A. Shaabani et al.
Yield 0.31 g; m.p. > 300°C. Anal. Calcd for C12
27 3 5
H N O Si (%): C,
Results and discussion
4
(
1
(
4.84; H, 8.47; N, 13.07. Found (%): C, 43.97; H, 9.01; N, 12.98. FT-IR
ꢀ
1
Preparation and characterization of catalyst
KBr, cm ): 3389, 3303, 2972, 2867, 1678, 1627, 1586, 1405, 1375,
1
145. H NMR (300 MHz, CDCl
2 H, s, NH ), 4.19 (2 H, s, CH COOH), 3.53 (6 H, q, JHH = 5.3 Hz,
CH CH
m, CH
3
, δ, ppm): 8.08 (1 H, s, NH), 4.97
The Cu/GA/Fe O @SiO nanocatalyst was prepared with a multi-
3
3
4
2
2
2
step reaction. Initially, iron oxide NCPs as a magnetic core were
coated with a silica layer via a sol–gel method in isopropyl alcohol.
For immobilization of the organic catalyst on the surface of the in-
organic support, first, the surface was modified using an appropri-
ate coupling agent to make covalent bonds with the active
species. It is known that organosilanes can act as a linker between
the organic species and the support. Next, some of the linker’s
chloride was replaced by nitrogen of GA via a S 2 reaction. The
GA was anchored onto the surface of modified-SiO /Fe to ob-
tain the bifunctional modified magnetic NCPs of GA/Fe @SiO
A procedure for the synthesis of GA/Fe O @SiO was carried out
3
3
2
–OSi), 3.12 (2 H, t, JHH = 5.4 Hz, CH
2 2
CH CH
2
NH), 1.54 (2 H,
3
2
CH
2
CH
2
NH), 1.24 (9 H, t, J = 5.3 Hz, CH
3
CH –OSi), 0.47 (2 H,
2
3
13
t, J = 5.4 Hz, CH CH CH NH). C NMR (75 MHz, CDCl , δ, ppm):
2
2
2
3
1
(
2.7 (SiCH –), 19.1 (CH ), 26.8 (SiCH CH ), 40.2 (–CH CH NH), 42.5
2 3 2 2 2 2
CH COOH), 56.9 (CH CH O), 156.2 (NCNH ), 179.8 (C¼O).
2
3
2
2
The [N′-(3-triethoxysilanepropyl)guanidino]acetic acid was added
[
30]
to solution of copper(II) chloride dehydrate (0.17 g, 1.00 mmol) in
deionized water. The reaction mixture was stirred for 12 h at room
temperature. Subsequently, the reaction mixture was separated
using an external magnet and washed with deionized water
N
2
3 4
O
O
3 4
2
.
3
4
2
(
(
7
2 × 5 ml). Finally, the obtained solid was dried at 100°C for 12 h
using an ultrasonic-assisted method which involved grafting GA
onto surface of modified NCPs in aqueous medium. Subsequently,
GA/Fe O @SiO was added to aqueous CuCl solution to afford the
Cu/GA/CPTES). Anal. Calcd for C H CuN O Si (%): C, 40.92; H,
24
52
6 10 2
.44; N, 11.93. Found (%): C, 41.84; H, 7.92; N, 13.43. The content
ꢀ
1
3
4
2
2
of the copper was 1.48 mmol g as measured using ICP-OES.
supported Cu catalyst (Cu/GA/Fe O @SiO ) (Scheme 2, pathway 1).
3
4
2
To ensure the presence of new functional groups, each step of the
catalyst preparation procedure was monitored using FT-IR, TGA and
CHN. It is possible to attach both amine groups of GA to the surface.
To clarify how GA moieties are connected to the surface of modified
NCPs, GA and CPTES were reacted under ultrasonic irradiation for
General procedure for synthesis of benzodiazepine derivatives
in presence of Cu/GA/Fe O @SiO NCPs
3 4 2
To a mixture of a o-phenylenediamine (1) (0.11 g, 1 mmol) and
dimedone (2) (0.14 g, 1 mmol) in EtOH (5 ml) was added Cu/GA/
Fe O @SiO (0.01 g, 0.72 mol%), and the mixture was stirred at
3 4 2
room temperature for 5–10 min to give an intermediate product.
After confirmation of the formation of the intermediate using TLC
1
h in water. The formation of [N′-(3-triethoxysilanepropyl)
guanidino]acetic acid 3 that was the only product of the mentioned
1
reaction was identified using H NMR (Scheme 2). GA/Fe O @SiO
3
4
2
was produced by grafting of 3 onto the surface of Fe O @SiO ,
3
4
2
(EtOAc–n-hexane, 2:1), an aldehyde (3) (1 mmol) was added and
which supports the proposed catalyst structure (Scheme 2, path-
way 2). Cu/GA/CPTES was prepared by the chelation of copper by
GA/CPTES in water as solution (pathway 3).
FT-IR spectroscopy was used to identify the incorporation of GA-
based dendrimers on the silica surface. The FT-IR spectra for modi-
the reaction was continued for 15–30 min at 60°C. After completion,
as indicated by TLC (EtOAc–n-hexane, 3:1), the catalyst was sepa-
rated from the mixture using an external magnet, and the solvent
was evaporated. Finally, the product was recrystallized from
EtOH–water (1:1) to afford pure benzodiazepine.
fied Fe
3
O
4
@SiO
2
, GA/Fe
3
O
4
@SiO
2
and Cu/GA/Fe
3
O
4
@SiO
2
are
3
,3-Dimethyl-11-p-tolyl-2,3,4,5,10,11-hexahydrodibenzo[b,
ꢀ1
shown in Fig. 1. The broad band at 580 cm is characteristic of
ꢀ
1
e][1,4]diazepin-1-one (1f). Green powder. FT-IR (KBr, cm ): 3327,
3 4
stretching vibration of Fe–O–Fe, characteristic of magnetite Fe O ,
1
3
265, 3043, 2962, 1595, 1382, 1530, 1317, 1461. H NMR (300 MHz,
DMSO, δ, ppm): 1.01(3 H, s, CH ), 1.09 (3 H, s, CH ), 2.01 (2 H, ABq,
J = 16 Hz, CH ), 2.08 (3 H, s, CH –Ar), 2.59 (2 H, s, –CH
–C¼O), 5.69
1 H, s, N–H), 5.89 (1 H, s, CH), 6.23–6.93 (8 H, m, ArH), 8.55 (1 H, s,
ꢀ1
and the peak at 1635 cm can be assigned to the OH deformation
3
3
of water molecules adsorbed on the materials The typical Si–O–Si
2
3
2
ꢀ1
bands at 453, 792 and 1085 cm present in the spectra of all sam-
(
ples are attributed to the condensed silica network. The strong ab-
1
3
N–H). C NMR (75 MHz, DMSO, δ, ppm): 21.8 (CH –Ar), 29.1 (CH ),
ꢀ1
3
3
sorption band at about 3425 cm (Figs 1(b) and (c)) is attributed to
3
2.4 ((CH ) C(CH ) ), 45.0 (CH C), 50.1 (CH CO), 54.6 (CH), 111.6
3 2 2 2 2 2
the OH stretching vibrations of silanol groups. The stretching bands
(CCO), 119.8, 120.2, 121.1, 122.9, 126.2, 127.5, 127.9, 131.5, 138.1,
ꢀ1
at 2880 and 2945 cm are attributed to asymmetric and symmet-
1
45.1, 155.1 (C–Ar and CH CNH), 192.5 (C¼O).
[31]
2
ric C–H stretching in the propyl chain. The GA exists as a zwitter-
ion on the surface of NCPs. This is demonstrated by the existence of
+
ꢀ1
3
the δ(NH ) band at 2070 cm . The lack of this band in the spectra
Typical procedure for synthesis of 2-(4-methylphenyl)-4,5-
diphenylimidazole in presence of Cu/GA/Fe O @SiO NCPs
of the complexes shows the copper coordination by the amine
3
4
2
terminal group of the GA ligand. Also, two vibrations for the
ꢀ
1
A mixture of 4-methylbenzaldehyde (0.12 g, 1 mmol), benzil or
benzoin (1 mmol), ammonium acetate (0.30 g, 4 mmol) and
Cu/GA/Fe O @SiO (0.01 g, 0.72 mol%) was heated at 90°C for
COO– moiety (νas(COO–) at 1550 cm
s
and ν (COO–) at
ꢀ
1
1413 cm ) are observed in the zwitterion. After coordination there
is a lowering of the frequency of one of these bands, due to the
generation of the Cu–O bond, and an increase of the other, because
3
4
2
3
0 min under solvent-free conditions. The solid residue was
washed with acetone and the solvent was evaporated to give
the crude product. For further purification, it was recrystallized
from 9:1 acetone–water mixture to afford pure product 2d as a
colourless powder.
a C¼O double bond is partially reconstructed. In our complexes, ν
s
ꢀ
1
(COO–) shifts to low frequencies (1389–1397 cm ) and νas(COO–)
ꢀ
1
is at 1485 cm . For GA/Fe
O @SiO and Cu/GA/Fe O @SiO , the
3 4 2 3 4 2
C¼N stretching peak of GA overlaps with the broader and stronger
ꢀ
1
1
[32]
FT-IR (KBr, cm ): 1441, 1495, 1610, 3023. H NMR (300 MHz,
CDCl , δ, ppm): 2.30 (3 H, s, CH ), 7.26–7.64 (12 H, m, Ar), 7.71 (2 H,
d, J = 8 Hz, Ar), 9.60 (1 H, s, NH). C NMR (75 MHz, CDCl
bands of Si–O–Si.
These results confirm the successful
functionalization of NCPs with GA and Cu-chelating GA groups
on NCPs.
The crystalline structure of magnetite nanoparticles (before and
after silica coating) was identified with the XRD technique. Figure 2
3
3
13
3
, δ, ppm):
–Ar), 124.7, 127.4, 128.8, 128.9, 129.2, 129.6, 129.8, 130.0,
39.2 (C–Ar), 146.6 (–NCNH).
2
1
1.8 (CH
3
wileyonlinelibrary.com/journal/aoc
Copyright © 2016 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2016, 30, 414–421