Rice husk ash supported FeCl2·2H2O: A mild and highly efficient heterogeneous catalyst for the synthesis of polysubstituted quinolines by Friedlaender heteroannulation

Article abstract of DOI:10.1016/S1872-2067(12)60684-6

Rice husk ash was used as a new, green, and cheap adsorbent for FeCl ₃. Characterization of the obtained reagent showed that rice husk ash supported FeCl₂·2H₂O was formed. This reagent is efficient at catalyzing the synthe

Full text of DOI:10.1016/S1872-2067(12)60684-6

Chinese Journal of Catalysis 34 (2013) 2200–2208
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
Article
Rice husk ash supported FeCl2·2H2O: A mild and highly efficient
heterogeneous catalyst for the synthesis of polysubstituted
quinolines by Friedländer heteroannulation
Farhad Shirini*, Somayeh Akbari‐Dadamahaleh, Ali Mohammad‐Khah
Department of Chemistry, College of Sciences, University of Guilan, Rasht 41335, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
Rice husk ash was used as a new, green, and cheap adsorbent for FeCl3. Characterization of the ob‐
tained reagent showed that rice husk ash supported FeCl2·2H2O was formed. This reagent is effi‐
cient at catalyzing the synthesis of multisubstituted quinolines by the Friedländer heteroannulation
of o‐aminoaryl ketones with ketones or β‐diketones under mild reaction conditions. This method‐
ology allows for the synthesis of a broad range of substituted quinolines in high yields and with
excellent regioselectivity in the absence of a solvent.
Received 15 July 2013
Accepted 16 August 2013
Published 20 December 2013
Keywords:
Rice husk ash
Supported FeCl2·2H2O
Quinolines
© 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Published by Elsevier B.V. All rights reserved.
2‐Amino benzophenone
Solvent‐free
Friedländer heteoannulation
1. Introduction
‐SiO2 [23], amberlyst‐15 [24], dodecylphosphonic acid [25],
o‐benzenedisulfonimide [26], SnCl2 [27], FeCl3 [28], Mg(ClO4)2
Quinolines are well‐known structural units in alkaloids,
therapeutics, and synthetic analogues with interesting biologi‐
cal activities [1–7]. These compounds are also valuable rea‐
gents for the synthesis of nano‐ and mesostructures with en‐
hanced electronic and photonic properties [8–10].
Various procedures such as those of Skraup [11], Conrad‐
Limpach‐Knorr [12,13], Pfitzinger [14,15], Friedländer [16,17],
and Combes [18,19] have been developed for the synthesis of
quinoline derivatives. Among these, Friedländer reaction is the
most popular, which is a condensation reaction followed by a
cyclodehydration between an aromatic 2‐aminoaldehyde or
ketone and an aldehyde or ketone with a methylene function
under acidic or basic conditions [20].
[29], Nd(NO3)3 [30], Y(OTf)3 [31], NiCl2 [32], I2/CAN [33], Na‐
HSO4‐SiO2 [34], poly(N‐bromo‐N‐ethylbenzene‐1,3‐disulfona‐
mide) [35], and KOtBu [36].
However, many of the reported procedures have significant
drawbacks such as low product yields, long reaction time,
harsh reaction conditions, difficulties in work‐up, and the use of
stoichiometric and/or relatively expensive reagents. Moreover,
the main disadvantage of almost all existing methods is that the
catalysts are spent in the work‐up procedure and cannot be
recovered or reused. Thus, the development of more efficient
procedures for the synthesis of quinolines is still needed.
With growing concern over the environmental impact of
chemicals and strict legislation, the development of greener
chemical processes in synthetic chemistry is required. Green
chemistry is mainly concerned with alternative reaction media.
Various solid acid catalysts have been used in the Friedlän‐
der reaction such as Ag3PW12O40 [21], sulfamic acid [22], HClO4
* Corresponding author. Tel/Fax: +98‐131‐3233262; E‐mail: shirini@guilan.ac.ir
DOI: 10.1016/S1872‐2067(12)60684‐6 | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 34, No. 12, December 2013

Farhad Shirini et al. / Chinese Journal of Catalysis 34 (2013) 2200–2208
These media are the basis of many of the cleaner chemical
for 48 h.
RiHA was produced during the combustion of RiH. The ideal
temperature is between 600 and 700 °C.
The FeCl2·2H2O‐RiHA catalyst was prepared by the
impregnation of RiHA (50 g) with a solution of FeCl3 (0.053
mol, 8.62 g) in acetone. The solvent was evaporated at 60 °C
under reduced pressure. The sample was then heated at 120 °C
for 8 h to give FeCl2·2H2O‐RiHA (55 g).
technologies that have undergone commercial development.
The major goals in green chemistry are to increase process
selectivity, maximize the use of starting materials, and to re‐
place hazardous and stoichiometric reagents with eco‐friendly
catalysts to facilitate the easy separation of final reaction mix‐
tures, including catalyst recovery.
Ferric chloride is a conventional homogeneous acid catalyst,
but it has several disadvantages such as a high degree of corro‐
siveness, long work‐up, necessity of stoichiometric quantities,
the presence of several undesirable side products, and the sin‐
gle use of catalysts. Therefore, it is highly undesirable from an
ecological point of view [36]. Although FeCl3 is very active dur‐
ing the synthesis of polymers, it has low regioselectivity, which
can lead to polymers with regioirregular structures and many
side products [37,38]. The inhalation of FeCl3 dust can result in
gastrointestinal or respiratory tract irritation leading to
coughing, sneezing, or a burning sensation. Overexposure can
produce lung pain, choking, unconsciousness, or death. This
substance is toxic to lungs and mucous membranes, and vari‐
ous methods to mitigate these disadvantages have been con‐
sidered by researchers.
One method to address these limitations is the preparation
of supported solid FeCl3 catalysts and the following supports
have been reported: poly(3‐alkyithiophenes) [39], NH3BH3
[40], polyaniline nanofiber [41], nanopore silica [42], clays and
Si‐MCM‐41 [43], andalumina [44], etc.
Rice husk consists of a thin but abrasive skin, which covers
edible rice kernels. It contains cellulose, hemicellulose, lignin,
silica, solubles, and moisture [45]. During the combustion of
rice husk (RiH), rice husk ash (RiHA) is produced. RiHA is con‐
sidered to be the most economical source of silica [46], which
has been used as an adsorbent for metal ions such as Cd2+, Zn2+,
Ni2+, and heavy metals such as lead and mercury from aqueous
solutions [47–49]. In this paper, we wish to report the use of
RiHA as a green, cheap, and available absorbent for FeCl3 and
the applicability of the obtained reagent in the synthesis of
multisubstituted quinolines.
2.3. Characterization of the catalyst
FT‐IR spectra were obtained on a Perkin‐Elmer bio‐spec‐
1
trometer. H‐NMR (400 MHz) and 13C‐NMR (100 MHz) were
obtained on a Bruker Avance DPX‐250 FT‐NMR spectrometer.
Microanalyses were performed on a Perkin‐Elmer 240‐B
microanalyzer. Melting points were recorded on a Büchi B‐545
apparatus in open capillary tubes. The RiH was characterized
by scanning electron microscopy (SEM‐Philips XL30) with a
field emission gun and using energy dispersive spectroscopy
(EDS). Before placing samples in the microscope the RiH parti‐
cles were coated with gold under vacuum (SCD 005 sputter
coater, Bal‐Tec, Swiss) and then examined at an acceleration
voltage of 17 kV.
2.4. A typical procedure for Friedländer reaction
A mixture of 2‐amino benzophenone (1.0 mmol), dimedone
(1.2 mmol), and FeCl2·2H2O‐RiHA (0.3 g) was stirred under
solvent‐free conditions at 90 °C for 35 min. The reaction was
monitored by TLC. Upon completion, hot ethanol was added,
and the catalyst was removed by filtration. The solution was
concentrated, and the product was recrystallized in EtOH‐H2O
(4:1). The solid was washed with cold EtOH and dried to afford
the desired product in 86% yield. Reaction conversions were
determined by GC on a Shimadzu model GC‐16A instrument
using a 25 m CBPI‐S25 (0.32 mm ID, 0.5 m coating) capillary
column.
The spectral data of the obtained products are as follows.
1‐(2‐Methyl‐4‐phenylquinolin‐3‐yl)ethanone (Table 4, entry
1). M.p. 107–108 °C. IR (KBr, cm–1): ν 3058, 2902, 1691, 1265;
1H‐NMR (CDCl3, 400 MHz): δ 1.92 (s, 3H), 2.61 (s, 3H),
7.27–7.30 (m, 2H), 7.31–7.34 (m, 1H), 7.40–7.45 (m, 3H), 7.51
(dd, J = 1 Hz, 8.1 Hz, 1H), 7.61–7.66 (m, 1H), 8.00 (d, J = 8.4 Hz,
1H); 13C‐NMR (CDCl3, 100 MHz): δ 24.2, 32.9, 124.5, 125.6,
126.7, 128.1, 128.3, 129.0, 129.9, 130.0, 134.2, 135.3, 144.0,
146.8, 153.7, 206.3.
2‐Methyl‐4‐phenyl‐quinoline‐3‐carboxylic acid methyl ester
(Table 4, entry 2). M.p. 107–109 °C. IR (KBr, cm–1): ν 3047,
2942, 1735; 1H‐NMR (CDCl3, 400 MHz): δ 3.27 (s, 3H), 3.52 (s,
3H), 7.28–7.32 (m, 2H), 7.58–7.65 (m, 3H), 7.69–7.74 (m, 2H),
8.04 (t, J = 6.8 Hz, 1H), 8.63 (m, 1H); 13C‐NMR (CDCl3, 100
MHz): δ 22.6, 52.2, 122.7, 126.1, 127.3, 127.9, 129.0, 129.9,
130.5, 131.8, 133.1, 134.9, 145.0, 146.1, 146.4, 155.1, 171.1.
Ethyl 2‐methyl‐4‐phenylquinoline‐3‐carboxylate (Table 4,
entry 3). M.p. 99–101 °C. IR (KBr, cm–1): ν 3046, 2934, 1716;
1H‐NMR (CDCl3, 400 MHz): δ 0.98 (t, J = 7.6 Hz, 3H), 2.74 (s,
3H), 4.02–4.13 (m, 2H), 7.34–7.42 (m, 6H), 7.54 (d, J = 8.4 Hz,
2. Experimental
2.1. General
All chemicals were purchased from Fluka, Merck, Aldrich, or
Southern Clay Products. Yields refer to isolated products. All
the products were fully characterized by spectroscopic
1
methods such as FT‐IR, H‐NMR, and 13C‐NMR as well as by
melting point. The purity of the substrates and reaction
monitoring were accomplished by thin‐layer chromatography
(TLC) on silica‐gel polygram SILG/UV 254 plates.
2.2. Preparation of RiH, RiHA, and FeCl2·2H2O‐RiHA
The rice sample (designated Hassani) was obtained from
Rasht (Guilan Provience) in the north of Iran. RiH was obtained
from a local mill, washed several times with distilled water to
remove any adhering materials, and dried at room temperature

Farhad Shirini et al. / Chinese Journal of Catalysis 34 (2013) 2200–2208
1H), 7.64 (t, J = 8.4 Hz, 1H), 8.03 (d, J = 8.4 Hz, 1H); 13C‐
3H), 7.26–7.92 (m, 8H); 13C‐NMR (CDCl3, 100 MHz): δ 23.4,
52.62, 125.1, 125.9, 127.9, 128.6, 128.9, 129.1, 130.4, 131.1,
132.5, 134.9, 145.6, 146.1, 154.8, 168.7.
NMR(CDCl3, 100 MHz): δ 13.8, 22.9, 61.0, 125.1, 126.1, 128.0,
128.4, 128.7, 129.3, 130.0, 135.3, 146.3, 147.8, 153.9, 168.8.
(2‐Methyl‐4‐phenylquinoline‐3‐yl)(phenyl)methanone (Ta‐
ble 4, entry 4). M.p. 140–143 °C. IR (KBr, cm–1): ν 3052, 2908,
Ethyl 6‐chloro‐2‐methyl‐4‐phenylquinoline‐3‐carboxylate
(Table 4, entry 12). M.p. 98–100 °C. IR (KBr, cm–1): ν 3042,
1
1
1680. H‐NMR (CDCl3, 400 MHz): δ 2.67 (s, 3H), 7.21 (m, 7H),
2936, 1712; H‐NMR (CDCl3, 400 MHz): δ 0.90 (t, J = 7.0 Hz,
7.34 (m, 2H), 7.58 (m, 3H), 7.70 (m, 1H), 8.08 (d, J = 8.4 Hz, 1H).
13C‐NMR (CDCl3, 100 MHz): δ 23.9, 124.9, 126.0, 126.4, 127.8,
128.2, 128.3, 128.8, 129.1, 129.6, 129.9, 132.2, 133.3, 134.6,
136.9, 145.3, 147.6, 154.4, 197.5.
3H), 2.73 (s, 3H), 3.88 (q, J = 7.0 Hz, 2H), 7.30–7.47 (m, 6H),
7.51 (dd, J1 = 8.8 Hz, J2 = 2.4, 1H), 7.88 (d, J = 8.8 Hz, 1H);
13C‐NMR (CDCl3, 100 MHz): δ 13.5, 23.8, 59.9, 124.5, 125.8,
127.9, 128.4, 128.2, 128.9, 130.1, 130.8, 132.2, 134.6, 144.9,
145.4, 154.7, 167.8.
9‐Phenyl‐3,4‐dihydroacridin‐1(2H)‐one (Table 4, entry 5).
1
M.p. 151–153 °C. IR (KBr, cm–1): ν 3045, 2956, 1695; H‐NMR
(6‐Chloro‐2‐methyl‐4‐phenylquinolin‐3‐yl)(phenyl)methan
one (Table 4, entry 13). M.p. 209–211 °C. IR (KBr, cm–1): ν 2925,
(CDCl3, 400 MHz): δ 2.22 (m, 2H), 2.71 (t, J = 6.5 Hz, 2H), 3.29 (t,
J = 6.20 Hz, 2H), 7.14 (m, 2H), 7.45 (m, 5H), 7.77 (m, 1H), 8.21
(d, J = 8.6 Hz, 1H); 13C‐NMR (CDCl3, 100 MHz): δ 22.4, 34.6, 42.7,
123.7, 126.2, 127.4, 127.8, 127.9, 128.0, 128.3, 131.5, 137.5,
148.5, 151.0, 162.0, 197.5.
1
2851, 1680, 1240; H‐NMR (CDCl3, 400 MHz): δ 2.49 (s, 3H),
7.12 (m, 7H), 7.41 (m, 1H), 7.46 (m, 3H), 7.66 (d, J = 2.40 Hz,
1H), 7.96 (d, J = 8.8 Hz, 1H). 13C‐NMR (CDCl3, 100 MHz): δ 23.8,
124.7, 125.9, 128.1, 128.3, 128.4, 129.0, 129.7, 130.4, 130.8,
132.3, 133.0, 133.5, 133.9, 136.7, 144.6, 146.0, 154.8, 199.9.
7‐Chloro‐9‐phenyl‐3,4‐dihydro‐1‐2H‐acridinone (Table 4,
entry 14). M.p. 187–189 °C. IR (KBr, cm–1): ν 3032, 2967, 2875,
3,3‐Dimethyl‐9‐phenyl‐3,4‐dihydro‐2H‐acridin‐1‐one (Ta‐
ble 4, entry 6). M.p. 190–191 °C. IR (KBr, cm–1): ν 3074, 2901,
1
1670; H‐NMR (CDCl3, 400 MHz): δ 1.23 (s, 6H), 2.65 (s, 2H),
1
3.37 (s, 2H), 7.13–7.21 (m, 2H), 7.34–7.38 (m, 1H), 7.43–7.52
(m, 4H), 7.72–7.76 (m, 1H), 8.08 (d, J = 8.4 Hz, 1H); 13C‐NMR
(CDCl3, 100 MHz): δ 29.1, 29.7, 49.1, 53.8, 123.2, 126.5, 126.9,
127.6, 127.8, 127.9, 128.2, 128.3, 132.3, 137.6, 150.1, 151.2,
161.0, 198.0.
9‐Pheyl‐1,2,3,4‐tetrahydroacridine (Table 4, entry 7). M.p.
138–139 °C. IR (KBr, cm–1): ν 3071, 2952, 1568, 1470, 1451;
1H‐NMR (CDCl3, 400 MHz): δ 1.73–1.82 (m, 2H), 1.94–2.00 (m,
2H), 2.61 (t, J = 6.8 Hz, 2H), 3.23 (t, J = 6.8 Hz, 2H), 7.23–7.32
(m, 4H), 7.42–7.56 (m, 3H), 7.64–7.66 (m, 1H), 8.17 (d, J = 8.4
Hz, 1H); 13C‐NMR (CDCl3, 100 MHz): δ 22.5, 22.8, 28.0, 33.1,
126.1, 126.2, 127.4, 127.9, 128.7, 128.8, 129.1, 136.6, 144.8,
150.3, 159.0.
1688, 1549. H‐NMR (CDCl3, 400 MHz): δ 2.24 (q, J = 6.4 Hz,
2H), 2.70 (t, J = 6.4 Hz, 2H), 3.32 (t, J = 6.4 Hz, 2H), 7.15 (t, 2H),
7.41 (s, H), 7.52 (m, 3H), 7.59 (d, J = 8.4 Hz, 1H, ), 7.98 (d, J = 8.4
Hz, 1H); 13C‐NMR (CDCl3, 100 MHz): δ 20.9, 34.2, 40.3, 124.2,
126.3, 127.8, 130.0, 132.2, 136.6, 146.7, 149.9, 162.2, 197.0.
7‐Chloro‐3,3‐dimethyl‐9‐phenyl‐3,4‐dihydro‐2H‐acridin‐1‐o
ne (Table 4, entry 15). M.p. 207–209 °C. IR (KBr, cm–1): ν 3071,
2946, 1693; 1H‐NMR (CDCl3, 400 MHz): δ 1.12 (s, 6H), 2.53 (s,
2H), 3.25 (s, 2H), 7.13–7.16 (m, 2H), 7.28 (d, J = 2.4 Hz, 1H),
7.42–7.55 (m, 3H), 7.71 (dd, J1 = 8.8 Hz, J2 = 2.8 Hz, 1H), 8.05 (d,
J = 8.8 Hz, 1H); 13C‐NMR (CDCl3, 100 MHz): δ 28.4, 32.3, 48.4,
54.3, 123.5, 126.8, 127.7, 127.9, 128.1, 128.2, 130.0, 132.3,
132.5, 136.8, 147.2, 150.2, 161.2, 197.5.
2,3‐Dihydro‐9‐phenyl‐1H‐cyclopenta[b]uinolone (Table 4,
entry 8). M.p. 129–131 °C. IR (KBr, cm–1): ν 3062, 2915, 1575,
1485; 1H‐NMR (CDCl3, 400 MHz): δ 2.16–2.20 (m, 2H), 2.93 (t, J
= 7.4 Hz, 2H), 3.27 (t, J = 7.6 Hz, 2H), 7.37–7.43 (m, 3H),
7.48–7.56 (m, 3H), 7.62–7.66 (m, 2H), 8.07–8.09 (m, 1H);
13C‐NMR (CDCl3, 100 MHz): δ 24.0, 29.9, 35.3, 124.9, 125.7,
126.4, 128.6, 128.3, 129.3, 133.7, 137.0, 142.5, 148.0, 167.6.
6‐Phenyl‐7H‐indeno[1,2‐b]quinolin‐7‐one (Table 4, entry
9). M.p. 180–182 °C. IR (KBr, cm–1): ν 3074, 2929, 1621, 1455;
1H‐NMR (CDCl3, 400 MHz): δ 7.44 (t, J = 8.0 Hz, 2H), 7.50–7.59
(m, 4H), 7.60–7.74 (t, J = 8.0 Hz, 3H), 7.81–7.85 (t, J = 8.0 Hz,
1H), 8.32 (s, 2H) 13C‐NMR (CDCl3, 100 MHz): δ 29.7, 123.0,
124.1, 127.0, 127.7, 128.1, 128.7, 128.9, 129.3, 131.7, 140.0,
133.0, 135.4, 137.7, 163.1.
7‐Chloro‐9‐phenyl‐1,2,3,4‐tetrahydroacridine (Table 4, en‐
try 16). M.p. 160–163 °C. IR (KBr, cm–1): ν 3060, 2944, 1604,
1572, 1481, 1215, 703; 1H‐NMR(CDCl3, 400 MHz): δ 1.71–1.83
(m, 2H), 1.92–1.96 (m, 2H), 2.58 (t, J = 6.2 Hz, 2H), 3.30 (t, J =
6.2 Hz, 2H), 7.21–7.32 (m, 4H), 7.48–7.69 (m, 3H), 7.94 (d, J =
8.6 Hz, 1H); 13C‐NMR (CDCl3, 100 MHz): δ 22.6, 27.7, 35.6,
124.2, 126.9, 128.1, 128.8, 128.9, 129.0, 129.5, 130.4, 131.6,
136.8, 144.9, 145.9, 129.8.
7‐Chloro‐2,3‐dihydro‐9‐phenyl‐1H‐cyclopenta[b]uinolone
(Table 4, entry 17). M.p. 97–98 °C. IR (KBr, cm–1): ν 3043, 2941,
1608, 1481; 1H‐NMR (CDCl3, 400 MHz): δ 2.23 (m, 2H), 2.94 (t, J
= 7.4 Hz, 2H), 3.24 (t, J = 7.4 Hz, 2H), 7.41–7.32 (m, 2H),
7.41–7.55 (m, 5H), 7.96 (d, J = 8.8 Hz, 1H); 13C‐NMR (CDCl3, 100
MHz): δ 23.3, 31.4, 36.2, 126.5, 128.0, 128.1, 128.6, 128.8,
129.0, 130.2, 131.3, 134.7, 136.0, 141.9, 146.9, 168.5.
8‐Chloro‐10‐phenyl‐11H‐indeno[1,2‐b]quinolin‐11‐one
(Table 4, entry 18). M.p. 240–243 °C. IR (KBr, cm–1): ν 3045,
2917, 1717, 1611.51, 1572, 1442; 1H‐NMR (CDCl3, 400 MHz): δ
7.43–7.46 (m, 2H), 7.51–7.55 (td, J1 = 7.60 Hz, J2 = 0.80 Hz, 1H),
7.60–7.634 (m, 3H), 7.66–7.67 (d, J = 2.00 Hz, 1H), 7.69–7.70 (d,
J = 2.40 Hz, 1H), 7.72–7.75 (m, 1H), 8.10‐8.15 (t, J = 9.80 Hz, 2H)
13C‐NMR (CDCl3, 100 MHz): δ 121.7, 123.3, 124.0, 127.4, 128.4,
128.7, 129.3, 129.4, 131.3, 131.8, 132.4, 133.1, 135.5, 137.5,
143.1, 147.1, 148.8, 162.2, 189.9.
1‐(6‐Chloro‐2‐methyl‐4‐phenylquinolin‐3‐yl)ethanone (Ta‐
ble 4, entry 10). M.p. 159–160 °C. IR (KBr, cm–1): ν 3056, 2938,
1
1675 cm–1; H‐NMR (CDCl3, 400 MHz): δ 1.94 (s, 3H), 2.68 (s,
3H), 7.31–7.34 (m, 2H), 7.49–7.56 (m, 4H), 7.60–7.64 (m, 1H),
7.99 (d, J = 9.4 Hz, 1H); 13C‐NMR (CDCl3, 100 MHz): δ 23.5, 31.9,
124.6, 125.8, 128.7, 129.2, 129.7, 130.2, 130.6, 132.4, 134.5,
135.6, 143.1, 145.6, 153.9, 205.0.
Methyl 6‐chloro‐2‐methyl‐4‐phenylquinoline‐3‐carboxylate
(Table 4, entry 11). M.p. 131–133 °C; IR (KBr, cm–1): ν 3063,
2945, 1735; 1H‐NMR (CDCl3, 400 MHz): δ 2.56 (s, 3H), 3.54 (s,

Farhad Shirini et al. / Chinese Journal of Catalysis 34 (2013) 2200–2208
3. Results and discussion
3.1. Characterization results
3.1.1. FT‐IR analysis
Figure
1 shows the FT‐IR spectra of RiHA and
FeCl2·2H2O‐RiHA catalysts. The broad band at 3430–3480 cm−1
comes from O–H stretching vibrations of silanol OH groups and
adsorbed water bound to the silica surface [50]. The band at
1620–1640 cm−1 comes from the bending vibration of water
molecules, which are trapped in the matrix of the adsrorbent.
The strong peak at 1095 cm−1 comes from the structural
siloxane bond, Si–O–Si. This peak is observed in both RiHA and
metal incorporated RiHA. The bands at 800–805 and 465–475
cm−1 in all spectra come from Si–O bond deformation [51]. In
FeCl2·2H2O‐RiHA the shoulder at 1002.16 cm−1 comes from the
Fe–O–Si vibration [52].
Fig. 1. FT‐IR spectra of RiHA (1) and FeCl2·2H2O‐RiHA (2).
3.1.3. XRD analysis
The XRD patterns of the samples are shown in Fig. 3. As
indicated by the featureless diffractograms and the appearance
of a diffuse maximum at 2θ = 25°, which is typical for
amorphous silica [54], it can be concluded that the RiHA and
the FeCl2·2H2O‐RiHA are completely amorphous and do not
have a crystalline structure. This XRD pattern indicates that
one of the Cl atoms from Fe has been removed and that
FeCl2·2H2O‐RiHA was obtained after final heating. The
interaction of the Fe species with the Brönsted and the silanol
sites of the support results in HCl formation during the reaction
[55].
3.1.2. SEM analysis
SEM was used to investigate the structures of both the bare
RiHA support and the FeCl2·2H2O‐RiHA catalyst precursors. A
clean and smooth RiHA support surface is evident in Fig.
2(a–c). Images of the FeCl2·2H2O‐RiHA catalyst precursors are
shown in Fig. 2(d–e). They clearly reveal the presence of struc‐
tures with different diameters after metal ion sorption. These
structures were absent on the RiHA before the sorption pro‐
cess. The FeCl2·2H2O particles that cover the substrate are
0.5–3 μm in diameter. The surface morphology and spherical
structure of the particles are retained even when the RiHA
sample was modified with FeCl3. These SEM observations
prove that the RiHA supported FeCl2·2H2O catalyst was suc‐
cessfully prepared. These results are in accordance with an
earlier report [53].
3.1.4. XRF analysis
XRF is the emission of characteristic “secondary” (or fluo‐
rescent) X‐rays from a material that has been excited upon
bombardment with high energy X‐rays or gamma rays. XRF
technology provides one of the simplest, most accurate, and
(b)
(a)
(c)
(d)
(e)
(f)
Fig. 2. SEM micrographs of RiHA (a–c) and FeCl2·2H2O‐RiHA (d–f).

Farhad Shirini et al. / Chinese Journal of Catalysis 34 (2013) 2200–2208
FeCl3 + H+
FeCl2 + HCl (g)
+
FeCl2·2H2O
OH2
Si
O
Cl
FeCl2·2H2O-RiHA =
Si
Fe
O
Si
Cl
(2)
(1)
OH2
Scheme 1. Removal of Cl from FeCl3.
10
20
30
40
2θ/ ( o )
50
60
70
80
3.2. Catalytic performance of FeCl2·2H2O‐RiHA for Friedländer
reaction
Fig. 3. XRD patterns of RiHA (1) and FeCl2·2H2O‐RiHA (2).
We recently reported the preparation of RiH supported
FeCl3 nanoparticles and its application in the 1,1‐diacetate pro‐
tection and deprotection of aldehydes [56] as well as applica‐
tion in multi‐component reactions [57]. In a continuation of
these studies we were interested in the preparation of FeCl3
supported RiHA and the influence of a change in support on
this type of reaction. Our investigations, especially XRD analy‐
sis, showed that when RiHA was used instead of RiH,
FeCl2·2H2O‐RiHA was obtained as the product. After the prep‐
aration and identification of FeCl2·2H2O‐RiHA, we found that
this reagent efficiently catalyzed the synthesis of uinolone de‐
rivatives by the Friedländer reaction (Scheme 2).
To optimize the amount of catalyst and the temperature,
reaction between 5‐chloro‐2‐amino uinoloneon and dimedone
as a model one was performed in the presence of varying
amounts of catalyst FeCl2·2H2O‐RiHA (Table 2). The product
yield increased, and the time for reaction completion decreased
upon an increase in the amount of FeCl2·2H2O‐RiHA up to 0.3 g
catalyst and 90 °C. Any further increase in the amount of
FeCl2·2H2O‐RiHA or the temperature did not significantly im‐
prove the results. It is important to note that in the absence of
catalyst no product was observed (Table 2, entry 14).
most economic analytical methods for the determination of the
chemical composition of many types of materials.
The loss on ignition (L.O.I) of RiHA and FeCl2·2H2O‐RiHA
was determined by heating 3 g of each sample at 1000 °C for 1
h in air to remove moisture and any coexistent unburned car‐
bon. Table 1 shows the elemental composition of the obtained
RiHA with silica as the major component (~80.82%). Other
metallic elements are also present in the RiHA as minor ele‐
ments. The composition of the FeCl2·2H2O supported on RiHA
as determined by XRF is also listed in Table 1. The results
clearly show that the Fe content is higher in the FeCl2·
2H2O‐RiHA (Table 1).
3.1.5. Surface area and pore distribution measurements
N2 adsorption is a powerful tool for nano‐ or mesoporous
material characterization and was carried out in this study to
obtain information about the modified porous silica materials.
The textural properties of the RiHA were substantially altered
upon reaction with FeCl3. When the RiHA was converted to
FeCl2·2H2O‐RiHA a decrease of surface area from 250 to 190
m2/g occurred. This suggests that FeCl2·2H2O may be
well‐confined in the pores of the RiHA and indicates the or‐
dered mesoporosity of the support even after modification.
The role of the solvent in the synthesis of 7‐chloro‐3,4‐di‐
hydro‐3,3‐dimethyl‐9‐phenylacridin‐1(2H)‐one was investi‐
gated in the presence of FeCl2·2H2O‐RiHA as the catalyst. We
established that solvent‐free conditions were the best (Table
3).
After the optimization of the reaction conditions and to
show the generality of the method we used the optimized con‐
ditions for the synthesis of different types of uinolone deriva‐
3.1.6. Catalyst structure
On the basis of the above‐mentioned characterization, espe‐
cially XRD analysis, we conclude that FeCl2·2H2O‐RiHA is the
prepared catalyst. This result can be explained by considering
that the interaction of the Fe species with the Brönsted and the
silanol sites of the support results in HCl formation during the
reaction [55]. After this interaction, Fe is stabilized by the RiHA
matrix in the form of isolated mononuclear complexes located
at the Brönsted sites. These Fe complexes consist of tetrahe‐
drally coordinated Fe3+ bound to the framework by two O at‐
oms and are further surrounded by two Cl atoms (Scheme 1).
Ph
Ph
X
2
O
R
O
FeCl ·2H O-RiHA
2
2
2
R
+
1
o
R
1
NH
90 C, solvent-free
2
R
N
X = H, Cl
Scheme 2. Friedländer reaction catalyzed by FeCl2·2H2O‐RiHA.
Table 1
XRF analysis of RiHA and FeCl2·2H2O‐RiHA.
Element composition (%)
Sample
L.O.I a
12.70
30.15
Al2O3
0.25
0.14
SiO2
80.82
45.75
P2O5
0.44
0.25
SO3
0.39
0.27
K2O
1.25
0.62
CaO
0.82
0.48
Fe2O3
0.38
9.54
Cl
1.99
12.16
Na2O
0.96
0.64
RiHA
FeCl2·2H2O‐RiHA
a Loss on ignition.

Farhad Shirini et al. / Chinese Journal of Catalysis 34 (2013) 2200–2208
Table 2
Table 3
Effect of the amount of catalyst and temperature on the reaction time
and conversion to 7‐chloro‐3,4‐dihydro‐3,3‐dimethyl‐9‐phenylacridin‐
1(2H)‐one.
Effect of the solvent on the preparation of 7‐chloro‐3,4‐dihydro‐3,3‐
dimethyl‐9‐phenylacridin‐1(2H)‐one in the presence of FeCl2·2H2O‐
RiHA.
Catalyst amount Temperature
Time
(min)
Conversion
(%)
Entry
Solvent
solvent‐free
ethanol
CH2Cl2
CH3CN
Time (min)
45
Yield (%)
92
65
trace
30
Entry
(g)
(°C)
1
2
3
4
1
2
3
4
5
6
7
8
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.3
0.3
0.3
0.4
0.4
0.0
25
50
90
100
25
50
90
100
50
90
100
50
90
90
90
90
60
60
60
60
60
45
45
50
45
90
20
35
50
50
40
60
80
80
80
100
100
90
100
0
120
120
120
corresponding substituted uinolone. Interestingly, cyclic ke‐
tones such uinoloneone and cyclopentanone reacted with
2‐aminoaryl ketones to afford the respective tricyclic quino‐
lines. The reaction is fairly general, clean, rapid, and efficient.
The experimental procedure is very simple and the products
are obtained in high yields in relatively short reaction times.
After the completion of the reaction, the catalyst was sepa‐
rated and washed well with ethyl acetate and then dried at 100
°C before activity testing in a subsequent run and thus fresh
catalyst was not added. It was found that the catalyst had very
good reusability (Fig. 4).
9
10
11
12
13
14
90
100
tives. The results are summarized in Table 4. Various 1,3‐
diketones were reacted with 2‐aminoaryl ketones to give the
Table 4
Preparation of uinolone derivatives using FeCl2·2H2O‐RiHA as the catalyst.
Entry
1
Substrate
Ketone
Product
Time (min)
30
Yield a (%)
88
Melting point (°C)
107–108
Ref.
O
O
O
O
[58]
NH
O
2
2
2
2
2
N
O
O
O
2
3
4
5
6
7
8
20
25
75
25
35
40
35
91
93
86
94
86
89
90
107–109
99–101
[59]
[59]
[25]
[59]
[59]
[59]
[59]
OMe
OMe
OEt
Ph
NH
O
N
O
O
O
OEt
NH
O
N
O
O
O
140–143
154–156
190–191
138–139
129–131
Ph
NH
O
N
O
O
O
O
O
NH
O
N
O
NH
O
2
N
O
NH
O
2
N
N
O
NH
O
2
O
O
9
45
95
180–182
[59]
NH
2
O
N
(To be continued)

Farhad Shirini et al. / Chinese Journal of Catalysis 34 (2013) 2200–2208
Table 4 (continued)
Entry
10
Substrate
Ketone
Product
Time (min)
50
Yield a (%)
93
Melting point (°C)
159–160
Ref.
O
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
O
O
O
[59]
Cl
NH
O
2
N
O
O
O
11
12
13
14
15
16
17
35
40
90
35
40
90
45
92
90
87
94
85
89
91
131–133
98–100
209–211
187–189
207–209
160–163
97–98
[59]
[53]
[59]
[59]
[59]
[60]
[59]
Cl
OMe
OMe
NH2
O
N
O
O
O
Cl
OEt
OEt
Ph
NH2
O
N
O
O
O
Cl
Ph
NH2
O
N
O
O
O
O
O
Cl
NH2
O
N
O
Cl
NH2
O
N
O
O
Cl
NH2
O
N
Cl
NH2
O
N
O
Cl
O
Cl
18
60
94
240–243
this work
NH2
O
N
a Isolated yield.
We compared the results obtained from the reaction be‐
tween 5‐chloro‐2‐amino benzophenone and acetylacetone in
the presence of FeCl2·2H2O‐RiHA with other catalysts in similar
reactions (Table 5). This comparison clearly shows that with
our method the desired product is obtained in a shorter reac‐
tion time and under relatively milder reaction conditions.
Two possible reaction mechanisms may explain our results
and these are shown in Scheme 3. On the basis of these mecha‐
nisms the carbonyl group is activated in the first step by
FeCl2·2H2O‐RiHA in a cross‐aldol reaction creating an amino
ketone (I or II). This intermediate subsequently condenses with
itself and produces a ring with the concomitant formation of a
C=N bond.
100
80
60
40
20
0
100
80
60
40
20
0
Time
Yield
Table 5
Effect of different catalysts in the preparation of 1‐(6‐chloro‐2‐methyl‐
4‐phenylquinolin‐3‐yl)ethanone compared with FeCl2·2H2O‐RiHA.
Time Yield
(min) (%)
Entry
Catalyst
Conditions
CH3CN, r.t.
Ref.
1
2
3
4
5
6
Y(OTf)3
[Hbim]BF4
TBBDA
Amberlyst‐15
Zr(NO3)4
360
81
93
94
90
86
[30]
[61]
[34]
[62]
[63]
100 °C/solvent‐free 198
1
2
3
H2O/reflux
EtOH/reflux
H2O/reflux
300
120
360
50
Cycle
Fig. 4. Reusability of FeCl2·2H2O‐RiHA in the synthesis of 7‐chloro‐3,4‐
dihydro‐3,3‐dimethyl‐9‐phenylacridin‐1(2H)‐one (Table 3, entry 15).
FeCl2·2H2O‐RiHA 90 °C/solvent‐free
93 this work

Farhad Shirini et al. / Chinese Journal of Catalysis 34 (2013) 2200–2208
FeCl2·2H2O-RiHA
+ 
O
FeCl2·2H2O-RiHA
R2
Ph
HO
R2
R1
Ph
+
H
O

O
R2
Ph
N
NH2
R2
R1
R1
R1
NH2
O
Ph
Ph
R2
R1
R2
R1
R2
-H2O
-H2O
R1
O
N
H
NH2
OH
(I)
FeCl2·2H2O-RiHA
O
Ph
N
Ph
O
+
R2
R1
R2
R1
O
Ph
NH2
R2
R1
+
N
H
(II)
Scheme 3. Proposed mechanisms of the synthesis of quinoline derivatives by Friedländer reaction using FeCl2·2H2O‐RiHA catalyst.
[8] Agrawal A K, Jenekhe S A. Macromolecules, 1991, 24: 6806
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We have developed an environmentally friendly, high yield‐
ing and mild condition protocol for the synthesis of quinoline
derivatives by the Friedländer reaction using FeCl2·2H2O‐RiHA
as a catalyst. This method has several advantages compared to
those reported in the literature, i.e., the introduction of a new,
green and cheap adsorbent for FeCl3, the promotion of
Friedländer heteroannulation under mild reaction conditions,
high product yields, the heterogeneous nature of the reaction,
reusability of the catalyst as well as a simple procedure. It is
thus a useful and attractive strategy for the synthesis of quino‐
line derivatives.
Acknowledgements
We are thankful to the University of Guilan Research Council
for the partial support of this work.
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Farhad Shirini et al. / Chinese Journal of Catalysis 34 (2013) 2200–2208
Graphical Abstract
Chin. J. Catal., 2013, 34: 2200–2208 doi: 10.1016/S1872‐2067(12)60684‐6
Rice husk ash supported FeCl2·2H2O: A mild and highly efficient
heterogeneous catalyst for the synthesis of polysubstituted
quinolines by Friedländer heteroannulation
Rice husk
Rice husk ash
FeCl2·2H2O-Rice husk ash
FeCl2·2H2O-RiHA
Farhad Shirini*, Somayeh Akbari‐Dadamahaleh, Ali Mohammad‐Khah
University of Guilan, Iran
Ph
X
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FeCl2·2H2O-RiHA
NH2
+
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R2
R1
X = H, Cl
Ph
N
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R2
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