Fries rearrangement of anilides in the presence of phosphorus pentoxide in methanesulfonic acid

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Fries Rearrangement of Anilides in the
Presence of Phosphorus Pentoxide in
Methanesulfonic Acid
Babak Kaboudin a & Yaghoub Abedi a
a Department of Chemistry, Institute for Advanced Studies in Basic
Sciences, Gava Zang, Zanjan, Iran
Published online: 01 Jun 2009.
To cite this article: Babak Kaboudin & Yaghoub Abedi (2009) Fries Rearrangement of Anilides
in the Presence of Phosphorus Pentoxide in Methanesulfonic Acid, Organic Preparations
and Procedures International: The New Journal for Organic Synthesis, 41:3, 229-236, DOI:
10.1080/00304940902956093
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Organic Preparations and Procedures International, 41:229–236, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 0030-4948 print
DOI: 10.1080/00304940902956093
Fries Rearrangement of Anilides in the Presence
of Phosphorus Pentoxide in Methanesulfonic Acid
Babak Kaboudin and Yaghoub Abedi
Department of Chemistry, Institute for Advanced Studies in Basic Sciences Gava
Zang, Zanjan, Iran
Aminoaryl ketones are an important class of compounds that exhibit a variety of interesting
and useful properties.1–3 Some aminoaryl ketones are useful intermediates for the synthesis
of benzodiazepines exhibiting activity as peptide antagonists, antivirals, antimalarials, and
inhibitors of DNA interactions.4–7 Moreover, p-aminoaryl ketones are useful intermedi-
ates in the synthesis of other compounds that are used as sunscreens, anti-inflammatory
agents, dyes, and inhibitors of MAP kinases.8–11 The Fries reaction of aryl esters is an
important rearrangement in aromatic chemistry.12–14 In contrast to the widely studied Fries
rearrangement of phenolic esters, relatively few papers have been reported on the Fries rear-
rangement of anilides12 to o- and p-aminoaryl ketones, by photolysis or thermolysis (above
200–350◦C) with various Lewis acids such as ZnCl2, SnCl4, TiCl4, ThCl4 and BiCl3.15–18
The Fries rearrangement of acetanilide has been also reported over zeolite catalysts at
280◦C with 50% conversion.19 Recently a Fries-type rearrangement of anilides has been
reported by using strong bases via an anionic rearrangement.20
Methanesulfonic acid is a Bro¨nsted acid that is used as catalyst and solvent for con-
densation or rearrangement reactions.21–23 Its use as catalyst in the Fries rearrangement of
phenolic esters is already known.24–26 Addition of P2O5 increased the solubility of organic
compounds in methanesulfonic acid that has been used extensively in organic synthesis.27
As a part of our effort to explore methodologies for organic transformations,28–45 we de-
scribed a new method for the Fries rearrangement of phenolic esters for the synthesis of
acylaryl methane sulfonates in the presence of POCl3 in methanesulfonic acid.46 Herein,
we report the Fries rearrangement of anilides in the presence of a mixture of P2O5 in
methanesulfonic acid (1:7) as an efficient reagent for the selective synthesis of p-aminoaryl
ketones.
The Fries rearrangement of benzanilide (1a), chosen as a model compound, was studied
in the presence of P2O5 in methanesulfonic acid, and the progress of the reaction monitored
by TLC (Scheme 1 and Table 1). Treatment of 1a with a mixture of P2O5 in methanesulfonic
Dedicated to Professor Hashem Sharghi on the occasion of his 60th birthday.
Received October 24, 2008; in final form March 27, 2009.
Address correspondence to Babak Kaboudin, Department of Chemistry, Institute for Advanced
Studies in Basic Sciences, Gava Zang, Zanjan 45195-1159, Iran. E-mail: kaboudin@iasbs.ac.ir
229

230
Kaboudin and Abedi
Scheme 1
acid (1:12) gave 4-aminobenzophenone (2a) in 8% yield after 48 h at 100◦C (Table 1,
Entry 2). Surprisingly, we found that increasing the amount of P2O5 led to acceleration
of the reaction rate and an increase in the yield of 2a (Entries 3–6). We obtained the best
results with 1:7 ratio of P2O5 in methanesulfonic acid (Entry 6). The yield of the reaction
did not change with increasing amounts of P2O5. Increasing the reaction temperature to
110◦C also let to an increase in yield (Entry 9). Decomposition occurred when the reaction
1
temperature was raised to 120◦C. H NMR studies on the Fries rearrangement of 1a at
different temperatures showed that at the beginning of the reaction, p-benzoyl- benzanilide
(3a) is the major product. Sulfonated products 5 and 8a (Table 2) were detected in low
yields (<10%) in the reaction mixture after 48 h. In a separate experiment, when compound
Table 1
Fries Rearrangement of 1a in the Presence of Phosphorus Pentoxide in Methanesulfonic
Acid
P2O5:CH3SO3H
(w:w)
Temperature
(◦ C)
Yielda,b (%)
Entry
Solvent
2a
1
2
3
4
5
6
7
8
9
0:1
1:12
1:10
1:9
1:8
1:7
1:7
1:7
1:7
1:7
1:7
1:7
—
—
—
—
—
—
—
—
—
100
100
100
100
100
100
80
—
8
20
28
35
43
8
15
46
—
—
—
90
110c
reflux
100
100
10
11
12
ClCH2CH2Cl
C6H5NO2
C6H5Cl
a) Isolated yields.
b) Reactions carried out for 48 h.
c) Reaction mixture decomposed at 120◦ C

Fries Rearrangement of Anilides
231
Table 2
The Fries Rearrangement of Anilides in a Mixture of Methanesulfonic Acid/Phosphorus
Pentoxide (7:1) for 48 h
Substrate
R
Product
Temperature (◦C) Yield (%)a
Ratiob
1a
1b
1c
1d
1e
1f
4a
4a
9a
H
m-Cl
o-Cl
2a + 3a
110
110
100
100
100
110
110
115
85
51
61
45
45
56
65
—
50
32
9:1 (2a:3a)
3:1 (2b:3b)
—
3:2 (2d:3d)
3:1 (2e:3e)
—
2b + 3b
2c
2d + 3d
p-CH3
m-CH3 2e + 3e
p-NO2
CH3
CH3
Ph
8f
—
—
5 + 6a + 7a
1:1:1 (5:6a:7a)
—
10a
a) Yield refers to isolated yield by column chromatography.
b) Ratio of products was calculated after separation by column chromatography.
3a was added to a mixture of P2O5/methanesulfonic acid (1:7) and stirred for 48 h at 100◦C,
compound 2a was formed in 90% yield.
These results may be explained by considering the initial formation of 3a which
undergoes decomposition to 2a. The Fries rearrangement of benzanilide (1a) failed with
a mixture of P2O5/methanesulfonic acid (1:7) in 1,2-dichloroethane, nitrobenzene, and
chlorobenzene respectively at 100◦C for 48 h.
The process was successfully extended to other anilides as summarized in Table 2. The
Fries rearrangement of benzanilides (1b-e) with P2O5/methanesulfonic acid (1:7) afforded
the desired products in 45–61% yields (Table 2). The reaction of p-nitrobezoyl benzanilide
(1f) in the presence of this reagent led only to sulfonated product (8f) as the major product.
Treatment of acetanilide (4a) in the presence of P2O5 in methanesulfonic acid failed for
48 h at 110◦C failed. However at 115◦C this reaction gave three products: 5, 6a, and 7a in
1:1:1 ratio in 50% total yield. With this reagent, N-benzoyl-1-naphthylamine (9a) gave 10a

232
Kaboudin and Abedi
in 32% yield after 48 h at 85◦C, decomposition occurred after 48 h at 110 ◦C. In the case
of N-phenylcinnamamide (4b), the cyclization product 11 was obtained as major product
in 68% yield (Scheme 2). A sulfonated product 12 was also detected as a side- product in
the reaction mixture (20% yield).
Scheme 2
In summary, P2O5/methanesulfonic acid (1:7) was shown as an efficient reagent in the
Fries rearrangement of anilides to p-aminoaryl ketones. Studies on the reaction mixture
showed that the reaction proceeded via the formation of p-acylated anilide (3). Some of the
major advantages of this protocol are simple procedure, easy work-up, good yields, inexpen-
sive and non-toxic catalyst, mild reaction conditions relative to other current methodologies,
a lower reaction temperature than other methodologies and reactions with high selectivity
for providing p-aminoaryl ketones. All reported methods to give a mixtiure of two products
p- and o-aminoaryl ketones including other unknown mixture products. All NMR data
could be assigned and are in good agreement with the product structures (Tables 3 and 4).
Experimental Section
All chemicals were commercial products and distilled or recrystallized before use. All
melting points were obtained on a Buchi 510 apparatus and are uncorrected. Infrared (IR)
spectra were determined using a FT-IR Brucker-Vector 22. NMR spectra were obtained
on a DMX-250 Bruker Avance spectrometer in CDCl3. Silica gel column chromatography
was carried out on Silica gel 100 (Merck No. 10184). Merck Silica-gel 60 F254 plates were
used for preparative TLC.
General Procedure for the Preparation of Anilides (1, 4, and 9)
Acid chloride or anhydride (10 mmol) was added to a stirred solution of anilide (10 mmol)
in THF (50 mL). The mixture was stirred for 2 h at room temperature. A white solid
precipitated which was filtered and washed with H2O (5 × 20 mL). Pure anilide was
obtained after recrystallization from AcOEt.

Fries Rearrangement of Anilides
233
Table 3
1H NMR and 13C NMR of 2a-e, 3a-d, 5, 6a, 7a, 8f, and 10aa
Cmpd
1H NMR (δ)
13C NMR (δ)
2a
4.46 (s, 2H, NH2), 6.67 (d, 2H, J = 8.5
Hz), 7.41–7.60 (m, 3H), 7.68–7.78
(m, 4H)
113.6, 127.3, 128.1, 129.5, 131.4, 132.9,
138.9, 151.0, 195.4
2b
2c
6.25 (s, 2H, NH2), 6.58 (d, 2H, J =
113.1, 123.5, 127.8, 128.6, 130.6, 131.2,
133.1, 133.5, 141.6, 154.6, 192.2
113.7, 126.4, 126.6, 128.7, 129.7, 130.5,
130.9, 139.4, 152.2, 193.5
8.5 Hz), 7.45–7.65 (m, 6H)
4.37 (s, 2H, NH2), 6.58 (d, 2H, J =
8.0 Hz), 7.25–7.65 (m, 4H), 7.71
(d, 2H, J = 8.0 Hz)
2d
2.43 (s, 3H), 4.15 (s, 2H, NH2), 6.67
(d, 2H, J = 8.5 Hz), 7.25 (d, 2H,
J = 8.0 Hz), 7.65 (d, 2H, J = 8.0 Hz),
7.71 (d, 2H, J = 8.5 Hz)
21.6, 113.6, 127.7, 128.8, 129.8, 132.8,
135.9, 142.1, 150.7, 195.3
2e
3a
3b
3d
3e
2.37 (s, 3H), 4.35 (s, 2H, NH2), 6.61
(d, 2H, J = 8.5 Hz), 7.25–7.55 (m, 4H),
7.67 (d, 2H, J = 8.5 Hz)
21.4, 113.6, 126.7, 127.5, 127.9, 130.0,
132.2, 132.9, 137.9, 139.2 150.9, 161.7
7.45–8.10 (m, 14H), 8.24 (s, 1H, NH)
119.2, 127.2, 128.3, 128.9, 129.9, 131.7,
132.3, 133.2, 134.4, 137.7, 141.9, 166.0,
195.8
120.1, 127.1, 128.0, 128.5, 129.2, 131.0,
131.6, 131.8, 132.4, 133.8, 136.9, 140.0,
165.1, 193.7
21.6, 21.7, 119.2, 127.2, 129.0, 129.5,
130.2, 131.5, 133.2, 135.0, 142.0, 142.8,
143.1, 166.0, 195.7
21.3, 21.4, 119.4, 124.3, 127.2, 128.0,
128.1, 128.5, 130.3, 131.6, 132.8, 133.0,
133.1, 134.5, 137.8, 138.1, 138.6, 142.4,
166.6, 196.2
7.45–8.05 (m, 12H), 10.72 (s, 1H, NH)
2.40 (s, 3H), 2.44 (s, 3H), 7.15–7.30
(m, 4H), 7.60–7.90 (m, 8H), 8.43
(s, 1H, NH)
2.34 (s, 3H), 2.42 (s, 3H), 7.20–7.90
(m, 14H), 8.80 (s, 1H, NH)
5
3.21 (s, 3H), 5.01 (s, 2H, NH2), 6.75
(d, 1H,
42.2, 117.6, 118.0, 129.4, 135.1, 146.2
J = 8.0 Hz), 6.83 (t, 1H, J = 8.0 Hz),
7.39 (t, 1H, J = 8.0 Hz),
7.24 (d, 1H, J = 8.0 Hz)
6a
7a
2.01 (s, 3H), 3.14 (s, 3H), 7.70–7.90
(m, 4H), 10.37 (s, 1H, NH)
2.20 (s, 3H), 2.60 (s, 3H), 7.40 (s, 1H,
NH), 7.61 (d, 2H, J = 8.5 Hz), 7.94
(d, 2H, J = 8.5 Hz)
24.6, 43.5, 119.1, 119.2, 128.6, 144.2,
169.6
24.6, 26.8, 118.6, 129.9, 131.9, 144.1,
169.4, 196.9
8f
3.19 (s, 3H), 7.88 (d, 2H, J = 8.7 Hz),
44.2, 120.6, 124.1, 128.6, 129.9, 136.0,
140.4, 143.7, 149.8, 165.0
8.03 (d, 2H,
J = 8.7 Hz), 8.18 (d, 2H, J = 8.7 Hz),
8.38 (d, 2H, J = 8.7 Hz),
10.97 (s, 1H, NH)
10a
7.52–8.25 (m, 16H), 10.78 (s, 1H, NH)
122.4, 124.5, 125.8, 126.9, 127.9, 128.3,
128.4, 128.9, 129.3, 129.4, 130.3, 131.6,
132.3, 133.9, 134.0, 134.8, 137.4, 138.3,
166.8, 197.3.
a) All compounds showed IR absorption at 3150–3420 for N-H and 1620–1680 cm−1 for C=O

234
Kaboudin and Abedi
Table 4
Mps and Combustion Data of 2a-e, 3a-d, 5, 6a, 7a, 8f, and 10a
Elemental Analysis (Found)
Cmpd
mp (◦C)
lit. (◦C)
C
H
N
2a
2b
2c
2d
2e
3a
3b
3d
3e
5
124–125
152–153
112–113
190–191
117–119
156–158
163–165
176–178
169–171
57–58
12413
154–15514
11219
—
—
—
—
—
—
—
—
—
—
189–19115
—
—
—
79.58 (79.65)
—
65.03 (64.95)
80.21 (80.12)
80.21 (80.02)
—
6.21 (6.03)
—
3.55 (3.45)
5.92 (5.80)
5.92 (5.70)
—
6.63 (6.46)
—
3.79 (3.73)
4.25 (4.15)
4.25 (4.10)
—
157–15916
—
—
—
58–5917
183–18418
166–16716
—
6a
7a
8f
181–183
166–168
282–284
167–169
—
—
—
—
—
—
52.49 (52.55)
82.02 (81.85)
3.79 (3.70)
4.89 (4.82)
8.75 (8.60)
3.99 (4.05)
10a
—
General Procedure for the Fries Rearrangement of Anilides in the Presence of P2O5
in Methanesulfonic Acid
In a 50 mL round bottom flask, a mixture of P2O5 (1 g) in methanesulfonic acid (5 mL)
was stirred for 10 min at 80◦C. The anilide (3 mmol) was added to the mixture and the
reaction mixture was heated at 100–115◦C for 48 h (The reaction progress was followed by
TLC). The reaction mixture was quenched by adding water, neutralized with NaOH solution
(50 mL, 10%) and extracted with chloroform (2 × 50 mL). The p-aminoaryl ketone was
easily removed from the reaction mixture by extraction with HCl (50 mL, 10%). The
aqueous phase was neutralized with NaOH (50 mL, 10%) and the product extracted with
diethyl ether (4 × 25 mL). The solvent was evaporated and the product recrystallized from
acetone. After separation of the p-aminoaryl ketone from the reaction mixture, the mother
liquor (chloroform) containing unreacted anilide and other rearrangement products that
were separated by column chromatography with n-hexane/ethyl acetate as eluting solvents
(the ratio of solvent depends on the amides).
4-Phenyl-3,4-dihydroquinolin-2(1H)-one (11) white crystals, mp. 187–189◦C (n-
1
hexane/EtOAc); HNMR (250 MHz, CDCl3): δ 2.95 (d, 2H, J = 7.0 Hz), 4.31 (t,
1H, J = 7.2 Hz), 6.90–7.05 (m, 3H), 7.15–7.48(m, 6H), 9.52 (s, 1H, NH); 13C-NMR
(62.9 MHz, CDCl3): 38.4, 41.9, 115.8, 123.4, 126.6, 127.2, 127.8, 128.0, 128.3, 128.9,
137.0, 141.5, 171.2.
Anal. Calcd for C15H13NO: C, 80.68; H, 5.87; N, 6.28. Found: C, 80.45; H, 5.80; N,
6.21.
4-(4-(Methylsulfonyl)phenyl)-3,4-dihydroquinolin-2(1H)-one (12) white crystals,
mp. 233–235◦C (n-hexane/EtOAc); 1H NMR (250 MHz, CDCl3): δ 2.73 (dd, 1H, J = 6.5
and 16.0 Hz), 2.88 (dd, 1H, J = 6.5 and 16.0 Hz), 3.18 (s, 3H), 4.47 (t, 1H, J = 6.5 Hz),
6.85–6.98 (m, 3H), 7.15–7.25(m, 1H), 7.43 (d, 2H, J = 8.2 Hz), 7.94 (d, 2H, J = 8.2 Hz),

Fries Rearrangement of Anilides
235
10.31 (s, 1H, NH); 13C-NMR (62.9 MHz, CDCl3): δ 37.9, 38.9, 43.9, 116.0, 122.9, 125.7,
127.9, 128.5, 128.6, 128.9, 138.5, 139.8, 149.0, 169.2.
Anal. Calcd for C16H15NO3S: C, 63.77; H, 5.02; N, 4.65. Found: C, 63.70; H, 4.89; N, 4.50
Acknowledgement
The Institute for Advanced Studies in Basic Sciences (IASBS) is thanked for supporting
this work.
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