Copper-Catalyzed Oxidative Perfluoroalkylation of Aryl Boronic Acids

†School of Chemistry and Chemical Engineering, Hefei University of Technology, 193 Tunxi. Road, Anhui, 230000, People's Republic of China. ‡School...
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Note Cite This: J. Org. Chem. 2018, 83, 463−468

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Copper-Catalyzed Oxidative Perfluoroalkylation of Aryl Boronic Acids Using Perfluoroalkylzinc Reagents Xifei Bao,† Lihua Liu,‡ Junlan Li,† and Shilu Fan*,† †

School of Chemistry and Chemical Engineering, Hefei University of Technology, 193 Tunxi Road, Anhui 230000, People’s Republic of China ‡ School of Biological and Medical Engineering, Hefei University of Technology, 193 Tunxi Road, Anhui 230000, People’s Republic of China S Supporting Information *

ABSTRACT: An efficient and synthetically convenient method for copper-catalyzed cross-coupling of aryl boronic acids with perfluoroalkyl zinc reagents has been described. The reaction proceeds under mild reaction conditions with a high efficiency and broad substrate scope and provides a general access to perfluoroalkylated arenes, which are of interest in life and materials science.

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reagents with DMPU (1,3-dimethyltetrahydropyrimidin2(1H)-one) to form stable perfluoroalkyl zinc reagents, which were utilized in copper-catalyzed cross-coupling reactions with aryl iodides. However, coupling of perfluoroalkylating reagents (L2ZnRf2) with nucleophilic arylboronic acids has not been reported to date. Herein, we report a copper-catalyzed oxidative perfluoroalkylation of aryl boronic acids with stable perfluoroalkyl zinc reagents (Scheme 1).

he introduction of perfluoroalkyl (Rf) groups into organic molecules can substantially alter their chemical and metabolic stability, lipophilicity, and binding selectivity due to the strong electron-withdrawing effect and large hydrophobic domain of perfluoroalkyl groups.1,2 Accordingly, it has been of great synthetic interest to develop efficient methods for the incorporation of various perfluoroalkyl groups into aromatic compounds.3 A variety of Cu-,4 Pd-,5 and Pt6-based protocols have been developed for the perfluoroalkylation of aryl halides, arylboronic acids, and aromatic carbonhydrogen bonds using perfluoroalkyl halides, allowing efficient access to a diverse array of perfluoroalkylated analogues. The generation of aryl-Rf bonds, however, remains synthetically challenging, particularly via transition-metal catalysis.4a,d−h,7 Recent advances in photoredox-catalyzed C−H perfluoroalkylation protocols are particularly attractive because of obviating the need for prefunctionalization of the substrates,8 but poor regioselectivity is often encountered in this kind of reaction.6,8b,9 In 2010, Qing and co-workers reported a method for the copper-mediated oxidative trifluoromethylation of alkynes.10 Soon afterward, Qing,7h,11 Buchwald,12 Goossen,13 and Grushin14 independently applied this oxidative trifluoromethylation protocol to aryl boronic acids, allowing access to a variety of trifluoromethylated arenes. Analogous to this transformation, we postulated that a copper-catalyzed oxidative coupling could be used to access perfluoroalkyl arenes. In the above cases, nucleophilic/electrophilic perfluoroalkylating reagents have been employed. However, only CF3SiR3, C2F5SiR3, C3F7SiR3, Togni, and Umemoto reagents are commercially available. In 2011, Daugulis and co-workers synthesized Rf2Zn from 1Hperfluoroalkane by deprotonative metalation with TMP2Zn and used it in copper-catalyzed perfluoroalkylation of aromatic iodides.15 The intrinsic limitation of this method is that TMP2Zn is extremely water- and air-sensitive. The groups of Mikami16 and Uchiyama17 stabilized these sensitive zinc © 2017 American Chemical Society

Scheme 1. Copper-Cataylzed Perfluoroalkylation Reactions

We began our studies of perfluoroalkylation of [1,1′biphenyl]-4-ylboronic acid 1a by choosing perfluoroalkyl zinc reagents 2c as a substrate because it is easily prepared16 and thermally stable under the following conditions: 1a (0.2 mmol), 2c (0.2 mmol), CuI (10 mol %), 1,10-phenanthroline (10 mol %), KOAc (2.0 equiv), and AgOAc (1.2 equiv) in DMSO (2.0 mL) at 80 °C for 12 h (Table 1, entry 1). The desired crosscoupling product 3ac was isolated in 59% yield. We were pleased to observe the formation of 3ac in 81% isolated yield when oxygen was chosen as a co-oxidant (Table 1, entry 2). With the preliminary results in hand, different bases were examined and K3PO4 was found to be the optimum base, providing 3ac in 90% isolated yield (Table 1, entry 3). Other bases such as KOAc, CsOAc, Na2CO3, and K2CO3 proved to be less effective (Table 1, entries 4−7). Besides Cu(acac)2, many copper catalysts such as Cu(OAc)2, CuCN, and CuSCN Received: October 9, 2017 Published: December 1, 2017 463

DOI: 10.1021/acs.joc.7b02557 J. Org. Chem. 2018, 83, 463−468

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The Journal of Organic Chemistry

stitutes on the aromatic ring afforded satisfying results (3gc− 3nc). Unfortunately, the simple phenylboronic acid just gave a 21% NMR yield (3mc). Reactions with halogen-substituted aryl boronic acids also gave the desired products 3pc and 3qc in 29% and 45% 19F NMR yields, respectively. Additionally, heteroaromatic boronic acid was also tolerated in this reaction to give the desired product in a moderate yield (3rc). It is noteworthy that many versatile functional groups, such as aryl, ether, ester, ketone, sulfone, halogen, and heterocycle, were compatible with the reaction conditions. To further probe the applicability of this methodology, couplings of various perfluoroalkyl zinc reagents 2 with aryl boronic acids 1 were also tested (Scheme 3). Generally, moderate to high yields of desired products 3 were afforded under the standard conditions. Phenyl-substituted aromatic boronic acid 1a still shows a higher reactivity (3aa−3ad). Both electron-rich 3h and electron-deficient 3k aryl boronic acids furnished the desired products in moderate yields. It should be pointed out that (4-(methylsulfonyl)phenyl)boronic acid 1n was also a suitable substrate, and 3na−3nd were provided in moderate to high yields under the present reaction conditions. To gain some mechanistic insight into the present reaction, a radical inhibition experiment was performed (Scheme 4). When a reaction run under standard conditions was treated with the radical inhibitor TEMPO, the yield of 3ac was decreased to 62%. This preliminary study suggests against a purely free radical pathway and implicates the formation of organometallic intermediates (CuI/CuIII species). Although the exact mechanism of the reaction is still not clear, on the basis of the results reported by others,4c,15−17 there are several potential mechanisms for these reactions. One plausible mechanism is proposed and shown in Scheme 5. First, a Cu(I) species transmetalation with perfluoroalkyl zinc reagent 2 would afford the RfCuILn species I as the key intermediate. A subsequent reaction with aryl boronic acid to form (aryl)Cu I RfL n species II, which could be oxidized to the corresponding (aryl)CuIIIRfLn intermediate III, would occur. As the final step of the catalytic cycle, reductive elimination of III produces perfluoroalkylated arenes 3 upon the regeneration of the Cu(I) species. An alternative mechanistic possibility would involve the Cu/base-promoted generation of a free perfluoroalkyl radical that could react with the aromatic boronic acids under copper-catalyzed conditions.4c

Table 1. Representative Results for Optimization of CopperCatalyzed Perfluoroalkylation of Aromatic Boronic Acid 1aa

entry

CuX

base

solvent

yield (%)b

c

CuI CuI CuI CuI CuI CuI CuI Cu(OAc)2 CuCN CuSCN Cu(acac)2 CuI CuI CuI CuI CuI ... CuI CuI

KOAc KOAc K3PO4 KOAc CsOAc Na2CO3 K2CO3 K3PO4 K3PO4 K3PO4 K3PO4 K3PO4 K3PO4 K3PO4 K3PO4 K3PO4 K3PO4 K3PO4 K3PO4

DMSO DMSO DMSO DMSO DMSO DMSO DMSO DMSO DMSO DMSO DMSO DMPU Toluene DMF Dioxane DMSO DMSO DMSO DMSO

(59) (81) (90) (78) (89) (86) (74) (70) (69) (81) 18 (63) 31 41 19 (86) 0 (64) 25

1 2d 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18e 19f a

Conditions: 1a (0.2 mmol), 2c (0.2 mmol), CuX (10 mol %), phen (10 mol %), base (2.0 equiv), AgOAc (0.6 equiv), O2 (1 atm), in solvent (2.0 mL), 80 °C, 12 h. bNMR yield determined by 19F NMR using fluorobenzene as an internal standard, and the number in parentheses is the isolated yield. c1.2 equiv of AgOAc and without an oxygen balloon. d1.2 equiv of AgOAc. eReaction run without phen. f Reaction run without AgOAc.

showed good yields (Table 1, entries 8−11). The reaction was found to be sensitive to the nature of the solvents (Table 1, entries 12−15). The reaction preferred to be run in polar solvents (such as DMPU and DMF). Further optimization showed that a good yield of isolated product (86%) was afforded by decreasing the CuI loading to 5 mol % with use of phen (1,10-phenanthroline) (5 mol %; Table 1, entry 16). In addition, CuI is essential for the reaction because the absence of it failed to give any desired product, therefore indicating the copper intermediate involved in this catalytic cycle (Table 1, entry 17). Interestingly, a 64% isolated yield was obtained in a ligand-free condition (Table 1, entry 18). Oxygen showed less activity (Table 1, entry 19). With the optimum reaction conditions (Table 1, entry 3) in hand, the substrate scope of the perfluoroalkylation of aryl boronic acids 1 was tested and the representative results were illustrated in Scheme 2. It was found that a variety of aromatic boronic acids can be successfully perfluoroalkylated to the desired product in modest to good yields. Phenyl-substituted aryl boronic acids were found to undergo the desired transformation, providing the corresponding perfluoroalkylated compounds in good to excellent yields (3ac−3dc). The sterically hindered aromatic boronic acid 1e was also a suitable substrate, providing compound 3ec in a synthetically useful yield. To our delight, aryl diboronic acid 1f run with 2c smoothly and a 61% yield was obtained (3fc). A series of aryl boronic acids with electron-rich and electron-deficient sub-

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CONCLUSION In summary, we have disclosed an efficient and synthetically convenient method for the synthesis of perfluoroalkyl arenes from perfluoroalkyl zinc reagents and broadly available aryl boronic acids through a copper-catalyzed process. The reactions are an improvement over current perfluoroalkylation reactions of aryl iodides because arylboronic acids are significantly less expensive and more stable than aryl iodides. Ongoing studies will focus on probing the mechanism and expanding the scope of this transformation.

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EXPERIMENTAL SECTION

General Information. 1H NMR and 13C NMR spectra were recorded on a Bruker 600 MHz spectrometer in CDCl3 and (CD3)2SO. Data for 1H NMR are reported as follows: chemical shift (ppm, scale), multiplicity, coupling constant (Hz), and integration. Data for 13C NMR are reported in terms of chemical shift (ppm, scale), multiplicity, and coupling constant (Hz). High-resolution mass spectra were obtained by ESI on a TOF mass analyzer. 464

DOI: 10.1021/acs.joc.7b02557 J. Org. Chem. 2018, 83, 463−468

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The Journal of Organic Chemistry Scheme 2. Copper-Catalyzed Perfluoroalkylation of Aromatic Boronic Acids 1a

a Conditions: 1 (0.2 mmol), 2c (0.2 mmol), CuI (10 mol %), 1,10-phenanthroline (10 mol %), K3PO4 (2.0 equiv), AgOAc (0.6 equiv), O2 (1 atm), in DMSO (2.0 mL), 80 °C, 12 h. bConditions: 1 (0.2 mmol), 2c (0.2 mmol), CuI (10 mol %), 4,4′-dimethyl-2,2′-dipyridyl (10 mol %), K3PO4 (2.0 equiv), AgOAc (0.6 equiv), O2 (1 atm), in DMSO (2.0 mL), 80 °C, 12 h. cNMR yield determined by 19F NMR using fluorobenzene as an internal standard.

Scheme 3. Copper-Catalyzed Perfluoroalkylation of Aryl Boronic Acids 1 with Various Perfluoroalkylznic Reagents 2a

a Conditions: 1 (0.2 mmol), 2 (0.2 mmol), CuI (10 mol %), 1,10-phenanthroline (10 mol %), K3PO4 (2.0 equiv), AgOAc (0.6 equiv), O2 (1 atm), in DMSO (2.0 mL), 80 °C, 12 h. bConditions: 1 (0.2 mmol), 2 (0.2 mmol), CuI (10 mol %), 4,4′-dimethyl-2,2′-dipyridyl (10 mol %), K3PO4 (2.0 equiv), AgOAc (0.6 equiv), O2 (1 atm), in DMSO (2.0 mL), 80 °C, 12 h.

Materials. All reagents were used as received from commercial sources, unless specified otherwise, or prepared as described in the literature. All reagents were weighed, handled in air, and refilled with an inert atmosphere of N2 at room temperature. DMF, DMSO,

DMPU, and NMP were distilled under reduced pressure from CaH2. DCE was distilled from CaH2. Toluene, 1,4-dioxane, THF, diglyme, and DME were distilled from sodium and benzophenone immediately before use. 465

DOI: 10.1021/acs.joc.7b02557 J. Org. Chem. 2018, 83, 463−468

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The Journal of Organic Chemistry

three times and dried under a vacuum to give Zn(C6F13)2(DMPU)2 as a white powder (8.4 g, 88% yield). This compound is known.16 Representative General Procedure for Copper-Catalyzed Perfluoroalklation of Boronic Acids. To a septum capped 25 mL Schlenk tube equipped with a magnetic stir bar were added 4-biphenylboronic acid(40 mg, 0.2 mmol), Zn(C4F9)2(DMPU)2 (151 mg, 0.2 mmol), AgOAc (20 mg, 0.12 mmol), K3PO4 (85 mg, 0.4 mmol), CuI (3.8 mg, 0.02 mmol), and phen (3.6 mg, 0.02 mmol) under an O2 atmosphere. Then an O2 balloon was attached to the Schlenk tube, followed by DMSO (2.0 mL) with stirring. The Schlenk tube was heated to 80 °C (oil bath). After stirring for 12 h, the reaction mixture was cooled to room temperature, diluted with ethyl acetate, washed with brine, dried over Na2SO4, filtered, and concentrated. The residue was purified by silica gel chromatography to provide a pure product. 4-(Perfluorobutyl)-1,1′-biphenyl (3ac). The product (66 mg, 90% yield) was purified by silica gel chromatography (petroleum ether (100%)) as a white solid: 1H NMR (600 MHz, CDCl3) δ 7.73 (d, J = 7.8 Hz, 2H), 7.68 (d, J = 8.4 Hz, 2H), 7.63 (d, J = 7.2 Hz, 2H), 7.49 (t, J = 7.8 Hz, 2H), 7.42 (t, J = 7.2 Hz, 1H); 19F NMR (564 MHz, CDCl3) δ −81.1 (m, 3F), −110.9 (t, J = 13.0 Hz, 2F), −122.8 (m, 2F), −125.6 (m, 2F). This compound is known.7q 3-(Perfluorobutyl)-1,1′-biphenyl (3bc). The product (50 mg, 67% yield) was purified by silica gel chromatography (petroleum ether (100%)) as a colorless oil: 1H NMR (600 MHz, CDCl3) δ 7.80 (m, 2H), 7.60 (m, 4H), 7.49 (m, 2H), 7.41 (m, 1H); 13C NMR (150.8 MHz, CDCl3) δ 144.6, 142.4, 133.3, 132.1 (t, J = 22.6 Hz), 131.8, 131.7, 130.7, 129.9, 128.2 (m), 121.1, 120.2, 119.2, 118.5; 19F NMR (564 MHz, CDCl3) δ −81.6 (tt, J = 9.6, 2.8 Hz, 3F), −111.00 (t, J = 12.4 Hz, 2F), −122.7 (m, 2F), −125.6 (m, 2F); IR (neat) v 1241, 1134, 742 cm−1; MS (EI) m/z (%), 372 (M+), 353, 203 (100); HRMS calcd for C16H9F9 372.0561, found 372.0551. 2-(Perfluorobutyl)-1,1′-biphenyl (3cc). The product (24 mg, 32%) was purified by silica gel chromatography (petroleum ether (100%)) as a colorless oil: 1H NMR (600 MHz, CDCl3) δ 7.67 (d, J = 7.8 Hz, 1H), 7.57 (t, J = 7.2 Hz, 1H), 7.51 (t, J = 7.8 Hz, 1H), 7.37 (m, 3H), 7.30 (d, J = 7.8 Hz, 1H), 7.26 (m, 2H); 19F NMR (564 MHz, CDCl3) δ −81.1 (m, 3F), −103.1 (m, 2F), −120.7 (m, 2F), −125.9 (m, 2F). This compound is known.17 2-(Perfluorobutyl)naphthalene (3dc). The product (50 mg, 73% yield) was purified by silica gel chromatography (petroleum ether (100%)) as a pale yellow oil: 1H NMR (600 MHz, CDCl3) δ 8.15 (s, 1H), 7.96 (m, 2H), 7.92 (d, J = 7.8 Hz, 1H), 7.62 (m, 3H); 19F NMR (564 MHz, CDCl3) δ −81.0 (tt, J = 9.6 Hz, 2.8 Hz, 3F), −110.4 (t, J = 13.0 Hz, 2F), −122.5 (m, 2F), −125.6 (m, 2F). This compound is known.7q 9-(Perfluorobutyl)phenanthrene (3ec). The product (52 mg, 65% yield) was purified by silica gel chromatography (petroleum ether (100%)) as a white solid: mp 79.5−81 °C; 1H NMR (600 MHz, CDCl3) δ 8.77 (d, J = 8.4 Hz, 1H), 8.70 (d, J = 8.4 Hz, 1H), 8.31 (d, J = 8.4 Hz, 1H), 8.17 (s, 1H), 7.97 (d, J = 8.4 Hz, 1H), 7.80 (t, J = 7.8 Hz, 1H), 7.74−7.76 (m, 3H); 13C NMR (150.8 MHz, CDCl3) δ 134.6, 133.7, 133.3 (t, J = 10.4 Hz), 132.6, 132.1, 131.9, 130.6, 129.9, 129.8, 128.4, 125.9 (t, J = 21.4 Hz), 125.8, 125.3, 122.1, 121.2, 120.4, 119.3; 19 F NMR (564 MHz, CDCl3) δ −80.9 (m, 3F), −104.6 (t, J = 14.0 Hz, 2F), −120.7 (m, 2F), −125.6 (m, 2F); IR (neat) v 1244, 1129, 718 cm−1; MS (EI) m/z (%), 396 (M+), 372, 227 (100); HRMS calcd for C18H9F9 396.0561, found 396.0551. 4,4′-Bis(perfluorobutyl)-1,1′-biphenyl (3fc). The product (72 mg, 61% yield) was purified by silica gel chromatography (petroleum ether (100%)) as a white solid: 1H NMR (600 MHz, CDCl3) δ 7.74 (d, J = 8.4 Hz, 4H), 7.70 (d, J = 8.4 Hz, 4H); 19F NMR (564 MHz, CDCl3) δ −81.5 (m, 3F), −111.0 (t, J = 13.0 Hz, 2F), −122.7 (m, 2F), −125.6 (m, 2F). This compound is known.7q 1-Methoxy-4-(perfluorobutyl)benzene (3gc). The product (26 mg, 41% yield) was purified by silica gel chromatography (petroleum ether/ethyl ether = 20:1) as a colorless oil: 1H NMR (600 MHz, CDCl3) δ 7.38 (d, J = 9.0 Hz, 2H), 6.80 (d, J = 9.0 Hz, 2H), 3.78 (s, 3H); 19F NMR (564 MHz, CDCl3) δ −81.1 (m, 3F), −110.9 (t, J = 18.6 Hz, 2F), −122.8 (m, 2F), −125.6 (m, 2F). This compound is known.7p

Scheme 4. Radical Inhibition Experiment

Scheme 5. Proposed Reaction Mechanism

Preparation of Bis(pentafluoroethyl)zinc Reagent Zn(C2F5)2(DMPU)2. To an oven-dried 100 mL two-neck round-bottom flask equipped with a magnetic stir bar were added toluene (15 mL) and DMPU (2.4 mL, 20 mmol) under an argon atmosphere. Pentafluoroethyl iodide (3.0 mL, 25 mmol) was added to the solution. A diethyl zinc solution (1.0 M in hexanes, 10 mL, 10 mmol) was then added dropwise at −35 °C. After the reaction mixture was stirred at −5 °C for 24 h, the precipitate was obtained. After removing the solution, the precipitate obtained was washed with hexane (50 mL) three times and dried under a vacuum to give Zn(C2F5)2(DMPU)2 as a white powder (5.4 g, 95% yield). This compound is known.16 Preparation of Bis(heptafluoropropyl)zinc Reagent Zn(C3F7)2(DMPU)2. To an oven-dried 100 mL two-neck round-bottom flask equipped with a magnetic stir bar were added toluene (15 mL) and DMPU (2.4 mL, 20 mmol) under an argon atmosphere. Heptafluoropropyl iodide (3.6 mL, 25 mmol) was added to the solution. A diethyl zinc solution (1.0 M in hexanes, 10 mL, 10 mmol) was then added dropwise at −35 °C. After the reaction mixture was stirred at −5 °C for 24 h, the precipitate was obtained. After removing the solution, the precipitate obtained was washed with hexane (50 mL) three times and dried under a vacuum to give Zn(C3F7)2(DMPU)2 as a white powder (6.1 g, 93% yield). This compound is known.16 Preparation of Bis(perfluorobutyl)zinc Reagent Zn(C4F9)2(DMPU)2. To an oven-dried 100 mL two-neck round-bottom flask equipped with a magnetic stir bar were added toluene (15 mL) and DMPU (2.4 mL, 20 mmol) under an argon atmosphere. Perfluorobutyl iodide (4.3 mL, 25 mmol) was added to the solution. A diethyl zinc solution (1.0 M in hexanes, 10 mL, 10 mmol) was then added dropwise at −35 °C. After the reaction mixture was stirred at −5 °C for 24 h, the precipitate was obtained. After removing the solution, the precipitate obtained was washed with hexane (50 mL) three times and dried under a vacuum to give Zn(C4F9)2(DMPU)2 as a white powder (6.9 g, 89% yield). This compound is known.16 Preparation of Bis(tridecafluorohexyl)zinc Reagent Zn(C6F13)2(DMPU)2. To an oven-dried 100 mL two-neck round-bottom flask equipped with a magnetic stir bar were added toluene (15 mL) and DMPU (2.4 mL, 20 mmol) under an argon atmosphere. Tridecafluorohexyl iodide (5.4 mL, 25 mmol) was added to the solution. A diethyl zinc solution (1.0 M in hexanes, 10 mL, 10 mmol) was then added dropwise at −35 °C. After the reaction mixture was stirred at −5 °C for 24 h, the precipitate was obtained. After removing the solution, the precipitate obtained was washed with hexane (50 mL) 466

DOI: 10.1021/acs.joc.7b02557 J. Org. Chem. 2018, 83, 463−468

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The Journal of Organic Chemistry 1-Methoxy-3-(perfluorobutyl)benzene (3hc). The product (32 mg, 49% yield) was purified by silica gel chromatography (petroleum ether/ethyl ether = 20:1) as a yellow oil: 1H NMR (600 MHz, CDCl3) δ 7.36 (t, J = 8.4 Hz, 1H), 7.19 (dd, J = 8.4 Hz, 2.2 Hz, 1H), 7.13 (, 1H), 6.91 (dd, J = 8.4Hz, 2.2 Hz, 1H), 3.87 (s, 3H); 19F NMR (564 MHz, CDCl3) δ −81.0 (t, J = 9.6 Hz, 3F), −110.9 (t, J = 13.0 Hz, 2F), −122.8 (m, 2F), −125.7 (m, 2F). This compound is known.7p 1-(Perfluorobutyl)-4-phenoxybenzene (3ic). The product (49 mg, 63% yield) was purified by silica gel chromatography (petroleum ether (100%)) as a pale yellow oil: 1H NMR (600 MHz, CDCl3) δ 7.81 (d, J = 7.8 Hz, 2H), 7.61 (d, J = 7.2 Hz, 2H), 7.59 (m, 2H), 7.49 (t, J = 7.8 Hz, 2H), 7.42 (t, J = 7.2 Hz, 1H); 13C NMR (150.8 MHz, CDCl3) δ 144.6, 142.4, 133.3 (m), 132.2 (t, J = 24.3 Hz), 131.7, 131.6, 130.7, 129.9, 128.2 (m), 121.1, 120.2, 119.2, 118.7; 19F NMR (564 MHz, CDCl3) δ −81.0 (m, 3F), −110.0 (t, J = 13.0 Hz, 2F), −122.7 (m, 2F), −125.6 (m, 2F); IR (neat) v 1235, 1138, 718 cm−1; MS (EI) m/z (%) 353, 203 (100); HRMS calcd for C16H9F9O 388.0510, found 388.0502. Ethyl 4-(Perfluorobutyl)benzoate (3jc). The product (37 mg, 50% yield) was purified by silica gel chromatography (petroleum ether/ ethyl ether = 20:1) as a pale yellow oil: 1H NMR (600 MHz, CDCl3) δ 8.17 (d, J = 8.4 Hz, 2H), 7.66 (d, J = 8.4 Hz, 2H), 4.11 (q, J = 7.2 Hz, 2H), 4.22 (t, J = 7.2 Hz, 3H); 13C NMR (150.8 MHz, CDCl3) δ 167.9, 136.6, 135.4 (t, J = 24.3 Hz), 132.3, 129.5 (t, J = 6.0 Hz), 121.0, 119.8, 119.1, 118.1, 64.3, 16.7; 19F NMR (564 MHz, CDCl3) δ −81.0 (m, 3F), −111.5 (t, J = 13.0 Hz, 2F), −122.7 (m, 2F), −125.6 (m, 2F); IR (neat) v 1730, 1236, 715 cm−1; MS (EI) m/z (%) 368 (M+), 323 (100), 171; HRMS calcd for C13H9F9O2 368.0459, found 368.0461. Methyl 4-(Perfluorobutyl)benzoate (3kc). The product (35 mg, 50% yield) was purified by silica gel chromatography (petroleum ether/ethyl ether = 20:1) as a colorless oil: 1H NMR (600 MHz, CDCl3) δ 8.17 (d, J = 8.4 Hz, 2H), 7.68 (t, J = 7.8 Hz, 2H), 3.96 (s, 3H); 19F NMR (564 MHz, CDCl3) δ −81.0 (m, 3F), −111.5 (d, J = 14.7 Hz, 2F), −122.7 (d, J = 9.6 Hz, 2F), −125.6 (m, 2F). This compound is known.7p Ethyl 3-(Perfluorobutyl)benzoate (3lc). The product (23 mg, 31% yield) was purified by silica gel chromatography (petroleum ether/ ethyl ether = 20:1) as a pale yellow oil: 1H NMR (600 MHz, CDCl3) δ 8.24 (d, J = 9.0 Hz, 2H), 7.76 (d, J = 7.8 Hz, 1H), 7.59 (t, J = 7.8 Hz, 1H), 4.43 (q, J = 7.2 Hz, 2H), 1.41 (t, J = 7.2 Hz, 3H), 3.77 (s, 3H); 13 C NMR (150.8 MHz, CDCl3) δ 167.8, 135.6, 134.0, 133.5 (t, J = 6.0 Hz), 132.0 (t, J = 24 Hz), 131.5, 130.6 (t, J = 6.0 Hz), 121.2, 119.9, 118.1, 116.4, 64.2, 16.8; 19F NMR (564 MHz, CDCl3) δ −81.2 (t, J = 7.9 Hz, 3F), −111.2 (t, J = 13.0 Hz, 2F), −122.7 (m, 2F), −125.7 (t, J = 12.4 Hz, 2F); IR (neat) v 1728, 1241 cm−1; MS (EI) m/z (%) 368 (M+), 323 (100), 171; HRMS calcd for C13H9F9O2 368.0459, found 368.0454. 1-(3-(Perfluorobutyl)phenyl)ethan-1-one (3mc). The product (29 mg, 43% yield) was purified by silica gel chromatography (petroleum ether/ethyl ether = 20:1) as a colorless oil: 1H NMR (600 MHz, CDCl3) δ 8.16 (d, J = 6.6 Hz, 2H), 7.78 (d, J = 7.8 Hz, 1H), 7.63 (t, J = 8.4 Hz, 1H); 19F NMR (564 MHz, CDCl3) δ −81.1 (t, J = 9.6 Hz, 3F), −111.2 (t, J = 13.5 Hz, 2F), −122.7 (m, 2F), −125.6 (m, 2F). This compound is known.7q 1-(Methylsulfonyl)-4-(perfluoropentyl)benzene (3nc). The product (59 mg, 79% yield) was purified by silica gel chromatography (petroleum ether/ethyl ether = 3:1) as a white solid: mp 89.5−91 °C; 1 H NMR (600 MHz, CDCl3) δ 8.11 (d, J = 8.4 Hz, 2H), 7.82 (d, J = 8.4 Hz, 2H), 3.11 (s, 3H); 13C NMR (150.8 MHz, CDCl3) δ 146.9, 136.7 (t, J = 24.6 Hz), 130.8 (t, J = 6.5 Hz), 130.5, 122.8, 120.9, 119.0, 117.7, 46.9; 19F NMR (564 MHz, CDCl3) δ −81.0 (t, J = 9.6 Hz, 3F), −111.6 (t, J = 13.5 Hz, 2F), −122.6 (m, 2F), −125.6 (m, 2F); IR (neat) v 1129, 752 cm−1; MS (EI) m/z (%) 374 (M+), 205, 143 (100); HRMS calcd for C11H7F9O2S 374.0023, found 374.0026. 4-(Perfluoroethyl)-1,1′-biphenyl (3aa). The product (50 mg, 92%) was purified by silica gel chromatography (petroleum ether (100%)) as a white solid: 1H NMR (600 MHz, CDCl3) δ 7.72 (d, J = 7.2 Hz, 2H), 7.68 (d, J = 7.2 Hz, 2H), 7.62 (d, J = 6.6 Hz, 2H), 7.49 (d, J = 6.6 Hz, 2H), 7.43 (d, J = 6.6 Hz, 1H); 19F NMR (564 MHz, CDCl3) δ −84.7 (s, 3F), −114.8 (s, 2F). This compound is known.7q

4-(Perfluoropropyl)-1,1′-biphenyl (3ab). The product (42 mg, 65%) was purified by silica gel chromatography (petroleum ether (100%)) as a white solid: 1H NMR (600 MHz, CDCl3) δ 7.72 (d, J = 7.8 Hz, 2H), 7.66 (d, J = 8.4 Hz, 2H), 7.62 (d, J = 7.2 Hz, 2H), 7.49 (t, J = 7.8 Hz, 2H), 7.42 (m, 1H); 19F NMR (564 MHz, CDCl3) δ −80.0 (m, 3F), −111.6 (m, 2F), −126.4 (s, 2F). This compound is known.7q 4-(Perfluorohexyl)-1,1′-biphenyl (3ad). The product (53 mg, 56%) was purified by silica gel chromatography (petroleum ether (100%)) as a white solid: 1H NMR (600 MHz, CDCl3) δ 7.72 (d, J = 7.8 Hz, 2H), 7.67 (d, J = 7.8 Hz, 2H), 7.62 (d, J = 7.8 Hz, 2H), 7.49 (t, J = 7.2 Hz, 2H), 7.42 (t, J = 7.2 Hz, 1H); 19F NMR (564 MHz, CDCl3) δ −80.9 (t, J = 10.2 Hz, 3F), −110.7 (t, J = 14.7 Hz, 2F), −121.6 (s, 2F), −121.9 (s, 2F), −122.9 (m, 2F), −126.3 (m, 2F). This compound is known.18 1-Methoxy-3-(perfluoroethyl)benzene (3ha). The product (19 mg, 41% yield) was purified by silica gel chromatography (petroleum ether/ethyl ether = 20:1) as a colorless oil: 1H NMR (600 MHz, CDCl3) δ 7.36 (t, J = 7.8 Hz, 1H), 7.18 (d, J = 7.8 Hz, 1H), 7.12 (m, 1H), 6.91 (m, 1H), 3.84 (s, 3H); 19F NMR (564 MHz, CDCl3) δ −84.7 (s, 3F), −114.8 (s, 2F). This compound is known.7q Methyl 4-(Perfluorohexyl)benzoate (3hd). The product (31 mg, 36% yield) was purified by silica gel chromatography (petroleum ether/ethyl ether = 20:1) as a colorless oil: 1H NMR (600 MHz, CDCl3) δ 7.36 (t, J = 7.8 Hz, 1H), 7.18 (d, J = 7.8 Hz, 1H), 7.12 (m, H), 6.90 (m, 1H), 3.87 (s, 3H); 19F NMR (564 MHz, CDCl3) δ −81.0 (m, 3F), −111.3 (m, 2F), −121.5 (s, 2F), −121.9 (m, 2F), −122.9 (s, 2F), −126.3 (m, 2F). This compound is known.7q Methyl 4-(Perfluoroethyl)benzoate (3ka). The product (25 mg, 49% yield) was purified by silica gel chromatography (petroleum ether/ethyl ether = 20:1) as a colorless oil: 1H NMR (600 MHz, CDCl3) δ 8.16 (d, J = 8.4 Hz, 2H), 7.68 (d, J = 8.4 Hz, 2H), 3.96 (s, 3H); 19F NMR (564 MHz, CDCl3) δ −84.5 (s, 3F), −115.5 (t, 2F). This compound is known.7q Methyl 4-(Perfluorohexyl)benzoate (3kd). The product (39 mg, 43% yield) was purified by silica gel chromatography (petroleum ether/ethyl ether = 20:1) as a colorless oil: 1H NMR (600 MHz, CDCl3) δ 8.17 (d, J = 8.4 Hz, 2H), 7.68 (d, J = 8.4 Hz, 2H), 3.96 (s, 3H); 19F NMR (564 MHz, CDCl3) δ −80.9 (t, J = 9.56 Hz, 3F), −111.3 (t, J = 14.7 Hz, 2F), −121.5 (s, 2F), −121.9 (m, 2F), −122.9 (m, 2F), −126.2 (m, 2F). This compound is known.7q 1-(Methylsulfonyl)-4-(perfluoroethyl)benzene (3na). The product (45 mg, 82%) was purified by silica gel chromatography (petroleum ether/ethyl ether = 3:1) as a white solid: mp 85−87.5 °C; 1H NMR (600 MHz, CDCl3) δ 8.11 (d, J = 7.8 Hz, 2H), 7.83 (d, J = 7.8 Hz, 2H), 3.10 (s, 3H); 13C NMR (150.4 MHz, CDCl3) δ 146.8, 136.6 (t, J = 24.1 Hz), 130.6, 130.5 (t, J = 6.0 Hz), 122.3, 120.4, 46.9; 19F NMR (564 MHz, CDCl3) δ −89.3 (s, 3F), −120.2 (s, 2F); IR (neat) v 1212, 769 cm−1; MS (EI) m/z (%) 274 (M+), 195, 145 (100); HRMS calcd for C9H7F5O2S 274.0087, found 274.0081. 1-(Methylsulfonyl)-4-(perfluoropropyl)benzene (3nb). The product (47 mg, 73%) was purified by silica gel chromatography (petroleum ether/ethyl ether = 3:1) as a white solid: mp 92−93.5 °C; 1H NMR (600 MHz, CDCl3) δ 8.11 (d, J = 7.8 Hz, 2H), 7.82 (d, J = 8.4 Hz, 2H), 3.11 (s, 3H); 13C NMR (150.8 MHz, CDCl3) δ 146.9, 136.8 (t, J = 24.1 Hz), 130.8 (t, J = 6.0 Hz), 130.5, 120.7, 118.8, 117.8, 46.9; 19F NMR (564 MHz, CDCl3) δ −79.9 (t, J = 10.2 Hz, 3F), −122.5 (m, 2F), −126.2 (m, 2F); IR (neat) v 1156, 730 cm−1; MS (EI) m/z (%) 325 (M+ + H), 324 (M+), 143 (100); HRMS calcd for C10H7F7O2S 324.0055, found 324.0056. 1-(Methylsulfonyl)-4-(perfluorohexyl)benzene (3nd). The product (60 mg, 63%) was purified by silica gel chromatography (petroleum ether/ethyl ether = 3:1) as a white solid: mp 92.5−94 °C; 1H NMR (600 MHz, CDCl3) δ 8.12 (d, J = 7.8 Hz, 2H), 7.83 (d, J = 7.8 Hz, 2H), 8.11 (s, 3H); 13C NMR (150.8 MHz, CDCl3) δ 146.9, 136.6 (t, J = 24.1 Hz), 130.7 (t, J = 6.3 Hz), 130.5, 121.4, 119.5, 117.2, 115.5, 111.3, 111.0, 46.9; 19F NMR (564 MHz, CDCl3) δ −80.80 (m, 3F), −111.4 (t, J = 13.5 Hz, 2F), −121.5 (s, 2F), −121.7 (s, 2F), −122.9 (s, 2F), −126.2 (s, 2F); IR (neat) v 1117, 789 cm−1; MS (EI) m/z (%) 475 (M+ + H), 474 (M+), 205 (100); HRMS calcd for C13H7F13O2S 473.9959, found 473.9950. 467

DOI: 10.1021/acs.joc.7b02557 J. Org. Chem. 2018, 83, 463−468

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The Journal of Organic Chemistry

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3933−3938. (e) Dubinina, G. G.; Ogikubo, J.; Vicic, D. A. Organometallics 2008, 27, 6233−6235. (f) Ye, Y.; Ball, N. D.; Kampf, J. W.; Sanford, M. S. J. Am. Chem. Soc. 2010, 132, 14682− 14687. (g) Ball, N. D.; Kampf, J. W.; Sanford, M. S. J. Am. Chem. Soc. 2010, 132, 2878−2879. (h) Chu, L.; Qing, F. L. Org. Lett. 2010, 12, 5060−5063. (i) Morimoto, H.; Tsubogo, T.; Litvinas, N. D.; Hartwig, J. F. Angew. Chem., Int. Ed. 2011, 50, 3793−3798. (j) Zanardi, A.; Novikov, M. A.; Martin, E.; Benet-Buchholz, J.; Grushin, V. V. J. Am. Chem. Soc. 2011, 133, 20901−20913. (k) Tomashenko, O. A.; Escudero-Adan, E. C.; Belmonte, M. M.; Grushin, V. V. Angew. Chem., Int. Ed. 2011, 50, 7655−7659. (l) Litvinas, N. D.; Fier, P. S.; Hartwig, J. F. Angew. Chem., Int. Ed. 2012, 51, 536−539. (m) Novák, P.; Lishchynskyi, A.; Grushin, V. V. Angew. Chem., Int. Ed. 2012, 51, 7767−7770. (n) Lishchynskyi, A.; Grushin, V. V. J. Am. Chem. Soc. 2013, 135, 12584−12587. (o) Mormino, M. G.; Fier, P. S.; Hartwig, J. F. Org. Lett. 2014, 16, 1744−1747. (p) Jiang, D.-F.; Liu, C.; Guo, Y.; Xiao, J.-C.; Chen, Q.-Y. Eur. J. Org. Chem. 2014, 2014, 6303−6309. (q) Huang, Y.; Ajitha, M. J.; Huang, K. W.; Zhang, Z.; Weng, Z. Dalton transactions 2016, 45, 8468−8474. (8) (a) Barata-Vallejo, S.; Flesia, M. M.; Lantaño, B.; Argüello, J. E.; Peñeń ̃ory, A. B.; Postigo, A. Eur. J. Org. Chem. 2013, 2013, 998−1008. (b) Yerien, D. E.; Conde, R.; Barata-Vallejo, S.; Camps, B.; Lantaño, B.; Postigo, A. RSC Adv. 2017, 7, 266−274. (c) Wang, Y.; Wang, J.; Li, G. X.; He, G.; Chen, G. Org. Lett. 2017, 19, 1442−1445. (d) Hossain, M. J.; Ono, T.; Wakiya, K.; Hisaeda, Y. Chem. Commun. 2017, 53, 10878−10881. (9) Barata-Vallejo, S.; Bonesi, S. M.; Postigo, A. RSC Adv. 2015, 5, 62498−62518. (10) Chu, L.; Qing, F. L. J. Am. Chem. Soc. 2010, 132, 7262−7263. (11) (a) Jiang, X.; Chu, L.; Qing, F. L. J. Org. Chem. 2012, 77, 1251− 1257. (b) Chu, L.; Qing, F. L. J. Am. Chem. Soc. 2012, 134, 1298− 1304. (12) Senecal, T. D.; Parsons, A. T.; Buchwald, S. L. J. Org. Chem. 2011, 76, 1174−1176. (13) Khan, B. A.; Buba, A. E.; Goossen, L. J. Chem. - Eur. J. 2012, 18, 1577−1581. (14) Nebra, N.; Grushin, V. V. J. Am. Chem. Soc. 2014, 136, 16998− 17001. (15) Popov, I.; Lindeman, S.; Daugulis, O. J. Am. Chem. Soc. 2011, 133, 9286−9289. (16) Aikawa, K.; Nakamura, Y.; Yokota, Y.; Toya, W.; Mikami, K. Chem. - Eur. J. 2015, 21, 96−100. (17) Kato, H.; Hirano, K.; Kurauchi, D.; Toriumi, N.; Uchiyama, M. Chem. - Eur. J. 2015, 21, 3895−3900. (18) Fialkov, Y. A.; Shelyazhenko, S. V.; Yagupol’Skii, L. M. Chem. Inform. 1983, 14, 1048−1053.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b02557. 1 H NMR, 19F NMR, and 13C NMR spectra for compounds (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Shilu Fan: 0000-0003-0315-7874 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (grant no. 21602041), the Natural Science Foundation of Anhui Province (grant no. 1708085QB38), and the Start-up Foundation of Hefei University of Technology. We thank Prof. Chun-Yang He and Prof. Hua Xiao for helpful discussions.

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REFERENCES

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DOI: 10.1021/acs.joc.7b02557 J. Org. Chem. 2018, 83, 463−468