A new ferrocene-based bulky pyridine as an efficient reusable homogeneous catalyst

Article abstract of DOI:10.1039/c3ra41674g

An effective approach to reusing a homogeneous catalyst has been demonstrated. A ferrocene-based bulky pyridine has been synthesized and utilized as a homogeneous catalyst for the synthesis of benzoylfumarates as well as for acetylation. After the reaction, the catalyst was separated by simple precipitation and reused without appreciable loss of activity. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3ra41674g

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A new ferrocene-based bulky pyridine as an efficient
reusable homogeneous catalyst3
Cite this: RSC Advances, 2013, 3,
15327
Bishwapran Kashyap and Prodeep Phukan*
Received 8th April 2013,
Accepted 13th June 2013
An effective approach to reusing a homogeneous catalyst has been demonstrated. A ferrocene-based
bulky pyridine has been synthesized and utilized as a homogeneous catalyst for the synthesis of
benzoylfumarates as well as for acetylation. After the reaction, the catalyst was separated by simple
precipitation and reused without appreciable loss of activity.
DOI: 10.1039/c3ra41674g
www.rsc.org/advances
Heterogeneous catalysts are widely used in industrial applica-
tions due to their ease of separation from the reaction mixture
and their recyclability. On the other hand, even though
homogeneous catalysts have many advantages such as high
selectivity and activity, they only have limited application in
industrial processes mainly due to the difficulty associated
with their separation from the reaction mixture. Accordingly, it
is highly desirable to develop a suitable approach that can
provide the advantages of both homogeneous as well as
method on the example of the synthesis of benzoylfumarates
by reacting benzaldehyde with dimethyl acetylenedicarboxy-
late (DMAD). Benzoylfumarates and their corresponding acids
are known to be important building blocks for agrochemicals,8
drugs9 and other organic reactions.10 Scarpati et al. have
reported a general method for the synthesis of 2-benzoylfu-
marates from 2-methoxyfuranes as part of their extensive
studies on the photosensitized oxidation of furanes.11 Nair
and co-workers and later Shi et al. have taken a better
approach and prepared benzoylfumarates by one-pot reaction
between DMAD and aldehydes in the presence of a Lewis base
as the catalyst.12 More recently, Bayat et al. obtained
benzoylfumarates as unexpected products during the multi-
component reaction between DMAD, aldehyde and PPh3,13
and a few other methods are known in the literature.14 In this
paper, we describe for the first time a ferrocene based
homogeneous reusable catalytic system for the preparation
of benzoylfumarates from an aldehyde and DMAD.
heterogeneous catalysts. Consequently,
a
number of
approaches have been explored for the separation and
recycling of homogeneous catalysts. Among these strategies,
the use of various supports for the immobilization of the
catalyst, especially soluble supports, has been receiving great
attention from synthetic chemists.1 Over the last few years,
soluble scaffolds such as perfluorinated tags,2 ROMP gels,3
JandaJel4 and other soluble polymers5 have been developed for
the immobilization of the catalyst and reagents. Recently, a
new technique known as ossification has also emerged as a
new method for the immobilization of homogeneous cata-
lysts.6 This technique involves the modification of the
coordinating ligands in such a way that the final catalytic
complex is insoluble in most polar and nonpolar solvents.
Eckart et al. have used tunable solvents for the separation of
homogeneous catalysts from the reaction mixture.7 Although
this approach is efficient in catalyst separation, the high cost
associated with this technique makes it unfavourable.
To realize our goal, we designed the two ferrocene-based,
bulky pyridines N-methyl-N-(pyridine-4-yl)ferroceneamide, (I)
and
N,N9-dimethyl-N,N9-di(pyridin-4-yl)ferrocene-1,19-dicar-
boxamide (II) by attaching a 4-(methylamino)pyridine moiety
to the ferrocene structure (Fig. 1).
We herein report an alternative method where the homo-
geneous catalyst could be efficiently separated from the
reaction mixture by simple precipitation. The product remains
in the solution phase. This method allows easy separation as
well as reuse of the catalyst. We have demonstrated the
Department of Chemistry, Gauhati University, Guwahati-781014, Assam, India.
E-mail: pphukan@yahoo.com
Electronic supplementary information (ESI) available: Analytical data and NMR
3
spectra of compounds, crystallographic information of catalyst I (CCDC 941950)
& II (CCDC 893849). For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3ra41674g
Fig. 1 Ferrocene based catalysts for the synthesis of benzoylfumarates and
acetylation reactions.
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The redox properties of the catalyst were investigated by
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cyclic voltammetry in the presence of 0.1 M TBAP as the
electrolyte in DMSO. The cyclic voltammograms of I and II
showed well-defined single electron wave that was reversible in
nature with E1/2 = 0.385 V and E1/2 = 0.275 V, respectively
(Fig. 2).
Compound I (N-methyl-N-(pyridin-4-yl)ferroceneamide) was
crystallized by slow evaporation from a 1 : 1 mixture of ethyl
acetate and petroleum ether. The ORTEP diagram of com-
pound I is shown in Fig. 3.
Similarly, compound II (N,N9-dimethyl-N,N9-di(pyridin-4-
yl)ferrocene-1,19-dicarboxamide) was crystallized by slow eva-
poration from a 1 : 1 mixture of ethyl acetate and petroleum
ether (PE). Diffraction quality, block morphology single
crystals were obtained after one day, and upon X-ray data
collection, the structure was solved and refined in the
monoclinic space group C2/c. The ORTEP diagram of
Fig. 3 ORTEP diagram of N-methyl-N-(pyridin-4-yl)ferroceneamide (I).
compound II is shown in Fig. 4. Crystallographic data of
compound II are presented in the ESI.
3
Initially, the reaction between 4-nitrobenzaldehyde and
DMAD was selected as a model reaction to investigate the best
reaction conditions (Table 1). In a typical reaction, a solution
of the catalyst in DME (2 mL) was added dropwise with the
help of a syringe to a mixture of 4-nitrobenzaldehyde (1 mmol)
and DMAD (1 mmol) in DME (4 mL) at 0 uC under a N2
atmosphere. The reaction was continued at room temperature
for an appropriate time. After the usual workup, the crude
product was purified using column chromatography to get the
pure product. When 10 mol% of catalyst I was used, the yield
of the product was found to be 79% after 10 h of reaction at
room temperature. A slightly better yield was found within a
shorter reaction time when catalyst II was used. The reaction
in other solvents such as THF and acetonitrile produced a
lower yield. The reaction in DCM did not proceed at all.
Further reactions using 20 mol% of catalyst II did not improve
the reaction. Finally, 10 mol% of catalyst II was found to be the
optimum amount giving the best yield.
Having established the optimized reaction conditions, a
variety of aldehydes were investigated under the same reaction
conditions as described in Table 2. The general efficiency of
Fig. 2 Cyclic voltammograms of compound I (A) and compound II (B) in DMSO
(0.1 M TBAP) at room temperature using glassy carbon as the working
electrode, Ag/AgCl (3 M solution) as the reference electrode and Pt wire grid as
´
´
Fig. 4 ORTEP diagram of N,N-dimethyl-N,N-di(pyridine-4-yl)ferrocene-
1,19-dicarboxamide (II).
the counter electrode; scan rate: 100 mV s21
.
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catalyst I could be achieved. Hence, compound II was found
to be suitable for the present study. To recover the catalyst
from the reaction mixture, the solvent was removed and the
residue dissolved in DCM (1 mL) followed by addition of PE
(10 mL). The supernatant liquid was separated and the residue
was washed three times with 1 : 10 DCM–PE. The combined
organic phases were concentrated and purified using column
chromatography to obtain the product. The residue was dried
under vacuum to remove traces of PE. The dried catalyst was
redissolved in DME (2 mL) and reused in the subsequent
batch.
The catalyst was reused three times without any significant
loss of activity (Table 2, entries 11–13). The efficiency of
separation of catalyst II was further checked by electrochemi-
cal analysis. After evaporation of the filtrate, the crude mixture
was analysed with the help of cyclic voltammetry, which
indicated the absence of compound II in the filtrate (Fig. S4 in
Table 1 Reaction of p-nitrobenzaldehyde with DMAD catalysed by I and II in
different solventsa
Entry Catalyst Amount (mol%) Solvent Time (h) Yield (%)b
1
2
3
4
5
6
7
I
10
10
10
10
10
20
0
DME
DME
THF
MeCN
DCM
DME
DME
10
7
12
12
12
6
79
81
72
30
Trace
82
0
II
II
II
II
II
II
24
a
Reaction conditions: 4-nitrobenzaldehyde (1 mmol), DMAD (1
b
mmol), solvent (6 mL), 0 uC to rt. Isolated yield.
Table 2 Reaction of aldehydes with DMAD catalysed by IIa
the ESI ). The cyclic voltammetry experiment confirms the full
3
recovery of catalyst II after the reaction. The 1H NMR spectrum
(Fig. S5 in the ESI ) of the recovered catalyst confirms its
3
stability.
To further extend the scope of our homogeneous reusable
catalyst, it was applied to the acetylation of various functional
groups. Initially, the acetylation of benzyl alcohol (1 mmol)
was optimized by using different amounts of catalysts I and II
and 1.2 mmol of acetic anhydride in different solvents (5 ml).
It was observed that the use of solvent does not result in any
good yields. However, when the reaction was performed
without any solvent, a sharp increase in the rate of reaction
as well as the yield was observed with both catalysts I and II. It
was observed that 10 mol% of catalyst I gives the best result. A
further increase of the catalyst does not have much effect on
the yield. Almost the same yield was observed with 10 mol% of
catalyst II in lesser time (Table 3, entry 13). It was further
observed that an increased amount of acetic anhydride does
Entry
Ar
Yieldb
1
2
3
4
5
6
7
8
C6H5 (4a)
56
77
73
81
82
71
69
66
52
48
79c
76d
76e
4-ClC6H4 (4b)
3-Cl C6H4 (4c)
4-NO2 C6H4 (4d)
4-Br C6H4 (4e)
3-Br C6H4 (4f)
4-F C6H4 (4g)
4-OMe C6H4 (4h)
C10H7 (4i)
9
10
11
12
13
4-Me C6H4 (4j)
4-NO2 C6H4
4-NO2 C6H4
4-NO2 C6H4
a
Reaction conditions: aldehyde (1 mmol), DMAD (1 mmol), catalyst
b
c
II (10 mol%), DME (6 mL), 0 uC to rt, 7 h. Isolated yield. Catalyst
II reused: 1st run. Catalyst II reused: 2nd run. Catalyst II reused:
Table 3 Acetylation of benzyl alcohol under different reaction conditionsa
d
e
3rd run.
this reaction is evident from the variety of aldehydes, which
react in good yields. It was observed that electron-withdrawing
groups in the ring favor the reaction, which is evident from the
high respective yields (Table 2, entries 2–8). However, the
presence of electron-donating groups results in low yields
(Table 2, entry 10).
Amount
(mmol)
Ac2O
(mmol)
Time
(min)
Yieldb
(%)
Entry
Catalyst
Solvent
1
2
3
4
5
6
7
8
I
II
I
II
I
II
I
I
I
I
I
I
II
—
5
5
5
5
5
5
5
10
15
20
10
10
10
—
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.5
2
DCM
DCM
EtOAc
EtOAc
CH3CN
CH3CN
—
—
—
—
—
120
70
120
65
150
80
65
60
60
40
60
60
62
70
73
75
79
82
91
93
90
92
92
95
0
After the reaction, the catalyst was recovered and reused. At
this point, a model experiment was performed to check the
feasibility of reusing catalysts I and II (Fig. S1–S3 in the ESI ).
3
9
In two separate experiments, PE (10 mL) was added to a
solution of compounds I and II in DCM (1 mL). We found that
compound II precipitated out completely from the solution,
whereas a small amount of compound I remained in solution,
even after addition of more PE. Catalyst II was recovered by
precipitation quantitatively, while only 70% recovery of
10
11
12
13
14
—
—
—
60
30
300
10
1.2
a
b
Reaction conditions: benzyl alcohol (1.2 mmol), rt. Isolated yield.
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Table 4 Acetylation of alcohols, phenols, amines and thiophenolsa
not influence the yield. Accordingly, the use of 10 mol% of
catalyst I or II was considered to be the optimum conditions
for the reaction. The results are depicted in Table 3.
After optimization, a comparative study was carried out
between both catalysts with a variety of alcohols, phenols,
amines and thiophenols. The results are depicted in Table 4.
It is apparent from Table 4 that different types of alcohols
including benzylic (entries 1, 12 and 13), primary (entries 14
and 17), secondary (entries 15, 16 and 37) and aliphatic (entry
18) were converted to their corresponding acetates in excellent
yield. Phenolic compounds (entries 2, 3, 4, 5, 6, 7, 8, 9, 10 and
11) reacted equally efficiently under the standard reaction
conditions. Next, the procedure was extended to a variety of
substrates such as amines and thiophenols. Aromatic (entries
19–28) as well as aliphatic (entry 29) amines were successfully
acetylated using catalyst II. Similarly, the catalysts were found
to be efficient in the acetylation of thiophenols (entries 30–33)
with excellent yields. A comparative study was carried out
between catalyst I and II for compounds 5I–5V (entries 1–5). In
all cases catalyst II was found to be more efficient than I.
The reusability of the catalysts was studied on benzyl
alcohol as the model compound. After completion of the
reaction, petroleum ether was added to the reaction mixture.
The supernatant liquid was separated and the residue washed
with petroleum ether three times. The combined organic
phases were washed successively with 10% NaHCO3 solution
and brine, and dried over Na2SO4. The organic phase was
passed through a short pad of silica gel and evaporated to give
the pure product. The recovered catalyst was washed with
petroleum ether and water successively, dissolved in DCM, and
dried over Na2SO4. The solvent was evaporated and the
recovered catalyst was kept in a desiccator over CaCl2
overnight before use. As the catalyst I is slightly soluble in
petroleum ether, a lower yield was observed in the subsequent
step during the reuse of catalyst I. On the other hand, catalyst
II was reused two times without any significant loss of activity.
Entry
1
Product
Catalyst
Time (min)
Yieldb (%)
I
II
60
30
91
95
2
3
4
I
II
70
30
98
98
I
II
120
35
84
91
I
II
140
40
85
90
5
I
II
120
30
80
88
6
7
II
II
25
20
92
95
8
9
II
II
25
40
90
88
Conclusions
10
11
II
II
35
30
90
87
In conclusion, we have developed an effective approach to
reuse a homogeneous ferrocene-based, bulky pyridine catalyst.
The method was demonstrated for the preparation of
benzoylfumarates from aromatic aldehydes. Various aromatic
aldehydes were converted to the corresponding fumarates in
high yield. After completion of the reaction, the catalyst was
separated by simple precipitation and reused three times
without any appreciable loss of activity.
12
13
II
II
20
25
90
92
Experimental section
All the chemicals used were of analytical grade. Melting points
were determined in open capillaries in a paraffin bath and are
uncorrected. IR spectra were recorded by using a Perkin Elmer
Spectrum RX
I FT-IR Spectrometer. Mass spectra were
recorded on a Perkin Elmer Clarus 600 C mass spectrometer.
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Table 4 (Continued)
Table 4 (Continued)
Entry
14
Product
Catalyst
Time (min)
20
Yieldb (%)
86
Entry
27
Product
Catalyst
Time (min)
Yieldb (%)
93
II
II
25
15
16
II
II
45
35
89
85
28
II
25
94
29
30
II
II
45
45
81
84
17
II
40
85
31
32
II
II
30
35
88
93
18
19
II
II
45
20
75
96
20
II
25
92
33
34
35
II
II
II
30
30
35
90
87
83
21
22
II
II
30
35
93
93
23
24
II
II
30
35
95
89
36
37
II
II
40
30
82
88
25
26
II
II
40
35
88
89
38
39
II
II
30
30
95c
93d
a
Reaction conditions: substrate (1 mmol), acetic anhydride (1.2
b
c
mmol), catalyst (10 mol%), rt. Isolated yield. Catalyst reused: 1st
run. Catalyst reused: 2nd run.
d
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1H and 13C-NMR spectra were obtained in CDCl3 using a
Bruker 300 MHz instrument.
it through a short silica gel column using ethyl acetate–
petroleum ether as the eluent.
Red solid. Mp: 129–131 uC. IR (KBr, cm21): n 829, 1114, 1350,
1496, 1585, 1643, 3421. 1H NMR (300 MHz, CDCl3, TMS): d
3.12 (s, 6H), 3.43 (s, 4H), 4.20 (s, 4H), 6.66–7.21 (m, 4H), 8.35–
8.90 (m, 4H). 13C NMR (75 MHz, CDCl3, TMS): d 37.49, 71.61,
73.25, 118.42, 120.99, 147.64, 150.59, 150.92, 152.30, 169.92.
LC-MS (m/z (%)): 456 (39) [M+], 455 (100), 109 (22). Anal.
calculated for C24H22FeN4O2: C 63.45, H 4.88, N 12.33%.
Found: C 63.56, H 4.79, N 12.42%.
Procedure for the synthesis of N-methyl-N-(pyridine-4-
yl)ferroceneamide (I)
A) Synthesis of chlorocarbonyl ferrocene1. Oxalyl chloride
was added dropwise to a suspension of ferrocene carboxylic
acid in dry DCM under nitrogen. After the evolution of gas
ceased, the reaction was stirred for a further 30 min. Then the
solvent was removed under reduced pressure and the residue
was extracted repeatedly with hexane. The combined organic
extracts were concentrated under reduced pressure to give a
dark red solid which was used directly in the next step without
further purification.
Typical procedure for the synthesis of benzoylfumarates
A solution of catalyst II in DME (2 mL) was added dropwise
with the help of a syringe to a mixture of 4-nitrobenzaldehyde
(1 mmol) and DMAD (1 mmol) in DME (4 mL) at 0 uC under a
N2 atmosphere. After completion of the reaction the solvent
was removed, and the residue was dissolved in DCM (1 mL)
followed by addition of petroleum ether (10 mL). The super-
natant liquid was separated and the residue was washed with
1 : 10 DCM–PE three times. The combined organic phases
were concentrated and purified using column chromatography
to obtain the product.
B) Synthesis of N-methyl-N-(pyridine-4-yl)ferroceneamide (I).
Chlorocarbonylferrocene (2.49 g, 0.01 mol) in DCM was added
dropwise with the aid of a dropping funnel to a mixture of 4-
(methylamino)pyridine (1.19 g, 0.011 mol), DMAP (0.05 g) and
triethylamine (1.52 mL, 0.021 mol) in dichloromethane (20
mL) at 0 uC and the mixture was stirred overnight at room
temperature. The reaction mixture was washed with water and
brine, and then dried over anhydrous Na2SO4. The pure
product (2.5 g, 75%) was isolated by passing it through a short
pad of silica gel using ethyl acetate–petroleum ether as the
eluent.
Dimethyl (2E)-2-benzoylbut-2-enedioate11,12 (4a). Colourless
crystalline solid. Yield: 56%. Mp: 79–81 uC. IR (KBr, cm21): n
1
1207, 1261, 1423, 1681, 1728, 2306, 2985, 3055. H NMR (300
MHz, CDCl3): d 3.64 (s, 3H), 3.79 (s, 3H), 7.11 (s, 1H), 7.3–7.55
(m, 2H), 7.56–7.65 (m, 1H), 7.7–7.98 (m, 2H). 13C NMR (75
MHz, CDCl3): d 52.49, 53.29, 128.66, 128.82, 130.47, 133.91,
135.47, 145.21, 163.58, 164.18, 192.20. GC-MS (m/z (%)): 248
(15) [M+], 217 (8), 105 (100), 77 (36), 28 (17).
Dimethyl (2E)-2-(4-chlorobenzoyl)but-2-enedioate12b,13 (4b).
Colourless crystalline solid. Yield: 77%. Mp: 78–80 uC. IR (KBr,
cm21): n 1207, 1273, 1423, 1589, 1685, 2985. 1H NMR (300
MHz, CDCl3): d 3.66 (s, 3H), 3.79 (s, 3H), 7.10 (s, 1H), 7.465 (d, J
= 9 Hz, 2H), 7.825(d, J = 9 Hz, 2H). 13C NMR (75 MHz, CDCl3): d
52.58, 53.35, 129.22, 129.97, 130.72, 133.90, 140.41, 144.79,
163.34, 164.14, 191.04. GC-MS (m/z (%)): 282 (26) [M+], 251
(15), 139 (100), 111 (62), 75 (35), 53 (18).
Red solid. Mp: 146–148 uC. IR (KBr, cm21): n 846, 1124, 1345,
1
1496, 1576, 1638. H NMR (300 MHz, CDCl3): d 3.42 (s, 3H),
4.17 (s, 5H), 4.20 (s, 2H), 4.17 (s, 2H), 7.02 (d, J = 6 Hz, 2H), 8.50
(d, J = 6 Hz, 2H). 13C NMR (75 MHz, CDCl3): d 37.5, 69.97,
70.11, 71.25, 102.67, 150.60, 152.38, 171.36. LC-MS (m/z (%)):
322 (100) [M+], 226 (20), 211 (15), 109 (60). Anal. calculated for
C17H16FeN2O: C 63.77, H 5.04, N 8.75%. Found: C, 63.7, H
5.14, N 8.82%.
Procedure for the synthesis of N,N9-dimethyl-N,N9-di(pyridin-4-
yl)ferrocene-1,19-dicarboxamide (II)
A) Synthesis of Fc(COCl)2. 1,19-Ferrocenedicarbonyl chloride
was prepared via the literature procedure.2 A mixture of
1,19-ferrocenedicarboxylic acid (8.79 g, 0.032 mol), oxalyl
chloride (14 mL, 0.160 mol) and pyridine (0.5 mL) in 140 ml
of dry dichloromethane was stirred under N2 in the dark for 4
h at room temperature and then refluxed overnight. The
reaction mixture was evaporated to dryness under reduced
pressure and the residue extracted repeatedly with hexane. The
solvent of the filtrate was removed under reduced pressure to
give a red solid (9.20 g, 92%) which was kept under N2 for
further use.
Dimethyl (2E)-2-(3-chlorobenzoyl)but-2-enedioate12b (4c).
Colourless crystalline solid. Yield: 73%. Mp: 76–77 uC IR
(KBr, cm21): n 774, 1072, 1253, 1424, 1580, 1731, 2976. 1H
NMR (300 MHz, CDCl3): d 3.65 (s, 3H), 3.78 (s, 3H), 7.10 (s,
1H), 7.37–7.48 (m, 1H), 7.555 (d, J = 9 Hz, 1H), 7.725 (d, J = 9
Hz, 1H), 7.85 (s, 1H). 13C NMR (75 MHz, CDCl3): d 52.53, 53.29,
126.72, 128.36, 130.11, 130.82, 133.73, 135.06, 136.92, 144.58,
163.14, 164.04, 190.92. GC-MS (m/z (%)): 282 (30) [M+], 251
(20), 223 (23), 191 (17), 139 (100), 111 (68), 75 (56), 53 (24).
Dimethyl (2E)-2-(4-nitrobenzoyl)but-2-enedioate12,13 (4d).
Yellow crystalline solid. Yield: 81%. Mp: 115–117 uC. IR (KBr,
cm21): n 1194, 1359, 1453, 1665, 1721, 2943.1H NMR (300 MHz,
CDCl3): d 3.65 (s, 3H), 3.78 (s, 3H), 7.12 (s, 1H), 8.025 (d, J = 9
Hz, 2H), 8.305 (d, J = 9 Hz, 2H). 13C NMR (75 MHz, CDCl3): d
52.66, 53.36, 123.96, 129.46, 131.24, 139.67, 144.25, 150.46,
162.84, 164.07, 190.69. GC-MS (m/z (%)): 293 (73) [M+], 262
(55), 234 (39), 171 (33), 150 (72), 120 (75), 104 (100), 92 (77), 76
(78), 53 (57).
B) Synthesis of N,N9-dimethyl-N,N9-di(pyridin-4-yl)ferrocene-
1,19-dicarboxamide (II). 1,19-Ferrocenedicarbonyl chloride
(3.11 g, 0.01 mol) in dichloromethane was added dropwise
through a dropping funnel to a mixture of 4-(methylamino)-
pyridine (2.27 g, 0.021 mol), N,N-dimethyl-4-aminopyridine
(0.1 g) and triethylamine (2.9 mL, 0.021 mol) in dichlor-
omethane (30 mL) at 0 uC, and the mixture was stirred
overnight at room temperature. The reaction mixture was
washed with water and brine, and then dried over anhydrous
Na2SO4. The pure product (3.8 g, 83%) was isolated by passing
Dimethyl (2E)-2-(4-bromobenzoyl)but-2-enedioate11–13 (4e).
White crystalline solid. Yield: 82%. Mp: 88–90 uC. IR (KBr,
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cm21): n 1192, 1271, 1425, 1576, 1725, 2951 1H NMR (300 MHz,
CDCl3): d 3.63 (s, 3H), 3.76 (s, 3H), 7.08 (s, 1H), 7.61 (d, J = 6
Hz, 2H), 7.73 (d, J = 6 Hz, 2H). 13C NMR (75 MHz, CDCl3): d
52.48, 53.23, 129.09, 129.95, 130.63, 132.08, 134.20, 144.64,
163.20, 164.02, 191.14. GC-MS (m/z (%)): 328 (22) [M+ + 2], 326
(22) [M+], 183 (100), 157 (44), 159 (45), 75 (52), 53 (35).
anhydrous Na2SO4, concentrated, and purified using column
chromatography to obtain the product. The recovered catalyst
was washed with petroleum ether, dried under vacuum and
then kept in a desiccator over CaCl2 overnight before reuse.
Benzyl acetate16,20,25 (5a). Thick oil. Yield: 95%. IR (KBr,
1
cm21): n 876,1050, 1234, 1348, 1527, 1745,3099. H NMR (300
MHz, CDCl3): d 2.12 (s, 3H), 5.15 (s, 2H), 8.08–8.34 (m, 5H). 13
C
Dimethyl (2E)-2-(3-bromobenzoyl)but-2-enedioate (4f).
Yellow oil. Yield: 71%. IR (KBr, cm21): n 1186, 121 254, 1430,
NMR (75 Hz, CDCl3): d 20.6, 66.3, 130.2, 132.7, 134.2, 135.7,
170.5. GC-MS (m/z (%)): 150 (94) [M+], 108 (68), 91 (100), 77
(81), 65 (50), 51 (49).
1
1577, 1732, 1941. H NMR (300 MHz, CDCl3): d 3.66 (s, 3H),
3.79 (s, 3H), 7.11 (s, 1H), 7.30–7.45 (m, 1H), 7.65–7.86 (m, 2H),
8.01 (s, 1H). 13C NMR (75 MHz, CDCl3): d 52.60, 53.36, 123.13,
127.22, 130.38, 130.90, 131.34, 136.69, 137.15, 144.59, 163.18,
164.09, 190.88. GC-MS (m/z (%)): 328 (14) [M+ + 2], 326 (14)
[M+], 185 (99), 183 (100), 157 (28), 155 (28), 75 (27), 53 (18).
Anal. calculated for C13H11BrO5: C 47.73, H 3.39%. Found: C
47.56; H 3.65%.
4-Nitrophenyl acetate16,21,28 (5b). White solid. Yield: 98%.
Mp: 77–78 uC. IR (KBr, cm21): n 746, 865, 967, 1142, 1345,
1
1423, 1568, 1545, 1611, 1775, 2851, 2912, 3077. H NMR (300
MHz, CDCl3): d 2.28 (s, 3H), 7.22 (dd, J = 6 Hz, 3 Hz, 2H), 8.18
(dd, J = 6 Hz, 3 Hz, 2H). 13C NMR (75 Hz, CDCl3): d 20.7, 122.2,
124.8, 144.9, 155.1, 168.2. GC-MS (m/z (%)): 181 (71) [M+], 139
(100), 123 (42), 109 (93), 63 (78).
Dimethyl (2E)-2-(4-fluorobenzoyl)but-2-enedioate15 (4g).
Yellow oil. Yield: 69%. IR (KBr, cm21): n 1397, 1422, 1674,
1729, 2955.1H NMR (300 MHz, CDCl3): d 3.66 (s, 3H), 3.79 (s,
3H), 7.10 (s, 1H), 7.11–7.22 (m, 2H), 7.86–7.97 (m, 2H). 13C
NMR (75 MHz, CDCl3): d 52.54, 53.31, 115.95, 116.24, 130.55,
131.26, 131.39, 144.91, 163.43, 164.15, 190.64. GC-MS (m/z
(%)): 266 (14) [M+], 235 (8), 123 (100), 95 (40), 75 (12), 28 (19).
Dimethyl (2E)-2-(4-methoxybenzoyl)but-2-enedioate13,15
(4h). Yellow oil. Yield: 66%. IR (KBr, cm21): n 1120, 1270,
4-Methoxyphenyl acetate21,28 (5c). Thick oil. Yield: 91%. IR
(KBr, cm21): n 731, 917, 1022, 1189, 1216, 1512, 1765. 1H NMR
(300 MHz, CDCl3): d 2.25 (s, 3H), 3.75 (s, 3H), 6.89 (d, J = 9 Hz,
2H), 7.02 (d, J = 9 Hz, 2H).13C NMR (75 Hz, CDCl3): d 20.6, 55.1,
114.0, 122.0, 143.8, 156.9, 169.5. GC-MS (m/z (%)): 166 (49)
[M+], 124 (49), 109 (100), 81 (44).
Naphthalen-2-yl acetate25,26 (5d). White solid. Yield: 90%.
Mp: 68–69 uC. IR (KBr, cm21): n 824, 954, 1025, 1130, 1233,
1
1
1382, 1443, 1519, 1586, 1742, 2935, 3052. H NMR (300 MHz,
1425, 1724, 2945. H NMR (300 MHz, CDCl3): d 3.64 (s, 3H),
CDCl3): d 2.39 (s, 3H), 7.25–7.35 (m, 1H), 7.47–7.69 (m, 3H),
7.81–8.11 (m, 3H).13C NMR (75 Hz, CDCl3): d 21.1, 118.4, 121.0,
125.6, 126.5, 127.5, 127.7, 129.3, 131.3, 133.6, 148.2, 169.6. GC-
MS (m/z (%)): 186 (53) [M+], 144 (100), 115 (81), 99 (25), 63 (25).
Naphthalen-1-yl acetate25,26,28 (5e). White solid. Yield: 88%.
Mp: 45–46 uC. IR (KBr, cm21): n 751, 823, 926, 1177, 1224,
1370, 1456, 1607, 1735, 2916. 1H NMR (300 MHz, CDCl3): d
2.50 (s, 3H), 7.32–7.46 (m, 1H), 7.50–7.73 (m, 3H), 7.78–7.89
(m, 1H), 7.91–8.13 (m, 2H). 13C NMR (75 Hz, CDCl3): d 20.7,
117.9, 120.9, 125.2, 125.8, 126.3, 126.6, 127.9, 134.4, 146.4,
169.3. GC-MS (m/z (%)): 186 (33) [M+], 144 (100), 115 (74), 99
(21), 63 (22).
2-Nitrophenyl acetate26 (5f). Thick oil. Yield: 92%. IR (KBr,
cm21): n 850, 935, 1197, 1356, 1543, 1600, 1782, 2955. 1H NMR
(300 MHz, CDCl3): d 2.29 (s, 3H), 7.11–7.25 (m, 1H), 7.26–7.41
(m, 1H), 7.52–7.70 (m, 1H), 7.94–8.12 (m, 1H). 13C NMR (75 Hz,
CDCl3): d 20.3, 124.9, 125.3, 126.4, 134.6, 141.3, 143.6, 168.3.
GC-MS (m/z (%)): 181 (15) [M+], 139 (100), 109 (27), 81 (29), 63
(62).
3.78 (s,3H), 3.88 (s, 3H), 6.955 (d, J = 9 Hz, 2H), 7.08 (s, 1H),
7.855 (d, J = 9 Hz, 2H). 13C NMR (75 MHz, CDCl3): d 52.28,
52.69, 53.46, 129.33, 130.08, 130.83, 134.01, 140.52, 144.90,
163.45, 164.25, 191.15. GC-MS (m/z (%)): 278 (17), [M+], 247 (6),
135 (100), 107 (12), 92 (13), 77 (18).
Dimethyl (2E)-2-(naphthalen-2-ylcaronyl)but-2-enedioate
(4i). Yellow oil. Yield: 52%. IR (KBr, cm21): n 1265, 1422,
1571, 1672, 1731, 2956.1H NMR (300 MHz, CDCl3): d 3.61 (s,
3H), 3.79 (s, 3H), 7.19 (s, 1H), 7.51–7.69 (m, 2H), 7.85–7.98 (m,
3H), 8.01–8.11 (m, 1H), 8.30 (s, 1H). 13C NMR (75 MHz, CDCl3):
52.47, 53.30, 123.53, 126.89, 127.87, 128.88, 129.69, 130.61,
131.12, 132.44, 133.01, 136.02, 145.27, 163.69, 164.17, 192.09.
GC-MS (m/z (%)): 298 (36) [M+], 207 (16), 155 (100), 127 (99), 77
(12). Anal. calculated for C17H14O5: C 68.45, H 4.73%. Found: C
68.58, H 4.82%.
Dimethyl (2E)-2-(4-methylbenzoyl)but-2-enedioate11a,12,13
(4j). Colourless crystalline solid. Yield: 48%. Mp: 85–87 uC.
1
IR (KBr, cm21): n 1169, 1278, 1433, 1609, 1721, 2956. H NMR
(300 MHz, CDCl3): d 2.42 (s, 3H), 3.64 (s, 3H), 3.78 (s, 3H), 7.09
(s, 1H), 7.285 (d, J = 9 Hz, 2H), 7.785 (d, J = 9 Hz, 2H). 13C NMR
(75 MHz, CDCl3): d 30.28, 53.05, 53.85, 129.39, 130.15, 130.84,
133.69, 145.57, 145.92, 164.28, 164.80, 192.41. GC-MS (m/z
(%)): 262 (26) [M+], 231 (12), 119 (100), 91 (74), 65 (28).
4-Chlorophenyl acetate16,26,28 (5g). Colourless liquid. Yield:
95%. IR (KBr, cm21): n 780, 1045, 1182, 1261, 1483, 1674, 2833,
3072. 1H NMR (300 MHz, CDCl3): d 2.30 (s, 3H), 7.04 (dd, J = 6
Hz, 3 Hz, 2H), 7.35 (dd, J = 6 Hz, 3 Hz, 2H). 13C NMR (75 Hz,
CDCl3): d 21.0, 122.9, 129.4, 131.1, 149.0, 169.2. GC-MS (m/z
(%)): 170 (37) [M+], 128 (100), 99 (23), 73 (25), 65 (30).
4-Fluorophenyl acetate28 (5h). Colourless liquid. Yield: 90%.
Typical procedure for the acetylation
To a stirred mixture of Ac2O (1.2 mmol) and the catalyst (10
mol%) at room temperature, the respective alcohol, phenol,
amine or thiophenol (1 mmol) was added with continuous
stirring. After completion of the reaction (TLC monitoring),
petroleum ether was added, the supernatant liquid was
separated, and the residue was washed with petroleum ether
three times. The combined organic phases were dried over
1
IR (KBr, cm21): n 770, 1011, 1190, 1226, 1668, 3112. H NMR
(300 MHz, CDCl3): d 2.26 (s, 3H), 6.98–7.25 (m, 2H). 13C NMR
(75 Hz, CDCl3): d 20.7, 116.0, 122.9, 146.3, 161.6, 169.3. GC-MS
(m/z (%)): 154 (68) [M+], 112 (100), 83 (98), 57 (83).
3-Methylphenyl acetate26 (5i). Colourless liquid. Yield: 88%.
IR (KBr, cm21): n 751, 1161, 1222, 1368, 1771. 1H NMR (300
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MHz, CDCl3): d 2.31 (s, 3H), 2.39 (s, 3H), 6.88–7.00 (m, 2H),
7.08 (d, J = 9 Hz, 1H), 7.29 (t, J = 6 Hz, 1H). 13C NMR (75 Hz,
CDCl3): d 20.9, 21.1, 118.4, 122.0, 126.5, 129.0, 139.4, 150.4,
169.5.
CDCl3): d 0.78 (t, J = 6 Hz, 3H), 1.08–1.44 (m, 9H), 1.44–1.75 (m,
3H), 1.93 (s, 3H), 3.94 (t, J = 6 Hz, 2H). 13C NMR (75 Hz, CDCl3):
d 13.8, 20.6, 22.4, 25.7, 28.4, 29.0, 31.6, 64.3, 170.8.
N-phenylacetamide16,17,23 (5s). White Solid. Yield: 96%. Mp:
115–116 uC. IR (KBr, cm21): n 692, 752, 1262, 1320, 1368, 1434,
1486, 1499, 1557, 1596, 1661. 1H NMR (300 MHz, CDCl3): d
2.13 (s, 3H), 7.05–7.16 (m, 1H), 7.23–7.36 (m, 2H), 7.50–7.63
(m, 2H), 8.71 (s, 1H).13C NMR (75 Hz, CDCl3): d 24.1, 120.2,
124.1, 128.7, 138.0, 169.3. GC-MS (m/z (%)): 135 (32) [M+], 93
(100), 66 (16), 51 (5).
4-Chloro-3-methylphenyl acetate27 (5j). Thick oil. Yield:
1
90%. IR (KBr, cm21): n 810, 1072, 1257, 1420, 1745, 3026. H
NMR (300 MHz, CDCl3): d 2.28 (s, 3H), 2.37 (s, 3H), 6.84–6.92
(m, 1H), 6.95–7.01 (m, 1H), 7.29–7.37 (m, 1H). 13C NMR (75 Hz,
CDCl3): d 20.0, 20.8, 120.1, 123,8, 129.5, 131.1, 137.2, 148.8,
169.2. GC-MS (m/z (%)): 184 (40) [M+], 142 (55), 107 (100), 77
(78), 51 (42).
N-(2-chlorophenyl)acetamide23 (5t). White Solid. Yield: 82%.
Mp: 90–92 uC. 1H NMR (300 MHz, CDCl3): d 2.09 (s, 3H), 6.84–
6.98 (m, 1H), 7.04–7.17 (m, 1H), 7.17–7.29 (m, 1H), 7.95–8.16
(m, 2H). 13C NMR (75 Hz, CDCl3): d 23.9, 122.5, 123.4, 124.6,
126.9, 128.6, 134.1, 168.5. GC-MS (m/z (%)): 169 (17) [M+], 134
(36), 127 (100), 92 (12), 63 (10).
2-Methoxy-4-(prop-2-en-1-yl)phenyl acetate20 (5k). Thick oil.
Yield: 87%. IR (KBr, cm21): n 908, 1190, 1247, 1350, 1443, 1503,
1
1591, 1609, 1765. H NMR (300 MHz, CDCl3): d 2.26 (s, 3H),
3.36 (d, J = 6 Hz, 2H), 3.75 (s, 3H), 5.04–5.24 (m, 2H), 5.87–6.08
(m, 1H), 6.70–6.88 (m, 2H), 6.91–7.07 (m, 1H).13C NMR (75 Hz,
CDCl3): d 19.9, 39.5, 55.0, 112.1, 115.5, 120.0, 122.0, 136.6,
137.5, 138.4, 150.4, 168.4. GC-MS (m/z (%)): 206 (15) [M+], 164
(100), 149 (39), 91 (37), 77 (44), 65 (34).
N-(3-chlorophenyl)acetamide23 (5u). White Solid. Yield:
93%. Mp: 77–78 uC. IR (KBr, cm21): n 791,1250, 1422, 1540,
1
1580, 1690, 3354. H NMR (300 MHz, CDCl3): d 2.16 (s, 3H),
4-Chlorobenzyl acetate16,25 (5l). Thick oil. Yield: 90%. IR
(KBr, cm21): n 1024, 1086, 1233, 1388, 1496, 1756, 2961. 1H
NMR (300 MHz, CDCl3): d 2.10 (s, 3H), 5.06 (s, 2H), 7.23–7.51
(m, 4H). 13C NMR (75 Hz, CDCl3): d 20.9, 65.4, 128.7, 129.6,
134.1, 134.3, 170.8. GC-MS (m/z (%)): 184 (63) [M+], 142 (95),
125 (100), 107 (77), 99 (85), 77 (36).
4-Methoxybenzyl acetate16,25 (5m). Thick oil. Yield: 92%. IR
(KBr, cm21): n 743, 1012, 1178, 1235, 1522, 1737, 2952. 1H
NMR (300 MHz, CDCl3): d 2.04 (s, 3H), 3.76 (s, 3H), 5.02 (s,
2H), 6.87 (d, J = 6 Hz, 2H), 7.28 (d, J = 6 Hz, 2H). 13C NMR (75
Hz, CDCl3): d 20.7, 54.9, 65.8, 113.6, 127.7, 129.8, 159.3, 170.6.
GC-MS (m/z (%)): 180 (74) [M+], 138 (27), 121 (100), 91 (53), 77
(52).
2-Phenylethyl acetate21 (5n). Thick oil. Yield: 86%. IR (KBr,
cm21): n 714, 1037, 1233, 1372, 1455, 1741, 2952, 3030. 1H
NMR (300 MHz, CDCl3): d 1.97 (s, 3H), 2.91 (t, J = 6 Hz, 2H),
4.27 (t, J = 6 Hz, 2H), 7.14–7.25 (m, 3H), 7.26–7.34 (m, 2H).13C
NMR (75 Hz, CDCl3): d 20.1, 34.5, 64.3, 126.0, 127.9, 128.3,
137.3, 170.1.
Cyclohexyl acetate16,25,26,28 (5o). Thick oil. Yield: 89%. IR
(KBr, cm21): n 988, 1020, 1228, 1350, 1449, 1753, 2948. 1H
NMR (300 MHz, CDCl3): d 0.99–1.56 (m, 6H), 1.57–1.88 (m,
4H), 1.94 (s, 3H), 4.55–4.90 (m, 1H). 13C NMR (75 Hz, CDCl3): d
14.9, 17.3, 18.9, 25.2, 66.2, 164.1. GC-MS (m/z (%)): 142 (2) [M+],
90 (10), 91 (75), 67 (100), 54 (42).
7.05 (d, J = 6 Hz, 1H), 9.19 (t, J = 6 Hz, 1H), 7.33 (d, J = 6 Hz,
1H), 7.65 (s, 1H), 8.46 (s, 1H).13C NMR (75 Hz, CDCl3): d 24.3,
118.0, 120.1, 124.2, 129.8, 134.3, 139.1, 169.3. GC-MS (m/z (%)):
169 (31) [M+], 129 (35), 127 (100), 92 (11), 63 (10).
16,23,26
N-(4-chlorophenyl)acetamide (5v).
White Solid. Yield:
93%. Mp: 178–180 uC. IR (KBr, cm21): n 850, 1330, 1500, 1607,
1675, 3300. 1H NMR (300 MHz, CDCl3): d 1.94 (s, 3H), 7.04 (d, J = 9
Hz, 2H), 7.37 (d, J = 9 Hz, 2H), 9.26 (s, 1H). 13C NMR (75 Hz,
CDCl3): d 24.1, 120.9, 128.5, 130.0, 137.5, 169.0. GC-MS (m/z (%)):
169 (32) [M+], 129 (33), 127 (100), 92 (13), 63 (12).
N-(4-bromophenyl)acetamide16 (5w). White Solid. Yield:
95%. Mp: 166–168 uC. IR (KBr, cm21): n 810, 1300, 1388,
1
1492, 1523, 1680, 3289. H NMR (300 MHz, CDCl3): d 2.04 (s,
3H), 7.28 (d, J = 9 Hz, 2H), 7.44 (d, J = 9 Hz, 2H), 9.57 (s, 1H).13C
NMR (75 Hz, CDCl3): d 23.4, 114.9, 120.6, 130.7, 137.5, 168.4.
GC-MS (m/z (%)): 213 (40) [M+], 215 (38) [M+ + 2], 171 (100), 92
(68), 65 (43).
N-(4-fluorophenyl)acetamide23 (5x). White Solid. Yield: 89%.
Mp: 152–153 uC. IR (KBr, cm21): n 836, 1235, 1507, 1617, 1662,
1
2853, 2923, 3071, 3290. H NMR (300 MHz, CDCl3): d 2.15 (s,
3H), 6.94–7.11 (m, 2H), 7.38–7.53 (m, 2H), 7.58 (s, 1H). 13C
NMR (75 Hz, CDCl3): d 24.3, 115.4, 121.7, 133.8, 157.7, 168.5.
GC-MS (m/z (%)):153 (64) [M+], 111 (100), 83 (34), 57 (19).
N-(3-nitrophenyl)acetamide16,17,26 (5y). White Solid. Yield:
88%. Mp: 152–153 uC. IR (KBr, cm21): n 832, 1021, 1199, 1322,
2-Methyl-5-(propan-2-yl)cyclohexyl acetate21,25,27,28 (5p).
Thick oil. Yield: 85%. IR (KBr, cm21): n 760, 1054, 1261,
1322, 1680, 1780, 3012. 1H NMR (300 MHz, CDCl3): d 0.48 (d, J
= 6 Hz, 3H), 1.02–1.49 (m, 4H), 1.50–1.83 (m, 6H), 1.88–1.99
(m, 2H), 4.34–4.46 (m, 1H). 13C NMR (75 Hz, CDCl3): d 15.6,
20.3, 21.3, 22.8, 25.6, 30.7, 33.6, 40.3, 46.4, 73.2, 169.6.
4-[2-(Acetyloxy)ethyl]phenyl acetate (5q). Thick oil. Yield:
85%. IR (KBr, cm21): n 777, 1025, 1196, 1338, 1452, 1690, 1765,
1
1449, 1548, 1688, 3352. H NMR (300 MHz, CDCl3): d 2.00 (s,
3H), 7.25 (t, J = 9 Hz, 1H), 7.64–7.71 (m, 1H), 7.77–7.85 (m, 1H),
7.33 (s, 1H), 9.77 (s, 1H).13C NMR (75 Hz, CDCl3): d 23.8, 113.7,
117.4, 124.9, 129.0, 139.8, 147.8, 169.2. GC-MS (m/z (%)): 180
(25) [M+], 138 (100), 92 (55), 65 (26).
N-(2-methyl-5-nitrophenyl)acetamide22 (5z). White Solid.
Yield: 89%. Mp: 150–151 uC. IR (KBr, cm21): n 780, 1472,
1489, 1322, 1651, 1554, 1709, 3356. 1H NMR (300 MHz, CDCl3):
d 2.24 (s, 3H), 2.34 (s, 3H), 7.23–7.38 (m, 1H), 7.42 (s, 1H), 7.90
(d, J = 6 Hz, 1H), 8.67 (s, 1H). 13C NMR (75 Hz, CDCl3): d 18.1,
24.2, 118.2, 119.8, 131.0, 136.5, 139.3, 146.7, 168.8. GC-MS (m/z
(%)): 194 (14) [M+], 177 (38), 152 (100), 106 (48), 77 (26).
N-(4-nitrophenyl)acetamide25,26 (5aa). White Solid. Yield:
93%. Mp: 113–115 uC. IR (KBr, cm21): n 725, 852, 1450, 1490,
1
3218. H NMR (300 MHz, CDCl3): d 2.03 (s, 3H), 2.28 (s, 3H),
2.92 (t, J = 6 Hz, 2H), 4.25 (t, J = 6 Hz, 2H), 7.02 (d, J = 9 Hz, 2H),
7.22 (d, J = 9 Hz, 2H). 13C NMR (75 Hz, CDCl3): d 21.0, 34.3,
64.6, 121.4, 129.7, 135.3, 149.2, 169.5, 170.9.
Octyl acetate26 (5r). Thick oil. Yield: 81%. IR (KBr, cm21): n
890, 1039, 1280, 1447, 1545, 1743, 2927. 1H NMR (300 MHz,
15334 | RSC Adv., 2013, 3, 15327–15336
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1353, 1511, 1575, 1683, 3350. 1H NMR (300 MHz, CDCl3): d
1.33 (s, 3H), 6.98 (d, J = 9 Hz, 2H), 7.29 (d, J = 9 Hz, 2H), 9.41 (s,
1H). 13C NMR (75 Hz, CDCl3): d 23.4, 117.7, 123.6, 141.4, 144.4,
168.5. GC-MS (m/z (%)): 180 (31) [M+], 138 (100), 108 (47), 92
(26), 65 (22).
N-(naphthalen-2-yl)acetamide24 (5ab). White Solid. Yield:
94%. Mp: 132–133 uC. IR (KBr, cm21): n 741, 866, 1276, 1351,
1394, 1472, 1562, 1590, 1669, 3277. 1H NMR (300 MHz, CDCl3):
d 2.22 (s, 3H), 7.34–7.57 (m, 3H), 7.69–7.96 (m, 4H), 8.19 (s,
1H). 13C NMR (75 Hz, CDCl3): d 24.6, 116.7, 119.9, 122.4, 125.0,
126.4, 127.6, 128.7, 130.6, 133.7, 135.3, 168.7. GC-MS (m/z (%)):
185 (35) [M+], 143 (100), 115 (41), 63 (6).
S-[3-(acetylamino)phenyl] ethanethioate (5ak). Thick oil.
Yield: 82%. IR (KBr, cm21): n 876, 1243, 1360, 1391, 1443,
1523, 1588, 1654, 1744, 3278. 1H NMR (300 MHz, CDCl3): d
1.98 (s, 3H), 2.38 (s, 3H), 7.01–7.14 (m, 1H), 7.19–7.31 (m, 1H),
7.32–7.47 (m, 1H), 7.67 (s, 1H), 8.73 (s, 1H). 13C NMR (75 Hz,
CDCl3): d 24.0, 30.1, 120.9, 125.5, 127.8, 129.3, 129.6, 139.0,
169.3, 195.5. GC-MS (m/z (%)): 209 (27) [M+], 167 (98), 125
(100), 97 (16), 80 (46).
1-(2-Oxopropyl)piperidin-4-yl acetate19 (5al). Thick oil. Yield:
1
88%. IR (KBr, cm21): n 778, 1043, 1267, 1670 1745, 3011. H
NMR (300 MHz, CDCl3): d 1.18–1.38 (m, 2H), 1.45–1.64 (m,
2H), 1.72 (s, 3H), 1.76 (s, 3H), 2.96–3.10 (m, 2H), 3.27–3.39 (m,
1H), 3.47–3.60 (m, 1H), 4.56–4.66 (m, 1H). 13C NMR (75 Hz,
CDCl3): d 29.4, 30.2, 37.7, 42.6, 68.4, 168.2, 169.4. GC-MS (m/z
(%)): 185 (36) [M+], 125 (37), 83 (100), 68 (36), 56 (28).
N-dodecylacetamide29 (5ac). White Solid. Yield: 81%. Mp:
51–52 uC. IR (KBr, cm21): n 610, 1420, 1543, 1665, 2921, 3290.
1H NMR (300 MHz, CDCl3): d 0.73 (t, J = 6 Hz, 3H), 1.04–1.26
(m, 18H), 1.29–1.44 (m, 2H), 1.83 (s, 3H), 2.99–3.14 (m, 2H),
6.98 (s, 1H).13C NMR (75 Hz, CDCl3): d 13.7, 22.3, 22.6, 29.0,
29.1, 29.2, 29.3, 29.31, 31.6, 39.4, 170.2. GC-MS (m/z (%)): 227
(10) [M+], 212 (9), 128 (17), 114 (42), 100 (40), 86 (52), 73 (100),
60 (43).
Acknowledgements
Financial Support from DST (Grant No. SR/S1/RFPC-07/2006
and SR/S1/OC-43/2011), India is gratefully acknowledged. BK
thanks CSIR for a research fellowship and Dr A. K. Sahoo,
Central University Hyderabad, for an academic stay under the
UGC networking programme and single crystal X-ray data.
S-phenyl ethanethioate16,28 (5ad). Thick Oil. Yield: 84%. IR
1
(KBr, cm21): n 756, 980, 1225, 1489, 1502, 1715. H NMR (300
MHz, CDCl3): d 2.42 (s, 3H), 7.34–7.57 (m, 5H). 13C NMR (75
Hz, CDCl3): d 29.9, 127.7, 128.9, 129.1, 134.2193.6. GC-MS (m/z
(%)): 152 (50) [M+], 110 (100), 84 (19), 65 (40), 51 (15).
S-(4-chlorophenyl) ethanethioate17 (5af). Thick Oil. Yield:
88%. IR (KBr, cm21): n 750, 980, 1198, 1222, 1503, 1745. 1H
NMR (300 MHz, CDCl3): d 2.40 (s, 3H), 7.23–7.76 (m, 4H). 13C
NMR (75 Hz, CDCl3): d 29.9, 126.1, 129.1, 135.4, 135.5, 193.0.
GC-MS (m/z (%)): 186 (31) [M+], 144 (100), 108 (55), 99 (14), 69
(21).
Notes and references
1 (a) A. Papp, G. Galbacs and A. Molnar, Tetrahedron Lett.,
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S-(4-bromophenyl) ethanethioate30 (5ag). White solid. Yield:
93%. Mp: 51–52 uC. IR (KBr, cm21): n 980, 1009, 1224, 1478,
1567, 1734. 1H NMR (300 MHz, CDCl3): d 2.42 (s, 3H), 7.27 (d, J
= 9 Hz, 2H), 7.54 (d, J = 9 Hz, 2H). 13C NMR (75 Hz, CDCl3): d
30.3, 124.1, 127.0, 132.4, 135.9, 193,2. GC-MS (m/z (%)): 230
(25) [M+], 232 (26) [M+ + 2], 188 (100), 108 (99), 82 (27), 69 (22).
S-(4-methoxyphenyl) ethanethioate17 (5ah). White solid.
Yield: 90%. Mp: 98–101 uC. IR (KBr, cm21): n 870, 1045,
´
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1189, 1256, 1601, 1766. H NMR (300 MHz, CDCl3): d 2.36 (s,
2 L. V. Dinh and J. A. Gladysz, Chem. Commun., 2004, 998.
3 (a) C. K. Ralph, O. M. Akotsi and S. H. Bergens,
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13C NMR (75 Hz, CDCl3): d 29.4, 54.9, 114.4, 118.3, 135.7,
160.3, 194.5. GC-MS (m/z (%)): 182 (55) [M+], 140 (100), 125
(95), 96 (37), 69 (25).
4-(Acetylsulfanyl)phenyl acetate30 (5ai). White solid. Yield:
¨
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87%. Mp: 71–72 uC. IR (KBr, cm21): n 983, 1124, 1378, 1511,
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1567, 1702, 1744. H NMR (300 MHz, CDCl3): d 2.17 (s, 3H),
2.30 (s, 3H), 7.09 (d, J = 6 Hz, 2H), 7.35 (d, J = 6 Hz, 2H). 13C
NMR (75 Hz, CDCl3): d 20.9, 30.0, 122.5, 125.1, 135.5, 151.6,
168.9, 193.5. GC-MS (m/z (%)): 210 (27) [M+], 168 (78), 125
(100), 97 (37), 69 (23).
5 (a) D. E. Bergbreiter, P. L. Osburn, T. Smith, C. Li and J.
D. Frels, J. Am. Chem. Soc., 2003, 125, 6254; (b) J.-H. Zhong,
A. Fishman and E. Lee-Ruff, Org. Lett., 2002, 4, 4415; (c)
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6 (a) B. R. Sarkar and R. V. Chaudhari, J. Catal., 2006, 242,
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S-[4-(acetylamino)phenyl] ethanethioate18 (5aj). White solid.
Yield: 83%. Mp: 127–129 uC. IR (KBr, cm21): n 850, 1455, 1493,
1367, 1501, 1575, 1673, 1733, 3350. 1H NMR (300 MHz, CDCl3):
d 1.90 (s, 3H), 2.15 (s, 3H), 7.06 (d, J = 9 Hz, 2H), 7.43 (d, J = 9
Hz, 2H), 9.37 (s, 1H). 13C NMR (75 Hz, CDCl3): d 23.7, 29.4,
119.5, 121.0, 134.5, 139.7, 168.7, 194.3. GC-MS (m/z (%)): 209
(18) [M+], 167 (84), 125 (100), 80 (16).
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