Efficient Palladium-catalyzed Suzuki-Miyaura reactions using phenolic Schiff
base ligands under ambient conditions in aqueous media
Zhonggao Zhou· Zhenyun Zhou · Aichen Chen · Xiuhua Zhou · Qi Qi · Yongrong
Xie
Experimental
Materials
All chemicals employed in the synthesis were analytical grade, obtained commercially,
and used as received without further purification. The solvents dioxane and
tetrahydrofuran were dried by standard methods, and other solvents were used directly.
The Schiff bases L1 [1], L2 [1], L3 [2] and L4 [3] were prepared as reported. NMR
spectra were recorded on a Bruker Avance III 400 MHz spectrometer, coupling
constants (J values) are given in Hertz.
Scheme 1. Some selected Schiff base ligands
L1, 1H NMR (CDCl3, 400 MHz, ppm): δ 12.94 (1H, s, -OH), 8.56 (1H, dq, J = 4.8 Hz,
Aryl-H), 8.48 (1H, s, -CH=N), 7.69 (1H, td, J = 8 Hz, Aryl-H), 7.44 (1H, d, J = 8 Hz,
Aryl-H) , 7.19 (1H, m, Aryl-H), 6.94 (2H, m, Aryl-H), 6.80 (1H, d, J = 2.6 Hz,
Aryl-H), 4.70 (1H, q, J = 14 Hz, CH), 3.78 (3H, s, -OCH3), 1.68 (3H, d, J = 8 Hz,
-CH3), ppm.
Z. Zhou () ·Z. Zhou · A. Chen · Q. Qi · Y. Xie ()
College of Chemistry and Chemical Engineering, Gannan Normal University, Ganzhou 341000, P. R.
China
E-mail: zhgzhou@foxmail.com · yongrongxie@foxmail.com
X. Zhou
Fujian Inspection and Research Institute for Product Quality, Fuzhou 35002, P. R. China
L2, 1H NMR (CDCl3, 400 MHz, ppm): δ 14.93 (1H, s, -OH), 9.00 (1H, s, -CH=N),
8.61 (1H, dq, J = 4.8 Hz, Aryl-H), 7.90 (1H, d, J = 8.4 Hz, Aryl-H), 7.70 (2H, m,
Aryl-H), 7.63 (1 H, dd, J = 8 Hz, Aryl-H), 7.44 (2H, m, Aryl-H), 7.22 (2H, m,
Aryl-H), 6.98 (1H, d, J = 9.3 Hz, py), 4.88 (1H, q, J = 14 Hz, CH), 1.79 (3H, d, J = 8
Hz, -CH3), ppm.
GC-MS analyses for all of the experiments were carried out on an Agilent 6890 GC
with 5973 mass 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 reaction
The appropriate amounts of ligand, base and metal precursor were added to the
required solvent (3.0 mL). The mixture was stirred for 30 min, then the aryl halide
(0.5 mmol) and aryl boronic acid (0.75 mmol) were added and the mixture was stirred
under reflux in air. The course of the reaction was monitored by GC-MS analysis, and
yields were calculated against the aryl halides. On completion of the reaction, the
solvent was removed under reduced pressure. The residue was diluted with H2O (3.0
mL) and Et2O (3.0 mL), followed by extraction with Et2O (2 × 3.0 mL). The organic
fraction was dried over anhydrous MgSO4 then filtered, and the solvent was
evaporated under reduced pressure. The crude product was purified by column
chromatography using 200-300 mesh silica gel and the purified products were
characterized by NMR spectra as 4-Methyl-1,1'-biphenyl (Table 4, entries 1, 2 and 8)
[4], 4-Cyano-1,1'-biphenyl (Table 4, entry 3) [5], 4-Methoxy-1,1'-biphenyl (Table 4,
entry 4) [6], 4-Acetyl-1,1'-biphenyl (Table 4, entry 5) [4], 2-Methyl-1,1'-biphenyl
(Table 4, entry 6) [6], Biphenyl (Table 4, entry 7) [7], 4-Trifluoromethyl-1,1'-biphenyl
(Table 4, entry 9) [8], 2-Methoxy-1,1'-biphenyl (Table 4, entry 10) [6],
4-Acetyl-3',4',5'-trifluoro-1,1'-biphenyl
4-Acetyl-3',5'-difluoro-1,1'-biphenyl
(Table
(Table
4,
4,
entry
entry
11)
[7],
12)
[9],
4-Acetyl-3',5'-ditrifluoromethyl-1,1'-biphenyl (Table 4, entry 13) [10].
4-Methyl-1,1'-biphenyl (Table 4, entries 1, 2 and 8); [4]
1
H NMR (400 MHz, CDCl3): δ 7.58 (d, J = 7.6 Hz, 2H, Ar-H), 7.50 (d, J = 8.4 Hz, 2H,
Ar-H), 7.44 (t, J = 7.2 Hz, 2H, Ar-H), 7.33 (t, J = 6.8 Hz, 1H, Ar-H), 7.25 (t, J = 3.2
Hz, 2H, Ar-H), 2.41 (s, 3H, CH3), ppm.
4-Cyano-1,1'-biphenyl (Table 4, entry 3);[5]
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.
4-Methoxy-1,1'-biphenyl (Table 4, entry 4);[6]
1
H NMR (400 MHz, CDCl3): δ 7.54 (t, J = 8.0 Hz, 4H, Ar-H), 7.42 (t, J = 7.6 Hz, 2H,
Ar-H), 7.31 (d, J = 7.2 Hz, 1H, Ar-H), 6.98 (d, J = 8.8 Hz, 2H, Ar-H), 3.86 (s, 3H,
OCH3), ppm.
4-Acetyl-1,1'-biphenyl (Table 4, entry 5);[4]
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.
2-Methyl-1,1'-biphenyl (Table 4, entry 6);[6]
1
H NMR (400 MHz, CDCl3): δ 7.39-7.43 (m, 2H, Ar-H), 7.31-7.35 (m, 3H, Ar-H),
7.24-7.26 (m, 4H, Ar-H), 2.25 (s, 3H, CH3), ppm.
Biphenyl (Table 4, entry 7);[11]
1
H NMR (400 MHz, CDCl3, δ): 7.35 (t, J = 5.6 Hz, 2 H, Ar-H), 7.43 (t, J = 8.0 Hz, 4
H, Ar-H), 7.59 (d, J = 7.2 Hz, 4 H, Ar-H), ppm.
4-Trifluoromethyl-1,1'-biphenyl (Table 4, entry 9);[8]
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.
2-Methoxy-1,1'-biphenyl (Table 4, entry 10);[6]
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.
4-Acetyl-3',4',5'-trifluoro-1,1'-biphenyl (Table 4, entry
11);[7]
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), 7.24 (m, 2 H, Ar-H), 2.65 (s, 3 H, CH3 ), ppm.
13
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.
4-Acetyl-3',5'-difluoro-1,1'-biphenyl (Table 4, entry 12);[9]
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), 7.11 (m, 2 H, Ar-H), 6.82 (m, 2 H, Ar-H), 2.64 (s, 3 H, CH3 ), ppm. 13C
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.
4-Acetyl-3',5'-ditrifluoromethyl-1,1'-biphenyl
(Table 4,
entry 13);[10]
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, Ar-H), 7.73(m, 2 H, J = 8.0 Hz, Ar-H), 2.68 (s, 3 H, CH3 ), ppm.
13
C
NMR (100 MHz, CDCl3): δ 197.38, 142.48, 142.04, 137.12, 132.38, 129.26, 127.50,
127.35, 124.57, 121.80, 119.14, 26.74, ppm.
NMR Spectra for the Products of Suzuki Cross-Coupling
Acknowledgments
This work was financially supported by the National Natural Science Foundation of
China (No. 21241005 and 21061001), the Key Laboratory of Jiangxi University for
Functional Materials Chemistry, and Gannan Normal University.
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