Catalytic Friedel-Crafts acylation: Magnetic nanopowder CuFe 2O4 as an efficient and magnetically separable catalyst

Article abstract of DOI:10.1016/j.tetlet.2013.01.081

Catalytic regioselective Friedel-Crafts acylation of an array of anisoles/arenes with various acid chlorides using 5-20 mol % of magnetic nanopowder CuFe₂O₄ is reported. Unlike the conventional Friedel-Crafts reactions, which are catalyzed by moisture sensitive homogeneous catalysts/promoters, the nanopowder CuFe₂O₄ catalyst is moisture insensitive and the product/ketone-catalyst isolation is easily achieved using the magnetic properties of CuFe₂O₄.

Full text of DOI:10.1016/j.tetlet.2013.01.081

Tetrahedron Letters 54 (2013) 1738–1742
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Catalytic Friedel–Crafts acylation: magnetic nanopowder CuFe2O4 as an
efficient and magnetically separable catalyst
⇑
Ramarao Parella, Naveen, Amit Kumar, Srinivasarao Arulananda Babu
Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Knowledge City, Sector 81, SAS Nagar, Mohali, Manauli PO, Punjab 140306, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Catalytic regioselective Friedel–Crafts acylation of an array of anisoles/arenes with various acid chlorides
using 5–20 mol % of magnetic nanopowder CuFe2O4 is reported. Unlike the conventional Friedel–Crafts
reactions, which are catalyzed by moisture sensitive homogeneous catalysts/promoters, the nanopowder
CuFe2O4 catalyst is moisture insensitive and the product/ketone-catalyst isolation is easily achieved using
the magnetic properties of CuFe2O4.
Received 6 November 2012
Revised 15 January 2013
Accepted 18 January 2013
Available online 26 January 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Acylation
Catalysis
CuFe2O4
Friedel–Crafts reaction
Ketones
Development of new catalytic transformations with easy sepa-
ration and recyclability of the catalyst is an essential task in chem-
moisture insensitive catalysts and efficient product/catalyst isola-
tion procedure.
ical synthesis. Friedel–Crafts (FC) reaction is
a
fundamental
In recent years, magnetic nano metal oxide-based catalysts (e.g.,
CuFe2O4 or Fe3O4) have been successfully used for accomplishing
several transformations.6–9 Several metal oxides for example cop-
per/iron oxide-based catalysts are environmentally compatible,
moisture insensitive and separation from the reaction medium is
highly possible by means of an external magnetic field. We present
a new catalytic synthetic protocol for performing the Friedel–
Crafts acylation of aromatic compounds using acid chlorides in
the presence of magnetic nanopowder, CuFe2O4.
method for obtaining functionalized aromatic ketones, which have
applications in chemical industries.1 Traditionally, the FC acylation
of benzenes with acid chlorides has been carried out in the pres-
ence of protic acids or highly moisture sensitive or strong Lewis
acid catalysts. The use of strong and moisture sensitive Lewis acids
(e.g., AlCl3) as the catalysts/promoters for performing the FC acyl-
ation is still in practice (Scheme 1).
Numerous FC acylation protocols1–5 based on homogenous or
heterogeneous catalysts (e.g., metal oxides, zeolite, clays, hetero-
poly acids, sulfated zirconia, and nafion) have been reported. In
some of the existing methods, the catalysts, especially, some of
the metal oxides need prior activation/acid treatment and special
efforts are needed to separate the catalysts from the reaction mix-
ture. Recycling of moisture sensitive homogenous catalysts for
example AlCl3, BF3.OEt2, SnCl4, and some metal oxide-based cata-
lysts is seldom possible while the recovery of some metal triflates
has been reported.1–5
New and improved catalytic protocols continue to attract the
attention of industries/chemical laboratories due to a very high
importance of the aromatic ketones which are key intermediates
in several fields including fine chemicals and pharmaceuticals.1–5
Hence, there is still a demand for developing new synthetic meth-
ods for carrying out the Friedel–Crafts acylation, which deal with
To the best of our knowledge the Friedel–Crafts acylation reac-
tion has not been reported by using the nanopowder CuFe2O4 (cop-
per ferrite) as
a
catalyst.6–8 We report that the magnetic
nanopowder CuFe2O4 is as an efficient and easily separable heter-
ogeneous catalyst for the FC acylation reaction.
At the outset, we carried out the optimization reactions (Table 1)
to find out an efficient metal oxide nanopowder, preferably, a mag-
netically separable catalyst for performing the Friedel–Crafts acyl-
ation of anisole. Among the various nano metal oxides employed in
this work, nanopowder CuFe2O4 (particle size = ꢀ50 nm)8e was
found to be the best catalyst. The reaction of 4-methylbenzoyl
chloride in neat anisole at rt gave the aromatic ketone 3a in 86%
and 98% yields by using 15 or 20 mol % of nano CuFe2O4, respec-
tively (entries 29 and 31, Table 1).
After the reaction, the purification of ketones and the catalyst
separation were carried out as stated in the following steps 1
and 2. Step 1: After the reaction period, EtOAc (1–2 mL) was added
to the reaction flask and gently stirred for 1–2 min. Step 2: A
⇑
Corresponding author. Tel./fax: +91 172 2240266.
E-mail address: sababu@iisermohali.ac.in (S.A. Babu).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.01.081

R. Parella et al. / Tetrahedron Letters 54 (2013) 1738–1742
1739
Table 2
R2
O
Nano CuFe2O4-catalyzed acylation of aryl ethers10
Hydrolysis
AlCl3
(> 1 equiv)
R2
R1
Cl
R1
Tedious work up
MeX
R1
R1
O
+
R2
MeX
R1
nano CuFe2O4 (10-20 mol%)
O
R4
+
AlCl3
O
R4
Cl
HCl
HCl
solvent (or) neat
+
R3
R2
O
AlCl3-ketone
complex
rt (or) 80 oC, 18-24 h
R2
Al(OH)3
(Waste)
MeO
MeO
OMe
This Work:
MeO
Cl
Catalytic amount
Magnetic nano
CuFe2O4
O
R2
R2
Simplework up
R1
Cl
O
O
R1
O
3d O
R1
b
c
3c;(83)b (80)c
b
;(98) (73)c
3b
;(85) (89)
+
Catalyst separation
with the help of
a magnet
R2
O
+
CuFe2O4
Magnet
MeO
NO2
MeO
Br
MeO
Cl
CuFe2O4
HCl
O
3gO
O
3e;(65)a
a
;(73) (61)b
3f;(81)e (98)b (80)f (98)c
Scheme 1. Theme of this work.
MeO
Br
Me
MeO
Cl
MeO
Cl
Br
Table 1
O
O
;(50)
a
a
Nano metal oxides in FC acylation10
;(66) (50)b
3h
3i
3j;(81)Oa (98)b
MeO
Cl
Me
MeO
Cl
Cl
MeO
Cl
Cl
O
MeO
Me
Nano MtxOy (mol%)
MeO
Cl
+
Conditions
O
;(61)
O
a
3Ok
3l
3m
;(96) (77)b
;(71) (75)b
a
a
Me
O
3a
1a
2a
(1.2 mmol)
(1 mmol)
MeS
MeS
MeS
Me
MeS
OMe
Entry
Catalyst (mol %)
Solventa
Conditionb
Yield (%)
O
O
O
a
d
d
3n
3o
3p
;(74)
;(82)
;(98)
1
2
3
4
5
6
7
8
No catalyst
No catalyst
Neat
Neat
THF
MeCN
MeCN
MeCN
MeCN
DCM
25–28 °C, 24 h
80 °C, 24 h
65 °C, 24 h
25–28 °C, 24 h
80 °C, 24 h
25–28 °C, 24 h
80 °C, 24 h
25–28 °C, 24 h
35 °C, 24 h
25–28 °C, 24 h
35 °C, 24 h
rt, 18 h
80 °C, 18 h
rt, 18 h
80 °C, 18 h
80 °C, 6 h
80 °C, 12 h
rt, 18 h
0
0
0
Br
MeO
Cl
MeO
Nano CuFe2O4 (20%)
Nano CuFe2O4 (15%)
Nano CuFe2O4 (15%)
Nano CuFe2O4 (20%)
Nano CuFe2O4 (20%)
Nano CuFe2O4 (15%)
Nano CuFe2O4 (15%)
Nano CuFe2O4 (20%)
Nano CuFe2O4 (20%)
Nano CuFe2O4 (5%)
Nano CuFe2O4 (5%)
Nano CuFe2O4 (10%)
Nano CuFe2O4 (10%)
Nano CuFe2O4 (20%)
Nano CuFe2O4 (20%)
Nano CuFe2O4 (20%)
Nano CuFe2O4 (20%)
Nano Fe3O4 (20%)
Nano ZnO (20%)
S
55
58
60
64
60
65
69
72
66
75
75
75
76
77
80
80
61
67
12
23
0
Br
O
O
O
OMe O
d
3r;(62)d (58)b
MeO
4;(50)b
3s;(74)a (87)b
MeO
3q
;(98)
MeO
MeO
9
DCM
DCM
DCM
( )2
O
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
O
O
O
a
3v;(69)a
a
b
a
b
3t
;(74) (76)
3u
MeO
;(83) (83)
3w
MeO
;(70)
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
MeO
MeO
Cl
Cl
( )9
( )3
a
( )4
( )4
O
O
O
O
;(75)
3y
3z
;(74)
3aa;(75)a
a
a
3x
;(55)
MeO
MeO
MeO
MeO
MeO
( )6
Ph
80 °C, 18 h
80 °C, 24 h
rt, 18 h
rt, 18 h
rt, 18 h
O
O
O
O
3ab;(72)a
3ac; (71)f (75)b 3ad;(69)a (73)f (79)b
OMe
3ae;(70)a
O
O
O
Nano CuO (20%)
Nano Bi2O3 (20%)
Nano Al2O3 (20%)
Nano CuFe2O4 (20%)
Na2CO3 (1.2 mmol)
Nano CuFe2O4 (20%)
NaHCO3 (1.2 mmol)
Nano CuFe2O4 (10%)
Nano CuFe2O4 (10%)
Nano CuFe2O4 (15%)
Nano CuFe2O4 (20%)
Nano CuFe2O4 (20%)
S
N
Cl
N
rt, 18 h
rt, 18 h
O
N
O
Me
Me
3ag
3Maei
b
g
g
h
; (91)
; (50)
; (52) (48)
; (57)g (48)h
70
3af
3ah
26
1,2-DCE
rt, 18 h
67
S
S
S
S
S
O
Cl
g
O
O
O
d
27
28
29
30
31
Neat
rt, 18 h
80 °C, 24 h
rt, 18 h
80 °C, 24 h
rt, 18 h
60
52
86
99
97
h
g
g
h
g
3aj
3ak
; (70)
3al
3am
; (72) (42)
; (73) (48)
; (69)
Neat
a The reaction was carried out using the Condition A. b The reaction was done using
d
Neat
c
d
the Condition B. The reaction was done by using the Condition C. The reaction
was done by using the Condition D. e The reaction was done by using the Condition
‘A’ and nano Fe3O4 (20 mol %) instead of CuFe2O4. f The reaction was done by using
Neatc
d
Neat
g
a
the Condition ‘A’ and nano CuFe2O4 (10 mol %) at rt (35–38 °C) for 18 h. Neat
2 mL solvent was used.
rt refers to 35–38 °C.
10 mmol of 1a was used.
Condition: neat, anisole (3.3 mmol).
b
c
condition, arene (14 mmol), 2 (1.3 mmol), nano CuFe2O4 (20 mol %), 80 °C, and 24 h.
h Neat condition, arene (5 mmol), 2 (1.3 mmol), nano CuFe2O4 (20 mol %), 80 °C, and
24 h. In all cases isolated yields (%) are given in the parenthesis.
d
mixture by silica gel column chromatography furnished the corre-
sponding ketones.
magnet was externally appended to the RB flask and the catalyst
was accumulated at the walls of the flask, the resulting clear solu-
tion was transferred into a fresh RB flask using a dropper. Next, the
steps 1 and 2 were repeated thrice. Then, the catalyst containing
flask was dried in an oven (at 100–110 °C, overnight). The catalyst
can be recycled up to two times. The combined organic layers were
concentrated in vacuum and purification of the resulting reaction
The generality of the nano CuFe2O4-catalyzed FC acylation is
shown by utilizing an array of anisoles and various aromatic acid
chlorides (Table 2). A variety of aromatic ketones (3b–r and 4)
were obtained from the FC acylation of various ortho-/para-/
meta-substituted anisoles with several ortho-/para-substituted
aromatic acid chlorides. Aromatic acid chlorides having electron-
withdrawing groups at the ortho/para positions (e.g., Cl, NO2) also
reacted with anisoles and furnished the corresponding ketones in

1740
R. Parella et al. / Tetrahedron Letters 54 (2013) 1738–1742
Table 3
Nano CuFe2O4-catalyzed acylation of arenes10
R3
R2
R4
O
R5
nano CuFe2O4 (10-20 mol%)
Cl
Arene
+
neat (or) solvent
rt (or) reflux
R1
O
R5
R4
Me
O 5
2
Me
OMe
Me
Me
O
O
g
5b; (96, p/o =95:5)d
d
5c
; (67, p/ o =83:17)
5a
; (98, p/o =95:5)
5e; (79, p/o =80:20)g
Me
a
NO2
Me
Cl
5d
;(62, p/o =90:10)
5e; (72, p/o =85:15)a
5d;(82, p/o =84:16)d
d
5e
; (70, p/o =85:15)
O
O
Me
Cl
O
O
Cl
O
O
5i; (70)g (70)d
g
5g; (68)g
5h
; (51)
5f; (68)g
F
Me
Me
Br
Cl
S
O
Cl
Me
O
Cl
g
O
Cl
g
O
5l; (64)g
6a; (61)b
5j
5k
; (43)
; (45)
Me
Me
Me
Me
OMe
Me
Me
Me
O
Me
Me
O
O
Cl
6b; (84)f (98)c (85)e
6c; (76)c
c
6d
; (98)
Me
Me
Cl
Me
O
Me
Me
Me
Me
Me
Me
O
Me
Me
Me
O
g
O 6g; (46)d
Me
6f
; (77)
6e; (74)b (79)c
Me
Me
Me
Me
OMe
Me
Me
Me
O
O
O
7c; (86)g (98)d
g
d
g
a
d
7a
; (75) (91)
7b
; (90) (71) (81)
Me
Me
Cl
Me
NO2
Me
Me
Me
O
Cl
O
O
a
d
7d; (71)d
7f; (97)g(82)d
7e
; (82) (98)
a The reaction was done by using the Condition A. b The reaction was done by using the Condition
c
d
B. The reaction was done by using the Condition C. The reaction was done by using the
e
Condition D. The reaction was done by using the Condition ‘C’ by employing only a 2 mmol of
arene. f The reaction was done by using the Condition ‘A’ and nano CuFe2O4 (10 mol %) at rt (35–
g
38 °C) for 18 h. Neat condition, arene (14 mmol), 2 (1.3 mmol), nano CuFe2O4 (20 mol %), 80 °C,
and 24 h. In all cases isolated yields (%) are given.
good yields. In these cases, the para-substituted compounds were
obtained selectively and in some cases the crude NMR spectra
showed the presence of traces of minor isomers. The nanopowder
CuFe2O4-catalyzed acylation of anisole with 2-thiophenecarbonyl
chloride, cyclohexanecarbonyl chloride, cyclopropanecarbonyl
chloride, and various aliphatic acid chlorides gave the correspond-
ing ketones 3s–z, 3aa, 3ab, and 3ac in good yields (Table 2). The
reaction of hydrocinnamoyl chloride with anisole selectively affor-
ded the intermolecular FC acylation product 3ad (79%). The reac-
tion of cinnamoyl chloride and 4-methoxybenzenesulfonyl
chloride with anisole gave the respective compounds 3ae (70%)
and 3af (91%, Table 2). The acylation of N-methylpyrrole and thio-
phene using various acid chlorides gave the corresponding ketones
3ag–3ai11a,b and 3aj–3am in moderate yields. It is a limitation that
benzoylation of furan was not successful11c (Table 2).
MeO
O
Cl
Ist use = (98)a
2nd use = (97)a
3rd use = (97)a
4th use = (89)a
5th use = (75)a
MeO
nano CuFe2O4
(20 mol%)
Cl
+
3f
2
O
Cl
1a
Representative Gram Scale Reactions
MeO
Me
O
Cl
nano CuFe2O4
MeO
3 g
Me
(20 mol%)
neat, rt,
+
Cl
Cl 3f;(98)
1.46 g
O
Me
nano CuFe2O4
(20 mol%)
Me
O
Cl
+
neat, rt
6b
; (84)
Me
O
3 g
1.62 g
Me
a
The reactions were done by using the Condition 'B' for 24 h. In all
cases isolated yields (%) are given in the parenthesis.10
The reactions of various acid chlorides in toluene catalyzed by
the nano CuFe2O4 (20 mol %) gave the corresponding ketones 5a–
e (67–98%, Table 3). Benzene and halobenzenes underwent the
FC benzoylations and afforded the corresponding products 5f–l in
51-70% yields. The reaction of various acid chlorides in mesitylene
Scheme 2. Recyclability of nano CuFe2O4 and gram scale reaction.
or p-xylene catalyzed by nano CuFe2O4 furnished the correspond-
ing ketones 6a–f (61–98%), 6g (46%), and 7a–f in very good yields
(71–98%). To explore the possibility of recycling the nano CuFe2O4,

R. Parella et al. / Tetrahedron Letters 54 (2013) 1738–1742
1741
Table 4
Nano CuFe2O4-catalyzed acylation of arenes10,12b
Me
Me
Me
nano CuFe2O4
(20 mol%)
O
Me
Me
No colour
EtOH
EtOH
Phenol
change
Ph Cl
+
Ph
red colour
red
colour
neat, rt 18 h
Me
Me
Me O
Me
Ph
Me
FeCl3
(10 mol%)
O
Me
Phenol
violet
colour
Ph Cl
+
red colour
1,2-DCE (2 mL)
rt 18 h
Me O
Me
Me
CH3
6h
Me
Me O
Me
6i
Me O
Figure 2. A = PXRD pattern of pure CuFe2O4 powder before use. B = PXRD pattern of
nanopowder CuFe2O4 after the 3rd usage in the FC acylation of 1a with 2 under
heating condition. C = PXRD pattern of nanopowder CuFe2O4 after the 1st usage in
the FC acylation of 1a with 2 under rt condition. D = XRD pattern of nanopowder
CuFe2O4 after the 2nd usage in the FC acylation of 1a with 2 under rt condition.
E = XRD pattern of nanopowder CuFe2O4 after the 3rd usage in the FC acylation of
1a with 2 under rt condition.
a
b
c
Isolated yields are given.
The reaction was done by using the Condition B.
The reaction was done by using the Condition C.
The reaction was done by using the Condition D.
The reactions were not performed.
d
e
are not possible to recover. Further, the nano CuFe2O4 catalyst is
moisture insensitive, commercially available, and easily separable
from the reaction mixture. Among all the other nano metal oxides
employed in this work, the magnetic nano CuFe2O4 was found to
be as an efficient catalyst.
the reaction of anisole and 2-chlorobenzoyl chloride was carried
out at rt for 18 h by using the recovered magnetic nano CuFe2O4
(Scheme 2) and notably, the yields of product 3f in the second
and third usages of the nano CuFe2O4 were relatively same as those
in the initial use. Nevertheless, the yields were relatively decreas-
ing in the subsequent (4th and 5th) usage; this may be due to a
slow metal leaching.12a At this stage, one can consider that the
nano CuFe2O4 is relatively a better catalyst than some of the exist-
ing catalysts as the use of nano CuFe2O4 in the FC acylation proto-
col showed a good sign of improvement when compared to the
conventionally employed catalysts (e.g., AlCl3 and SnCl4) which
Under the present experimental condition HCl is a by-product
and we cannot ignore the possibility of (a) metal leaching and
(b) the acylation process is homogenously catalyzed by small
amounts of leached FeCl3. Since the formation of FeCl3 in the pres-
ence of HCl from CuFe2O4 is an endothermic reaction, consequently
the formation of FeCl3 at room temperature will be slow. Further, it
has to be considered that HCl gas, which is liberated (slowly) over
the reaction period, would also be exiting the reaction mixture. To
eliminate some of these possibilities, we performed various reac-
tions as shown in Table 4. When the FC acylation reactions were
performed using a mixture of nano CuFe2O4 and dry HCl (gas),12b
the possibility of the formation of FeCl3 and its involvement in
the acylation process (as a homogeneous catalyst) under the exper-
imental condition could be eliminated (entries 1–3, Table 4). Fur-
ther, based on the phenol–FeCl3 spot test,12c the possibility of
involvement of FeCl3 as the catalyst could also be eliminated.
We were also interested to test the nature of the recovered nano
CuFe2O4 catalyst. Hence, we performed the FT-IR, PXRD, and
HRTEM analyses. The FT-IR spectra and PXRD patterns revealed
the absence of characteristic peaks of organic impurities in the
recovered catalyst. The HRTEM analysis of the recovered nano Cu-
Fe2O4 revealed that the morphology of the nano CuFe2O4 remains
unchanged (Figs. 1 and 2. See the Supplementary data file for en-
larged HRTEM images and FT-IR and PXRD data). On the basis of
these data a plausible reaction pathway is proposed (see the Sup-
plementary data file).
A
C
B
D
In summary, we have shown a new catalytic Friedel–Crafts acyl-
ation protocol using magnetically separable nano CuFe2O4 (5–
20 mol %) as the catalyst. The catalyst is moisture insensitive and
easily separable from the reaction medium.
A: CuFe2O4 before use.
B: CuFe2O4 after 1st use.
Acknowledgments
C: CuFe2O4 after 2nd use. D: CuFe2O4 after 3rd use
This research was funded by IISER-Mohali, we thank the staff of
NMR and PXRD facilities of IISER-M. R.P. and N. thank CSIR-UGC,
Figure 1. HRTEM images of CuFe2O4 (before and after use).

1742
R. Parella et al. / Tetrahedron Letters 54 (2013) 1738–1742
Ondruschka, B. Appl. Catal. A 2012, 443–444, 87; (h) Ghorpade, S. P.; Darshane,
V. S.; Dixit, S. G. Appl. Catal. A 1998, 166, 135; (i) Jadhav, S. R.; Sawant, M. R. J.
Chin. Chem. Soc. 2004, 51, 135.
New Delhi for fellowships. We thank CSMCRI-Bhavnagar for pro-
viding the HRTEM-analysis data.
9. Parella, R.; Naveen; Babu, S. A. Catal. Commun. 2012, 29, 118.
10. (a) The magnetic nanopowder CuFe2O4 is commercially available and the size
of the CuFe2O4 nanoparticles was checked by HRTEM analysis prior to use.
Typical experimental procedure: To a neat mixture of 4-methylbenzoyl chloride
(185 mg, 1.2 mmol) and anisole (356 mg, 3.3 mmol) was added nanopowder
CuFe2O4 (20 mol %, particle size = ꢀ50 nm) and the reaction mixture was
stirred at rt for 18 h. Purification of the resulting crude reaction mixture by
column chromatography on silica gel (EtOAc/hexanes = 90:10) gave the
product 3a (219 mg, 97%). Mostly, all the ketones obtained in this work are
known compounds and are identified by comparison with the data available in
the literature. Spectral data for the compound 3h: Colorless solid; mp 103–
Supplementary data
Supplementary data (procedures and HRTEM, FT-IR and PXRD
data) associated with this article can be found, in the online ver-
sion, at http://dx.doi.org/10.1016/j.tetlet.2013.01.081.
References and notes
;
105 °C; IR (KBr): 1645, 1590, 1270, 1051 749 cmÀ1 1H NMR (CDCl3, 400 MHz):
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d
8.02 (d, 1H, J = 2.0 Hz), 7.75 (dd, 1H, J1 = 8.5, J2 = 2.1 Hz), 7.64 (d, 2H,
J = 8.1 Hz), 7.26 (d, 2H, J = 8.0 Hz), 6.93 (d, 2H, J = 8.5 Hz), 3.95 (s, 3H), 2.41 (s,
3H); 13C NMR (CDCl3, 100 MHz): d 194.0, 159.1, 143.1, 135.3, 134.8, 131.4,
129.9, 129.0, 111.6, 110.9, 56.5, 21.6; MS (CI): m/z (%) 306 ([M+1]+, 100), 305
([M]+, 100), 259 (10), 227 (20). (b) The FC acylation of various benzenes with
acid chlorides was carried out in the presence of magnetic nano CuFe2O4
(particle size = ꢀ50 nm) by using one of the reaction condition (A–D) given
below. Condition A: Anisole/arene (1 mmol), acid chloride (1.2 mmol), nano
CuFe2O4 (20 mol %), 1,2-DCE (2 mL), 80 °C and 24 h. Condition B: Anisole/arene
(1 mmol), acid chloride (1.2 mmol), nano CuFe2O4 (20 mol %), 1,2-DCE (2 mL),
rt (35–38 °C) and 18 h. Condition C: Neat reaction, anisole/arene (3.3 mmol),
acid chloride (1.2 mmol), nano CuFe2O4 (20 mol %), rt (35–38 °C) and 18 h.
Condition D: Neat reaction, arene/anisole (3.3 mmol), acid chloride (1.2 mmol),
nano CuFe2O4 (20 mol %), 80 °C and 18 h.
11. (a) Interestingly, we obtained N-methyl-3-acylpyrroles under the experimental
conditions. For a reference see, Carson, J. R.; Davis, N. M. J. Org. Chem. 1981, 46,
839. (b) The acylation of indole failed in our case. The acylation of indole is
relatively a difficult reaction, which needs a special catalyst, for example Lewis
acid with suitable hard/soft acidity and charge density of the metal cation; for
a recent successful method describing this aspect on the acylation of indole,
see, Guchhait, S. K.; Kashyap, M.; Kamble, H. J. Org. Chem. 2011, 76, 4753. (c)
The acylation of furan failed in our case. The furan has a low boiling point and it
is perhaps exiting the reaction flask rapidly under the experimental condition
(since the acylation reaction is being carried out at 80 °C).
12. (a) However, various analytical data of the recovered catalysts showed that the
catalyst is stable (Figs. 1 and 2. See the Supplementary data file for enlarged
HRTEM images and FT-IR and PXRD data). (b) The reactions were carried out by
constantly purging dry HCl (generated from NaCl upon a very slow addition of
Con. H2SO4). (c) After the Friedel–Crafts acylation reaction period, we have
added EtOH (2 mL) to the reaction mixture. Then the ethanolic solution was
added to phenol or sodium phenoxide in
colorimetric test).
a test tube (to perform the