Perchloric acid impregnated on silica gel (HClO4/SiO 2): A versatile catalyst for Michael addition of thiols to the electron-deficient alkenes

Article abstract of DOI:10.1002/ejoc.200600006

Perchloric acid adsorbed on silica gel (HClO₄X/SiO₂) has been found to be a highly efficient and versatile catalyst for the Michael addition of thiols to a wide variety of conjugated alkenes such as α,α-unsaturated ketones, carboxylic esters, nitriles, amides and chalcones in dichloromethane or methanol at room temperature. The reactions are completed within 2-20 min in high yields. Some of the additional advantages are: no aqueous work-up is necessary, and the catalyst is also reusable. Moreover, the solid product can be obtained without chromatographic separation. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejoc.200600006

FULL PAPER
DOI: 10.1002/ejoc.200600006
Perchloric Acid Impregnated on Silica Gel (HClO4/SiO2): A Versatile Catalyst
for Michael Addition of Thiols to the Electron-Deficient Alkenes
Abu T. Khan,*[a] Subrata Ghosh,[a] and Lokman H. Choudhury[a]
Keywords: Thiols / Electron-deficient alkenes / Michael addition / Silica-supported perchloric acid
Perchloric acid adsorbed on silica gel (HClO4/SiO2) has been
found to be a highly efficient and versatile catalyst for the
Michael addition of thiols to a wide variety of conjugated
alkenes such as α,β-unsaturated ketones, carboxylic esters,
nitriles, amides and chalcones in dichloromethane or meth-
anol at room temperature. The reactions are completed
within 2–20 min in high yields. Some of the additional advan-
tages are: no aqueous work-up is necessary, and the catalyst
is also reusable. Moreover, the solid product can be obtained
without chromatographic separation.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
dodecyl sulfate (SDS),[27] and azaphosphatrane nitrate
salt.[28] Unfortunately, many of these procedures have one
or the other disadvantages such as longer reaction time, use
of excessive expensive catalyst, harsh reaction conditions,
failure to provide addition product and tedious experimen-
tal procedure. Therefore, the development of an efficient
and mild synthetic protocol is always in great demand to
make the available procedures more convenient and simpler.
Very recently, solid-supported reagents[29] have gained con-
siderable interest in organic synthesis because of their
unique properties of the reagents such as high efficiency due
to more surface area, more stability and reusability, greater
selectivity and ease of handling. In continuation of our on-
going research programme to develop better and newer syn-
thetic methodologies, we perceived that HClO4/SiO2 might
be a very useful catalyst for thia-Michael reaction. The cat-
alyst, HClO4/SiO2 has been utilized so far by others for
acetylation of phenols, thiols, alcohols and amines,[30] per-
acetylation of carbohydrates,[31] acetalization followed by
acetylation,[32] glycosylation reaction[33] and for Ferrier re-
arrangement of glycals.[34] Very recently, we also noticed
that the same catalyst is highly effective for the gem diacyl-
ation of aldehydes.[35] In this paper, we wish to report that
HClO4/SiO2 is an efficient and valuable catalyst for the 1,4-
Inltroduction
The addition of thiols to α,β-unsaturated carbonyl com-
pounds is a very important process in carbon–sulfur bond
formation.[1] By employing this process, the olefinic double
bond of a conjugated carbonyl compound can selectively
be protected, and deprotection can be easily done either by
copper() induced elimination[2] or by oxidation followed by
thermolytic elimination.[3] Thia-Michael addition prod-
uct(s) of α,β-unsaturated carbonyl compounds are very im-
portant building blocks for the synthesis of bioactive com-
pounds,[4] heterocycles,[5] and are also used as chiral auxil-
iary for the synthesis of optically active α-hydroxy alde-
hydes.[6] Therefore, the development of an efficient and se-
lective catalyst for the construction of carbon–sulfur bond
is of interest in organic synthesis. Thia-Michael reaction is
classically carried out by employing a base under homogen-
eous conditions.[6a,7] Under heterogeneous conditions, vari-
ous solid catalysts have been found to be useful. For exam-
ple, natural phosphate or phosphate doped with potassium
fluoride,[8] zeolite,[9] clay-supported NiBr2 and FeCl3,[10]
Fluoroapatite,[11] polymer-supported Nafion® SAC-13[12]
and dodecatungstophosphoric acid (H3PW12O40).[13] More-
over, a wide variety of Lewis acid catalyst and other rea-
gents have been used over the years for the similar transfor-
mation. Among them some of the reported catalysts are:
Hf(OTf)4,[14] InBr3,[15] InCl3,[16] Bi(NO3)3,[17] Bi(OTf)3,[18]
Cu(BF4)2·xH2O,[19] nickel() perchlorate,[20] [pmIm]Br,[21]
[Bmim]PF6/H2O,[22] RuCl3 in poly(ethyleneglycol),[23]
molten tetrabutylammonium bromide,[24] chiral N,NЈ-diox-
ide–cadmium iodide,[25] I2,[26] micellar solution of sodium
[a] Department of Chemistry, Indian Institute of Technology Gu-
wahati,
Guwahati 781039, India
Scheme 1.
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Thia-Michael Additions to Electron-Deficient Alkenes
FULL PAPER
conjugate addition of thiols to a wide variety of conjugated summarized in Table 2. Next, we were interested to see
alkenes such as α,β-unsaturated ketones, carboxylic esters, whether the same catalyst is useful for the Michael reaction
nitriles and amides as shown in Scheme 1.
of acyclic α,β-unsaturated ketones or not. Remarkably, an
enone 4, such as 16-dehydropregnenolone acetate (16-
DPA), was also treated with ethanethiol (A) and thiophenol
(B) independently to give the 1,4-addition products 4a and
4b, respectively, in fairly good yields using the same catalyst
under similar reaction conditions. In addition, the use of
methanol as the solvent, makes it possible to access the
Michael addition products 5a and 5b from the correspond-
ing chalcone (5) in very good yields. Notably, by employing
our protocol, from naturally occurring α,β-unsaturated
ketones such as (S)-(+)-carvone (6) and (R)-(+)-pulegone
(7), we obtained the corresponding Michael addition prod-
ucts, 6a, 7a and 7e, respectively, as a diastereomeric mixture
on treatment with thiols under identical reaction condi-
tions. It is noteworthy to point out that the addition reac-
tion of (R)-(+)-pulegone (7) with phenylmethanethiol (E)
took much longer reaction time under basic conditions.[6a]
One more advantage of the present method is that the reac-
tion does not need to be carried out under N2.
Results and Discussion
For our investigations, HClO4/SiO2 was prepared accord-
ing to the literature procedure.[30] To evaluate the better
catalytic activity of HClO4/SiO2 over silica gel or aqueous
perchloric acid, a model study was carried out with thio-
phenol and ethyl acrylate using various catalytic conditions,
as shown in Scheme 2 and Table 1. From the study, it clearly
demonstrated that the silica-supported perchloric acid is in-
deed an effective catalyst in terms of reaction time and
yield.
Scheme 2.
Table 1. The result of the reaction of ethyl acrylate (2 mmol) with
thiophenol (2.2 mmol) under different catalytic conditions in
dichloromethane at room temperature.
Run Catalyst
Time
Yield [%][a,b]
I
II
III
IV
No catalyst
SiO2 (10 mg /mmol)
Aqueous HClO4 (0.5 mol-%)
HClO4/SiO2 (10 mg/mmol, 0.5 mol-%)
24 h
24 h
1 h
52
63
82
95
Scheme 3.
10 min
All the final products were characterized by recording
[a] Isolated yield. [b] All the compounds were characterized by re-
1
IR, H NMR, 13C NMR spectra and elemental analysis.
1
cording IR, H NMR, 13C NMR and elemental analyses.
The structure of compound 4b was determined by X-ray
The thia-Michael reaction of 2-cyclopenten-1-one (1) crystallography. The ORTEP diagram is shown in Figure 1.
with ethanethiol (A) using 0.5 mol-% of catalyst in dichlo-
Each unit cell contains two identical molecules. The tor-
romethane at room temperature (run 1) proceeded within sion angles between H32–C16–C17–H46, S1–C16–C17–H46,
5 min and the pure product 3-(ethylthio)cyclopentanone H32–C16–C17–C20 and C20–C17–C16–S1 are 155.27°, 31.32°,
(1a) was isolated in 92% yield as a gummy liquid by fil- 32.44° and 92.49°, respectively. These results are in accord-
tration through a short silica gel column. The product was ance with the fact that H46 and H32 as well as C20 and S1
1
characterized by IR, H NMR, 13C NMR spectra and ele- are in an anti orientation as shown in Figure 2.
mental analysis, and it was agreeable with the 1,4-addition
Moreover, by employing the present protocol, various
product. Various thiols used for Michael addition are given α,β-unsaturated esters namely methyl acrylate (8), methyl
in Scheme 3. The enone 1 also treated with thiophenol (B) methacrylate (9) and ethyl acrylate (10) furnished the de-
in the presence of same catalyst under identical conditions sired Michael addition products 8b, 9b and 10b respectively,
to provide the desired addition product 1b in 98% yield on reaction with thiophenol (B) in good yields. Further-
(run 2), in quicker time with better yield compared to the more, our methodology can be extended for 1,4-conjugate
recently reported procedures.[15,22] Likewise, 1,2-ethanedi- addition reaction of thiols with acrylonitrile (11) and acryl-
thiol (C) on reaction with two molecules of the enone 1 amide (12) under identical conditions. We have also studied
smoothly provided the bis-Michael addition product 1c the recyclability of the catalyst by the following way. The
within 5 min in good yield without any difficulty. By follow- reaction of acrylonitrile (100 mmol) with thiophenol
ing identical reaction procedure, 2-cyclohexen-1-one (2) (110 mmol) was carried out in the presence of HClO4/SiO2
also treated with ethanethiol (A), thiophenol (B) and 1,3- (0.5 mol-%, 1 g). After completion, the catalyst was filtered
propanedithiol (D) (run 4–6) to furnish the desired Michael off and activated by heating at 80 °C under vacuum for
addition products 2a, 2b and 2d, respectively, in good yields. 1 hour and reused for thia-Michael reaction of a fresh lot
We observed that the present protocol is highly efficient in of acrylonitrile (100 mmol) with thiophenol (110 mmol) af-
terms of mol-% of the catalyst used and yields, relative to fording 85% yield of the desired product after 20 min.
a very recently reported procedure.[19] 4,4-Dimethyl-2- Again, the catalyst was recovered, reactivated and reused
cyclohexen-1-one (3) was readily converted into 3b on reac- repeatedly for three more consecutive times for thia-
tion with thiophenol (B) in good yields. The results are Michael reactions with acrylonitrile (100 mmol) affording
Eur. J. Org. Chem. 2006, 2226–2231
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. T. Khan, S. Ghosh, L. H. Choudhury
FULL PAPER
Table 2. Michael addition of thiols to conjugated alkenes catalyzed
by silica-supported perchloric acid (HClO4/SiO2).
Table 2. (Continued).
[a] All the compounds were characterized by recording IR, 1H
NMR, 13C NMR and elemental analyses. [b] Isolated yield. [c] The
reaction was carried out in methanol instead of dichloromethane.
[d] The corresponding reference for spectroscopic data.
Figure 1. ORTEP plot of the molecule with atom numbering
scheme; hydrogen atoms are omitted for clarity.
Figure 2. Front view of a selected portion.
81%, 76% and 70% yields respectively, in 25, 30 and
35 min. From this observation, it is clear that the reaction
can be performed in a large scale as well as the catalyst can
be reused although efficiency of the catalyst is lesser in fur-
ther cycles. As the reaction took a longer time and gave
lower yields during the reusability test, the following experi-
ments were performed to rule out leaching of the actual
catalyst perchloric acid. A reaction of ethyl acrylate
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Eur. J. Org. Chem. 2006, 2226–2231

Thia-Michael Additions to Electron-Deficient Alkenes
FULL PAPER
from the mixture of ethyl acetate/hexane (1:9) for compound 4a,
4b, and from methanol for compound 3b, 5a, 5b, 12b.
(2 mmol) and thiophenol (2.2 mmol) was carried out fol-
lowing the same experimental procedure. After completion
of the reaction, the catalyst was removed by filtration
through a Whatman 40 filter paper. To the filtrate was
added another 2.2 mmol of thiophenol and 2 mmol of cy-
clohexenone and stirring was continued. A parallel reaction
was performed with 2.2 mmol of thiophenol and 2 mmol of
cyclohexenone in dichloromethane without any catalyst.
The isolated yields of 2b from the above two reactions were
30% and 27%, respectively, after five hours. From this ob-
servation, it is clear that no leaching has occurred during
the experiment. But may be due to the poisoning of the
surface of the catalyst, isolated yields are less and required
longer reaction time in the recycling experiments.
1a: Yield: 0.265 g, 92%. IR (neat): ν = 1748 (C=O) cm–1. 1H NMR
˜
(400 MHz, CDCl3): δ = 1.28 (t, J = 7.2 Hz, 3 HSCH2CH3), 1.89–
1.98 (m, 1 H), 2.15–2.23 (m, 2 H), 2.30–2.48 (m, 2 H), 2.56–2.62
(m, 3 H), 3.46 (quin, J = 6.8 Hz, 1 H, =CHSCH2CH3) ppm. 13C
NMR (100 MHz, CDCl3): δ = 14.7, 25.1, 29.7, 36.9, 39.8, 45.5,
216.2 ppm. C7H12OS (144.23): calcd. C 58.29, H 8.39, S 22.23;
found C 58.08, H 8.35, S, 22.01.
3b: Yield: 0.385 g, 82%, m.p. 68 °C. IR (KBr): ν = 1711 (C=O)
˜
cm–1. 1H NMR (400 MHz, CDCl3): δ = 1.17 (s, 3 H), 1.23 (s, 3 H),
1.59–1.62 (m, 1 H), 1.82–1.86 (m, 1 H), 2.23–2.28 (m, 1 H), 2.37–
2.41 (m, 1 H), 2.50–2.58 (m, 2 H), 3.11–3.15 (m, 1 H), 7.17–7.37
(m, 5 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.0, 29.0, 34.6,
37.8, 38.6, 45.4, 57.6, 127.4, 129.1 (2 C), 132.7 (2 C), 134.6,
209.0 ppm. C14H18OS (234.36): calcd. C 71.75, H 7.74, S 13.68;
found C 71.49, H 7.67, S 13.45.
Conclusion
4a: Yield: 0.660 g, 79%, m.p. 126 °C (mixture of diastereomers,
1:1). IR (KBr): ν = 1731, 1706 cm–1. 1H NMR (300 MHz, CDCl ):
˜
3
In conclusion, the unique properties of silica-supported
perchloric acid allowed us to demonstrate a new synthetic
methodology for the thia-Michael addition reaction. The
significant advantages of our protocol are: very good yields,
mild conditions, short reaction times, non-aqueous work-
δ = 0.62 (s, 3 H), 0.98–1.10 (m, 12 H), 1.01(s, 3 H), 1.02 (s, 3 H),
1.06 (s, 3 H), 1.23 (t, J = 7.2 Hz, 6 H), 1.49–1.58 (m, 16 H), 1.86
(d, J = 9.6 Hz, 2 H), 1.97 (d, J = 9.3 Hz, 2 H), 2.03 (s, 6 H), 2.16
(s, 3 H), 2.19 (s, 3 H), 2.32 (d, J = 9.6 Hz, 2 H), 2.41–2.62 (m, 4
H), 2.69 (d, J = 9.9 Hz, 2 H), 3.42–3.48 (m, 1 H), 3.72–3.76 (m, 1
up procedure and involvement of non-expensive reusable H), 4.61 (m, 2 H), 5.37 (m, 2 H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 13.9, 14.2, 14.6, 14.7, 19.3 (2 C), 20.4, 20.8, 21.4 (2 C), 26.4,
27.7 (2 C), 28.0, 30.9, 31.4, 31.5, 31.7, 31.8, 34.8, 36.5, 36.6 (2 C),
36.9, 37.8, 38.0 (2 C), 38.5, 38.7, 40.5, 42.7, 42.8, 45.3 (2 C), 49.7,
50.1, 54.9, 55.8, 67.2, 72.1, 73.7, 73.8, 122.1 (2 C), 139.6, 139.9,
170.5 (2 C), 207.4 (2 C) ppm. C25H38O3S (418.64): calcd. C 71.73,
H 9.15, S 7.66; found C 71.48, H 9.10, S 7.42.
catalyst.
Experimental Section
Melting points were recorded with a Büchi B-545 melting point
apparatus and were uncorrected. IR spectra were recorded in KBr
or neat with a Nicolet Impact 410 spectrophotometer. 1H NMR
spectra and 13C NMR spectra were recorded either with a Jeol
300 MHz or Varian 400 spectrometer and Jeol 75 MHz or Varian
100 MHz, respectively, in CDCl3 using TMS as internal reference.
Elemental analyses were carried out in a Perkin–Elmer 2400 auto-
matic carbon, hydrogen, nitrogen and sulfur analyzer. X-ray dif-
fraction data were collected with a Bruker Apex II smart dif-
fractometer with CCD area detectors using graphite-monochro-
mated Mo-Kα radiation (λ = 0.71073 Å). Column chromatographic
separations were done on SRL silica gel (60–120 mesh).
CCDC-298160 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
4b: Yield: 0.765 g, 82%, m.p. 134 °C. IR (KBr): ν = 1731 (C=O),
˜
1
1711 (COCH3) cm–1. H NMR (400 MHz, CDCl3): δ = 0.66 (s, 3
H), 1.00 (s, 3 H), 0.92–1.02 (m, 5 H), 1.40–1.80 (m, 8 H), 1.82 (d,
J = 10.8 Hz, 2 H), 1.83–1.97 (m, 4 H), 2.01 (s, 3 H), 2.29–2.32 (m,
1 H), 2.60 (d, J = 8.4 Hz, 1 H), 4.10–4.22 (m, 1 H), 4.55–4.62 (m,
1 H), 5.35–5.37 (m, 1 H), 7.10–7.20 (m, 5 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 14.2, 19.4, 20.9, 21.5, 27.8, 31.4, 31.7, 31.8,
34.7, 36.6, 36.9, 38.1, 38.9, 43.6, 45.4, 49.7, 54.9, 70.9, 73.9, 121.9,
126.4, 128.7 (2C), 130.8 (2C), 135.9, 139.4, 170.2, 206.4 ppm.
C29H38O3S (466.68): calcd. C 74.64, H 8.21, S 6.87; found C 74.35,
H 8.14, S 6.62.
5a: Yield: 0.503 g, 93%, m.p. 61–62 °C. IR (KBr): ν = 1693 (C=O)
˜
1
cm–1. H NMR (400 MHz, CDCl3): δ = 1.16 (t, J = 7.2 Hz, 3 H),
2.30–2.39 (m, 2 H), 3.52 (d, J = 7.6 Hz, 2 H), 4.57 (t, J = 7.2 Hz,
1 H), 7.18 (t, J = 7.2 Hz, 1 H), 7.28 (t, J = 8.0 Hz, 2 H), 7.38–7.43
(m, 4 H), 7.52 (t, J = 7.2 Hz, 1 H), 7.89 (d, J = 7.6 Hz, 2 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 14.8, 25.9, 44.4, 45.8, 127.4,
128.0 (2 C), 128.3 (2 C), 128.7 (2 C), 128.8 (2 C), 133.4, 137.0,
142.4, 196.9 ppm. C17H18OS (270.39): calcd. C 75.52, H 6.71, S
11.86; found C 75.18, H 6.63, S 11.58.
Preparation of HClO4/SiO2 Catalyst:[30] HClO4 (1.8 g, 12.5 mmol,
as a 70% aq. solution) was added to a suspension of SiO2 (230–
400 mesh, 23.7 g) in Et2O (70.0 mL). The mixture was concentrated
and the residue was heated at 100 °C for 72 hours under vacuum to
furnish HClO4/SiO2 (0.5 mmol/g) as a free flowing powder (50 mg,
0.025 mmol of HClO4).
5b: Yield: 0.605 g, 95%, m.p. 114–115 °C. IR (KBr): ν = 1685
˜
Typical Experimental Procedure: To a magnetically stirred solution
of 2-cyclohexene-1-one (2) (0.192 g, 2 mmol) and thiophenol
(0.242 g, 2.2 mmol) in dichloromethane (2 mL) was added HClO4/
(C=O) cm–1. 1H NMR (400 MHz, CDCl3): δ = 3.56 (dd, J =
6.0 Hz, J = 17.2 Hz, 1 H), 3.64 (dd, J = 8.4 Hz, J = 17.2 Hz, 1 H),
4.93 (dd, J = 6.0 Hz, J = 8.4 Hz, 1 H), 7.14–7.23 (m, 6 H), 7.28–
SiO2 (20 mg, 0.5 mol-%). The reaction was instantly completed as 7.31 (m, 4 H), 7.40 (t, J = 7.6 Hz, 2 H), 7.51 (t, J = 7.6 Hz, 1 H),
checked by TLC. After completion of the reaction, the reaction
mixture was directly passed through a silica gel column to obtain
pure desired Michael addition product (2b) (0.400 g, 97%) as a
colourless oily liquid. In case of solid product, it was obtained by
removing the catalyst by filtration followed by recrystallization
7.85 (d, J = 8.0 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
44.8, 48.3, 127.2, 127.4, 127.6 (2 C), 127.9 (2 C), 128.3 (2 C), 128.4
(2 C), 128.7 (2 C), 132.6 (2 C), 133.1, 134.1, 136.6, 141.0,
196.7 ppm. C21H18OS (318.43): calcd. C 79.21, H 5.70, S 10.07;
found C 78.95, H 5.65, S 9.87.
Eur. J. Org. Chem. 2006, 2226–2231
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. T. Khan, S. Ghosh, L. H. Choudhury
FULL PAPER
6a: (data for the major isomer), yield: 0.403 g, 95%. IR (neat): ν =
to the Director, IITG for general facilities to carry out our research
˜
1
1711 (C=O) cm–1. H NMR (400 MHz, CDCl3): δ = 1.15 (d, J = works. We are thankful to the referees valuable comments and
7.2 Hz, 3 H), 1.24 (t, J = 7.6 Hz, 3 H), 1.76 (s, 3 H), 1.95–2.02 (m, suggestions. We are grateful to Dr. V. Manivannan and Dr. Gopal
1 H), 2.15–2.25 (m, 2 H), 2.40–2.60 (m, 3 H), 2.76–2.84 (m, 1 H),
2.87–3.15 (m, 1 H), 3.42 (dd, J = 3.2 Hz, J = 8.4 Hz, 1 H), 4.73 (d,
J = 20 Hz, 1 H), 4.81 (d, J = 15.2 Hz, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 12.7, 14.8, 20.9, 26.1, 35.9, 40.7, 46.0, 48.8,
49.2, 110.0, 146.9, 209.5 ppm. C12H20OS (212.35): calcd. C 67.87,
H 9.49, S 15.10; found C 67.55, H 9.40, S 14.95.
Das, Department of Chemistry for their help during manuscript
preparation.
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7a: (data for the major isomer), yield: 0.343 g, 80%. IR (neat): ν =
˜
1
1718 (C=O) cm–1. H NMR (400 MHz, CDCl3): δ = 1.00 (d, J =
6.0 Hz, 3 H), 1.21 (t, J = 7.6 Hz, 3 H, SCH2CH3), 1.36 (s, 3 H),
1.40–1.60 (m, 2 H), 1.52 (s, 3 H), 1.82–2.20 (m, 3 H), 2.27–2.30 (m,
1 H), 2.42 (dd, J = 3.6 Hz, J = 11.6 Hz, 1 H), 2.48–2.57 (m, 3
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 14.5, 21.7, 22.3, 24.1,
28.0, 29.7, 34.8, 36.7, 46.9, 52.4, 58.1, 210.3, ppm. C12H22OS
(214.37): calcd. C 67.24, H 10.34, S 14.96; found C 67.01, H, 10.28,
S 14.68.
8b: Yield: 0.345 g, 88%. IR (neat): ν = 1744 (C=O) cm–1. 1H NMR
˜
(300 MHz, CDCl3): δ = 2.64 (t, J = 7.5 Hz, 2 H), 3.17 (t, J =
7.5 Hz, 2 H), 3.68 (s, 3 H), 7.19–7.39 (m, 5 H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 29.0, 34.2, 51.8, 126.6, 129.0 (2 C), 130.1 (2
C), 135.1, 172.2 ppm. C10H12O2S (196.27): calcd. C 61.20, H 6.16,
S 16.34; found C 61.01, H 6.12, S 16.12.
9b: Yield: 0.382 g, 91%. IR (neat): ν = 1742 (C=O) cm–1. 1H NMR
˜
(300 MHz, CDCl3): δ = 1.27 (d, J = 6.9 Hz, 3 H), 2.70 (dd, J =
6.9 Hz, J = 13.8 Hz, 1 H), 2.93 (dd, J = 6.9 Hz, J = 13.2 Hz, 1 H),
3.27 (dd, J = 6.9 Hz, J = 13.2 Hz, 1 H), 3.67 (s, 3 H), 7.20–7.38
(m, 5 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 16.8, 37.4, 39.7,
51.9, 126.3, 128.8 (2 C), 129.8 (2 C), 135.5, 175.1 ppm. C11H14O2S
(210.29): calcd: C 62.83, H 6.71, S 15.25; found C 62.61, H 6.68, S
14.95.
10b: Yield: 0.383 g, 95%. IR (neat): ν = 1743 (C=O) cm–1. 1H
˜
NMR (400 MHz, CDCl3): δ = 1.24 (t, J = 7.2 Hz, 3 H), 2.61 (t, J
= 7.2 Hz, 2 H), 3.15 (t, J = 7.2 Hz, 2 H), 4.13 (q, J = 7.2 Hz, 2 H),
7.18 (t, J = 7.6 Hz, 1 H), 7.27 (t, J = 7.6 H, 2 Hz), 7.34 (d, J =
8.0 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 14.2, 29.0,
34.4, 60.6, 126.3, 128.8 (2 C), 129.8 (2 C), 135.0, 171.4 ppm.
C11H14O2S (210.29): calcd. C 62.83, H 6.71, S 15.25; found C 62.66,
H 6.62, S 14.99.
[15] M. Bandini, P. G. Cozzi, M. Giacomini, P. Melchiorre, S. Selva,
A. Umani-Ronchi, J. Org. Chem. 2002, 67, 3700–3704.
[16] B. C. Ranu, S. S. Dey, S. Samanta, ARKIVOC 2005, 44–50.
[17] N. Srivastava, B. K. Banik, J. Org. Chem. 2003, 68, 2109–2114.
[18] a) M. M. Alam, R. Varala, S. R. Adapa, Tetrahedron Lett.
2003, 44, 5115; b) H. Gaspard-Iloughmane, C. Le Roux, Eur.
J. Org. Chem. 2004, 2517–2532.
11b: Yield: 0.317 g, 97%. IR (neat): ν = 2250 (CN) cm–1. 1H NMR
˜
(400 MHz, CDCl3): δ = 2.58 (t, J = 7.2 Hz, 2 H), 3.12 (t, J = 7.2 H,
2 Hz), 7.26–7.34 (m, 3 H), 7.40 (d, J = 8.0 Hz, 2 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 18.4, 30.4, 117.8, 127.6, 129.2 (2 C),
131.3 (2 C), 133.0 ppm. C9H9NS (163.24): calcd. C 66.22, H 5.56,
N 8.58, S 19.64; found C 66.01, H 5.47, N 8.49, S 19.39.
[19] S. K. Garg, R. Kumar, A. K. Chakraborti, Tetrahedron Lett.
2005, 46, 1721–1724.
[20] S. Kanemasa, Y. Oderaotoshi, E. Wada, J. Am. Chem. Soc.
1999, 121, 8675–8676.
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[22] J. S. Yadav, B. V. S. Reddy, G. Baishya, J. Org. Chem. 2003, 68,
7098–7100.
12b: Yield: 0.330 g, 91%, m.p. 125 °C. IR (KBr): ν = 1657
˜
(CONH2) cm–1. 1H NMR (400 MHz, CDCl3): δ = 2.53 (t, J =
7.2 Hz, 2 H), 3.22 (t, J = 7.2 Hz, 2 H), 5.56 (br. s, 2 H), 7.20 (t, J
= 8.4 Hz, 1 H), 7.29 (t, J = 8.8 Hz, 2 H), 7.36 (d, J = 8.0 Hz, 2 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 29.2, 35.4, 126.3, 128.9 (2
C), 129.6 (2 C), 135.1, 173.2 ppm. C9H11NOS (181.25): calcd. C
59.64, H 6.12, N 7.73, S 17.69; found C 59.40, H 6.04, N 7.59, S
17.51.
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2129–2136.
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2421.
[25] M. Saito, M. Nakajima, S. Hashimoto, Tetrahedron 2000, 56,
9589–9594.
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2005, 46, 4971–4974.
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2005, 347, 655–661.
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440–456.
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16, 2425–2428; b) A. R. Hajipour, A. E. Ruoho, Tetrahedron
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Jun-Ping, Chem. Lett. 2005, 34, 1042–1043; d) W. Lan-Zhou,
Acknowledgments
A.T. K. acknowledges to the Department of Science and Technol-
ogy (DST), New Delhi for research grant (Grant No. SP/S1/G-35/
98). L. H. C. is thankful to the CSIR, Govt. of India and S. G. is
grateful to IITG for their research fellowships. We are also grateful
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2226–2231

Thia-Michael Additions to Electron-Deficient Alkenes
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Received: January 6, 2006
Published Online: March 6, 2006
Eur. J. Org. Chem. 2006, 2226–2231
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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