HETEROCYCLES

Paper | Special issue | Vol. 86, No. 1, 2012, pp. 255-266
Received, 19th March, 2012, Accepted, 26th April, 2012, Published online, 8th May, 2012.
DOI: 10.3987/COM-12-S(N)6

■ C-H Arylation of 3-Substituted Thiophene with Regioselective Deprotonation by TMPMgCl·LiCl and Transition Metal Catalyzed Cross Coupling

Shota Tanaka, Shunsuke Tamba, Atsushi Sugie, and Atsunori Mori*

Department of Chemical Science and Engineering, Faculty of Engineering, Kobe University, Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan

Abstract

The reaction of 3-hexylthiophene with Knochel-Hauser base (TMPMgCl⋅LiCl) induced the metalation at the 5-position of the thiophene ring selectively. Following addition of several aryl halides in the presence of a nickel or palladium catalyst afforded regioselectively arylated thiophene in good to excellent yields.

INTRODUCTION
C−H functionalization of heteroaromatic compounds recently attracts much attention1,2 since a variety of organic compounds bearing heteroaromatic moiety in the structure are found in a wide range of advanced organic materials3 as well as biologically active molecules.4 Therefore, development of a practical synthetic strategy for such molecules is an important issue in organic synthesis. We have been engaged in the development of synthetic methodologies to afford functionalized heteroaromotics via transition metal catalyzed C−H functionalization.5 Several functionalization reactions, which take place at a carbon atom of an electron-deficient6 and enriched7 C−H bond have been achieved. Accordingly, the selective functionalization based on the electronic characteristics of the C−H bond of heteroaromatic compounds becomes indeed plausible. By contrast, selection of an electronically similar C−H bond based on stereochemical differentiation has not been extensively studied so far and thus controlled functionalization of such C−H bond is intriguing. We have recently found the reaction of 3-hexylthiophene in the presence of Knochel-Hauser base TMPMgCl·LiCl8 (TMP = 2,2,6,6-tetramethylpiperidine) induces the metalation at room temperature for 3 h at the 5-position selectively. And we have shown novel synthetic methodology leading to head-to-tail-type oligothiophene with regioselective metalation of 3-substituted thiophene and nickel-catalyzed cross coupling of halothiophenes.9 (Scheme 1). We envisaged that such a regioselective metalating system of 3-substituted thiophenes is also effective not only for the coupling to form thiophene‒thiophene bond but also for the reaction with various aryl halides. Herein, we describe regiocontrolled C−H arylation of several 3-substituted thiophene derivatives that occurs at the less hindered position selectively with TMPMgCl·LiCl.

RESULTS AND DISCUSSION
We first studied the reaction of 3-hexylthiophene (1a) that possessed two possible C−H bonds at the 2- and 5- positions with aryl halides under several conditions. The reaction with tBuOLi as a base10 in the presence of 4-methyl-1-bromobenzene (2a) and 2.0 mol% of a palladium catalyst resulted to afford a mixture of 5-Aryl (27%), 2-Aryl (9%) and 2,5-diaryl (20%) suggesting that uncontrollable metalation occurred at both 2- and 5-positions. The use of a catalytic amount of PdCl2(PPh3)2 (2.0 mol%) and AgNO3/KF7c resulted in giving a mixture of 5-Aryl (21%), 2-Aryl (8%) and 2,5-diarylated product (24%). The similar trend was observed in the arylation with K2CO3/tBuCOONa.4d By contrast, the perfect selectivity was achieved when TMPMgCl⋅LiCl was employed as a base, to afford 5-arylated product in 91% yield. The use of diisopropyl amide (iPr2NMgCl·LiCl) instead of TMPMgCl·LiCl decreased the selectivity and the reactivity. These results are summarized in Table 1.
The arylation reaction with several 3-substituted thiophenes is then examined to study the selectivity of the C−H bond as summarized in Table 2. The reaction of 4-methoxy-1-bromobenzene (2b) with 3-methylthiophene (1b), and 3-fluoroalkylated thiophene 1c, 3-arylated thiophene 1d also occurred regioselectively at the 5-position. By contrast, the reaction of 3-methoxythiophene (1f) resulted to

afford 2-arylated product predominantly probably due to the directing effect of the methoxy group in the reaction of magnesium amide.11 Less selective metalation was found to occur with an alkynyl group-substituted thiophene 1e. Although the metalation reaction of 3-bromothiophene (1g) and N,N-diethyl-3-thiophenecarboxamide (1h) with TMPMgCl·LiCl proceeded smoothly in non-selective (40:60) and 2-selective (0/100) manners, respectively, following coupling with aryl halide in the presence of a palladium catalyst resulted in no arylation.

Our further concern is the scope of the regioselective C−H arylation of 3-hexylthiophene (1a) with several aryl bromides. Results are summarized in Table 3. The reaction of 1a with 4-methyl-1-bromobenzene (2a) was found to take place at room temperature to afford 3aa in excellent yield when a palladium catalyst with NHC ligand PEPPSI-IPr12 was employed. On the other hand, the use of a palladium catalyst with bulky phosphine ligand Pd(PtBu3)2 resulted in poor yield (20%). The reaction with 2.0 mol% of nickel catalyst of bidentate diphosphine NiCl2(dppf) at room temperature for 20 h proceeded smoothly to give 3aa in 81% yield. The reaction with NiCl2(dppe) also gave 3aa in a reasonable yield (63%), whereas other nickel catalyst, NiCl2(PCy3)2 and NiCl2(dppb) was found to be ineffective. The use of Ni(cod)2/2SIPr, which showed excellent performance in the reaction of 1a with 2-bromo-3-hexylthiophene,8 resulted in poor yield (7%). Various aryl bromides bearing an electron-withdrawing or donating substituent (2b-2e) reacted with 1a to afford the coupling products in good to excellent yields. Although the reaction with ethyl 4-bromobenzoate (2f) proceeded, the yield was slightly inferior (35%).

It is also remarkable that the reaction with aryl chlorides proceeded under similar conditions. The reaction of 1a with 4-methyl-1-chlorobenzene (4a) took place at room temperature for 20 h with NiCl2(dppf) to afford 3aa in 82% yield. As shown in Table 4, several aryl chlorides such as 4b, 4c and 4e reacted smoothly with 1a to afford the corresponding coupling products in good to excellent yields. The reaction of 1a with 2-chlorobenzothiazole (4g) in the presence of PEPPSI-IPr proceeded to give 3ag in 83%.

By employing the selective 5-arylation method of thiophene it is possible to undergo concise synthesis of differently-substituted 2,5-diarylthiophene derivatives as illustrated in Scheme 2. The reaction at the sterically-hindered position was found to be operative when tBuOLi was used as an additive in the presence of a palladium catalyst, Pd(PtBu3)2.10a The reaction of 3aa with 4-methoxy-1-bromobenzene (2b) also afforded the corresponding 2,5-diarylated thiophene 3aab in 70% yield. When AgNO3/KF was employed as additives,7c the reaction of 3aa with ethyl 4-iodobenzoate in the presence of 2.0 mol% of PdCl2(PPh3)2 also proceeded at the 2-position to afford 3aaf in 45% yield.

CONCLUSION
In summary, we have shown that regioselective C−H arylation of 3-substituted thiophene derivatives is achieved with TMPMgCl·LiCl, in which selective reaction takes place at the less hindered C−H bond. Accordingly, it was revealed that the regiocontrolled C−H functionalization with TMPMgCl·LiCl is not only effective for the formation of thiophene‒thiophene bond but also for the arylation reaction of 3-substituted thiophene with aryl bromides and chlorides. Since the reaction proceeds under mild conditions, the method is potentially practical for syntheses of regioselectively arylated thiophenes.

EXPERIMENTAL
General. All the reactions were carried out under nitrogen atmosphere. 1H NMR (300 MHz) and 13C NMR (75 MHz) spectra were measured on Varian Gemini 300 as a CDCl3 solution unless noted. The chemical shifts were expressed in ppm with CHCl3 (7.26 ppm for 1H) or CDCl3 (77.0 ppm for 13C) as internal standards. IR spectra were recorded on Bruker Alpha with an ATR attachment (Ge). High resolution mass spectra (HRMS) were measured by JEOL JMS-T100LP AccuTOF LC-Plus (ESI) with a JEOL MS-5414DART attachment or JEOL JMS-700 MStation (EI) at the Graduate School of Material Science, Nara Institute of Science and Technology. For thin layer chromatoraphy (TLC) analyses throughout this work, Merck precoated TLC plates (silica gel 60 F254) were used. Purification by HPLC with preparative SEC column (JAI-GEL-2H) was performed by JAI LC-9201. Gas chromatography analyses were carried out with SHIMADZU GCMS-QP2010 Plus. TMPMgCl·LiCl was prepared by following the literature procedure13 and stored in the freezer as 1.0 M THF solution. Nickel catalysts, NiCl2(dppe), NiCl2(dppp), NiCl2(dppb), NiCl2(dppf), and NiCl2(PCy3)2 were prepared according to the literature procedures.14 Other chemicals were purchased and used without further purification.

General procedure for the reaction of 3-hexylthiophene (1a) with aryl bromide in the presence of Knochel-Hauser base: To 25 mL Schlenk tube equipped with a magnetic stirring bar was added TMPMgCl·LiCl (0.60 mmol, 1.0 M in THF) at room temperature. To the resulting mixture 3-hexylthiophene (1a, 0.099 mL, 0.50 mmol) was added and stirring was continued for 3 h. Then, THF (1.4 mL), 4-methyl-1-bromobenzene (0.074 mL, 0.60 mmol) and PEPPSI-IPr (6.79 mg, 0.01 mmol) were added successively. The mixture was stirred at room temperature for 20 h and quenched by hydrochloric acid (1.0 M, 1.0 mL). The solution was poured into the mixture of Et2O/water and two phases were separated. The aqueous phase was extracted with Et2O twice and the combined organic phase was dried over anhydrous sodium sulfate. Removal of the solvent left a crude oil, which was purified by chromatography on silica gel using hexanes as an eluent to afford 117.2 mg of 5-(4-methyphenyl)-3-hexylthiophene (3aa, colorless oil, 91%): 1H NMR δ 0.90 (t, J = 6.6 Hz, 3H), 1.23-1.44 (m, 6H), 1.58-1.73 (m, 2H), 2.36 (s, 3H), 2.61 (t, J = 7.7 Hz, 2H) , 6.83 (d, J = 1.3 Hz, 1H), 7.11 (d, J = 1.3 Hz, 1H), 7.17 (d, J = 8.2 Hz, 2H), 7.49 (d, J = 8.2 Hz, 2H); 13C NMR δ 14.1, 21.1, 22.6, 29.0, 30.4, 30.6, 31.7, 118.9, 124.0, 125.6 (×2), 129.4 (×2), 131.9, 137.1, 144.1, 144.2; IR (ATR) 2955, 2926, 2856, 1511, 1465, 1458, 812, 729, 649, 639 cm-1; HRMS (EI+) Calcd for C17H22S [M]+: 258.1442; found: m/z 258.1439.

5-(4-Methoxyphenyl)-3-methylthiophene (3bb, colorless solid, 87%): 1H NMR δ 2.28 (s, 3H), 3.83 (s, 3H), 6.80 (s, 1H), 6.91 (d, J = 8.8 Hz, 2H), 7.02 (s, 1H), 7.52 (d, J = 8.8 Hz, 2H); 13C NMR δ 15.8, 55.3, 114.2 (×2), 119.1, 124.5, 127.0 (×2), 127.5, 138.5, 144.0, 159.1; IR (ATR) 3004, 2960, 2934, 2836, 1606, 1510, 1289, 1248, 1184, 1031, 826, 810, 746, 734, 707 cm-1; HRMS (EI+) Calcd for C12H12OS [M]+: 204.0609; found: m/z 204.0609.

5-(4-Methoxyphenyl)-3-(4,4,5,5,6,6,7,7,7-nonafluoroheptan-1-yl)thiophene (3cb, colorless oil, 64%): 1H NMR δ 1.89-2.06 (m, 2H), 2.07-2.23 (m, 2H), 2.72 (t, J = 7.3 Hz, 2H), 3.84 (s, 3H), 6.84 (d, J = 1.1 Hz, 1H), 6.91 (d, J = 8.8 Hz, 2H), 7.03 (d, J = 1.1 Hz, 1H), 7.51 (d, J = 8.8 Hz, 2H); 13C NMR δ 20.9 (t, JC-F = 3.7 Hz), 29.7, 30.2 (t, JC-F = 22 Hz), 55.2, 114.2 (×2), 119.2, 122.8, 127.0 (×2), 127.2, 141.7, 144.7, 159.2; IR (ATR) 1513, 1357, 1295, 1274, 1253, 1216, 1181, 1170, 1132, 1091, 1031, 1009, 878, 867, 851, 824, 741, 723, 709, 649, 604 cm-1; HRMS (DART-ESI+) Calcd for C18H16F9OS [M+H]+: 451.0778; found: m/z 451.0781.

3-(4-Methoxyphenyl)-5-(4-methylphenyl)thiophene (3da): 56% yield. 1H NMR δ 2.38 (s, 3H), 3.85 (s, 3H), 6.95 (d, J = 8.8 Hz, 2H), 7.21 (d, J = 8.0 Hz, 2H), 7.25 (d, J = 1.4 Hz, 1H), 7.50 (d, J = 1.4 Hz, 1H), 7.54 (d, J = 8.0 Hz, 2H), 7.56 (d, J = 8.8 Hz, 2H); 13C NMR δ 21.2, 55.3, 114.2 (×2), 117.9, 121.8, 125.7 (×2), 127.4 (×2), 128.8, 129.6 (×2), 131.6, 137.5, 142.7, 145.0, 158.9; IR (ATR) 1500, 1295, 1254, 1183, 1029, 830, 812, 751 cm-1; HRMS (EI+) Calcd for C18H16OS [M]+: 280.0922; found: m/z 280.0922.

3-Methoxy-2-(4-methoxyphenyl)thiophene (3fb, brown oil, 51 mg, 45%). 1H NMR δ 3.83 (s, 3H), 3.90 (s, 3H), 6.92 (d, J = 5.5 Hz, 1H), 6.92 (d, J = 8.8 Hz, 2H), 7.10 (d, J = 5.5 Hz, 1H), 7.66 (d, J = 8.8 Hz, 2H); 13C NMR δ 55.3, 58.7, 114.0 (×2), 117.5, 121.1, 126.1, 126.7, 128.2 (×2), 152.8, 158.2; IR (ATR) 2956, 2936, 2847, 2836, 1609, 1549, 1510, 1462, 1378, 1291, 1266, 1246, 1180, 1098, 1070, 1035, 926, 830, 795, 707, 643 cm-1; HRMS (EI+) Calcd for C12H12O2S [M]+: 220.0558; found: m/z 220.0561.

The reaction of 3-(1-octyn-1-yl)thiophene (1e) with aryl bromide in the presence of Knochel-Hauser base: The reaction was carried out in a similar manner to that of 1a with aryl bromide in the presence of Knochel-Hauser base with 3-(1-octyn-1-yl)thiophene (1e, 96.2 mg, 0.50 mmol), TMPMgCl·LiCl (0.60 mmol, 1.0 M in THF), 4-bromoanisole (2b, 0.075 mL, 0.60 mmol) and PEPPSI-IPr (6.79 mg, 0.01 mmol) at room temperature for 21 h to afford the mixture of 2-arylated and 5-arylated products. The ratio of 2-Ar/5-Ar was determined to be 35:65 by 1H NMR analysis.

5-(4-Methoxyphenyl)-3-hexylthiophene (3ab): 1H NMR δ 0.90 (t, J = 6.6 Hz, 3H), 1.24-1.43 (m, 6H), 1.57-1.71 (m, 2H), 1.86-2.20 (4H, m), 2.60 (t, J = 7.7 Hz, 2H), 3.83 (s, 3H), 6.80 (d, J = 1.1 Hz, 1H), 6.90 (d, J = 8.8 Hz, 2H), 7.04 (d, J = 1.4 Hz, 1H), 7.51 (d, J = 8.8 Hz, 2H); 13C NMR δ 14.1, 22.6, 29.0, 30.4, 30.6, 31.7, 55.3, 114.2 (×2), 118.4, 123.5, 127.0 (×2), 127.6, 143.8, 144.2, 159.0; IR (ATR) 2956, 2926, 2851, 1608, 1511, 1296, 1255, 1181, 1032, 824, 712, 649 cm-1; HRMS (EI+) Calcd for C17H22OS [M]+: 274.1391; found: m/z 274.1389.

5-Phenyl-3-hexylthiophene (3ac): 1H NMR δ 0.79 (t, J = 6.9 Hz, 3H), 1.19-1.46 (m, 6H), 1.57-1.72 (m, 2H), 1.86-2.20 (4H, m), 2.61 (t, J = 7.7 Hz, 2H), 2.85 (t, J = 7.5 Hz, 2H), 6.86 (d, J = 1.1 Hz, 1H), 7.15 (d, J = 1.4 Hz, 1H), 7.26 (ddd, J = 8.0, 6.6, 1.4 Hz, 1H), 7.36 (td, J = 6.6, 1.4 Hz, 1H), 7.59 (dd, J = 8.0, 1.4 Hz, 1H); 13C NMR δ 14.1, 22.6, 29.0, 30.4, 30.6, 31.7, 119.4, 124.5, 125.7 (×2), 127.2, 128.8 (×2), 134.7, 143.9, 144.2; IR (ATR) 2955, 2926, 2854, 1496, 1453, 837, 758, 715, 690 cm-1; HRMS (EI+) Calcd for C16H20S [M]+: 244.1286; found: m/z 244.1283.

5-(4-Fluorophenyl)-3-hexylthiophene (3ad): 1H NMR δ 0.93 (t, J = 6.6 Hz, 3H), 1.23-1.49 (m, 6H), 1.59-1.75 (m, 2H), 2.63 (t, J = 7.7 Hz, 2H), 6.87 (d, J = 1.1 Hz, 1H), 7.07 (dd, J = 8.8 Hz, JH-F = 8.8 Hz, 2H), 7.10 (s, 1H), 7.56 (dd, J = 8.8 Hz, JH-F = 5.2 Hz, 2H); 13C NMR δ 14.1, 22.6, 29.0, 30.4, 30.6, 31.7, 115.7 (×2, d, JC-F = 21.8 Hz), 119.4, 127.2 (×2, d, JC-F = 8.0 Hz), 130.9 (d, JC-F = 3.4 Hz), 142.8, 144.3, 162.2 (d, JC-F = 247 Hz); IR (ATR) 2955, 2927, 2856, 1509, 1465, 1232, 1159, 1095, 826, 810, 734 cm-1; HRMS (EI+) Calcd for C16H19FS [M]+: 262.1191; found: m/z 262.1193.

5-(4-Trifluoromethylphenyl)-3-hexylthiophene (3ae): 1H NMR δ 0.90 (t, J = 6.9 Hz, 3H), 1.21-1.45 (m, 6H), 1.58-1.72 (m, 2H), 2.62 (t, J = 7.6 Hz, 2H), 6.95 (d, J = 1.1 Hz, 1H), 7.23 (d, J = 1.1 Hz, 1H), 7.60 (d, J = 8.5 Hz, 2H), 7.68 (d, J = 8.5 Hz, 2H); 13C NMR δ 14.1, 22.6, 29.0, 30.4, 30.6, 31.7, 120.9, 125.7, 125.8, 129.0 (q, JC-F = 33 Hz), 129.4, 138.0, 142.1, 144.6; IR (ATR) 2956, 2927, 2857, 1615, 1324, 1166, 1124, 1068, 1017, 831 cm-1; HRMS (EI+) Calcd for C17H19F3S [M]+: 312.1160; found: m/z 312.1160.

Ethyl 4-(3-hexylthiophen-2-yl)benzoate (3af): 1H NMR δ 0.90 (t, J = 6.6 Hz, 3H), 1.41 (t, J = 7.1 Hz, 3H), 1.24-1.38 (m, 6H), 1.54-1.71 (m, 2H), 2.62 (t, J = 7.7 Hz, 2H), 4.39 (q, J = 7.1 Hz, 2H), 6.94 (s, 1H), 7.26 (s, 1H), 7.64 (d, J = 8.5 Hz, 2H), 8.03 (d, J = 8.5 Hz, 2H); 13C NMR δ 14.0, 14.3, 22.5, 28.9, 30.4, 30.5, 31.6, 60.9, 120.9, 125.2 (×2), 125.8, 128.9, 130.1 (×2), 138.8, 142.6, 144.6, 166.3; IR (ATR) 2953, 2925, 2856, 1707, 1606, 1274, 1181, 1107, 770, 695 cm-1; HRMS (DART-ESI+) Calcd for C19H25O2S [M+H]+: 317.1575; found: m/z 317.1575.

5-(Benzothiazole-2-yl)-3-hexylthiophene (3ag): 1H NMR δ 0.90 (t, J = 6.7 Hz, 3H), 1.20-1.47 (m, 6H), 1.59-1.77 (m, 2H), 2.64 (t, J = 7.7 Hz, 2H), 7.10 (d, J = 1.3 Hz, 1H), 7.32-7.40 (m, 1H), 7.43-7.50 (m, 1H), 7.50 (d, J = 1.3 Hz, 1H), 7.81-7.89 (m, 1H), 7.98-8.05 (m, 1H); 13C NMR δ 14.0, 22.5, 28.9, 30.28, 30.33, 31.6, 121.3, 122.8, 124.1, 125.0, 126.3, 129.7, 134.6, 136.7, 144.3, 153.7, 161.6; IR (ATR) 2956, 2923, 2856, 1502, 1466, 1456, 1437, 1429, 1312, 1256, 1217, 1192, 1131, 1016, 901, 865, 832, 823, 793, 754, 727, 705, 672 cm-1; HRMS (DART-ESI+) Calcd for C17H20NS2 [M+H]+: 302.1037; found: m/z 302.1038.

2-(4-Methoxyphenyl)-5-(4-methylphenyl)-3-hexylthiophene (3aab)10a: The reaction was carried out in a manner described previously with 5-(4-methyphenyl)-3-hexylthiophene (3aa, 129.2 mg, 0.50 mmol), 4-methoxy-l-bromobenzene (0.075 mL, 0.60 mmol), LiOtBu (1.5 mmol) in 1.0 mL of DMF at 100 ºC for 20 h to afford 128.5 mg of 3aab as a colorless oil (70%). 1H NMR δ 0.87 (t, J = 6.7 Hz, 3H), 1.17-1.41 (m, 6H), 1.56-1.73 (m, 2H), 2.36 (s, 3H), 2.62 (t, J = 7.8 Hz, 2H), 3.85 (s, 3H), 6.95 (d, J = 8.8 Hz, 2H), 7.14 (s, 1H), 7.18 (d, J = 8.8 Hz, 2H), 7.39 (d, J = 8.8 Hz, 2H), 7.50 (d, J = 8.8 Hz, 2H); 13C NMR δ 14.1, 21.1, 22.6, 28.8, 29.2, 30.9, 31.6, 55.2, 113.9 (×2), 125.0, 125.4 (×2), 127.2, 129.5 (×2), 130.4 (×2), 131.8, 136.7, 137.0, 139.0, 141.6, 158.9; IR (ATR) 2955, 2927, 2857, 1608, 1504, 1462, 1441, 1289, 1248, 1177, 1037, 1111, 908, 830, 812, 793, 757, 735, 669, 622 cm-1; HRMS (ESI+) Calcd for C24H29OS [M+H]+: 365.1939; found: m/z 365.1939.

2-(4-Ethoxycarbonylphenyl)-5-(4-methylphenyl)-3-hexylthiophene (3aaf)7c: The reaction was carried out in a manner described previously with 5-(4-methyphenyl)-3-hexylthiophene (3aa, 129.2 mg, 0.50 mmol), 4-iodobenzoate (0.100 mL, 0.60 mmol), AgNO3 (212.5 mg, 1.25 mmol), KF (72.6 mg, 1.25 mmol) in 3.0 mL of DMSO at 100 ºC for 27 h to afford 3aaf as a colorless oil (45%). 1H NMR δ 0.86 (t, J = 6.7 Hz, 3H), 1.15-1.37 (m, 6H), 1.41 (t, J = 7.1 Hz, 3H), 1.59-1.73 (m, 2H), 2.37 (s, 3H), 2.68 (t, J = 7.9 Hz, 2H), 3.85 (q, J = 7.1 Hz, 2H), 7.18 (s, 1H), 7.19 (d, J = 8.3 Hz, 2H), 7.51 (d, J = 8.3 Hz, 2H), 7.53 (d, J = 8.3 Hz, 2H), 8.09 (d, J = 8.3 Hz, 2H); 13C NMR δ 14.0, 14.4, 21.2, 22.6, 29.1, 29.2, 30.9, 31.6, 61.0, 125.49, 125.52 (×2), 128.8 (×2), 128.9, 129.6 (×2), 129.8 (×2), 131.4, 135.5, 137.5, 139.4, 140.7, 143.4, 166.4; IR (ATR) 2954, 2925, 2856, 1716, 1605, 1503, 1457, 1405, 1366, 1308, 1271, 1178, 1104, 1021, 854, 812, 771, 721, 701 cm-1; HRMS (DART-ESI+) Calcd for C24H31O2S [M+H]+: 407.2045; found: m/z 407.2040.

ACKNOWLEDGEMENTS
This work was partially supported by KAKENHI (21655051) for Challenging Exploratory Research by Japan Society for the Promotion of Science (JSPS). The authors thank Nara Insititute of Science and Technology for measurements of high-resolution mass spectra.

References

1. F. Diederich and P. J. Stang, Eds. Metal-Catalyzed Cross-Coupling Reaction; Wiley-VCH: Weinheim, 1998. CrossRef
2. Reviews on C–H functionalization of heteroaromatic compounds: a) L.-C. Campeau and K. Fagnou, Chem. Commun., 2006, 1253; CrossRef b) L. Ackermann, R. Vicente, and A. R. Kapdi, Angew. Chem. Int. Ed., 2009, 48, 9792; CrossRef c) G. P. McGlacken and L. M. Bateman, Chem. Soc. Rev., 2009, 38, 2447; CrossRef d) D. Alberico, M. E. Scott, and M. Lautens, Chem. Rev., 2007, 107, 174; CrossRef e) I. V. Seregin and V. Gevorgyan, Chem. Soc. Rev., 2007, 36, 1173; CrossRef f) S. H. Cho, J. Y. Kim, J. Kwak, and S. Chang, Chem. Soc. Rev., 2011, 40, 5068; CrossRef g) O. Daugulis and H.-Q. Do, D. Shabashov, Acc. Chem. Res., 2009, 42, 1074; CrossRef h) T. Satoh and M. Miura, Chem. Lett., 2007, 36, 200; CrossRef i) D. Lapointe and K. Fagnou, Chem. Lett., 2010, 39, 1118. CrossRef
3. a) I. Osaka and R. D. McCullough, Acc. Chem. Res., 2008, 41, 1202; CrossRef b) K. Takimiya, S. Shinamura, I. Osaka, and E. Miyazaki, Adv. Mater., 2011, 23, 4347; CrossRef c) A. Pron, P. Gawrys, M. Zagorska, D. Djurado, and R. Demadrille, Chem. Soc. Rev., 2010, 39, 2577; CrossRef d) D. J. Schipper and K. Fagnou, Chem. Mater., 2011, 23, 1594. CrossRef
4. a) L. McMurray, F. O’Hara, and M. J. Gaunt, Chem. Soc. Rev., 2011, 40, 1885; CrossRef b) K. C. Nicolaou, J. S. Chen, D. J. Edmonds, and A. A. Estrada, Angew. Chem. Int. Ed., 2009, 48, 660; CrossRef c) K. C. Nicolaou, P. G. Bulger, and D. Sarlah, Angew. Chem. Int. Ed., 2005, 44, 4442; CrossRef d) B. Liégault, I. Petrov, S. I. Gorelsky, and K. Fagnou, J. Org. Chem., 2010, 75, 1047. CrossRef
5. a) A. Sugie and A. Mori, Bull. Chem. Soc. Jpn., 2008, 81, 548; CrossRef b) A. Mori, J. Synth. Org. Chem. Jpn., 2011, 69, 1202. CrossRef
6. a) A. Mori, A. Sekiguchi, K. Masui, T. Shimada, M. Horie, K. Osakada, M. Kawamoto, and T. Ikeda J. Am. Chem. Soc., 2003, 125, 1700; CrossRef b) T. Miyaoku and A. Mori, Heterocycles, 2009, 77, 151. CrossRef
7. a) K. Masui, A. Mori, K. Okano, K. Takamura, M. Kinoshita, and T. Ikeda, Org. Lett., 2004, 6, 201; CrossRef b) K. Masui, H. Ikegami, and A. Mori, J. Am. Chem. Soc., 2004, 126, 5074; CrossRef c) K. Kobayashi, A. Sugie, M. Takahashi, K. Masui, and A. Mori, Org. Lett., 2005, 7, 5083; CrossRef d) M. Takahashi, K. Masui, H. Sekiguchi, N. Kobayashi, A. Mori, M. Funahashi, and N. Tamaoki, J. Am. Chem. Soc., 2006, 128, 10930. CrossRef
8. a) B. Haag, M. Mosrin, H. Ila, V. Malakhov, and P. Knochel, Angew. Chem. Int. Ed., 2011, 50, 9794; CrossRef b) A. Krasovskiy, V. Krasovskaya, and P. Knochel, Angew. Chem. Int. Ed., 2006, 45, 2958; CrossRef c) C. R. Hauser and F. C. Frostick, J. Am. Chem. Soc., 1949, 71, 1350. CrossRef
9. S. Tanaka, S. Tamba, D. Tanaka, A. Sugie, and A. Mori, J. Am. Chem. Soc., 2011, 133, 16734. CrossRef
10. a) S. Tamba, Y. Okubo, S. Tanaka, D. Monguchi, and A. Mori, J. Org. Chem., 2010, 75, 6998; CrossRef b) H.-Q. Do, R. M. Kashif Khan, and O. Daugulis, J. Am. Chem. Soc., 2008, 130, 15185. CrossRef
11. N. Boudet and P. Knochel, Org. Lett., 2006, 8, 3737. CrossRef
12. PEPPSITM stands for pyridine-enhanced precatalyst preparation stabilization and initiation. See: C. J. O’ Brien, E. A. B. Kantchev, C.Valente, N. Hadei, G. A. Chass, A. Lough, A. C. Hopkinson, and M. G. Organ, Chem.-Eur. J., 2006, 12, 4743. CrossRef
13. H.-Q. Do and O. Daugulis, J. Am. Chem. Soc., 2009, 131, 17052. CrossRef
14. G. Booth and J. Chatt, J. Chem. Soc., 1965, 3238. CrossRef