Simple and convenient copper-catalyzed amination of aryl halides to primary arylamines using NH4OH

Tetrahedron 72 (2016) 5988e5993

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Simple and convenient copper-catalyzed amination of aryl halides to primary arylamines using NH4OH Hee Seon Jung, Taeil Yun, Yungyeong Cho, Heung Bae Jeon * Department of Chemistry, Kwangwoon University, Seoul 139-701, Republic of Korea

a r t i c l e i n f o

a b s t r a c t

Article history: Received 25 April 2016 Received in revised form 29 June 2016 Accepted 5 July 2016 Available online 6 July 2016

In this study, we investigated the direct synthesis of primary arylamines from aryl iodides and bromides by Cu-catalyzed amination using ammonium hydroxide (27% NH3 in H2O) as nucleophile. In this article, two protocols are described: (1) a variety of aryl halides were treated with CuI (10 mol %) and DMEDA (15 mol %) in NH4OH/DMSO, or (2) with only CuI (10 mol %) in NH4OH/PEG300. In each case, the desired primary arylamines were obtained in excellent yields. Although DMEDA and PEG have previously been employed as a ligand or solvent, respectively, the substrates were limited or additional ligands were required for successful conversion. Notably, our new protocols do not require additional inorganic bases, whereas previous methods have used a base. As such, these new protocols are one of the most simple, convenient, and efficient methods that have been reported, to date. Ó 2016 Published by Elsevier Ltd.

Keywords: Cu-catalyzed amination Primary arylamines Inorganic base-free Ammonium hydroxide

1. Introduction Primary arylamines are one of the most important intermediates in the chemical industry and have been widely used in the manufacturing of pharmaceuticals, agrochemicals, dyes, pigments, and polymer materials.1 Traditional methods for preparing these compounds include amination through aryne intermediates of aryl halides with ammonia2 or the nitration of arenes followed by hydrogenation.3 However, these synthetic routes can cause serious problems, for example, complicated mixtures of side products arising from the highly unstable aryne intermediate4 or significant environmental issues resulting from the use of large excesses of HNO3 and H2SO4 used for the nitration of arenes.5 For these reasons, the possibility of using transition metals to catalyze the synthesis of primary arylamines from aryl halides has been studied because transition metal-catalyzed CeN bond formation has become a powerful and reliable method for the synthesis of arylamines under convenient reaction conditions.6 While ammonia is one of the most inexpensive chemicals and an attractive nitrogen source for primary arylamines, its use in the direct transition metal-catalyzed amination should include the consideration of expected problems, for example, a high ammonia concentration can displace supporting ligands from the metal, resulting in catalyst deactivation,7 and the primary arylamine products generated during the reaction can further react with the

* Corresponding author. Tel.: þ82 2 940 5583; fax: þ82 2 911 8584; e-mail address: [email protected] (H.B. Jeon). http://dx.doi.org/10.1016/j.tet.2016.07.021 0040-4020/Ó 2016 Published by Elsevier Ltd.

starting aryl halides to form undesired di- or triarylamine byproducts.5,8 Despite these disadvantages, the transition metalcatalyzed amination of aryl halides employing ammonia itself has been extensively investigated, although ammonia surrogates such as allylamine,6j benzophenone imine,6g,9 benzylamine,10 azides,11 trifluoroacetamide,12 and others6b,f,13 have also been employed. For the direct amination of aryl halides using transition metals and ammonia, several groups have recently reported their methods employing palladium or copper as a metal catalyst. Since Hartwig8b and Buchwald14 reported the successful use of a palladium catalyst for this amination reaction, these and other groups have developed a variety of palladium-based catalytic systems.15 Although these catalytic systems revealed remarkable catalytic efficiencies and conveniently available reaction conditions, the significant cost of either the palladium catalyst or phosphine-derived ligands remains a limiting factor. These constraints have consequently led to the investigation of other metals and strategies for the synthesis of primary arylamines. Copper catalysis has emerged as a promising alternative to palladium-based methods, and protocols for the amination of aryl halides with ammonia have been realized. Although copper catalysts display lower efficiency than palladium, these copper catalytic systems have several advantages relative to their palladium-based counterparts in terms of higher stability, easier catalyst handling, lower toxicity, and, in particular, a greater abundance of copper on earth and a less expensive metal-ligand system. Early studies of the copper-catalyzed amination of aryl halides with ammonia required unfavorable, harsh reaction conditions and provided unsatisfactory

H.S. Jung et al. / Tetrahedron 72 (2016) 5988e5993

yields.16,17 In 2001, Lang et al. reported the Cu2O-catalyzed direct amination of electron-poor aryl halides, including bromopyridines, with ammonia in ethylene glycol at 100 j.18 Since then, several other ligands have been developed as effective ligands for coppercatalyzed coupling reactions of aryl halides with ammonia, including L-proline,19 L-trans-4-hydroxyproline,20 1,3-diketones,21 2pyridinyl ketones,22 ascorbic acid,23 D-glucosamine,24 N,N-dime0 thylethylenediamine (DMEDA),25 and N2,N2 -diisopropyloxalohy26 drazide. Recently, diamination of phenylene dihalides by using a dicopper complex [Cu2(bpnp) (OH) (CF3COO)3] (bpnp¼2,7bis(pyridine-2-yl)-1,8-naphthyridine) as catalyst27 and ligandless copper-catalyzed amination of heteroaryl bromides with gaseous ammonia28 were also reported for the synthesis of primary arylamines. More recently, the use of N,N0 -bis(2-phenyl-4methylphenyl)-oxalamide (BPMPO) as a ligand was reported for the conversion of aryl chlorides into the corresponding anilines.29 However, there remains a need for more simple, efficient, and generally applicable new catalytic systems using a copper catalyst for the direct amination of aryl halides with ammonia. Herein, we describe the synthesis of primary arylamines from aryl iodides and aryl bromides through the copper-catalyzed direct amination using DMEDA or PEG-300 as a ligand. Notably, these two new methods are carried out under inorganic base-free conditions, whereas almost all amination coupling reactions have previously employed an equivalent amount of inorganic bases such as K3PO4, K2CO3, or Cs2CO3.

2. Results and discussion 2.1. Amination of aryl iodides and bromides to primary arylamines using CuI/DMEDA Initial experiments were performed with 4-bromoanisole as a model substrate for the optimization of the reaction conditions. Selected results from our screening experiments are summarized in Table 1. When the reactions were carried out under the same conditions with the exception of different co-solvents, such as EtOH, DMF, and DMSO, with NH4OH, the best result was obtained in DMSO. Next, when the reactions were performed in various ratios of NH4OH and DMSO, the best yield resulted from a 3:1 ratio. Then, we employed ethylenediamine, N,N0 -dimethylethylenediamine (DMEDA) or N,N,N0 ,N0 -tetramethylethylenediamine (TMEDA), as a ligand with various amounts of sodium ascorbate, which might increase the reaction rate as a reducing agent of Cu(II) salt generated during the reaction.30 As shown in Table 1, when CuSO4 (entry

5989

1) or CuI (entry 2) was used as a catalyst with DMEDA (15 mol %) and Na ascorbate (10 mol %) at 150  C, CuI resulted in a better conversion. Because we noted the generation of a reduced byproduct (anisole) we performed the reaction with a decreased amount of Na ascorbate. The use of 5 mol % Na ascorbate lowered the conversion, but the formation of anisole was also decreased (entry 3). When we attempted the reaction at 130  C (entry 4), the result was almost same as that at 150  C. Changing the ligand to ethylenediamine (entry 5) or TMEDA (entry 6) under the same reaction conditions decreased the conversion yields. At 130  C, variation of the Na ascorbate amount (10, 2, and 0 mol %) revealed that Na ascorbate increased the conversion yield at a given reaction time but the formation of anisole, the reduced byproduct, also increased (entries 7e9). Also of note, in the absence of Na ascorbate, no anisole was generated, although the reaction rate is somewhat slow. Next, the generality of these optimized reaction conditions for the direct synthesis of primary arylamines from aryl halides with NH4OH was investigated, as shown in Table 2. The reactions of aryl halide (1 mmol) with CuI (10 mol %, 0.1 mmol) and DMEDA (15 mol %, 0.15 mmol) in NH4OH (1.5 mL) and DMSO (0.5 mL) were carried out at 130  C for the given reaction times. All aryl iodides and bromides investigated were converted to the corresponding primary arylamines in excellent yields. The reaction proceeded smoothly and tolerated various functional groups, such as methyl-, chloro-, fluoro-, methoxy-, acetyl-, nitro-, cyano, amino-, dimethylamino-, and methylenedioxy groups. Generally, aryl iodides required shorter reaction times than aryl bromides, and the reaction rates of aryl halides bearing electron-withdrawing groups were faster than those of other aryl halides, as expected. Particularly, aryl iodides bearing ortho-substituent groups were readily converted to the primary arylamines at 110  C. Although DMEDA was previously employed as a ligand with a copper catalyst, the substrates investigated were limited to pyridyl bromides, and K2CO3 was also required for the conversion.25 Our new protocol does not use a base and expanded the substrates to include aryl halides with electron-donating substituents.

2.2. Amination of aryl iodides and bromides to primary arylamines using CuI/PEG300 In an effort to develop a more convenient protocol for the synthesis of primary arylamines from aryl halides, we considered employing polyethylene glycols (PEGs) as a ligand and co-solvent in place of DMEDA and DMSO, which were used in our previous study

Table 1 Amination of 4-bromoanisole in a variety of conditions

Entry b,c

1 2b 3b 4 5 6 7 8 9 a b c

Ligand

Na ascorbate (mol %)

Conversion (%)a (yield of 2:3)

DMEDA DMEDA DMEDA DMEDA Ethylenediamine TMEDA DMEDA DMEDA DMEDA

10 10 5 5 5 5 10 2

79 97 91 90 77 78 97 74 70

The reaction products were determined by 1H NMR analysis. The reaction was carried out at 150  C. CuSO4 was used instead of CuI.

(86:14) (87:13) (95:5) (95:5) (94:6) (95:5) (90:10) (96:4) (100:0)

5990

H.S. Jung et al. / Tetrahedron 72 (2016) 5988e5993

(entry 3). On the other hand, the addition of an inorganic base, K3PO4, did not alter the reaction efficiency (entry 5). After the optimal conditions were in hand, we performed reactions with a variety of aryl iodides and bromides using PEG300 as shown in Table 4. The reactions of aryl halide (1 mmol) with CuI (10 mol %, 0.1 mmol) in NH4OH (1.5 mL) and PEG300 (0.5 g) were carried out at 130  C for the given reaction times. All aryl iodides and bromides investigated were readily converted to the corresponding primary arylamines in excellent yields. The reaction proceeded smoothly and tolerated various functional groups. Although PEG has been used previously for this conversion, reported methods employed sucrose as a ligand and K3PO4 or Na3PO4 as an additional base.31 Comparatively, new protocol is more simple and convenient. In addition, this protocol produced the desired primary arylamines in higher yields than previously reported.31

Table 2 Amination of aryl halides with CuI/DMEDA in NH4OH/DMSOa

3. Conclusion In conclusion, we have obtained primary arylamines in excellent yields when aryl iodides and bromides were treated with either CuI/DMEDA in NH4OH/DMSO or with only CuI in NH4OH/PEG300. Although DMEDA and PEG were previously employed as a ligand or solvent, the substrates were limited or another ligand was required for successful conversion. Notably, our new protocol does not use any additional base and could be considered one of the most simple and convenient methods. Accordingly, this protocol shows promise in broad applications in organic synthesis. Table 4 Amination of aryl halides with CuI in NH4OH/PEG300a

a

Isolated yields.

b

The reaction was performed at 110 °C.

as shown in Table 2. At first, we performed test reactions with various PEGs. As shown in Table 3, when PEG4500 was used, the reaction gave 4-aminoanisole in only 50% yield (entry 1), however, the reactions with PEG400, 300, and 200 afforded the desired product in excellent yields (entries 2e4). Although these PEGs did not result in large differences, PEG300 displayed the best result

Table 3 Amination of 4-bromoanisole with various PEGs

Entry

PEG

Yield (%)

1 2 3 4 5a

4500 400 300 200 400

50 89 93 91 90

a

The reaction was performed with K3PO4 (1 equiv).

a

Isolated yields.

b

The reaction was performed at 110 °C.

H.S. Jung et al. / Tetrahedron 72 (2016) 5988e5993

4. Experimental section 4.1. General All reactions were conducted under a positive pressure of argon after flushing with argon in a 10-mL sealed tube. All reagents were purchased from commercial suppliers and used without further purification. Flash column chromatography was performed employing 230e400 mesh silica gel (Merck). NMR spectra were recorded on a Jeol 400 MHz NMR spectrometer. Chemical shifts are reported in ppm from tetramethylsilane, with the residual solvent resonance as the internal standard (CDCl3: 1H d 7.27 ppm, 13C d 77.16 ppm). Low-resolution MS were obtained on an Agilent 6590N GC spectrometer. 4.2. General procedure for the synthesis of primary arylamines using CuI/DMEDA in NH4OH/DMSO (Method A) A 10 mL-sealed tube was charged with aryl iodides or bromides (1 mmol), CuI (19 mg, 0.1 mmol), and DMEDA (13 mg/16 mL, 0.15 mmol) in NH4OH (1.5 mL, 27% NH3 in H2O) and DMSO (0.5 mL). The tube was flushed with Ar gas before being capped. The solution was stirred for the given times at 130  C or 110  C. The resulting suspension was cooled to room temperature and saturated aqueous Na2SO4 solution (5 mL) was added. The resulting solution was extracted with EtOAc (20 mL3). The organic layer was separated, dried over MgSO4, filtered and concentrated. The residue was purified by flash column chromatography (hexanes/EtOAc¼5/1/1/2 or EtOAc) to give the desired primary arylamines. 4.3. General procedure for the synthesis of primary arylamines using CuI in NH4OH/PEG300 (Method B) A 10 mL-sealed tube was charged with aryl iodides or bromides (1 mmol), CuI (19 mg, 0.1 mmol) in NH4OH (1.5 mL, 27% NH3 in H2O) and PEG300 (0.5 g). The tube was flushed with Ar gas before being capped. The solution was stirred for the given times at 130  C or 110  C. The resulting suspension was cooled to room temperature and saturated aqueous Na2SO4 solution (5 mL) was added. The resulting solution was extracted with EtOAc (20 mL3). The organic layer was separated, dried over MgSO4, filtered and concentrated. The residue was purified by flash column chromatography (hexanes/EtOAc¼5/1/1/2 or EtOAc) to give the desired primary arylamines. 4.4. Spectroscopic data 4.4.1. 4-Methoxyaniline (2). Following the general procedure and purification by flash column chromatography (hexanes/EtOAc¼3/ 1), the product was obtained in 97% (119 mg, Method A) and 92% (113 mg, Method B) yields from iodide. From bromide, the product was obtained in 99% (122 mg, Method A and B, respectively) yield. Rf (hexanes/EtOAc¼3/1) 0.20; 1H NMR (400 MHz, CDCl3) d 6.76 (d, J¼8.7 Hz, 2H), 6.66 (d, J¼8.4 Hz, 2H), 3.75 (s, 3H), 3.42 (br s, 2H); 13C NMR (100 MHz, CDCl3) d 152.9, 139.9, 116.4, 114.8, 55.7. ESI MS m/z 123 [Mþ]. These spectroscopic data are in agreement with known literature values.26 4.4.2. p-Toluidine (5a). Following the general procedure and purification by flash column chromatography (hexanes/EtOAc¼5/1), the product was obtained in 89% (95 mg, Method A and B, respectively) yield from iodide. From bromide, the product was obtained in 88% (94 mg, Method A) and 82% (88 mg, Method B) yields. Rf (hexanes/EtOAc¼5/1) 0.21; 1H NMR (400 MHz, CDCl3) d 6.97 (d,

5991

J¼8.5 Hz, 2H), 6.62 (d, J¼8.3 Hz, 2H), 3.53 (br s, 2H), 2.25 (s, 3H); 13C NMR (100 MHz, CDCl3) d 143.9, 129.8, 127.9, 115.3, 20.4. ESI MS m/z 107 [Mþ]. These spectroscopic data are in agreement with known literature values.26 4.4.3. 4-Chloroaniline (5b). Following the general procedure and purification by flash column chromatography (hexanes/EtOAc¼3/ 1), the product was obtained in 91% (116 mg, Method A and B, respectively) yield from iodide. Rf (hexanes/EtOAc¼3/1) 0.34; 1H NMR (400 MHz, CDCl3) d 7.11 (d, J¼9.7 Hz, 2H), 6.62 (d, J¼9.7 Hz, 2H), 3.66 (br s, 2H); 13C NMR (100 MHz, CDCl3) d 145.0, 129.1, 123.1, 116.22. ESI MS m/z 127 (35Cl) and 129 (37Cl) [Mþ]. These spectroscopic data are in agreement with known literature values.26 4.4.4. 4-Fluoroaniline (5c). Following the general procedure and purification by flash column chromatography (hexanes/EtOAc¼3/ 1), the product was obtained in 88% (98 mg, Method A) and 90% (100 mg, Method B) yields from iodide. From bromide, the product was obtained in 91% (101 mg, Method A) and 92% (102 mg, Method B) yields. Rf (hexanes/EtOAc¼3/1) 0.32; 1H NMR (400 MHz, CDCl3) d 6.89e6.83 (m, 2H), 6.65e6.61 (m, 2H), 3.54 (br s, 2H); 13C NMR (100 MHz, CDCl3) d 156.5 (d, J¼235 Hz), 142.4 (d, J¼2.0 Hz), 116.0 (d, J¼30 Hz), 115.8 (d, J¼45 Hz). ESI MS m/z 111 [Mþ]. These spectroscopic data are in agreement with known literature values.26 4.4.5. 1-(4-Aminophenyl)ethanone (5d). Following the general procedure and purification by flash column chromatography (hexanes/EtOAc¼1/1), the product was obtained in 99% (134 mg, Method A) and 97% (131 mg, Method B) yields from iodide. From bromide, the product was obtained in 96% (130 mg, Method A and B, respectively) yield. Rf (hexanes/EtOAc¼1/1) 0.50; 1H NMR (400 MHz, CDCl3) d 7.82 (d, J¼8.6 Hz, 2H), 6.66 (d, J¼8.8 Hz, 2H), 4.10 (br s, 2H), 2.52 (s, 3H); 13C NMR (100 MHz, CDCl3) d 193.6, 151.3, 130.8, 127.7, 113.7, 25.9. ESI MS m/z 135 [Mþ]. These spectroscopic data are in agreement with known literature values.26 4.4.6. 4-Nitroaniline (5e). Following the general procedure and purification by flash column chromatography (hexanes/EtOAc¼3/ 1), the product was obtained in 91% (126 mg, Method A) yield from iodide. From bromide, the product was obtained in 93% (129 mg, Method A) yield. Rf (hexanes/EtOAc¼3/1) 0.14; 1H NMR (400 MHz, CDCl3) d 8.09 (d, J¼9.0 Hz, 2H), 6.63 (d, J¼9.0 Hz, 2H), 4.35 (br s, 2H); 13 C NMR (100 MHz, CDCl3) d 152.5, 139.2, 126.4, 113.4. ESI MS m/z 138 [Mþ]. These spectroscopic data are in agreement with known literature values.31a 4.4.7. 4-Aminobenzonitrile (5f). Following the general procedure and purification by flash column chromatography (hexanes/ EtOAc¼3/1), the product was obtained in 97% (115 mg, Method A) yield from bromide. Rf (hexanes/EtOAc¼3/1) 0.17; 1H NMR (400 MHz, CDCl3) d 7.43 (d, J¼8.6 Hz, 2H), 6.66 (d, J¼9.0 Hz, 2H), 4.14 (br s, 2H); 13C NMR (100 MHz, CDCl3) d 150.6, 133.8, 120.2, 114.4, 100.0. ESI MS m/z 118 [Mþ]. These spectroscopic data are in agreement with known literature values.29 4.4.8. 1-(2-Aminophenyl)ethanone (5g). Following the general procedure and purification by flash column chromatography (hexanes/EtOAc¼3/1), the product was obtained in 84% (114 mg, Method A) and 85% (115 mg, Method B) yields from iodide. From bromide, the product was obtained in 84% (114 mg, Method A) and 83% (112 mg, Method B) yields. Rf (hexanes/EtOAc¼3/1) 0.46; 1H NMR (400 MHz, CDCl3) d 7.73 (d, J¼8.3 Hz, 1H), 7.27 (t, J¼8.4 Hz, 1H), 6.67e6.64 (m, 2H), 6.28 (br s, 2H), 2.59 (s, 3H); 13C NMR (100 MHz, CDCl3) d 200.9, 150.3, 134.4, 132.1, 118.3, 117.2, 115.8, 27.8. ESI MS m/z

5992

H.S. Jung et al. / Tetrahedron 72 (2016) 5988e5993

135 [Mþ]. These spectroscopic data are in agreement with known literature values.24 4.4.9. 2-Nitroaniline (5h). Following the general procedure and purification by flash column chromatography (hexanes/EtOAc¼3/ 1), the product was obtained in 82% (113 mg, Method A) yield from iodide. From bromide, the product was obtained in 95% (131 mg, Method A) and 92% (127 mg, Method B) yields. Rf (hexanes/ EtOAc¼3/1) 0.17; 1H NMR (400 MHz, CDCl3) d 8.13 (d, J¼8.8 Hz, 1H), 7.37 (t, J¼8.5 Hz, 1H), 6.81 (d, J¼8.3 Hz, 1H), 6.72 (t, J¼8.6 Hz, 1H), 6.06 (br s, 2H); 13C NMR (100 MHz, CDCl3) d 144.7, 135.7, 132.3, 126.3, 118.8, 117.0. ESI MS m/z 138 [Mþ]. These spectroscopic data are in agreement with known literature values.31a 4.4.10. 1,2-Benzenediamine (5i). Following the general procedure and purification by flash column chromatography (hexanes/ EtOAc¼1/2), the product was obtained in 92% (99 mg, Method A) and 83% (90 mg, Method B) yields from iodide. From bromide, the product was obtained in 92% (99 mg, Method A) and 94% (102 mg, Method B) yields. Rf (hexanes/EtOAc¼1/2) 0.32; 1H NMR (400 MHz, CDCl3) d 6.76e6.70 (m, 4H), 3.39 (br s, 4H); 13C NMR (100 MHz, CDCl3) d 134.8, 120.3, 116.8. ESI MS m/z 108 [Mþ]. These spectroscopic data are in agreement with known literature values.32 4.4.11. N,N-Dimethyl-1,4-benzenediamine (5j). Following the general procedure and purification by flash column chromatography (EtOAc), the product was obtained in 92% (125 mg, Method A) and 95% (130 mg, Method B) yields from bromide. Rf (EtOAc) 0.45; 1H NMR (400 MHz, CDCl3) d 6.71 (d, J¼8.5 Hz, 2H), 6.67 (d, J¼9.0 Hz, 2H), 3.36 (br s, 2H), 2.83 (s, 6H); 13C NMR (100 MHz, CDCl3) d 144.9, 137.9, 116.6, 115.6, 42.0. ESI MS m/z 136 [Mþ]. These spectroscopic data are in agreement with known literature values.31a 4.4.12. 3,4-(Methylenedioxy)aniline (5k). Following the general procedure and purification by flash column chromatography (hexanes/EtOAc¼4/1), the product was obtained in 90% (123 mg, Method A) and 98% (134 mg, Method B) yields from bromide. Rf (hexanes/EtOAc¼4/1) 0.25; 1H NMR (400 MHz, CDCl3) d 6.63 (d, J¼8.3 Hz, 1H), 6.29 (s, 1H), 6.15 (d, J¼8.2 Hz, 1H), 5.87 (s, 2H), 3.47 (br s, 2H); 13C NMR (100 MHz, CDCl3) d 148.2, 141.4, 140.3, 108.5, 106.8, 100.6, 98.0. ESI MS m/z 137 [Mþ]. These spectroscopic data are in agreement with known literature values.31a 4.4.13. 2-Naphthalenamine (5l). Following the general procedure and purification by flash column chromatography (hexanes/ EtOAc¼5/1), the product was obtained in 91% (130 mg, Method B) yield from iodide. From bromide, the product was obtained in 89% (127 mg, Method A and B, respectively) yield. Rf (hexanes/ EtOAc¼5/1) 0.23; 1H NMR (400 MHz, CDCl3) d 7.70 (d, J¼8.0 Hz, 1H), 7.67 (d, J¼8.5 Hz, 1H), 7.60 (d, J¼8.3 Hz, 1H), 7.39e7.35 (m, 1H), 7.25e7.21 (m, 1H), 7.00 (s, 1H), 6.96 (dd, J¼8.5 Hz, 2.5 Hz, 1H), 3.87 (br s, 2H); 13C NMR (100 MHz, CDCl3) d 144.2, 134.9, 129.3, 128.0, 127.8, 126.4, 125.8, 122.5, 118.3, 108.6. ESI MS m/z 143 [Mþ]. These spectroscopic data are in agreement with known literature values.29

Acknowledgements We are grateful for support by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2010-0027963) and a research grant of Kwangwoon University in 2014 for this work.

Supplementary data Supplementary data (1H and 13C NMR spectra) associated with this article can be found, in the online version, at http://dx.doi.org/ 10.1016/j.tet.2016.07.021. References and notes 1. (a) Lawrence, S. A. Amines: Synthesis, Properties and Applications; Cambridge University Press: Cambridge, 2004; (b) Arpe, H.-J. Industrial Organic Chemistry; Wiley-VCH: Weinheim, 2003; (c) Roundhill, D. M. Chem. Rev. 1992, 92, 1. 2. Larock, R. C. In Comprehensive Organic Transformations, 2nd ed.; Wiley-VCH: New York, 1999; p 823. 3. (a) Hartwig, J. F.; Shekhar, S.; Shen, Q.; Barrios-Landeros, F. In Patai’s Chemistry of Functional Groups; Wiley & Sons: New York, 2009; (b) Downing, R. S.; Kunkeler, P. J.; van Bekkum, H. Catal. Today 1997, 37, 121. 4. (a) Xie, C.; Zhang, Y. Org. Lett. 2007, 9, 781; (b) Peelissier, H.; Santelli, M. Tetrahedron 2003, 59, 701; (c) Wenk, H. H.; Winkler, M.; Sander, W. Angew. Chem., Int. Ed. 2003, 42, 502. 5. Enthaler, S. ChemSusChem 2010, 3, 1024. 6. 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