Poly(Ethylene Glycol)-Functionalized N-Heterocyclic Carbene Ligands for Efficient Pd-Catalyzed

Efficient PdCl2–catalyzed Suzuki reactions using simple dicationic imidazolium salts as ligands in aqueous DMF Qing Huang ·· Jiabin Qiu · Limei Li · Guohai Xu · Zhonggao ZhouR1 X 80 oC 0.1 - 6 h R1 R2 Pd/L K2CO3 DMF/H2O R 2 B(OH)2 26 examples Cat. 0.1 mol % Yield 85 - 99 % Cl Cl L = Me N N N N Me 1, o-. 2, m-. 3, p-.ExperimentalGeneral considerationsMaterials and methodsAll chemicals employed in the synthesis were obtained commercially, and used as received without further purification. NMR spectra were recorded on a Bruker Avance III 400 MHz spectrometer. GC–MS analyses were carried out on an Agilent 6890 GC with 5973 mass detector. The dicationic imidazolium salts 1, 2, and 3 were prepared by following the literature method.GC-MS analysisAll of the experiments were carried out on an agilent 6890 GC with 5973 mass spectral detector, using an AT.SE-30 column of 50 m length, 0.32 mm diameter and 0.5 μm film thicknesses. GC parameters for Suzuki reactions were as follows: injector temperature 280◦C; detector temperature 280 ◦C; initial temperature 100 ◦C; initial time 5 min; temperature ramp 1, 30 ◦C min−1; final temperature 200 ◦C; ramp 2, 20 ◦C min−1; final temperature 250 ◦C; run time 30 min; inject 1.0 μL; helium as the GC carrier gas; pressure of the system was 3.5 bar.General procedure for the Suzuki reactions* College of Chemistry and Chemical Engineering, Gannan Normal University, Ganzhou 341000, P. R. China E-mail: [email protected] (Z.-G. Zhou) The appropriate amounts of the required dicationic imidazolium ligand, base (2.0 equivalents) and Pd metal precursor were added to 1,4-dioxane. The mixture was stirred at 60 oC for 30 min under nitrogen, after which the palladium catalyst was formed in situ. The 1,4-dioxane was then removed under reduced pressure and the required solvent, aryl halide (1.0 equivalent), aryl boronic acid (1.5 equivalent), and decane (internal standard) were added.The reaction was monitored by GC–MS, and the GC yields were calculated against the added decane. On completion of the reaction, the residue was extracted with ether (3 × 3.0 mL) and the organic solvent was evaporated under reduced pressure. The crude product was purified by column chromatography, and the products were characterized by 1H and 13C NMR spectra.The crude product was purified by column chromatography, and the products were characterized by 1H, 13C NMR spectra and the datas could be found in following.(1) Me 4a4-Methyl-1,1'-biphenyl (Table 3, entries 1, 2 and 9),1 H NMR (400 MHz, CDCl3): δ 7.58 (d, J = 7.6 Hz, 2 H, Ar-H), 7.50 (d, J = 8.4 Hz, 2 H, Ar-H),7.44 (t, J = 7.2 Hz, 2 H, Ar-H), 7.33 (t, J = 6.8 Hz, 1 H, Ar-H), 7.25 (t, J = 3.2 Hz, 2 H, Ar-H),2.41 (s, 3 H, CH3) ppm.(2) NC 4b[1,1'-biphenyl]-4-carbonitrile (Table 3, entry 3)1 H NMR (400 MHz, CDCl3): δ 7.53–7.64 (m, 4 H , Ar-H), 7.50 (d, 2 H, J = 7.8 Hz, Ar-H), 7.35–7.42 (m, 3 H, Ar-H), ppm.(3) MeO 4c4-Methoxy-1,1'-biphenyl (Table 3, entry 4),1 H NMR (400 MHz, CDCl3): δ 7.54 (t, J = 8.0 Hz, 4 H, Ar-H), 7.42 (t, J = 7.6 Hz, 2 H, Ar-H), 7.31 (d, J = 7.2 Hz, 1 H, Ar-H), 6.98 (d, J = 8.8 Hz, 2 H, Ar-H), 3.86 (s, 3 H, OCH3) ppm.(4) MeOC 4d1-([1,1'-biphenyl]-4-yl)ethanone (Table 3, entry 5),1 H NMR (400 MHz, CDCl3): δ 8.19 (d, J = 7.6 Hz, 1 H, Ar-H), 7.97 (d, J = 8.0 Hz, 2 H, Ar-H),7.33~7.63 (m, 5 H, Ar-H), 7.18 (s, 1 H, Ar-H), 2.57 (s, 3 H, CH3) ppm.(5) 4e Me2-Methyl-1,1'-biphenyl (Table 3, entry 6),1 H NMR (400 MHz, CDCl3): δ 7.39-7.43 (m, 2 H, Ar-H), 7.31-7.35 (m, 3 H, Ar-H), 7.24-7.26(m, 4 H, Ar-H), 2.25 (s, 3 H, CH3) ppm.(6) 4fBiphenyl (Table 3, entry 7),1 H NMR (400 MHz, CDCl3, TMS) δ 7.60 (d, 4 H, J = 7.5 Hz), 7.44 (t, 4 H, J = 7.2 Hz), 7.35 (t,2 H, J = 7.2 Hz) ppm.(7) 4g OMe2-methoxy-1,1'-biphenyl (Table 3, entry 8)1H NMR (400 MHz, CDCl3): δ 7.58–7.56 (m, 2H, Ar-H), 7.43–7.39 (m, 2H, Ar-H), 7.35–7.31(m, 2H, Ar-H), 7.17–7.12 (m, 2H, Ar-H), 6.87 (dd, J = 8.4 and 2.4 Hz, 1H, Ar-H), 3.82 (s, 3H, CH3), ppm.(8) F3C 4h4-(trifluoromethyl)-1,1'-biphenyl (Table 3, entry 10), 1 H NMR (400 MHz, CDCl3): δ 7.33 (t, J = 7.2 Hz, 1 H, Ar-H), 7.40 (t, J = 7.4 Hz, 2 H, Ar-H),7.54 (d, J = 6.8 Hz, 2 H, Ar-H), 7.62 (s, 4 H, Ar-H) ppm.F(9) MeOC F 4iF1-(3',4',5'-trifluoro-[1,1'-biphenyl]-4-yl)ethanone (Figure 1),1 H NMR (400 MHz, CDCl3): δ 8.04 (d, 2 H, J = 8.0 Hz, Ar-H), 7.60 (d, 2 H, J = 8.0 Hz, Ar-H),13 7.24 (m, 2 H, Ar-H), 2.65 (s, 3 H, CH3 ), ppm. C NMR (100 MHz, CDCl3, δ): 197.41, 151.52,142.47, 139.79, 136.72, 135.97, 129.12, 127.03, 111.42, 111.26, 26.69, ppm. F(10) MeOC 4jF1-(3',5'-difluoro-[1,1'-biphenyl]-4-yl)ethanone (Figure 1),1 H NMR (400 MHz, CDCl3): δ 8.03 (d, 2 H, J = 8.0 Hz, Ar-H), 7.62 (d, 2 H, J = 8.0 Hz, Ar-H),13 7.11 (m, 2 H, Ar-H), 6.82 (m, 2 H, Ar-H), 2.64 (s, 3 H, CH3 ), ppm. C NMR (100 MHz, CDCl3,δ): 197.45, 164.56, 162.08, 143.37, 143.11, 136.76, 129.04, 127.16, 110.24, 110.05, 103.41,26.65 ppm.(11) MeOC CH3 4k1-(4'-methyl-[1,1'-biphenyl]-4-yl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3): δ8.02 (d, J = 8.0 Hz, 2 H, Ar-H) 7.67 (d, J = 8.0 Hz, 2 H, Ar-H),7.53 (d, J =8.0 Hz, 2 H, Ar-H), 7.28 (d, J = 8.0 Hz, 2 H, Ar-H), 2.63 (s, 3 H, CH3), 2.41 (s, 3 H,13 CH3), ppm. C NMR (100 MHz, CDCl3) δ 197.5, 141.1, 140.2, 135.6, 129.1, 126.8, 126.4,126.2, 122.1, 26.6 ppm. (12) MeOC 4l OH1-(4'-(hydroxymethyl)-[1,1'-biphenyl]-4-yl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3): δ 8.02 (d, 2 H, J = 8.0 Hz, Ar-H), 7.68 (d, 4 H, J = 8.0 Hz, Ar-H),7.47 (d, 2 H, J = 8.0 Hz, Ar-H), 4.76 (s, 2 H, CH2), 2.64 (s, 2 H, CH3) ppm.13 C NMR (101 MHz, CDCl3) δ 197.71, 145.39, 141.00, 139.21, 135.91, 128.93, 127.52, 127.43, 127.13, 64.93, 26.61 ppm(13) MeOC F 4m1-(4'-fluoro-[1,1'-biphenyl]-4-yl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3): δ 8.03 (d, 2 H, J = 8.0 Hz, Ar-H), 7.60 (m, 4 H, Ar-H), 7.16 (t, 2 H,13 J = 12.0 Hz, Ar-H), 2.64 (s, 3 H, CH3) ppm. C NMR (100 MHz, CDCl3): δ197.70, 164.24,161.78, 144.75, 135.99, 135.84, 128.99, 128.90, 127.08, 116.04, 115.83, 26.79 ppm.(14) MeOC CF3 4n1-(4'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)ethanone (Figure 1).1 H NMR (400 MHz, CDCl3): δ 8.06 (d, 2 H, J = 8.0 Hz, Ar-H), 7.73 (s, 2 H, Ar-H), 7.68 (d, 2 H,13 J = 8.0 Hz, Ar-H), 2.65 (s, 3 H, CH3), ppm. C NMR (100 MHz, CDCl3): δ 197.50, 144.10,143.37, 136.61, 130.20, 129.02, 127.58, 127.42, 125.87, 125.48, 122.77, 26.61 ppm.(15) MeOC CN 4o4'-acetyl-[1,1'-biphenyl]-4-carbonitrile (Figure 1)1 H NMR (400 MHz, CDCl3): δ 8.07(d, 2 H, J = 8.0 Hz, Ar-H), 7.75 (m, 4 H, Ar-H), 7.69 (d, 2 H,13 J = 8.0 Hz, Ar-H), 2.65 (s, 3 H, CH3), ppm. C NMR (100 MHz, CDCl3): δ197.47, 144.27,143.48, 136.89, 132.73, 129.12, 127.93, 127.45, 118.65, 111.86, 26.73. ppm.(16) MeOC O 4p 1-(4'-phenoxy-[1,1'-biphenyl]-4-yl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3, TMS) δ 8.01 (d, J = 8.0 Hz, 2 H, Ar-H), 7.65 (d, J = 8.0 Hz, 2 H, Ar-H), 7.59 (d, J = 8.0 Hz, 2 H, Ar-H), 7.37 (t, J = 8.0 Hz, 4 H, Ar-H), 7.14 (t, J = 8.0 Hz, 1 H, Ar-13 H), 7.05 (t, J = 8.0 Hz, 4 H, Ar-H), 2.63 (s, 3 H, CH3); C NMR (100 MHz, CDCl3, δ): 197.64,157.84, 156.79, 145.09, 135.67, 134.69, 129.87, 128.97, 128.61, 126.87, 123.70, 119.28,118.98, 26.60 ppm.O MeOC (17) 4q O MeEthyl 4'-acetyl-[1,1'-biphenyl]-4-carboxylate (Figure 1)1 H NMR (400 MHz, CDCl3, TMS) δ 8.14 (d, J = 8.0 Hz, 2 H, Ar-H), 8.06 (d, J = 8.0 Hz, 2 H, Ar-H), 7.72 (d, J = 8.0 Hz, 2 H, Ar-H), 7.69 (t, J = 8.0 Hz, 2 H, Ar-H), 4.41 (q, J = 7.2 Hz, 2 H,13 CH2), 2.63 (s, 3 H, COCH3), 1.43 (t, J = 7.2 Hz, 2 H, CH3); C NMR (100 MHz, CDCl3, δ):197.65, 166.30, 144.53, 144.01, 136.48, 130.20, 128.99, 127.45, 127.20, 113.69, 61.14,26.72, 14.36 ppm.(18) MeOC N 4r1-(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3, TMS) δ 8.00 (d, J = 8.0 Hz, 2 H, Ar-H), 7.65 (d, J = 8.0 Hz, 2 H, Ar-H), 7.50 (d, J = 8.0 Hz, 2 H, Ar-H), 7.28 (t, J = 8.0 Hz, 4 H, Ar-H), 7.13 (d, J = 8.0 Hz, 6 H, Ar-13 H), 7.05 (t, J = 8.0 Hz, 2 H, Ar-H), 2.62 (s, 3 H, CH3); C NMR (100 MHz, CDCl3, δ): 197.63,148.19, 147.43, 145.21, 135.34, 133.14, 129.39, 128.98, 127.93, 126.50, 124.79, 123.37,123.29, 26.63 ppm.CF3(19) MeOC 4s1-(3'-(trifluoromethyl)-[1,1'-biphenyl]-4-yl)ethanone (Figure 1) 1 H NMR (400 MHz, CDCl3): δ 8.08 (d, 2 H, J = 8.0 Hz, Ar-H), 7.87 (s, 1 H, Ar-H), 7.80 (d, 1 H,13 J = 8.0 Hz, Ar-H), 7.67 (m, 3 H, Ar-H), 7.60 (m, 1 H, Ar-H), 2.66 (s, 3 H, CH3), ppm. C NMR(100 MHz, CDCl3): δ 197.57, 144.10, 140.67, 136.47, 131.20, 130.55, 129.50, 129.07,127.32, 124.86, 124.82, 124.02, 26.65 ppm.(20) 4t MeOC1-([1,1':3',1''-terphenyl]-4-yl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3, TMS) δ 8.03 (d, J = 8.0 Hz, 2 H, Ar-H), 7.81 (s, 1 H, Ar-H), 7.71 (d,J = 8.0 Hz, 2 H, Ar-H), 7.62 (m, 4 H, Ar-H), 7.52 (d, J = 8.0 Hz, 2 H, Ar-H), 7.37 (d, J = 8.0 Hz,13 2 H, Ar-H), 2.62 (s, 3 H, CH3); C NMR (100 MHz, CDCl3, δ): 197.86, 145.76, 142.075,140.89, 140.45, 135.99, 129.44, 129.00, 128.92, 127.64, 127.37, 127.28, 127.11, 126.23,26.707 ppm.NO2 (21) 4u MeOC1-(3'-nitro-[1,1'-biphenyl]-4-yl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3) δ 8.45 (s, 1 H, Ar-H), 8.23 (d, J = 8.0 Hz, 1 H, Ar-H), 8.07 (d, J =8.0 Hz, 2 H, Ar-H), 7.95 (d, J = 8.0 Hz,1 H, Ar-H), 7.72 (d, J = 8.0 Hz, 2 H, Ar-H), 7.66 (t, J =13 8.0 Hz, 2 H, Ar-H), 2.66 (s, 3 H, CH3) 2.66 ppm. C NMR (100 MHz, CDCl3) δ 197.42, 148.73,142.90, 141.47, 136.83, 133.12, 130.00, 129.16, 127.32, 122.85, 122.01, 77.44, 77.12, 76.80,26.68 ppmMeOC (22) O 4v O1-(4-(benzo[d][1,3]dioxol-5-yl)phenyl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3, TMS) δ 7.92 (s, 2 H, Ar-H), 7.53 (s, 2 H, Ar-H), 7.03 (s, 2 H, Ar-H),13 6.84 (s, 1 H, Ar-H), 5.95 (s, 2 H, CH3), 2.56 (s, 3 H, CH3) ppm; C NMR (100 MHz, CDCl3) δ 197.70, 148.34, 147.89, 145.36, 135.44, 134.01, 128.93, 126.78, 121.05, 108.73, 107.56,101.39, 26.64 ppm.CF3(23) MeOC 4wCF31-(3',5'-bis(trifluoromethyl)-[1,1'-biphenyl]-4-yl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3): δ 8.10 (m, 2 H, J = 8.0 Hz, Ar-H), 8.06 (s, 2 H, Ar-H), 7.92 (s, 1 H,13 Ar-H), 7.73(m, 2 H, J = 8.0 Hz, Ar-H), 2.68 (s, 3 H, CH3 ), ppm. C NMR (100 MHz, CDCl3): δ197.38, 142.48, 142.04, 137.12, 132.38, 129.26, 127.50, 127.35, 124.57, 121.80, 119.14,26.74 ppm.MeOC (24) 4x1-(4-(naphthalen-1-yl)phenyl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3): δ 8.00 (d, 2 H, J = 8.0 Hz, Ar-H), 7.83–7.74 (m, 3H, Ar-H), 7.51–7.46 (m, 2H, Ar-H), 7.43–7.36 (m, 2H, Ar-H), 7.33–7.31 (m, 2H, Ar-H), 2.58 (s, 3H, CH3 ) ppm.13 C NMR (100 MHz, CDCl3): δ 197.8, 145.7, 138.9, 135.9, 133.7, 131.1, 130.3, 128.3, 126.9,126.3, 125.9, 125.3, 26.7 ppm.MeOC (25) 4y1-(4-(naphthalen-2-yl)phenyl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3) δ 8.07 (m, 3 H, Ar-H), 7.89 (m, 3 H, Ar-H), 7.79 (d, J = 8.0 Hz, 2 H,13 Ar-H), 7.74 (d, J = 8.0 Hz, 1 H, Ar-H), 7.51(m, 3 H, Ar-H), 2.64 (s, 3 H, CH3); C NMR (100Hz, CDCl3) δ 197.74, 145.68, 137.15, 135.89, 133.57, 133.03, 128.99, 128.72, 128.37,127.70, 127.46, 126.58, 126.50, 126.38, 125.17, 6.68 ppm. Me(26) MeOC 4z Me1-(3',5'-dimethyl-[1,1'-biphenyl]-4-yl)ethanone (Figure 1)1 H NMR (400 MHz, CDCl3) δ 7.97 (d, J = 8.0 Hz, 2 H, Ar-H), 7.62 (d, J = 8.0 Hz, 2 H, Ar-H),13 7.20 (s, 2 H, Ar-H), 7.01 (s, 1 H, Ar-H), 2.59 (s, 3 H, CH3), 2.36 (s, 6 H, CH3); C NMR (100Hz, CDCl3) δ 197.88, 146.08, 139.83, 138.49, 137.89, 135.69, 129.93, 129.72, 128.86,127.20, 125.17, 26.60, 21.41 ppm.Acknowledgments We gratefully thank the financial support from The National NaturalScience Foundation of China (No. 21241005 and 21201040), the Key Laboratory of JiangxiUniversity for Functional Materials Chemistry.References[1] E. Alcalde, N. Mesquida, M. Alemany, C. Alvarez-Rúa, S. García-Granda, P. Pacheco, G. Lluïsa Pérez, Eur. J. Org. Chem. 2002, 2002, 1221. [2] S. Mohanty, D. Suresh, M. S. Balakrishna, J. T. Mague, Tetrahedron 2008, 64, 240. [3] Z. G. Zhou, M. Y. Liu, X. L. Wu, H. W. Yu, G. H. Xu, Y. R. Xie, Appl. Organomet. Chem. 2013, 27, 562. [4] H. W. Yu, J. C. Shi, H. Zhang, P. Y. Yang, X. P. Wang, Z. 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Poly(Ethylene Glycol)-Functionalized N-Heterocyclic Carbene Ligands for Efficient Pd-Catalyzed

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