Synthesis of Diaryl Ketones through Oxidative Cleavage of C‒C

Apr 30, 1986 - 7.65 (dd, J = 3.6 Hz, J = 0.9 Hz, 1H), 7.61 (dd, J = 4.9 Hz, J = 0.8 Hz, 1H), 7.14-7.12 (m, 1H), 6.67 ...... Yadagiri, D.; Anbarasan, D...
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Cite This: J. Org. Chem. 2018, 83, 3486−3496

Synthesis of Diaryl Ketones through Oxidative Cleavage of the C−C Double Bonds in N‑Sulfonyl Enamides Hyunseok Kim,† Sangjune Park,† Yonghyeon Baek, Kyusik Um, Gi Uk Han, Da-Hye Jeon, Sang Hoon Han, and Phil Ho Lee* Department of Chemistry, Kangwon National University, Chuncheon 24341, Republic of Korea S Supporting Information *

ABSTRACT: An oxidative cleavage of a C−C double bond is developed from the photochemical [2+2]-cycloaddition of diaryl N-tosyl enamides, aryl heteroaryl N-tosyl enamides, and N-tosyl cyclic enamides with singlet molecular oxygen, followed by a ring-opening reaction mediated by Cs2CO3 under air and sunlight without the use of photosesitizer, producing symmetrical and unsymmetrical diaryl, heterodiaryl, and cyclic ketones in good to excellent yields. Moreover, the oxidative cleavage of C−C triple bonds from 1-alkynes is demonstrated for the synthesis of symmetrical and unsymmetrical ketones from the Cu-catalyzed [3+2]-cycloaddition, Rhcatalyzed alkoxyarylation, photooxygenation, and ring-opening reaction in one-pot. Because the synthesis of the symmetrical and unsymmetrical diaryl and/or heterodiaryl ketones bearing an electron-donating group is not easy, the present method is notable.

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acid derivatives (eq 1),3 transition metal-catalyzed crosscoupling of organometallic species with carboxylic acid derivatives (eq 2),4 carbonylative cross-coupling of organometallic species with aryl halides (eq 3),5 cross-coupling of acyl anion equivalents with electrophiles (eq 4),6 oxidative cleavage of the C−C double bond using oxidants7 and photooxygenation using singlet molecular oxygen (1O2) in the presence of photosensitizer (eq 5),8 oxidative C−C bond cleavage of aldehydes through visible light photoredox catalysis (eq 6),9 and metal-free oxidative C−C bond cleavage of aldehydes by O2 (10 atm) (eq 7).10 Recently, we reported a synthetic method for aryl azulenyl ketones through oxidative cleavage of the C−C double bond by the reaction of N-sulfonyl enamides having azulene moiety, which is a non-benzenoid aromatic compound, with cesium carbonate (Cs2CO3) without use of a photosensitizer under air and natural sunlight (eq 8).11

INTRODUCTION Ketones have been recognized as one of the most significant and convertible functional groups in organic chemistry.1 Moreover, diaryl ketones are an element of an ordinary structural motif that is not only found in many natural products and biologically active compounds but also in valuable building blocks and intermediates (Scheme 1).2 Accordingly, the development of various synthetic approaches to prepare diaryl ketones has been the important theme, which has been investigated by many groups. To date, a number of synthetic methods for diaryl ketones have been reported, and these methods can be generally divided into some categories (Scheme 2): Friedel−Crafts acylation of arenes with Scheme 1. Important Compounds Containing Diaryl Ketone Moiety

In this regard, the expansion of the limited scope of substrates bearing the azulene motif is highly required. In our continuing efforts to develop the oxidative cleavage of C−C multiple bonds, we envisioned that if a wide range of aromatic, heteroaromatic, and cyclic N-sulfonyl enamides were treated with base, the oxidative cleavage of the C−C double bond would take place to afford the valuable diaryl, aryl heteroaryl, and cyclic ketones. In addition, because synthesis of the Received: December 5, 2017 Published: March 22, 2018 © 2018 American Chemical Society

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DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

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The Journal of Organic Chemistry Scheme 2. Previously Reported Synthetic Methods for Diaryl Ketone

Scheme 3. Synthesis of Diaryl Ketones via Oxidative Cleavage of the C−C Double and Triple Bonds

Table 1. Reaction Optimizationa

symmetrical and unsymmetrical diaryl and/or heterodiaryl ketones bearing an electron-donating group is not easy, the development of efficient method is still very attractive and a significant challenge. Herein, we report an oxidative cleavage of the C−C double bond through photochemical [2+2]-cycloaddition of diaryl N-tosyl enamides, aryl heteroaryl N-tosyl enamides, and N-tosyl cyclic enamides with singlet molecular oxygen (1O2), followed by a ring-opening reaction under air and sunlight without the use of a photosesitizer, producing symmetrical and unsymmetrical diaryl and/or heterodiaryl ketones. Moreover, the oxidative cleavage of the C−C triple bonds from 1-alkynes and N-tosyl azide is described for the synthesis of diaryl ketones from Cu-catalyzed [3+2]-cycloaddition, Rh-catalyzed alkoxyarylation, photooxygenation, and ring-opening reaction in one-pot (Scheme 3).

entry

base

solvent

temp (°C)

yield (%)b

1 2 3 4 5 6 7 8 9 10e 11f 12

Li2CO3 K2CO3 Na2CO3 K2PO4 Cs2CO3 Cs2CO3 Cs2CO3 Cs2CO3 Cs2CO3 Cs2CO3 Cs2CO3

toluene toluene toluene toluene toluene THF dioxane DMF toluene toluene toluene toluene

80 80 80 80 80 80 80 80 25 80 80 80

78 85 10 15 99 (97)c (35)d 5 40 45 0 32 74 0

a Reactions were carried out with N-tosyl enamide 1a (0.2 mmol) in solvent (1.0 mL) at 80 °C for 2 h under an air atmosphere and sunlight. bNMR yield using dibromomethane as an internal standard. c Isolated yield. dIsolated yield of 3. eCs2CO3 (1.0 equiv) was used. f Cs2CO3 (2.0 equiv) was used.

diethylaminophenyl phenyl ketone (2a), in 78 and 85% yields, respectively (entries 1 and 2). Then, 2-(4-(diethylamino)phenyl)-2-phenylacetaldehyde (A) from hydrolysis of enamide was not observed. However, Na2CO3 and K2PO4 were ineffective (entries 3 and 4). Next, we applied the optimum reaction conditions [Cs2CO3 (3.0 equiv), toluene, 80 °C, 2 h] obtained from the N-sulfonylaminoalkenylation of azulenes to the oxidative cleavage of the C−C double bond in 1a, resulting in the formation of 2a in a quantitative yield (97% isolated yield) together with 4-methylbenzenesulfonylformamide (3) in 35% yield (entry 5). However, this reaction did not proceed at 25 °C (entry 9). These results indicate that the oxidative cleavage of the C−C double bonds in the N-sulfonyl enamide 1a smoothly took place at 80 °C, and the substrate scope of the present oxidative cleavage reaction was not restricted to Nsulfonylaminoalkenyl azulenes.11,13 Screening of solvents revealed that toluene was an optimum solvent, but other solvents, such as THF, dioxane, and DMF, gave inferior results

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RESULTS AND DISCUSSION To validate the strategy through the conversion of N-sulfonyl enamides to unsymmetrical diaryl ketones, the oxidative cleavage of the C−C double bonds of N-(2-(4-(diethylamino)phenyl)-2-phenyl-vinyl)-4-methylbenzenesulfonamide (1a) using a base was examined as a model reaction under various conditions (Table 1). N-Tosyl enamide 1a was easily prepared from Rh-catalyzed direct arylation of 4-phenyl-N-sulfonyl-1,2,3triazole with N,N-diethylaniline.12 Treatment of 1a with Li2CO3 and K2CO3 in toluene (80 °C, 2 h) gratifyingly provided the desired oxidatively cleaved compound, 43487

DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

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The Journal of Organic Chemistry (entries 6, 7, and 8). Use of Cs2CO3 (1.0 and 2.0 equiv) provided 2a in 32 and 74% yields, respectively (entries 10 and 11). The present reaction did not proceed without Cs2CO3, indicating that the base was essential for successful oxidative cleavage of the C−C double bond of the N-sulfonyl enamide (entry 12).

Scheme 4. Synthesis of Aryl 4-Diethylaminophenyl Ketones via Oxidative Cleavage of the C−C Double Bond in N-Tosyl Enamidesa

To demonstrate the synthetic utility of the present oxidative cleavage protocol, a reaction of diaryl N-tosyl enamide (1a) with Cs2CO3 was performed on a 5 mmol scale of diaryl Ntosyl enamide (eq 9). Gratifyingly, the efficiency of the

oxidative cleavage was found to be maintained at a high level in this large scale to provide the desired ketone product 2a in 90% (1.1 g) yield. To establish the scope and efficiency of the present method, we applied the oxidative cleavage of the C−C double bond to a wide range of unsymmetrical diaryl N-tosyl enamides (Scheme 4). Electronic modification of substituents on the aryl group of N-2-aryl-2-(4-diethylaminophenyl)vinyl-4-methylbenzenesulfonamides 1 slightly effected the reaction efficiency. For example, substrates bearing electron-donating groups, such as 2-methyl, 4-methyl, 4-tert-butyl, and 4-methoxy, were smoothly converted to the corresponding diaryl ketones (2b−2e) in good to excellent yields varying from 71 to 92%. Likewise, N-tosyl enamides bearing electron-withdrawing groups, such as 4fluoro, 4-chloro, 4-bromo, 4-trifluoromethyl, and 4-methoxycarbonyl, afforded the desired aryl 4-diethylaminophenyl ketones (2f, 2g, and 2i−2k) in high yields. However, an oxidative cleavage of the C−C double bond of the N-tosyl enamide having a 2-bromo group proceeded to afford 2h in 62% yield, as a result of steric effects. Treatment of the 2naphthyl-substituted N-tosyl enamide with Cs2CO3 produced the cleaved product, 4-diethylaminophenyl 2-naphthyl ketone (2l), in a quantitative yield. N-Tosyl enamide with a 2-thienyl group was also cleaved to give the desired ketone (2m) in 80% yield. Next, the scope of the substituents on the aryl group of N-(2(4-aminoaryl)-2-phenyl)-vinyl-4-methylbenzenesulfonamides 1 was examined (Scheme 5). N-Sulfonyl enamides bearing symmetrically N,N-disubstituted aniline derivatives afforded the corresponding aryl ketones 4a, 4b, and 4c in 90, 91, and 98% yield, respectively. Also, N-sulfonyl enamides possessing unsymmetrically N,N-disubstituted nitrogen in aniline gave the ketones 4d and 4e in excellent yield. In addition, meta-methyl substituted N,N-diethylaniline provided the corresponding ketone 4f in 87% yield. However, meta-bromo-substituted N,N-diethylaniline was less reactive and provided the desired ketone 4g in 50% yield. Gratifyingly, the oxidative cleavage reaction of N-sulfonyl enamides bearing N-based heterocyclic

a Reaction conditions: 1 (0.2 mmol) and Cs2CO3 (3.0 equiv) were heated in toluene (1.0 mL) at 80 °C under an air atmosphere and sunlight.

arenes, such as indoline, tetrahydroquinoline, and dibenzoazepine, smoothly took place, producing the corresponding ketones (4h, 4i, and 4j) in good yields varying from 50 to 76%. On the basis of these results, the oxidative cleavage of a wide range of N-tosyl enamides having an aryl and 4-methoxyphenyl group was examined (Scheme 6). For instance, N-tosyl enamide14 having phenyl and 4-methoxyphenyl was quantitatively converted to 4-methoxyphenyl phenyl ketone 5a. Electronic variation of the substituents on the aryl group of N-tosyl enamides 5b−5f effected the reaction efficiency. Although 3-methylphenyl-substituted enamide gave the corresponding ketone 5b in 67% yield, 4-methoxy-, 3-chloro-, and 4trifluoromethylphenyl-substituted enamides were transformed to the corresponding ketones (5c−5e) in quantitative yields. However, 4-nitrophenyl-substituted enamide was less reactive, and the 4-methoxyphenyl 4-nitrophenyl ketone 5f was obtained in 43% yield. Thiophen-3-yl-substituted enamide was applied to the present method, providing 5g in 72% yield. The oxidative cleavage reaction was amenable with respect to 4-methoxynaphthalen-1-yl and 2,4-dimethoxyphen-1-yl-substituted enamides to provide the corresponding ketones (5h and 5i) in good yields. When N-tosyl enamides bearing 4-ethoxy and 4phenoxy groups were employed, the desired ketones, 5j and 5k, were obtained in excellent yields. In the case of the substrate having a triple bond, the C−C double bond was selectively cleavaged, and the desired ketone 5l was obtained in 63% yield. N-Tosyl enamide having a hydrobenzofuranyl and phenyl group took part in the oxidative cleavage reaction to deliver 5m 3488

DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

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The Journal of Organic Chemistry Scheme 5. Synthesis of Phenyl 4-Disubstituted Aminoaryl Ketones via Oxidative Cleavage of the C−C Double Bond in N-Tosyl Enamidesa

Scheme 6. Synthesis of Alkoxyaryl Aryl Ketones via Oxidative Cleavage of the C−C Double Bond in N-Tosyl Enamidesa

a

Reaction conditions: 1 (0.2 mmol) and Cs2CO3 (3.0 equiv) were heated in toluene (1.0 mL) at 80 °C under an air atmosphere and sunlight. a

in 99% yield. Because the N-tosyl enamides used in the present method were prepared from the Rh-catalyzed denitrogenative arylation reaction of triazoles with aniline or anisole derivatives, the scope of substrates is limited to diaryl N-tosyl enamides bearing an electron-donating group on the aryl group. However, because the synthesis of the symmetrical and unsymmetrical diaryl and/or heterodiaryl ketones bearing an electron-donating group is difficult, it is noteworthy. We next investigated the synthesis of bi- and tricyclic ketones through the oxidative cleavage of the C−C double bond in Ntosyl cyclic enamides (Table 2). N-Tosyl enamide 6a having a dihydroindenyl moiety underwent the oxidative cleavage with Cs2CO3 to give 2,3-dihydro-1H-inden-1-one 7a in 92% yield (entry 1). 9H-Fluorenyl-substituted N-tosyl enamide 6b was compatible with the reaction conditions, leading to the formation of 3-methoxy-9H-fluoren-9-one 7b in 95% yield (entry 2). When 4H-indeno[1,2-b]furanyl and 4H-indeno[1,2b]thiophenyl-substituted enamides 6c and 6d were employed, the desired ketones 7c and 7d were obtained in 66 and 88% yields (enties 3 and 4). It was noted that N-tosyl cyclic enamide 6e was applied to the present method, providing a unique heterocycle 7e in 56% yield through the oxidative cleavage reaction, followed by the intramolecular addition and elimination of 4-methylbenzenesulfonic acid (eq 10). Under the optimimum reaction conditions, the generality of the present method was examined with various aryl indol-3-yl enamides (Table 3). N-Tosyl enamide15 having a phenyl and N-methylindol-3-yl group was smoothly cleaved to produce indol-3-yl phenyl ketone (9a) in 98% yield (entry 1).

Reaction conditions: 1 (0.2 mmol) and Cs2CO3 (3.0 equiv) were heated in toluene (1.0 mL) at 70 °C under an air atmosphere and sunlight.

Futhermore, when N-tosyl enamides bearing 4-methyl or 4methoxyphenyl and N-methyl-2-methylindol-3yl were treated with Cs2CO3, the corresponding indol-3-yl 4-phenyl or 4methoxyphenyl ketones (9b and 9c) were obtained in 85 and 90% yields, respectively. The substrate having 4-trifluoromethylphenyl and N-methyl-2-methylindol-3yl was less reactive and gave the desired ketone 9d in 68% yield. In general, a wide range of N-tosyl enamides were prepared from the reaction of the electron-rich anisole with triazoles obtained from Cu-catalyzed [3+2]-cycloaddition of terminal alkyne with N-tosyl azide in the presence of CuTC [copper(I)thiophene-2-carboxylate].16 In this regard, we envisioned that oxidative cleavage of the C−C triple bonds from 1-alkynes might occur in one-pot through tandem Cu-catalyzed [3+2]cycloaddition, Rh-catalyzed alkoxyarylation, photooxygenation, and ring-opening reaction, producing the corresponding ketone compounds (Scheme 7). Thus, we attempted four-step transformations in one-pot. After 4-methoxy-phenylacetylene (10) was reacted with N-tosyl azide in the presence of CuTC 3489

DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

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The Journal of Organic Chemistry Table 2. Synthesis of Cyclic Ketones via Oxidative Cleavage of the C−C Double Bond in N-Tosyl Enamidesa

Table 3. Synthesis of Aryl Indol-3-yl Ketones via Oxidative Cleavage of the C−C Double Bond in N-Tosyl Enamidesa

a Reaction conditions: 6 (0.2 mmol) and Cs2CO3 (3.0 equiv) were heated in toluene (1.0 mL) at 80 °C under air and sunlight.

(10.0 mol %) in toluene at 25 °C for 3 h, Rh2(esp)2 (1.0 mol %) and anisole were added to the reaction mixture. After 1 h at 100 °C, Cs2CO3 was added, and the reaction mixture was stirred at 100 °C for 0.5 h, resulting in the formation of di(4methoxyphenyl)ketone 5c in 55% yield (eq 11). Moreover, the present oxidative cleavage of the C−C triple bond works equally well through intramolecular reaction. For example, 2ethynyl-4′-methoxybiphenyl (12) was smoothly transformed to 3-methoxy-9H-fluoren-9-one 7b in 58% yield (eq 12). To shed light on the details of the reaction pathway, a series of mechanistic studies were designed (Scheme 8). First, two isotopic labeling experiments were conducted to investigate the origin of oxygen in the oxidative cleavage protocol. Although diaryl N-sulfonyl enamide 1a was reacted with Cs2CO3 in toluene and H218O under air and natural sunlight, the corresponding 18O-inserted-ketone 2a was not detected (eq 13). But, when the same reaction was conducted under an 18O2 atmosphere, the corresponding 18O-inserted-ketone 2a-[18O] was obtained in 85% yield (eq 14). These results suggest that oxygen in the oxidative cleavage protocol was originated from molecular oxygen, and that the dioxetane intermediate was involved in the reaction. However, this intermidiate was not observed. When TEMPO (1.0 equiv) was used in the current reaction under air, diaryl ketone 2a was only produced in 5% yield. This result demonstrates that radical species were involved in the oxidative cleavage reaction (eq 15). When the oxidative cleavage reaction was performed in dark conditions under air, no diaryl ketone 2a was observed to imply that

a

Reaction conditions: 8 (0.2 mmol) and Cs2CO3 (3.0 equiv) were heated in toluene (1.0 mL) at 80 °C under air and sunlight.

natural sunlight is essential for the oxidative cleavage reaction (eq 16). A plausible mechanism is described in Scheme 9. First, photo-oxidation of N-sulfonyl enamides (1) with singlet oxygen affords the dioxetane intermediate I.17 The oxidative cleavage reaction is initiated by the deprotonation of dioxetane I having a 2°-amine moiety by Cs2CO3, resulting in the production of N-sulfonyl amide anion II. However, the reaction did not proceed in the case of the 3°-amine, indicating that the initiation step of the reaction is the deprotonation of the amine.11 Then, the anion dioxetane intermediate II is converted to the biradical anion III through an intramolecular electron transfer (ETintra). This biradical anion III provides either a radical pair (path A) or another biradical anion (path B) through C−C bond cleavage.18 In the case of path A, the intermediate III is decomposed to form IV and V. After the radical pair is generated, an intermolecular back electron transfer (BETinter) occurs to afford the diaryl ketone 2 and Nsulfonyl formamide 3, which is isolated. Next, path B provides the desired ketone compound 2 and another biradical anion VI. Then, the biradical anion VI provides N-sulfonyl formamide through intramolecular BETintra. 3490

DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

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The Journal of Organic Chemistry Scheme 7. Oxidative Cleavage of the C−C Triple Bonds from 1-Alkynes in One-Pot

Scheme 8. Isotopic Labeling Experiments

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CONCLUSIONS

ketones bearing an electron-donating group is not easy, the present method is notable.

In conclusion, we have developed an oxidative cleavage of the C−C double bond from the photochemical [2+2]-cycloaddition of diaryl N-tosyl enamides, aryl heteroaryl N-tosyl enamides, and N-tosyl cyclic enamides with singlet molecular oxygen (1O2), followed by a ring-opening reaction mediated by Cs2CO3 under air and sunlight without the use of a photosesitizer, producing symmetrical and unsymmetrical diaryl, heterodiaryl, and cyclic ketones in good to excellent yields. The oxidative cleavage of the C−C triple bonds from 1alkynes is also demonstrated for the synthesis of symmetrical and unsymmetrical ketones from Cu-catalyzed [3+2]-cycloaddition, Rh-catalyzed alkoxyarylation, photooxygenation, and ring-opening reaction in one-pot. Because synthesis of the symmetrical and unsymmetrical diaryl and/or heterodiaryl

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EXPERIMENTAL SECTION

General. Reactions were carried out in oven-dried glassware under nitrogen atmosphere. Cs2CO3 was purchased and was used as received. Commercial available reagents were used without purification. Toluene and anisole were dried with CaH2. All reaction mixtures were stirred magnetically and were monitored by thin-layer chromatography using silica gel precoated glass plates, which were visualized with UV light and then developed using either iodine or a solution of anisaldehyde. Flash column chromatography was carried out using silica gel (230−400 mesh). 1H NMR (400 MHz), 13C{1H} NMR (100 MHz), and 19F NMR (377 MHz) spectra were recorded on a NMR spectrometer. Deuterated chloroform and benzene were used as the solvents, and chemical shift values (δ) are reported in parts per million relative to the residual signals of solvent [δ 7.26 for 1H 3491

DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

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The Journal of Organic Chemistry Scheme 9. Plausible Mechanism

1144, 952, 709 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C18H21NO, 267.1623; found, 267.1625. (4-(tert-Butyl)phenyl)(4-(diethylamino)phenyl)methanone (2d).22 Green oil (57.0 mg, 92%). Rf = 0.4 (acetone:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.80 (d, J = 9.0 Hz, 2H), 7.68 (t, J = 8.2 Hz, 2H), 7.46 (d, J = 8.4 Hz, 2H), 6.64 (d, J = 9.0 Hz, 2H), 3.42 (q, J = 7.1 Hz, 4H), 1.36 (s, 9H), 1.20 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 194.7, 154.6, 151.0, 136.7, 133.1, 129.5, 125.0, 124.4, 110.1, 44.6, 35.0, 31.3, 12.6. IR (film): 2965, 1731, 1639, 1591, 1269, 1147, 771 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C21H27NO, 309.2093; found, 309.2089. (4-(Diethylamino)phenyl)(4-methoxyphenyl)methanone (2e).23 Green oil (44.8 mg, 79%). Rf = 0.4 (acetone:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.76 (d, J = 7.8 Hz, 4H), 6.95 (d, J = 8.8 Hz, 2H), 6.65 (d, J = 9.0 Hz, 2H), 3.88 (s, 3H), 3.44 (q, J = 7.1 Hz, 4H), 1.22 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 193.9, 162.1, 150.8, 132.8, 131.9, 131.8, 124.5, 113.2, 110.0, 55.4, 44.5, 12.6. IR (film): 2970, 2359, 1730, 1592, 1253, 1170, 768 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C18H21NO2, 283.1572; found, 283.1570. (4-(Diethylamino)phenyl)(4-fluorophenyl)methanone (2f). Brown oil (45.0 mg, 83%). Rf = 0.4 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.77.74 (m, 4H), 7.12 (t, J = 8.7 Hz, 2H), 6.64 (d, J = 9.1 Hz, 2H), 3.43 (q, J = 7.1 Hz, 4H), 1.21 (t, J = 7.1 Hz, 6H). 13 C{1H} NMR (100 MHz, CDCl3, δ): 193.5, 164.6 (d, JCF = 251.4 Hz), 151.2, 135.7 (d, JCF = 3.1 Hz), 133.1, 131.9 (d, JCF = 8.8 Hz), 123.9, 115.2 (d, JCF = 21.7 Hz), 110.2, 44.7, 12.6; 19F NMR (376 MHz, CDCl3, δ): −108.7. IR (film): 2972, 2360, 1770, 1638, 1598, 1269, 1143, 765 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C17H18FNO, 271.1372; found, 271.1373. (4-Chlorophenyl)(4-(diethylamino)phenyl)methanone (2g).24 Brown oil (46.5 mg, 81%). Rf = 0.4 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.74 (d, J = 9.1 Hz, 2H), 7.67 (d, J = 8.5 Hz, 2H), 7.42 (d, J = 8.5 Hz, 2H), 6.64 (d, J = 9.1 Hz, 2H), 3.44 (q, J = 7.1 Hz, 4H), 1.22 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 193.6, 151.4, 137.9, 137.3, 133.1, 131.9, 128.4, 123.8, 110.3, 44.7, 12.7. IR (film): 2971, 2359, 1788, 1588, 1270, 1146, 755, 593 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C17H18ClNO, 287.1077; found, 287.1077. (2-Bromophenyl)(4-(diethylamino)phenyl)methanone (2h). Brown oil (41.4 mg, 62%). Rf = 0.4 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.68 (d, J = 9.0 Hz, 2H), 7.61 (d, J = 8.2 Hz, 1H), 7.39−7.35 (m, 1H), 7.31−7.28 (m, 2H), 6.61 (d, J = 9.2 Hz, 2H), 3.42 (q, J = 7.1 Hz, 4H), 1.21 (t, J = 7.1 Hz, 6H). 13C{ 1H} NMR (100 MHz, CDCl3, δ): 193.6, 151.9, 142.2, 133.1, 133.0, 130.3, 128.8, 127.1, 123.3, 119.7, 110.4, 44.6, 12.6. IR (film): 2971, 2341, 1638, 1591, 1319, 1269, 1197, 557 cm−1. HRMS (EI) (m/z): [M]+ Calcd for

(chloroform-d3) and δ 77.2 for 13C{1H} (chloroform-d3)]. Infrared spectra were recorded on a FT-IR spectrometer as either a thin neat pressed between two sodium chloride plates or as a solid suspended in a potassium bromide disk. High-resolution mass spectra (HRMS) were obtained by fast atom bombardment (FAB) using a double focusing magnetic sector mass spectrometer and electron impact (EI) ionization technique (magnetic sector-electric sector double focusing mass analyzer) from the KBSI (Korea Basic Science Institute, Daegu Center). Melting points were determined in an open capillary tube. General Procedure for the Oxidative Cleavage of the C−C Double Bond. Oxidative Cleavage of the C−C Double Bond in Diaryl N-Tosyl Enamides.12,14b N-(2-(4-(Diethylamino)phenyl)-2phenylvinyl)-4-methylbenzenesulfonamide (0.2 mmol), Cs2CO3 (0.6 mmol), and toluene (1.0 mL) were added to an oven-dried test tube equipped with a stirring bar under air. The mixture was stirred at 80 °C for 2 h under air. To remove Cs2CO3, the residue was passed through a pad of Celite and eluted with CH2Cl2. The filtrate was concentrated under reduced pressure, and the residue was purified by silica gel flash column chromatography (EtOAc:hexane). The crude residue was purified by silica gel column chromatography (EtOAc:hexane) to give compound 2. (4-(Diethylamino)phenyl)(phenyl)methanone (2a).19 Bright yellow oil (49.0 mg, 97%). Rf = 0.5 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.78 (d, J = 9.1 Hz, 2H), 7.73−7.71 (m, 2H), 7.53− 7.49 (m, 1H), 7.46−7.42 (m, 2H), 6.64 (d, J = 9.1 Hz, 2H), 3.42 (q, J = 7.1 Hz, 4H), 1.21 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 194.9, 151.1, 139.5, 133.1, 131.0, 129.4, 128.0, 124.0, 110.1, 44.6, 12.5. IR (film): 3056, 2973, 2930, 2900, 2871, 1643, 1589, 1523, 1408, 1271, 1199, 1144 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C17H19NO, 253.1467; found, 253.1465. (4-(Diethylamino)phenyl)(m-tolyl)methanone (2b).20 Yellow oil (44.6 mg, 75%). Rf = 0.5 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.78 (d, J = 9.1 Hz, 2H), 7.54 (s, 1H), 7.50−7.49 (m, 1H), 7.32−7.31 (m, 2H), 6.64 (d, J = 9.1 Hz, 2H), 3.42 (q, J = 7.1 Hz, 4H), 2.40 (s, 3H), 1.21 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.1, 151.2, 139.6, 137.9, 133.2, 131.8, 130.0, 127.9, 126.7, 124.3, 110.1, 44.7, 21.5, 12.6. IR (film): 2971, 2341, 1637, 1590, 1271, 1185, 754, 596 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C18H21NO, 267.1623; found, 267.1623. (4-(Diethylamino)phenyl)(p-tolyl)methanone (2c).21 Ivory solid (38 mg, 71%). mp 77−79 °C. Rf = 0.5 (EtOAc:hexane = 1:4). 1H NMR (400 MHz, CDCl3, δ): 7.67 (d, J = 8.9 Hz, 2H), 7.55 (d, J = 8.0 Hz, 2H), 7.14 (d, J = 7.9 Hz, 2H), 6.53 (d, J − 9.0 Hz, 2H), 3.31 (q, J = 7.1 Hz, 4H), 2.31 (s, 3H), 1.10 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 194.6, 150.9, 141.4, 136.6, 132.9, 129.6, 128.6, 124.2, 110.0, 44.5, 21.5, 12.5. IR (film): 3025, 2971, 2244, 1922, 1432, 3492

DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

Article

The Journal of Organic Chemistry

Phenyl(4-(pyrrolidin-1-yl)phenyl)methanone (4c).32 Yellow solid (51.2 mg, 98%). mp 142−144 °C. Rf = 0.3 (EtOAc:hexane = 1:10). 1H NMR (400 MHz, CDCl3, δ): 7.79 (d, J = 8.8 Hz, 2H), 7.72−7.70 (m, 2H), 7.53−7.50 (m, 1H), 7.46−7.43 (m, 2H), 6.54 (d, J = 8.8 Hz, 2H), 3.40−3.36 (m, 4H), 2.06−2.03 (m, 4H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.2, 151.0, 139.7, 133.1, 131.1, 129.5, 128.1, 124.4, 110.7, 47.7, 25.6. IR (film): 2931, 2341, 1637, 1448, 1276, 1092, 704, 579 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C17H17NO, 251.1310; found, 251.1312. (4-(Ethyl(methyl)amino)phenyl)(phenyl)methanonemethanone (4d).33 Yellow oil (43.6 mg, 91%). Rf = 0.4 (EtOAc:hexane = 1:10). 1H NMR (400 MHz, CDCl3, δ): 7.79 (d, J = 9.0 Hz, 2H), 7.72−7.70 (m, 2H), 7.53−7.49 (m, 1H), 7.46−7.42 (m, 2H), 6.67 (d, J = 9.0 Hz, 2H), 3.48 (q, J = 7.1 Hz, 2H), 3.02 (s, 3H), 1.18 (t, J = 7.1 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3, δ): 195.1, 152.3, 139.5, 133.0, 131.1, 129.5, 128.1, 124.6, 110.5, 46.7, 37.6, 11.7. IR (film): 3024, 2341, 1709, 1590, 1319, 1145, 740, 593 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C16H17NO, 239.1310; found, 239.1311. (4-(Ethyl(phenyl)amino)phenyl)(phenyl)methanone (4e).34 Yellow oil (58.7 mg, 98%). Rf = 0.4 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.73−7.70 (m, 4H), 7.52−7.49 (m, 1H), 7.46− 7.40 (m, 4H), 3−7.xx (m, 4H), 7.27−7.21 (m, 2H), 6.71 (d, J = 8.9 Hz, 2H), 3.83 (q, J = 7.1 Hz, 2H), 1.27 (t, J = 7.1 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.1, 151.9, 145.8, 139.2, 132.6, 131.3, 130.1, 129.6, 128.1, 127.4, 126.3, 126.1, 113.3, 46.9, 12.6. IR (film): 2973, 2067, 1643, 1585, 1318, 1271, 937, 699 cm−1. HRMS (EI) (m/ z): [M]+ Calcd for C21H19NO, 301.1467; found, 301.1465. (4-(Diethylamino)-2-methylphenyl)(phenyl)methanone (4f).35 Yellow oil (47.8 mg, 87%). Rf = 0.4 (actone:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.74−7.72 (m, 2H), 7.53−7.48 (m, 1H), 7.42 (t, J = 7.4 Hz, 2H), 7.33 (d, J = 8.8 Hz, 1H), 6.52 (d, J = 2.4 Hz, 1H), 6.42 (dd, J = 8.8 Hz, 2.6 Hz, 1H), 3.41 (q, J = 7.1 Hz, 4H), 2.52 (s, 3H), 1.21 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 197.0, 149.9, 142.3, 140.6, 134.7, 131.5, 129.9, 128.1, 124.3, 113.8, 107.1, 44.5, 22.3, 12.8. IR (film): 2970, 1771, 1598, 1257, 1106, 913, 700, 537 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C18H21NO, 267.1623; found, 267.1620. (2-Bromo-4-(diethylamino)phenyl)(phenyl)methanone (4g). Yellow oil (35.4 mg, 50%). Rf = 0.3 (actone:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.81−7.79 (m, 2H), 7.56−7.52 (m, 1H), 7.45−7.41 (m, 2H), 7.30 (d, J = 8.7 Hz, 1H), 6.87 (d, J = 2.5 Hz, 1H), 6.56 (dd, J = 8.8 Hz, 2.5 Hz, 1H), 3.39 (q, J = 7.1 Hz, 4H) 1.20 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.4, 150.3, 138.5, 133.1, 132.5, 130.3, 128.3, 125.7, 123.4, 115.9, 109.1, 44.6, 12.6. IR (film): 2971, 1716, 1652, 1590, 1250, 1023, 730 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C17H1879BrNO, 331.0572, C17H1881BrNO, 333.0572; found, 331.0573, 333.0556. (1-Ethylindolin-5-yl)(phenyl)methanone (4h). Green solid (36.1 mg, 70%). mp 92−94 °C. Rf = 0.5 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.71−7.68 (m, 2H), 7.63−7.60 (m, 2H), 7.53− 7.49 (m, 1H), 7.46−7.42 (m, 2H), 6.34 (d, J = 8.2 Hz, 1H), 3.55 (t, J = 8.6 Hz, 2H), 3.27 (q, J = 7.2 Hz, 2H), 3.03 (t, J = 8.5 Hz, 2H), 1.19 (t, J = 7.2 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.2, 156.0, 139.8, 133.5, 131.0, 129.9, 129.5, 128.1, 126.8, 126.1, 104.2, 51.6, 41.6, 27.6, 11.8. IR (film): 2961, 2851, 2359, 1629, 1320, 829, 703 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C17H17NO, 251.1310; found, 251.1308. (1-Ethyl-1,2,3,4-tetrahydroquinolin-6-yl)(phenyl)methanone (4i). Yellow oil (40.4 mg, 76%). Rf = 0.5 (EtOAc:hexane = 1:10). 1H NMR (400 MHz, CDCl3, δ): 7.71−7.69 (m, 2H), 7.60−7.55 (m, 2H), 7.52− 7.48 (m, 1H), 7.45−7.42 (m, 2H), 6.54 (d, J = 8.7 Hz, 1H), 3.43−3.34 (m, 4H), 2.76 (t, J = 6.2 Hz, 2H), 1.96 (quent, J = 6.0 Hz, 2H), 1.18 (t, J = 7.1 Hz, 3H).; 13C{1H} NMR (100 MHz, CDCl3, δ): 195.0, 148.9, 139.7, 131.8, 131.7, 130.9, 129.4, 128.0, 124.0, 121.4, 108.7, 48.8, 45.6, 28.2, 21.8, 11.2. IR (film): 2929, 1726, 1592, 1319, 1138, 712, 590, 524 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C18H19NO, 265.1467; found, 265.1465. (5-Ethyl-10,11-dihydro-5H-dibenzo[b,f]azepin-2-yl)(phenyl)methanone (4j). Yellow oil (32.8 mg, 50%). Rf = 0.7 (EtOAc:hexane = 1:10). 1H NMR (400 MHz, CDCl3, δ): 7.74−7.72 (m, 2H), 7.61−

C17H1879BrNO, 331.0572, C17H1881BrNO, 333.0572; found, 331.0569, 333.0555. (4-Bromophenyl)(4-(diethylamino)phenyl)methanone (2i).25 Ivory solid (46.5 mg, 70%). mp 94−96 °C. Rf = 0.4 (EtOAc:hexane = 1:4). 1H NMR (400 MHz, CDCl3, δ): 7.74 (d, J = 9.1 Hz, 2H), 7.59 (s, 4H), 6.64 (d, J = 9.1 Hz, 2H), 3.44 (q, J = 7.1 Hz, 4H), 1.21 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 193.6, 151.2, 138.2, 133.0, 131.2, 131.0, 125.7, 123.5, 110.1, 44.6, 12.5. IR (film): 2972, 2929, 2899, 1639, 1591, 1524, 1408, 1319, 1271, 1199, 1144, 1069, 1011, 926 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C 17 H 18 79 BrNO, 331.0572, C 17 H 18 81 BrNO, 333.0572; found, 331.0569, 333.0557. (4-(Diethylamino)phenyl)(4-(trifluoromethyl)phenyl)methanone (2j). Green oil (67.1 mg, 99%). Rf = 0.4 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.81−7.70 (m, 6H), 6.65 (d, J = 9.2 Hz, 2H), 3.45 (q, J = 7.1 Hz, 4H), 1.22 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 193.4, 151.6, 143.0, 133.2, 132.4 (q, JCF = 32.6 Hz), 129.5, 125.1 (q, JCF = 3.6 Hz), 124.0 (q, JCF = 272.5 Hz), 123.3, 110.3, 44.7, 12.6; 19F NMR (376 MHz, CDCl3, δ): −62.7. IR (film): 2974, 1590, 1321, 1144, 1064, 929, 770, 597 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C18H18F3NO, 321.1340; found, 321.1342. Methyl 4-(4-(diethylamino)benzoyl)benzoate (2k).26 Green oil (47.3 mg, 76%). Rf = 0.4 (EtOAc:hexane = 1:2). 1H NMR (400 MHz, CDCl3, δ): 8.12 (d, J = 8.2 Hz, 2H), 7.77−7.74 (m, 4H), 6.65 (d, J = 9.1 Hz, 2H), 3.96 (s, 3H), 3.44 (q, J = 7.1 Hz, 4H), 1.22 (t, J = 7.1 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 194.0, 166.7, 151.5, 143.7, 133.2, 132.1, 129.4, 129.2, 123.6, 110.3, 52.4, 44.7, 12.6. IR (film): 2972, 2341, 1821, 1725, 1590, 1271, 1143, 711 cm−1. HRMS (EI) (m/ z): [M]+ Calcd for C19H21NO3, 311.1521; found, 311.1524. (4-(Diethylamino)phenyl)(naphthalen-2-yl)methanone (2l).27 Yellow oil (61.0 mg, 99%). Rf = 0.3 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 8.21 (s, 1H), 7.93−7.83 (m, 6H), 7.59− 7.51 (m, 2H), 6.67 (d, J = 9.0 Hz, 2H), 3.45 (q, J = 7.1 Hz, 2H), 1.23 (t, J = 7.1 Hz, 3H). 13C{ 1H} NMR (100 MHz, CDCl3, δ): 194.9, 151.2, 136.8, 134.8, 133.3, 132.5, 130.3, 129.2, 128.0, 127.9, 127.6, 126.6, 126.3, 124.4, 110.3, 44.7, 12.7. IR (film): 2869, 2341, 1712, 1589, 1318, 1186, 761, 570 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C21H21NO, 303.1623; found, 303.1621. (4-(Diethylamino)phenyl)(thiophen-2-yl)methanone (2m).28 Yellow solid (41.4 mg, 80%). mp 54−56 °C. Rf = 0.4 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.89 (d, J = 9.0 Hz, 2H), 7.65 (dd, J = 3.6 Hz, J = 0.9 Hz, 1H), 7.61 (dd, J = 4.9 Hz, J = 0.8 Hz, 1H), 7.14−7.12 (m, 1H), 6.67 (d, J = 9.0 Hz, 2H), 3.43 (q, J = 7.1 Hz, 4H), 1.22 (t, J = 7.1 Hz, 6H). 13C{ 1H} NMR (100 MHz, CDCl3, δ): 186.0, 151.2, 144.7, 132.8, 132.3, 132.0, 127.5, 124.7, 110.3, 44.6, 12.6. IR (film): 2970, 2359, 1587, 1269, 1194, 1127, 841, 729 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C15H17NOS, 259.1031; found, 259.1028. N-Tosylformamide (3).29 Colorless oil. Rf = 0.1 (EtOAc:hexane = 1:2). 1H NMR (400 MHz, CDCl3, δ): 8.66 (brs, 2H), 7.80 (d, J = 8.0 Hz, 2H), 7.36 (d, J = 8.0 Hz, 2H), 2.46 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 161.8, 145.7, 136.2, 130.3, 127.0, 21.7. (4-(Dipropylamino)phenyl)(phenyl)methanone (4a).30 Green oil (51.3 mg, 90%). Rf = 0.4 (EtOAc:hexane = 1:10). 1H NMR (400 MHz, CDCl3, δ): 7.77 (d, J = 9.1 Hz, 2H), 7.73−7.70 (m, 2H), 7.53− 7.49 (m, 1H), 7.46−7.42 (m, 2H), 6.61 (d, J = 9.0 Hz, 2H), 3.32 (t, J = 7.8 Hz, 4H), 1.7−1.6 (m, 4H), 0.95 (t, J = 7.4 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.0, 151.7, 139.6, 133.1, 131.1, 129.5, 128.1, 124.1, 110.4, 52.9, 20.6, 11.5. IR (film): 2961, 2360, 1771, 1639, 1590, 1144, 700, 608 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C19H23NO, 281.1780; found, 281.1783. (4-(Dibutylamino)phenyl)(phenyl)methanone (4b).31 Yellow oil (56.4 mg, 91%). Rf = 0.5 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.77 (d, J = 9.1 Hz, 2H), 7.73−7.70 (m, 2H), 7.53−7.49 (m, 1H), 7.46−7.42 (m, 2H), 6.61 (d, J = 9.1 Hz, 2H), 3.34 (t, J = 7.7 Hz, 4H), 1.64−1.56 (m, 4H), 1.41−1.32 (m, 4H), 0.97 (t, J = 7.3 Hz, 6H). 13C{1H} NMR (100 MHz, CDCl3, δ): 194.9, 151.6, 139.6, 133.1, 131.0, 129.5, 128.1, 124.1, 110.3, 50.9, 29.5, 20.4, 14.1. IR (film): 2956, 2341, 1693, 1282, 1144, 700, 607, 505 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C21H27NO, 309.2093; found, 309.2093. 3493

DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

Article

The Journal of Organic Chemistry

129.7, 128.0, 121.5, 104.6, 98.8, 55.57, 55.55. IR (film): 3020, 2920, 1640, 1600, 1440, 1370, 1285, 1020 cm−1. (4-Ethoxyphenyl)(phenyl)methanone (5j).44 White solid (45.3 mg, 99%). Rf = 0.3 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.82 (d, J = 8.8 Hz, 2H), 7.75 (d, J = 7.8 Hz, 2H), 7.56 (t, J = 7.4 Hz, 1H), 7.47 (t, J = 7.6 Hz, 2H), 6.95 (d, J = 8.8 Hz, 2H), 4.12 (q, J = 7.0 Hz, 2H), 1.46 (t, J = 7.0 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.6, 162.7, 138.3, 132.6, 131.9, 129.9, 129.7, 128.2, 114.0, 63.8, 14.7. IR (film): 3014, 1665, 1608, 1444, 1282 cm−1. (4-phenoxyphenyl)(phenyl)methanone (5k).45 Colorless oil (52.8 mg, 96%). Rf = 0.3 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.84−7.81 (m, 2H), 7.79−7.77 (m, 2H), 7.60−7.56 (m, 1H), 7.50−7.46 (m, 2H), 7.43−7.38 (m, 2H) 7.23−7.19 (m, 1H), 7.11−7.09 (m, 2H), 7.05−7.01 (m, 2H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.5, 161.7, 155.5, 137.9, 132.5, 132.2, 131.9, 130.1, 129.8, 128.3, 124.6, 120.2, 117.2. IR (film): 2972, 2884, 1644, 1604, 1320, 1279, 1112 cm−1. (4-Methoxy-2-(pent-2-yn-1-yloxy)phenyl)(phenyl)methanone (5l). Colorless oil (37.2 mg, 63%). Rf = 0.4 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.80−7.77 (m, 2H), 7.56−7.51 (m, 1H), 7.44−7.39 (m, 3H), 6.63−6.60 (m, 2H), 4.73 (t, J = 2.1 Hz, 2H), 3.70 (s, 3H), 2.25 (qt, J = 12.5 Hz, 2.1 Hz, 2H), 1.16 (t, J = 7.5 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3, δ): 195.6, 161.5, 159.5, 138.7, 132.4, 132.0, 129.7, 128.0, 122.0, 105.5, 99.7, 90.2, 73.6, 56.7, 55.6, 13.6, 12.5. IR (film): 2977, 2938, 2877, 1653, 1604, 1448, 1316, 1275, 1199, 1166, 1121, 1016 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C19H18O3, 294.1256; found, 294.1253. (2,3-Dihydrobenzofuran-6-yl)(phenyl)methanone (5m). Colorless oil (44.5 mg, 99%). Rf = 0.4 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.77−7.73 (m, 3H), 7.65 (dd, J = 8.4 Hz, 1.9 Hz, 1H), 7.56 (tt, J = 7.4 Hz, 1.3 Hz, 1H), 7.49−7.45 (m, 2H), 6.82 (d, J = 8.4 Hz, 1H), 4.69 (t, J = 8.8 Hz, 2H), 3.27 (t, J = 8.8 Hz, 2H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.7, 164.2, 138.6, 132.5, 131.8, 130.4, 129.7, 128.2, 127.6, 127.5, 108.8, 72.2, 29.1. IR (film): 2970, 2899, 1650, 1604, 1488, 1444, 1280, 1095 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C15H12O2, 224.0837; found, 224.0839. Oxidative Cleavage of the C−C Double Bond in Cyclic N-Tosyl Enamides.46 The compound 7a was prepared according to the same procedure as that of the synthesis of 2a. The crude residue was purified by silica gel column chromatography (EtOAc:hexane) to give 7. 5-Methoxy-2,3-dihydro-1H-inden-1-one (7a).47 White solid (30.0 mg, 92%). mp 99−101 °C. Rf = 0.2 (EtOAc:hexane = 1:3). 1H NMR (400 MHz, CDCl3, δ): 7.69 (d, J = 9.1 Hz, 1H), 6.92−6.90 (m, 2H), 3.89 (s, 3H), 3.10 (t, J = 5.9 Hz, 2H), 2.70−2.67 (m, 2H). 13C{ 1H} NMR (100 MHz, CDCl3, δ): 205.3, 165.3, 158.2, 130.5, 125.4, 115.3, 109.8, 55.6, 36.4, 25.9. IR (film): 2954, 2917, 1692, 1604, 1308, 1256, 1096, 1038 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C10H10O2, 162.0681; found, 162.0680. 3-Methoxyfluoren-9-one (7b).48 Bright yellow solid (40.0 mg, 95%). Rf = 0.3 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.60 (dt, J = 7.3 Hz, 0.8 Hz, 1H), 7.45−7.39 (m, 3H), 7.20 (td, J = 7.2 Hz, 1.5 Hz, 2H), 6.98 (dd, J = 8.2 Hz, 2.5 Hz, 1H), 3.85 (s, 3H). 13 C{1H} NMR (100 MHz, CDCl3, δ): 193.9, 160.8, 144.9, 137.0, 135.9, 134.9, 134.3, 127.9, 124.4, 121.4, 120.3, 119.6, 109.4, 55.8. IR (film): 2952, 1688, 1610, 1296, 1244, 1089 cm−1. 4H-Indeno[1,2-b]furan-4-one (7c).49 Pinkish solid (22.5 mg, 66%). Rf = 0.5 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.45−7.42 (m, 2H), 7.32−7.28 (m, 1H), 7.20−7.16 (m, 1H), 7.12 (d, J = 7.2 Hz, 1H), 6.51 (d, J = 1.9 Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3, δ): 185.3, 175.4, 148.3, 138.6, 134.1, 133.0, 129.1, 123.8, 123.6, 117.2, 106.9. IR (film): 2918, 2853, 1708, 1429, 940, 864, 760, 713 cm−1. 4H-Indeno[1,2-b]thiophen-4-one (7d).50 Bright yellow solid (33.0 mg, 88%). Rf = 0.5 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.45 (dq, J = 7.2 Hz, 0.5 Hz, 1H), 7.33 (td, J = 11.2 Hz, 1.1 Hz, 1H), 7.20−7.13 (m, 4H). 13C{1H} NMR (100 MHz, CDCl3, δ): 187.4, 159.1, 142.0, 138.8, 136.5, 134.0, 129.1, 128.6, 123.7, 121.5, 119.4. IR (film): 2950, 1677, 1614, 1288, 1092 cm−1. 1-(4-Methoxyphenyl)-3H-benzo[c]azepin-3-one (7e). White solid (29.5 mg, 56%). mp 161−163 °C. Rf = 0.1 (EtOAc:hexane = 1:5). 1H

7.52 (m, 3H), 7.46−7.43 (m, 2H), 7.20−7.15 (m, 2H), 7.12−7.08 (m, 2H), 7.04−7.00 (m, 1H), 3.87 (q, J = 7.0 Hz, 2H), 3.17 (s, 4H), 1.18 (t, J = 7.0 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.8, 151.6, 147.8, 138.6, 137.0, 133.4, 131.8, 131.1, 129.9, 129.8, 129.3, 128.9, 128.2, 126.7, 124.0, 121.9, 118.6, 46.1, 34.0, 31.3, 14.0. IR (film): 2972, 2359, 1649, 1488, 1271, 1109, 707, 533 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C23H21NO, 327.1623; found, 327.1624. (4-Methoxyphenyl)(phenyl)methanone (5a).36 Colorless oil (43.2 mg, 99%). Rf = 0.2 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.85−7.82 (m, 2H), 7.77−7.75 (m, 2H), 7.59−7.55 (m, 1H), 7.49−7.46 (m, 2H), 6.98−6.95 (m, 2H), 3.89 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.6, 163.3, 138.3, 132.6, 131.9, 130.2, 129.7, 128.2, 113.6, 55.5. IR (film): 3059, 2933, 2839, 1651, 1599, 1257, 922, 844, 701 cm−1. (4-Methoxyphenyl)(m-tolyl)methanone (5b).36 Yellow oil (30.3 mg, 67%). Rf = 0.3 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.84−7.81 (m, 2H), 7.57 (s, 1H), 7.53 (dt, J = 7.1 Hz, 1.5 Hz, 1H), 7.38−7.32 (m, 2H), 6.97−6.94 (m, 2H), 3.88 (s, 3H), 2.41 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.8, 163.2, 138.4, 138.1, 132.7, 132.6, 130.4, 130.2, 128.0, 127.0, 113.5, 55.5, 21.4. IR (film): 2934, 2836, 1649, 1597, 1258, 1196, 846, 754 cm−1. (4-Methoxyphenyl)(m-tolyl)methanone (5c).37 White solid (48.5 mg, 99%). Rf = 0.3 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.81−7.77 (m, 4H), 6.98−6.95 (m, 4H), 3.89 (s, 6H). 13 C{1H} NMR (100 MHz, CDCl3, δ): 194.5, 162.8, 132.3, 130.8, 113.5, 55.5. IR (film): 2972, 2891, 1638, 1604, 1282, 1096 cm−1. (3-Chlorophenyl)(4-methoxyphenyl)methanone (5d).38 White solid (48.4 mg, 98%). Rf = 0.3 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.82−7.80 (m, 2H), 7.73 (t, J = 1.8 Hz, 1H), 7.62 (dt, J = 7.6 Hz, 1.3 Hz, 1H), 7.54 (dq, J = 8.0 Hz, 1.0 Hz, 1H), 7.41 (t, J = 7.8 Hz, 1H), 6.99−6.96 (m, 2H), 3.89 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 194.0, 163.6, 140.0, 134.4, 132.6, 131.9, 129.7, 129.6, 129.6, 127.8, 113.8, 55.6. IR (film): 2838, 1652, 1599, 1420, 1257, 1028, 844, 757 cm−1. (4-Methoxyphenyl)(4-(trifluoromethyl)phenyl)methanone (5e).39 White solid (55.0 mg, 98%). Rf = 0.3 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.86−7.81 (m, 4H), 7.75 (d, J = 8.1 Hz, 2H), 7.00−6.97 (m, 2H), 3.91 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 194.4, 163.9, 141.7, 133.4 (q, JCF = 32.5 Hz), 132.8, 129.9, 129.5, 125.4 (q, JCF = 3.7 Hz), 123.9 (q, JCF = 272.6 Hz), 114.0, 55.7. 19F NMR (376 MHz, CDCl3, δ): −62.9. IR (film): 2972, 2848, 1644, 1601, 1406, 1129, 1029, 861, 770 cm−1. (4-Methoxyphenyl)(4-nitrophenyl)methanone (5f).40 White solid (22.1 mg, 43%). Rf = 0.4 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 8.36−8.32 (m, 2H), 7.91−7.87 (m, 2H), 7.84−7.80 (m, 2H), 7.02−6.99 (m, 2H), 3.91 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 193.5, 164.0, 149.5, 143.8, 132.7, 130.4, 128.9, 123.5, 114.0, 55.6. IR (film): 3041, 2912, 2897, 1631, 1472, 981, 833, 718 cm−1. (4-Methoxyphenyl)(thiophen-3-yl)methanone (5g).41 White solid (31.5 mg, 72%). mp 48−50 °C. Rf = 0.3 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.89 (m, 3H), 7.56 (dd, J = 5.0 Hz, 1.2 Hz, 1H), 7.37 (dd, J = 5.0 Hz, 2.9 Hz, 1H), 6.99−6.95 (m, 2H), 3.89 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 188.9, 163.1, 141.5, 132.8, 131.9, 131.2, 128.7, 126.0, 113.6, 55.5. IR (film): 2970, 2359, 1587, 1269, 1194, 1127, 841, 729 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C12H10O2S, 218.0402; found, 218.0399. (4-Methoxynaphthalen-1-yl)(phenyl)methanone (5h).42 Yellow oil (43.5 mg, 83%). Rf = 0.3 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 8.39−8.34 (m, 2H), 7.84 (d, J = 7.2 Hz, 1H), 7.61− 7.51 (m, 4H), 7.84 (d, J = 7.2 Hz, 2H), 7.84 (d, J = 7.2 Hz, 1H), 4.05 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 197.4, 158.4, 139.5, 132.6, 132.5, 131.4, 130.3, 128.3, 128.1, 128.0, 125.9, 125.80, 125.76, 122.3, 102.0, 55.8. IR (film): 2972, 2891, 1642, 1602, 1284, 1093,1030 cm−1. (3,5-Dimethoxyphenyl)(phenyl)methanone (5i).43 White solid (45.0 mg, 87%). Rf = 0.3 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 7.78−7.76 (m, 2H), 7.52 (t, J = 7.3 Hz, 1H), 7.43− 7.39 (m, 3H), 6.56−6.51 (m, 2H), 3.86 (s, 3H), 3.69 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 195.6, 163.4, 159.6, 138.8, 132.4, 132.2, 3494

DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

Article

The Journal of Organic Chemistry NMR (400 MHz, CDCl3, δ): 8.00−7.96 (m, 2H), 7.91 (dd, J = 7.6 Hz, 1.2 Hz, 1H), 7.66 (td, J = 7.3 Hz, 1.4 Hz, 1H), 7.61 (td, J = 7.5 Hz, 1.4 Hz, 1H), 7.57 (d, J = 11.8 Hz, 1H), 7.56 (dd, J = 8.4 Hz, 1.0 Hz, 1H), 7.22 (d, J = 11.8 Hz, 1H), 6.98−6.94 (m, 2H), 3.87 (s, 3H). 13C{ 1H} NMR (100 MHz, CDCl3, δ): 177.7, 162.7, 160.0, 142.0, 137.5, 132.1, 131.4, 130.9, 130.8, 129.4, 129.2, 128.3, 125.7, 114.1, 55.5. IR (film): 2933, 1663, 1624, 1603, 1567, 1452, 1313, 1254, 1226, 1173, 1027 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C17H13NO2, 263.0946; found, 263.0944. Oxidative Cleavage of the C−C Double Bond in Aryl Indolyl NTosyl Enamide. (1-Methyl-1H-indol-3-yl)(phenyl)methanone (9a).51 Yellow solid (51.1 mg, 98%). Rf = 0.3 (EtOAc:hexane = 1:5). 1H NMR (400 MHz, CDCl3, δ): 8.44−8.42 (m, 1H), 7.82−7.80 (m, 2H), 7.56− 7.52 (m, 2H), 7.50−7.46 (m, 2H), 7.39−7.32 (m, 3H), 3.84 (s, 3H). 13 C{1H} NMR (100 MHz, CDCl3, δ): 191.0, 141.1, 138.0, 137.7, 131.2, 128.8, 128.4, 127.4, 123.8, 122.9, 122.8, 115.8, 109.7, 33.7. IR (film): 3053, 2359, 1615, 1524, 1233, 874, 670 cm−1. (1,2-Dimethyl-1H-indol-3-yl)(p-tolyl)methanone (9b).52 Yellow solid (44.7 mg, 85%). Rf = 0.3 (EtOAc:hexane = 1:7). 1H NMR (400 MHz, CDCl3, δ): 7.68 (d, J = 8.0 Hz, 2H), 7.33 (t, J = 8.5 Hz, 2H), 7.25−7.18 (m, 3H), 7.09−7.05 (m, 1H), 3.74 (s, 3H), 2.59 (s, 3H), 2.44 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 192.8, 144.4, 142.2, 138.8, 136.7, 129.5, 129.0, 127.3, 122.1, 121.4, 121.2, 113.9, 109.2, 29.8, 21.8, 12.6. IR (film): 2919, 1620, 1520, 1402, 1230, 886, 749, 559 cm−1. (1,2-Dimethyl-1H-indol-3-yl)(4-methoxyphenyl)methanone (9c).52 Yellow solid (50.3 mg, 90%). Rf = 0.4 (EtOAc:hexane = 1:5). 1 H NMR (400 MHz, CDCl3, δ): 7.80−7.78 (m, 2H), 7.37−7.31 (m, 2H), 7.23−7.19 (m, 1H), 7.09−7.05 (m, 1H), 6.95−6.92 (m, 2H), 3.89 (s, 3H), 3.74 (s, 3H), 2.60 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 191.8, 162.7, 144.0, 136.6, 134.0, 131.7, 127.3, 122.0, 121.3, 121.1, 114.0, 113.5, 109.2, 55.5, 29.8, 12.5. IR (film): 2359, 1624, 1408, 1323, 1125, 1066, 746, 559 cm−1. (1,2-Dimethyl-1H-indol-3-yl)(4-(trifluoromethyl)phenyl)methanone (9d).52 Yellow solid (42.8 mg, 68%). Rf = 0.4 (EtOAc:hexane = 1:10). 1H NMR (400 MHz, CDCl3, δ): 7.83 (d, J = 8.1 Hz, 2H), 7.71 (d, J = 8.1 Hz, 2H), 7.34−7.32 (m, 1H), 7.25− 7.19 (m, 2H), 7.10−7.06 (m, 1H), 3.74 (s, 3H), 2.60 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3, δ): 191.4, 145.7, 144.8, 136.8, 132.9 (q, JCF = 32.5 Hz), 129.3, 126.9, 125.4 (q, JCF = 3.8 Hz), 124.0 (q, JCF = 272.7 Hz), 122.5, 121.9, 120.8, 113.2, 109.5, 29.9, 12.7. 19F NMR (376 MHz, CDCl3, δ): −62.7. IR (film): 3053, 2359, 1808, 1408, 1324, 1127, 1066, 745 cm−1. Oxidative Cleavage of the C−C Triple Bond from 1-Alkynes in Semi-One-Pot. Toluene (4.0 mL) was added to a mixture of CuTC (10 mol %), Rh2(esp)2 (1.0 mol %), 2-ethynyl-4′-methoxy-1,1′biphenyl (0.4 mmol), and tosyl azide (0.4 mmol) in an oven-dried test tube equipped with a stirring bar. The mixture was stirred for 2 h at 25 °C until 2-ethynyl-4′-methoxy-1,1′-biphenyl was completely consumed according to TLC monitoring, and then the mixture was stirred for 1 h at 80 °C. After, Cs2CO3 (1.2 mmol) was added to the mixture under air, and the mixture was stirred at 80 °C for 5 h. The residue was passed through a pad of Celite and eluted with CH2Cl2. The filtrate was concentrated under reduced pressure, and the residue was purified by silica gel fresh column chromatography (EtOAc:hexane) to give compound 7b (48.8 mg, 58%) as a bright yellow solid. Labeling Experiment. N-(2-(4-(Diethylamino)phenyl)-2-phenylvinyl)-4-methylbenzenesulfonamide (0.2 mmol), Cs2CO3 (0.6 mmol), and degassed dry toluene (1.0 mL) were added to an flamedried soda lime glass test tube equipped with a stir bar under N2 atmosphere. The mixture was bubbled with a 18O2 balloon for 10 min and then was stirred at 80 °C for 2 h under an 18O2 atmosphere. To remove Cs2CO3, the residue was passed through a pad of Celite and eluted with CH2Cl2. The filtrate was concentrated under reduced pressure, and the residue was purified by silica gel flash column chromatography (EtOAc:hexane). The crude residue was purified by silica gel column chromatography (EtOAc:hexane) to give compound 2a (49.0 mg, 97%) as a bright yellow oil. (4-(Diethylamino)phenyl)(phenyl)methanone (2a-[18O]). Reaction time, 2 h. Bright yellow oil. Rf = 0.5 (EtOAc:hexane = 1:5). 1H

NMR (400 MHz, CDCl3, δ): 7.81−7.77 (m, 2H), 7.747.71 (m, 2H), 7.53−7.49 (m, 1H), 7.46−7.42 (m, 2H), 6.66−6.62 (m, 2H), 3.43 (q, J = 7.1 Hz, 4H), 1.21 (t, J = 7.1 Hz, 1H). 13C{1H} NMR (100 MHz, CDCl3, δ): 194.9, 151.1, 139.5, 133.1, 131.0, 129.4, 128.0, 124.0, 110.1, 44.6, 12.5. IR (film): 3056, 2973, 2930, 2900, 2871, 1643, 1589, 1523, 1408, 1271, 1199, 1144 cm−1. HRMS (EI) (m/z): [M]+ Calcd for C17H19N18O, 255.1509; found, 255.1510.

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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.7b03068. 1 H and 13C{1H} spectra for new compounds (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] ORCID

Phil Ho Lee: 0000-0001-8377-1107 Author Contributions †

H.K. and S.P. contributed equally to this work.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (2011-0018355 and 2015H1C1A1035955).

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DEDICATION This paper is dedicated to Professor Han-Young Kang (Chungbuk National University) on the occasion of his retirement.

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REFERENCES

(1) (a) Trost, B. M.; Fleming, I. Comprehensive Organic Synthesis; Pergamon: Oxford, 1991. (b) Smith, M. B.; March, J. Advanced Organic Chemistry; Wiley: New York, 2007. (c) Toh, Q. Y.; McNally, A.; Vera, S.; Erdmann, N.; Gaunt, M. J. J. Am. Chem. Soc. 2013, 135, 3772. (2) (a) Pettit, G. R.; Toki, B.; Herald, D. L.; Verdier-Pinard, P.; Boyd, M. R.; Hamel, E.; Pettit, R. K. J. Med. Chem. 1998, 41, 1688. (b) Deng, Y.; Chin, Y. W.; Chai, H.; Keller, W. J.; Kinghorn, A. D. J. Nat. Prod. 2007, 70, 2049. (c) Krick, A.; Kehraus, S.; Gerhauser, C.; Klimo, K.; Nieger, M.; Maier, A.; Fiebig, H. H.; Atodiresei, I.; Raabe, G.; Fleischhauer, J.; Konig, G. M. J. Nat. Prod. 2007, 70, 353. (d) Kim, H.; So, S. M.; Yen, C. P.-H.; Vinhato, E.; Lough, J.; Hong, J.-I.; Kim, H.-J.; Chin, J. Angew. Chem., Int. Ed. 2008, 47, 8657. (e) Seo, J. W.; Kim, H. J.; Lee, B. S.; Katzenellenbogen, J. A.; Chi, D. Y. J. Org. Chem. 2008, 73, 715. (3) (a) Sarvari, M. H.; Sharghi, H. J. Org. Chem. 2004, 69, 6953. (b) Chavan, S. P.; Garai, S.; Dutta, A. K.; Pal, S. Eur. J. Org. Chem. 2012, 2012, 6841. (4) (a) Metal-Catalyzed Cross-Coupling Reactions; 2nd ed.; de Meijere, A., Diederich, F., Eds.; Wiley-VCH: Weinheim, 2004; Vols. 1−2. (b) Handbook of Organopalladium Chemistry for Organic Synthesis; Negishi, E., Ed.; Wiley-Interscience: New York, 2002; Vols. 1−2. (c) Tsuji, J. Palladium Reagents and Catalysts: New Perspectives for the 21st Century; Wiley-VCH: Weinheim, 2004. Recent review. (d) Shen, Z.-L.; Wang, S.-Y.; Chok, Y.-K.; Xu, Y.-H.; Loh, T.-P. Chem. Rev. 2013, 113, 271 and references cited therein.. (5) (a) Wu, X.-F.; Neumann, H.; Beller, M. Chem. Soc. Rev. 2011, 40, 4986. (b) Ishiyama, T.; Kizaki, H.; Hayashi, T.; Suzuki, A.; Miyaura, N. J. Org. Chem. 1998, 63, 4726. (c) Jafarpour, F.; Rashidi-Ranjbar, P.; 3495

DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496

Article

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DOI: 10.1021/acs.joc.7b03068 J. Org. Chem. 2018, 83, 3486−3496