S. Verma et al. / Applied Catalysis A: General 472 (2014) 178–183
179
Br
H
Cl
H
1 (10 mol %)
Ethanol,1000C
O
R
O
N
+
(CH3)4NCl
N
R
. H2O
O
X
Cu
H
X
O
X=CH, N
2a-2o
3a-3n
H
Fig. 1. Trans-glycinato(II)copper complex 1.
Scheme 1. Glycinatocopper(II)-catalyzed chloride exchange reaction.
the reaction mixture was stirred at 100 ◦C for a period as mentioned
in Table 2 (the reaction progress was monitored by GC analysis).
After completion of the reaction, the solvent was removed under
reduced pressure. The residue obtained was purified via silica gel
chromatography (eluent: petroleum ether/ethyl acetate = 10/1) to
afford aryl chlorides. The yield of the products was determined by
high resolution GC–MS analysis and the identity of the products
was confirmed by comparing their physical and spectral data with
the known compounds.
2. Experimental
2.1. General
All the substrates and solvents were purchased from Acros
Organics and used as received. Copper(II) chloride was purchased
from Aldrich. The FTIR spectrum of the synthesized material was
recorded using a Thermo Scientific Nicolet 8700 Research FT-IR
spectrophotometer with a 4 cm−1 resolution using their KBr pel-
lets. Thermal decomposition of the synthesized copper catalyst was
determined by using a Diamond TG–DTA analyzer (Perkin-Elmer).
All samples were analyzed in the temperature range of 30–800 ◦C
under nitrogen flow. The morphology and structural features of
copper catalyst were determined by high resolution scanning elec-
tron microscopy. The 1H and 13C NMR spectra were recorded on
a Bruker Avance 500 Spectrometer in CDCl3 with CHCl3 (7.27 ppm
for 1H, 77 ppm for 13C) as a standard and the chemical shifts are
expressed in ı parts per million relative to tetramethylsilane (TMS)
as the internal standard.
2.4. Bromide–chloride exchange reaction by using CuCl2 and
glycine (1:1) mixture
A Schlenk tube was charged with 1-bromo 4-methyl benzene
(1 mmol) and CuCl2 (2 mol%), glycine (2 mol%) tetramethylam-
monium chloride (Me4NCl) (2.0 mmol), and EtOH (2.0 mL) under
nitrogen atmosphere. The Schlenk tube was sealed, and then the
reaction mixture was stirred at 100 ◦C for 10 h. After completion
of the reaction, the solvent was removed under reduced pressure.
The residue obtained was passed through a small column of sil-
ica gel and then subjected to GC and GCMS. Only trace amount of
the desired product was observed along with the recovery of the
original substrate.
2.2. Synthesis of glycinatocopper(II) complex
The copper (II) chloride and glycine were added in a 1:2 molar
ratio in 20 mL deionized water and the mixture was magnetically
stirred for 15 min at room temperature. Then the solution was
transferred into 50 mL stainless-steel autoclave lined with Teflon,
which was sealed and maintained at 100 ◦C for 2 h. The resulting
deep blue product was separated via centrifugation and washed
thoroughly with ethanol and dried in air. Analytical calculations
for C4H10N2O5Cu (%): C 20.91, H 4.39, N 12.20; found: C 20.79, H
4.22, N 12.33.
3. Results and discussion
During the present investigation, the required catalyst 1 was
synthesized from CuCl2·2H2O and glycine in a 1:2 molar ratio
(Fig. 1). The obtained deep blue solid was washed thoroughly with
ethanol and dried in air. The values of elemental analysis (found:
C, 20.79%; H 4.22%, N, 12.33%; calcd C, 20.91%, H, 4.39%, N, 12.20%)
suggested that the proposed formula of complex is [Cu(gly)2·H2O]
1. Further, in FTIR spectra (Fig. 2), a strong band at 1604 cm−1 corre-
sponding to carboxyl group and 3300 cm−1 corresponding to amino
group of glycine revealed the successful formation of 1. The thermal
stability of complex 1 was determined by the thermo-gravimetric
analysis (TGA) under nitrogen atmosphere. It was observed that the
2.3. General procedure for aryl and heteroaryl bromide–chloride
exchange reaction
A Schlenk tube was charged with catalyst 1 (10 mol %), aryl (or
heteroaryl) bromide (1.0 mmol), tetramethylammonium chloride
(Me4NCl) (2.0 mmol), and EtOH (2.0 mL) under nitrogen atmo-
sphere. The Schlenk tube was sealed with a Teflon valve, and then
Fig. 2. FTIR-spectrum of glycinatocopper(II) complex 1.