min. The reaction mixture was poured into water (15 mL) and extracted with CH2Cl2 (10 mL × 3). The combined organic layer was washed with aqueous solution (15 mL) of NaBF4 (0.548 g, 5.0 mmol) and dried over anhydrous Na2SO4. Evaporation of the solvent gave crude product 2, which was washed with hexane to give an NMR spectroscopically pure product. Further purification was conducted by column chromatography on silica gel with hexane/ EtOAc as eluent. (E)-2-Fluoro-1-octen-1-yl(phenyl)iodonium Tetrafluoroborate (2a). The product was obtained as white solids. Mp: 53−54 °C. Yield: 166 mg (79%). 1H NMR (400 MHz, CDCl3): δ = 0.86 (t, J = 7 Hz, 3H), 1.21−1.33 (m, 6H), 1.50−1.62 (m, 2H), 2.81 (dt, J = 7.5, 22.4 Hz, 2H), 6.69 (d, J = 14.4 Hz, 1H), 7.49 (t, J = 8 Hz, 2H), 7.63 (t, J = 8 Hz, 1H), 7.96 (d, J = 8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ = 13.8,22.1, 25.5, 28.3, 31.2, 31.9 (d, J = 23.3 Hz), 78.6 (d, J = 47.2 Hz), 112.2, 132.1, 132.4, 134.5, 175.8 (d, J = 284.9 Hz). 19F NMR (376 MHz, CDCl3): δ = −65.2, −145.9. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C14H19FI 333.0510, found 333.0515. (E)-2-Fluoro-1-hexen-1-yl(phenyl)iodonium Tetrafluoroborate (2b). The product was obtained as a brownish oil. Yield: 139 mg (71%). 1H NMR (400 MHz, CDCl3): δ = 0.85 (t, J = 7 Hz, 3H), 1.25−1.34 (m, 2H), 1.43−1.51 (m, 2H), 2.78 (dt, J = 7.6, 22.0 Hz, 2H), 6.76 (d, J = 14.8 Hz, 1H), 7.46 (t, J = 8 Hz, 2H), 7.60 (t, J = 8 Hz, 1H), 7.98 (d, J = 8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ = 13.3, 21.6, 27.5, 31.5 (d, J = 24.0 Hz), 78.5 (d, J = 47.2 Hz), 112.1, 132.1, 132.5, 134.5, 175.7 (d, J = 285.0 Hz). 19F NMR (376 MHz,

Scheme 4. Synthesis of β-Fluorovinyliodonium Salts Using Iodoarenes

Scheme 5. Possible Mechanism for Stereoselective Formation of 2

stereochemistry of 2 is governed by the ring-opening of the bridged iodonium species with fluoride ion.

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CONCLUSION In conclusion, we have developed convenient methods for the synthesis of β-fluorovinyliodonium salts from alkynes. The methods include the reaction of PhIO/HF reagent and, more conveniently, the use of iodobenzene in the presence of mCPBA. These methods are applicable to a wide variety of alkynes. In addition to good yields of the products, the convenient procedure facilitates the approach to the building block of fluoroalkenes.

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EXPERIMENTAL SECTION

Synthesis of Methyl 10-Undecynoate (1i).16 A solution of 10undecynoic acid (1.1 g, 6 mmol) and TsOH·H2O (2.3 mg, 0.012 mmol) in MeOH (25 mL) was refluxed for 17 h. After evaporation of the solvent, aqueous NaHCO3 was added and extracted with ether (10 mL × 3). The organic phase was washed with brine and dried over anhydrous Na2SO4. After evaporation of the solvent, the residue was submitted to column chromatography on silica gel. Elution with hexane/EtOAc (10:1) gave methyl 10-undecynoate (1i), 1.13 g (96%), as colorless oil. 1H NMR (400 MHz, CDCl3): δ 1.30−1.38 (m, 8H), 1.48−1.53 (m, 2H), 1.61−1.66 (m, 2H), 1.95 (s, 1H), 2.18 (t, J = 6.4 Hz, 2H), 2.31 (t, J = 7.6 Hz, 2H), 3.67 (s, 3H). 13C{1H} NMR 2776

DOI: 10.1021/acs.joc.7b03223 J. Org. Chem. 2018, 83, 2773−2778

Article

The Journal of Organic Chemistry CDCl3): δ = −66.05, −145.6. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C12H15FI 305.0197, found 305.0202. (E)-2-Fluoro-1-dodecen-1-yl(phenyl)iodonium Tetrafluoroborate (2c).6b The product was obtained as white solids. Mp: 65−67 °C. Yield: 190 mg (80%). 1H NMR (400 MHz, CDCl3): δ = 0.88 (t, J = 7 Hz, 3H), 1.18−1.32 (m, 14H), 1.52 (t, J = 7 Hz, 2H), 2.80 (dt, J = 7, 22.4 Hz, 2H), 6.70 (d, J = 14.8 Hz, 1H), 7.49 (t, J = 8 Hz, 2H), 7.63 (t, J = 8 Hz, 1H), 7.97 (d, J = 8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ = 13.8, 22.4, 25.5, 28.5, 29.0, 29.1 (two peaks overlapped), 29.2, 31.6, 31.8 (d, J = 24.0 Hz), 78.5 (d, J = 47.3 Hz), 112.0, 132.0, 132.3, 134.5, 175.7 (d, J = 285.0 Hz). 19F NMR (376 MHz, CDCl3): δ = −65.0, −145.8. (E)-2-Fluoro-5-methyl-1-hexen-1-yl(phenyl)iodonium Tetrafluoroborate (2d). The product was obtained as white solids. Mp: 83−86 °C. Yield: 150 mg (74%). 1H NMR (400 MHz, CDCl3): δ = 0.87 (d, J = 7 Hz, 6H), 1.38 (q, J = 7 Hz, 2H), 1.51−1.62 (m, 1H), 2.78 (dt, J = 8, 22.0 Hz, 2H), 6.71 (d, J = 14.4 Hz, 1H), 7.48 (t, J = 8 Hz, 2H), 7.63 (t, J = 8 Hz, 1H), 7.97 (d, J = 8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ = 21.8, 27.3, 30.0 (d, J = 23.2 Hz), 34.3, 78.2 (d, J = 48.0 Hz), 111.9, 132.1, 132.5, 134.5, 176.0 (d, J = 284.2 Hz). 19F NMR (376 MHz, CDCl3): δ = −64.9, −145.7. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C13H17FI 319.0353, found 319.0359. (E)-3-Cyclohexyl-2-fluoro-1-propen-1-yl(phenyl)iodonium Tetrafluoroborate (2e). The product was obtained as white solids. Mp: 125−126 °C. Yield: 179 mg (83%). 1H NMR (400 MHz, CDCl3): δ = 0.89−0.98 (m, 2H), 1.09−1.30 (m, 3H), 1.63−1.65 (m, 6H), 2.69 (dd, J = 7, 23.0 Hz, 2H), 6.74 (d, J = 14.4 Hz, 1H), 7.49 (t, J = 8 Hz, 2H), 7.63 (t, J = 8 Hz, 1H), 7.97 (d, J = 8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ = 26.0 (two peaks overlapped), 32.3, 35.5, 38.7 (d, J = 22.4 Hz), 85.0 (d, J = 40.3 Hz), 116.4, 132.1, 132.4, 135.2, 172.4 (d, J = 277.9 Hz). 19F NMR (376 MHz, CDCl3): δ = −62.4, −146.0. HRMS (FAB, double focusing): m/z [M-BF4]+ calcd for C15H19FI 345.0510, found 345.0517. (E)-4-Fluoro-3-hexen-3-yl(phenyl)iodonium Tetrafluoroborate (2f). The product was obtained as brownish oil. Yield: 118 mg (60%). 1H NMR (400 MHz, CDCl3): δ = 1.13 (t, J = 7 Hz, 3H), 1.22 (t, J = 7 Hz, 3H), 2.70−2.75 (m, 2H), 2.94 (dq, J = 7.4, 22.2 Hz, 2H), 7.52 (t, J = 8 Hz, 2H), 7.67 (t, J = 8 Hz, 1H), 7.94 (d, J = 8 Hz, 2H). 13 C{1H} NMR (100 MHz, CDCl3): δ = 10.4, 13.3, 25.6, 27.1 (d, J = 25.6 Hz), 106.4 (d, J = 41.0 Hz), 109, 132.3, 132.7, 134.8, 169.5 (d, J = 279.5 Hz). 19F NMR (376 MHz, CDCl3): δ = −80.8, −146.4. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C12H15FI 305.0197, found 305.0205. (E)-7-Fluoro-6-dodecen-6-yl(phenyl)iodonium Tetrafluoroborate (2g). The product was obtained as brownish solids. Mp: 68−69 °C. Yield: 186 mg (78%). 1H NMR (400 MHz, CD3OD): δ = 0.87 (t, J = 7 Hz, 3H), 0.90−0.96 (m, 3H), 1.21−1.33 (m, 4H), 1.33−1.45 (m, 4H), 1.51 (t, J = 7 Hz, 2H), 1.60−1.65 (m, 2H), 2.68−2.74 (m, 2H), 2.94 (dt, J = 7.6, 22.4 Hz, 2H), 7.61 (t, J = 8 Hz), 7.77 (t, J = 8 Hz, 1H), 8.11 (d, J = 8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ = 13.5 (two peaks overlapped), 21.7, 21.9, 25.7, 27.7, 30.0, 30.7, 31.9, 33.4 (d, J = 25.5 Hz), 105.0 (d, J = 40.2 Hz), 109.7, 132.2, 132.7, 134.6, 169.2 (d, J = 277.9 Hz). 19F NMR (376 MHz, CDCl3): δ = −77.1, −147.1. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C18H27FI: 389.1136, found 389.1142. (E)-2-Fluoro-4-phenyl-1-buten-1-yl(phenyl)iodonium Tetrafluoroborate (2h). The product was obtained as white solids. Mp: 111− 114 °C. Yield: 161 mg (73%). 1H NMR (400 MHz, CDCl3): δ = 2.96 (t, J = 7 Hz, 2H), 3.16 (dt, J = 7, 21.6 Hz, 2H), 6.54 (d, J = 14.4 Hz, 1H), 7.22−7.38 (m, 7H), 7.48 (d, J = 8 Hz, 2H), 7.56 (t, J = 8 Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3): δ = 31.2, 33.3 (d, J = 24.7 Hz), 84.9 (d, J = 39.5 Hz), 115.5, 126.9, 128.8, 128.9, 131.9, 132.2, 135.0, 139.6, 171.4 (d, J = 277.2 Hz). 19F NMR (376 MHz, CDCl3): δ −67.1, −146.4. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C16H15FI 353.0197, found 353.0202. (E)-2-Fluoro-10-methoxycarbonyl-1-decen-1-yl(phenyl)iodonium Tetrafluoroborate (2i). The product was obtained as a yellow oil. Yield: 187 mg (74%). 1H NMR (400 MHz, CDCl3): δ = 1.23−1.32 (m, 8H), 1.51−1.62 (m, 4H), 2.30 (t, J = 7.5 Hz, 2H), 2.80 (dt, J = 7.5,

22.4 Hz, 2H), 3.67 (s, 3H), 6.70 (d, J = 14.4 Hz, 1H), 7.50 (t, J = 8 Hz, 2H), 7.64 (t, J = 8 Hz, 1H), 7.96 (d, J = 8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ = 24.4, 25.3, 28.2, 28.39, 28.43, 28.47, 31.5 (d, J = 24.0 Hz), 33.5, 51.1, 78.6 (d, J = 47.2 Hz), 112.1, 131.9, 132.3, 134.3, 174.0, 175.4 (d, J = 277.2 Hz). 19F NMR (376 MHz, CDCl3): δ = −65.1, −146.1. HRMS (FAB, double focusing): m/z [M _ -BF4]+ calcd for C18H25FIO2 419.0878, found 419.0882. (E)-2-Fluoro-10-tosyloxy-1-decen-1-yl(phenyl)iodonium Tetrafluoroborate (2j). The product was obtained as white solids. Mp: 83−84 °C. Yield: 241 mg (78%). 1H NMR (400 MHz, CDCl3): δ = 1.15−1.30 (m, 8H), 1.48−1.53 (m, 2H), 1.58−1.65 (m, 2H), 2.45 (s, 3H), 2.79 (dt, J = 7.6, 22.0 Hz, 2H), 4.01 (t, J = 6.4 Hz, 2H), 6.72 (d, J = 14.0 Hz, 1H), 7.35 (t, J = 8 Hz, 2H), 7.48 (t, J = 8 Hz, 2H), 7.63 (t, J = 8 Hz, 1H), 7.78 (d, J = 8 Hz, 2H), 7.97 (d, J = 8 Hz, 2H). 13C{1H} NMR (100 MHz, DMSO-d6): δ = 20.9, 24.5, 25.0, 27.9 (two peaks overlapped), 28.0, 28.2, 31.3 (d, J = 24.0 Hz), 70.4, 78.3 (d, J = 47.2 Hz), 111.7, 127.1, 129.5, 131.8, 132.0, 132.2, 134.2, 144.5, 175.3 (d, J = 284.1 Hz). 19F NMR (376 MHz, CDCl3): δ = −65.3, −145.9. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C23H29FIO3S 531.0861, found 531.0866. (E)-2-Fluoro-10-phthalimido-1-decen-1-yl(phenyl)iodonium Tetrafluoroborate (2k). The product was obtained as white solids. Mp: 81−83 °C. Yield: 255 mg (86%). 1H NMR (400 MHz, CD3OD): δ = 1.23−1.35 (m, 8H), 1.46−1.54 (m, 2H), 1.62−1.68 (m, 2H), 2.84 (dt, J = 7.2, 22.0 Hz, 2H), 3.65 (t, J = 7 Hz, 2H), 7.03 (d, J = 15.6 Hz, 1H), 7.59 (t, J = 8 Hz, 2H), 7.72−7.84 (m, 5H), 8.10 (d, J = 8 Hz, 2H). 13 C{1H} NMR (100 MHz, CD3OD): δ = 26.6, 27.4, 29.2, 29.4, 29.6, 29.9, 32.5 (d, J = 23.4 Hz), 38.5, 81.7 (d, J = 43.6 Hz), 115.0, 123.8, 132.7, 133.0, 133.5, 135.2, 135.9, 169.4, 175.8 (d, J = 281.2 Hz). 19F NMR (376 MHz, CD3OD): δ = −65.5, −145.8. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C24H26FINO2 506.0987, found 506.0992. Synthesis of β-Fluorovinyliodonium Salts 2 Using Iodobenzene and m-CPBA. In a Teflon tube were placed PhI (0.153 g, 0.75 mmol), Py·HF (0.286 g, 10 mmol), m-CPBA (0.172 g, 0.75 mmol), and CH2Cl2 (2 mL). The mixture was stirred at room temperature for 3 h, and then alkyne 1 (0.5 mmol) was added at this temperature. After the mixture was cooled to −78 °C, BF3·Et2O (0.25 mL, 2.0 mmol) was added and the mixture stirred for 10 min. The reaction mixture was warmed to room temperature and stirred for 20 min. The reaction mixture was poured into water (15 mL) and extracted with CH2Cl2 (10 mL × 3). The combined organic layer was washed with an aqueous solution (15 mL) of NaBF4 (0.548 g, 5.0 mmol) and dried over anhydrous Na2SO4. After evaporation of the solvent, the residue was submitted to column chromatography on silica gel (5 g). Organic compounds containing m-chlorobenzoic acid were first eluted with hexane/EtOAc (9:1), and β-fluorovinyliodonium salts 2 were eluted with EtOAc. The same procedure was conducted for the reactions with 4-iodotoluene and 1-chloro-4-iodobenzene (Scheme 4). In the reaction using 1-chloro-4-iodobenzene, the mixture of 1-chloro-4iodobenzene, Py·HF, m-CPBA, and CH2Cl2 was stirred at room temperature for 6 h. (E)-2-Fluoro-1-dodecen-1-yl(4-methylphenyl)iodonium Tetrafluoroborate (3a).5b The product was obtained as white solids. Mp: 73−74 °C. Yield: 181 mg (74%). 1H NMR (400 MHz, CDCl3): δ = 0.89 (t, J = 7 Hz, 3H), 1.20−1.33 (m, 14H), 1.50−1.65 (m, 2H), 2.43 (s, 3H), 2.79 (dt, J = 7.2, 22.0 Hz, 2H), 6.66 (d, J = 14.4 Hz, 1H), 7.29 (d, J = 8.4 Hz, 2H), 7.83 (d, J = 8.4 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ = 13.8, 21.0, 22.4, 25.5, 28.6, 29.06, 29.13, 29.3, 31.6, 31.8 (d, J = 24.7 Hz), 78.7 (d, J = 47.2 Hz), 108.3, 132.7, 134.6, 143.4, 175.4 (d, J = 284.1 Hz). 19F NMR (376 MHz, CDCl3): δ = −65.4, −146.3. (E)-4-Chlorophenyl(2-fluoro-1-dodecen-1-yl)iodonium Tetrafluoroborate (3b). The product was obtained as yellowish solids. Mp: 96−99 °C. Yield: 174 mg (68%). 1H NMR (400 MHz, CDCl3): δ = 0.89 (t, J = 7 Hz, 3H), 1.18−1.30 (m, 14H), 1.48−1.60 (m, 2H), 2.79 (dt, J = 7.6, 22.0 Hz, 2H), 6.70 (d, J = 14.0 Hz, 1H), 7.44 (d, J = 8.8 Hz, 2H), 7.89 (d, J = 8.8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3): δ = 14.0, 22.5, 25.6, 28.7, 29.2, 29.3, 29.4, 31.7, 31.9 (d, J = 24.0 Hz), 78.9 (d, J = 48.0 Hz), 108.9, 132.0, 136.1, 139.3, 176.2 (d, J 2777

DOI: 10.1021/acs.joc.7b03223 J. Org. Chem. 2018, 83, 2773−2778

Article

The Journal of Organic Chemistry = 285.7 Hz). 19F NMR (376 MHz, CDCl3): δ = −64.4, −145.1. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C18H26ClFI 423.0746, found 423.0752. (E)-4-Bromophenyl(2-fluoro-1-dodecen-1-yl)iodonium Tetrafluoroborate (3c). The product was obtained as yellowish solids. Mp: 103−104 °C; yield: 174 mg (79%). 1H NMR (400 MHz, CDCl3): δ = 0.88 (t, J = 6.8 Hz, 3H), 1.19−1.24 (m, 14H), 1.47 (m, 2H), 2.76 (dt, J = 7.4, 22.0 Hz, 2H), 6.75 (d, J = 14.4 Hz, 1H), 7.54 (d, J = 8.6 Hz, 2H), 7.82 (d, J = 8.6 Hz, 2H). 13C{1H} NMR (100 MHz, CD3OD): δ = 14.5, 23.6, 26.8, 29.7, 30.28, 30.31, 30.4, 30.5, 32.7, 32.9, 82.2 (d, J = 44.9 Hz), 113.4, 128.2, 136.0, 137.6, 176.2 (d, J = 281.8 Hz). 19F NMR (376 MHz, CDCl3): δ = −65.0, −145.1. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C18H26BrFI: 467.0241, found 467.0248. (E)-2-Fluoro-1-dodecen-1-yl(2-methylphenyl)iodonium Tetrafluoroborate (3d). The product was obtained as white solids. Mp: 52−53 °C. Yield: 174 mg (66%). 1H NMR (400 MHz, CDCl3): δ = 0.88 (t, J = 6.8 Hz, 3H), 1.24 (m, 14H), 1.48−1.53 (m, 2H), 2.67 (s, 3H), 2.76 (dt, J = 7.4, 22.0 Hz, 2H), 6.55 (d, J = 14.4 Hz, 1H), 7.28 (t, J = 7 Hz, 1H), 7.49 (d, J = 7 Hz, 1H) 7.56 (t, J = 8 Hz, 1H), 8.02 (d, J = 8 Hz, 1H). 13C{1H} NMR (100 MHz, CD3OD): δ = 14.5, 23.6, 25.4, 26.8, 29.8, 30.3 (two peaks overlapped), 30.5, 32.6, 32.9 (two peaks overlapped), 80.8 (d, J = 43.4 Hz), 119.9, 130.5, 132.8, 134.2, 138.1, 142.0, 175.4 (d, J = 281 Hz). 19F NMR (376 MHz, CDCl3): δ = −65.7, −146.9. HRMS (FAB, double focusing): m/z [M − BF4]+ calcd for C19H29FI 403.1292, found 403.1298.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b03223. 1 H and 13C NMR spectra of 1i, 1j, and 1k; 1H, 13C and 19 F NMR spectra of 2 and 3 (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Tsugio Kitamura: 0000-0001-5592-5228 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by JSPS KAKENHI (Grant No. 16K05703). REFERENCES

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DOI: 10.1021/acs.joc.7b03223 J. Org. Chem. 2018, 83, 2773−2778