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7267
demonstrates that the region around Co atom possesses higher
reactivity than other parts of the catalyst. The condensed Fukui
function of individual atom (Fig. 4(b)), obtained from NBO analy-
sis,16 indicates that the Co atom should be the first choice for benzyl
chloride attack since its value of condensed Fukui function, 0.176, is
considerably larger than that of other atoms. This theoretical pre-
diction supports the proposed reaction mechanism in Fig. 3.
scan mode and collected for Lorentz and polarization effect
(SADABS). Anal. Calcd for C29H26CoN4O7: C, 57.89; H, 4.35; N, 9.32.
Found: C, 57.91; H, 4.36; N, 9.31. IR (KBr, cmꢁ1): 3423.6, 3053.7,
2756.2, 1585.6, 1561.3, 1423.3, 1282.4, 1222.8, 862.8, 747.8, 704.8,
609.5, 570.4, 526.0, 484.8, 424.3.
4.4. Synthesis of 2aeu
3. Conclusion
A 100 mL reactor equipped with Teflon-coated magnetic stir
bars was charged with n-Butyl alcohol (20 mL) and the catalyst
(0.5 mmol). The reactor was then taken out of the glove box and
pressured with carbon monoxide (1 atm). The mixture was stirred
2 h at 60 ꢀC, cooled to ambient temperature and slowly vented.
After benzyl chloride (10 mmol), NaOH (15 mL, 15%), and TBAI
(0.25 mmol) were added, the reactor was sealed and the reaction
mixtures were stirred for 22 h at 60 ꢀC under carbon monoxide
(1 atm). After the reaction, the water phase was detached and
washing the organic phase three times with H2O (3ꢂ5 mL), the
combined water layer was washed with Et2O, then the resulting
solution was cooled to 0 ꢀC and adjusted to pH¼1e2 with HCl
(6 mol/L). The product was filtered, dried in RT, and then
recrystallized.
In summary, an efficient and environmentally benign process
for the carbonylation of various substituted benzyl chloride has
been developed. The electron rich ligand, 2-(1H-benzimidazol-2-
yl) benzoic acid, enhances the catalytic activity according to ex-
perimental result, and the computer simulation also proved that
the excellent efficiency of the cobalt catalyst originates from in-
troduction of the benzimidazole ligand. This methodology repre-
sents a useful extension of benzimidazole used as ligand in metal
catalysis. The wide scope, mild reaction conditions, high activity,
and success of scale-up experiment indicate that the potential in-
dustrial production of phenylacetic acid derivatives is possible by
this method.
4. Experimental section
4.1. General methods
Acknowledgements
The project was supported by National Natural Science Foun-
dation of China (NSFC 20972124; 21272184; 21143010), Shaanxi
Provincial Natural Science Fund Project (No. 2012JQ2007), Shaanxi
Science and Technology Co-ordination Innovation Engineering
Project (No. 2011K12-77), the Special Science Research Foundation
of Education Committee in Shaanxi Province (No. 12JK0584), and
Xi’an City Science and Technology Project (No. CXY1123-1).
All carbonylation experiments were carried out in a custom-
made high-pressure reactor, which pressured with carbon mon-
oxide (1 atm). All solvents were dried and distilled by standard
procedures. All starting materials were obtained from commercial
suppliers and used as received. Products were purified by recrys-
tallized. NMR spectra were performed on a Varian Inova-400 MHz
spectrometer (at 400 MHz for 1H and 100 or 75 MHz for 13C) with
tetramethylsilane (TMS) as an internal standard. X-ray crystal data
were collected on Bruker Smart APEX II CCD diffractometer. The
structures were solved by direct methods and refined on F2 by full-
matrix least-squares techniques with SHELXS-97 program. IR
spectra were taken in KBr disks on a Bruker Tensor 27 spectrometer.
The C, H, N elemental analysis was carried out on a Vario EL III el-
ement analyzer.
Supplementary data
Copies of IR, 1H NMR and 13C NMR spectra can be found online at
References and notes
4.2. Synthesis of L1
In brief, a mixture of 1,2-benzenedicarboxylic acid (16.6 g,
0.1 mol), o-phenylenediamine (10.8 g, 0.1 mol) and 15 mL PPA was
added to a 150 mL over-dried flask. The mixture was stirred at
150 ꢀC for 2 h. After the reaction, the mixture was poured into water
(150 mL) and adjusted to pH¼8 with HCl (6 mol/L). The solid was
filtered and then air-dried. The crude product was recrystallized
from MeOH/H2O (v/v, 1:1) mixed solvent leaving 2-(1H-benzimi-
dazol-2-yl)-benzoic acid as white needle crystals (17.9 g, 75%, mp:
290e292 ꢀC). Anal. Calcd for C14H10N2O2: H, 4.23; C, 70.58; N, 11.76.
Found: H, 4.22; C, 70.60; N, 11.74.
ꢁ
4.3. Synthesis of Cat.1
With well stirring, the L1 (2.38 g, 0.01 mol) and NaOH (0.4 g,
0.01 mol) were dissolved in a sufficient amount of MeOH/H2O (v/v,
1:1) mixed solvent, CoCl2$6H2O solution (2.38 g, 0.01 mol) in 10 mL
H2O was added. After refluxing 4 h, the pink solid was filtered,
washed with methanol, and air-dried. Cat.1 was obtained (67%
yield). The pink single crystal of Cat.1 was obtained at room tem-
perature from its MeOH/H2O (v/v, 1:1) solution by slow evapora-
tion. The crystal data has been collected at 293 K by using Mo K
a
q u
range of 1.43e25.10ꢀ by using 4/
ꢀ
radiation (l¼0.71073 A) the