Mixed-donor N,N,O-tridentate ligands for palladium-catalyzed Suzuki reactions
Zhonggao Zhou· Ziyi Du · Qiaosheng Hu · Jicheng Shi · Yongrong Xie*· Yulan Liu
General considerations
All starting materials and reagents were supplied commercially from Aldrich or Alfa Aesar and used as
received.
2-(N-methylpiperazinyl-N’-methyl)-4,6-di-tert-butyl-phenol
(1)
and
2-(N-methylpiperazinyl-N’-phenyl)-4,6-di-tert-butyl-phenol (2) were prepared as reported [1]. Solvents
were dried with standard methods and freshly distilled prior to use. NMR spectra were recorded on a
Bruker Avance III 400 MHz (1H 400 MHz, 13C 100 MHz) spectrometer. The NMR studies were carried
out using CDCl3 as solvent and signals are quoted in ppm as δ downfield from TMS as internal
standard. Coupling constants are given in Hertz. NMR multiplicities are abbreviated as follows: s =
singlet, d = doublet, t = triplet, m = multiplet.
GLC analysis
GLC experiments were carried out on an Agilent 6890 chromatograph, using an AT.SE-30 column of
50 m length, 0.32 mm diameter and 0.5 μm film thicknesses. GLC parameters for Suzuki reactions
were as follows: injector temperature 280 ◦C; detector temperature 280 ◦C; initial temperature 60 ◦C;
initial time 5 min; temperature ramp 1, 30 ◦C min−1; final temperature 200 ◦C; ramp 2, 20 ◦C min−1;
Z. Zhou () · Z. Du · Q. Hu · Y. Xie ()
College of Chemistry and Chemical Engineering, Gannan Normal University, Ganzhou 341000, P. R.
China
E-mail: zhgzhou@foxmail.com · yongrongxie@foxmail.com
J. Shi
College of Chemistry and Materials Science, Fujian Normal University, Fuzhou 350007, P. R. China
Y. Liu
College of Architecture and Environment, Sichuan University, Chengdu 610207, P. R. China
final temperature 250 ◦C; run time 25 min; inject 1.0 μL; helium as the GLC carrier gas; pressure of the
system was 3.5 bar.
General procedure for the Suzuki reactions
The appropriate amounts of ligand, and metal precursor were added to the required solvent (3.0 mL).
The mixture was stirred for 5 min, then the aryl halide (0.5 mmol), phenylboronic acid (0.75 mmol),
and base (1.0 mmol) were added and the mixture was stirred and reacted under an inert atmosphere.
The course of the reaction was monitored by GLC-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 MgSO 4 then filtered and the solvent was
evaporated under reduced pressure. The crude product which was purified by column chromatography
using 100-200 mesh silica gel and the purified products were characterized by comparing their 1H
NMR spectra with those found in the literature, namely:
4-methylbiphenyl (Table 4, entries 1, 5, 12, 18 and 22) [2]
4-methoxybiphenyl (Table 4, entries 2, 3 and 14) [3]
2-methylbiphenyl (Table 4, entries 4 and 13) [3]
4-acetylbiphenyl (Table 4, entries 6 and 15) [4]
biphenyl (Table 4, entries 7 and 11) [2]
4-trifluoromethylbiphenyl (Table 4, entries 8, 9, 10 and 21) [5]
4,4'-dimethylbiphenyl (Table 4, entries 16, 19 and 23) [6]
4-methoxyl-4'-methyl-1,1'-biphenyl (Table 4, entries 17, 20 and 24) [7]
Acknowledgments
Financial support for this work was provided by the National Natural Science Foundation of China
(Contract No. 20861001 and 21061001), the Key Laboratory of Jiangxi University for Functional
Materials Chemistry, Gannan Normal University.
References
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