Convenient access to strained trisubstituted 2-azetines from enals and chloramine-T in aqueous media

Article abstract of DOI:10.1039/c2gc36331c

A new, convenient and ecofriendly one-pot procedure for the synthesis of trisubstituted 2-azetines from α,β-unsaturated enals and chloramine-T using iodine and K₂CO₃ in aqueous media is reported. Easily accessible substrates, operational simplicity, wide substrate scope and ambient temperature are salient features of the present investigation.

Full text of DOI:10.1039/c2gc36331c

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PAPER
Convenient access to strained trisubstituted 2-azetines from enals and
chloramine-T in aqueous media
Atul K. Singh, Ruchi Chawla and Lal Dhar S. Yadav*
Received 22nd August 2012, Accepted 27th September 2012
DOI: 10.1039/c2gc36331c
A new, convenient and ecofriendly one-pot procedure for the synthesis of trisubstituted 2-azetines from
α,β-unsaturated enals and chloramine-T using iodine and K2CO3 in aqueous media is reported. Easily
accessible substrates, operational simplicity, wide substrate scope and ambient temperature are salient
features of the present investigation.
Introduction
To design and implement new synthetic methodologies keeping
in mind the alarming environmental issues are the need of the
hour. Organic synthesis in aqueous media1 is one such area of
interest, which has provided chemists with exquisite alternatives
to overcome the environmental hazards concerned with classical
organic synthesis. The environmentally benign nature of water
Scheme 1 The synthesis of 2-azetines 3 and 4.
provides opportunities for clean processing and pollution preven-
tion. Besides the benefits linked with carrying out an organic
synthesis in water, if one can accomplish the synthesis of a
scaffold which otherwise is difficult to achieve then it
would definitely be a welcomed move.
Results and discussion
Chloramine-T, which is a well known commercially available
oxidising reagent, serves as a source of chloronium cations and/
or nitrogen anions, and synthetic applications of chloramine-T
have been developed by utilizing its reactivity towards a wide
variety of functional groups.10 Iodine catalysed transformations
using chloramine-T have been carried out with different types of
aromatic, aliphatic and functionalised olefins,11 such as allylic
alcohols, ethers, esters and halides, including electron-deficient
olefins like nitroolefins, α,β-unsaturated ketones, esters and
amides, but to the best of our knowledge, this catalytic trans-
formation has never been studied with α,β-unsaturated enals.
Taking all these aspects into consideration and in continuation of
our ongoing efforts to develop new synthetic processes from
easily available substrates,12 we decided to study in detail the
reaction of α,β-unsaturated enals with chloramine-T and iodine.
To explore the reactivity of α,β-unsaturated enals, chloramine-T
and iodine, we selected the model reaction between the cinnam-
aldehyde 1a and chloramine-T 2 in the presence of iodine and
potassium carbonate in water as solvent (Table 1).
No iodoamidated and aziridinated products were obtained
under the reaction conditions. Unexpectedly, substituted
2-azetine 3a was obtained in excellent yield (Table 1, entry 1).
Encouraged by the results, we next focused our investigation
towards the quantitative optimization of iodine and chloramine-T.
We found that the best yield of azetine 3a was obtained with
50 mol% of iodine (Table 1, entry 1). The yield of 3a decreased
in the presence of 30 mol% of iodine in comparison to 50 mol%
2-Azetines are an enamine based ring system, the utility of
which are manifested in the numerous types of reactions that
they undergo, viz. intermolecular [2 + 2] photodimerization2 or
radical additions,3 [4 + 2] and [2 + 2] cycloaddition reactions4,5
and their ring-opening reaction with atmospheric oxygen.6 The
synthesis of 2-azetines has been relatively less explored owing to
the highly constrained double bond present in the four-
membered aza-heterocycle, which makes it highly unstable and
difficult to access. However, N-acyl, N-methanesulfonyl and
N-nitro-2-azetines are stable and the most studied 2-azetines
available in the literature.2,7,8 Most of the reports available in the
literature are for the synthesis of unsubstituted 2-azetines, which
are obtained from the corresponding 3-(methanesulfonyloxy)-
azetidines via an elimination reaction in basic medium,9 for
which the results are not satisfactory in terms of yields, reaction
times, synthetic steps, substrate accessibility, scope and environ-
mental considerations. Developing a convenient route to substi-
tuted 2-azetines from easily available starting materials in an
environmentally benign manner was the objective of our present
investigation. We hypothesized the facile synthesis of this scaf-
fold from enals and chloramine-T in the presence of iodine and
potassium carbonate in water, as depicted in Scheme 1.
Green Synthesis Lab, Department of Chemistry, University of
Allahabad, Allahabad 211 002, India. E-mail: ldsyadav@hotmail.com;
Fax: (+91) 532-246-0533; Tel: (+91) 532-250-0652
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Table 1 Optimization of chloramine-T and iodine for the synthesis of
2-azetine 3aa
Table 3 Synthesis of azetines 3a and 4a
Entry Iodine mol% Chloramine-T mol% Time (h) Yieldb (%)
Entry
R
Product
Time (h)
Yieldb,c (%)
1
2
3
4
5
6
50
30
100
50
50
100
100
100
100
150
50
6
8
10
6
8
8
87
51
87
87
38
87
1
2
3
4
5
6
7
8
C6H5
3a
3b
3c
3d
3e
3f
3g
3h
4a
4b
4c
4c
6
7
7
6
7
7
7
6
7
7
8
9
87
85
82
95
91
83
80
92
85
81
77
76
4-MeOC6H4
4-CH3C6H4
4-NO2C6H4
4-ClC6H4
3-MeOC6H4
3-CH3C6H4
3-NO2C6H4
CH3
150
a For experimental procedure, see Experimental section. b Yield of
isolated and purified product 3a.
9
10
11
12
C2H5
C3H7
C4H9
Table 2 Comparison of solvents in the synthesis of 2-azetine 3aa
a For experimental procedure, see Experimental section. b Yield of
isolated and purified product. c All compounds gave C, H and N
analyses within 0.37% and satisfactory spectral (IR, 1H NMR, 13C
NMR and EIMS) data.
Entry
Solvent
Time (h)
Yieldb (%)
in high yield within a short time period (Table 3, entries 1–8).
α,β-Unsaturated enals bearing an electron-withdrawing group
gave higher yield in comparison to α,β-unsaturated enals bearing
an electron-donating group (Table 3, entries 4, 5, 8). After being
successful in the case of aromatic α,β-unsaturated enals, we
extended the procedure to various kinds of aliphatic α,β-unsatu-
rated enals. Interestingly, it was observed that aliphatic α,β-unsa-
turated enals gave the corresponding 3-iodo-1-tosylazete instead
of 1-tosylazet-2-ol (Table 3, entries 9–12).
This is understandable if we look at the mechanism of reaction
as depicted in Scheme 2. In the case of aromatic α,β-unsaturated
enals, elimination of the more acidic benzylic hydrogen and
iodide ion takes place from the intermediate 8 to form the more
stable product 3 (Table 3, entries 1–8), which is stabilised by
extended conjugation, whereas in the case of aliphatic α,β-un-
saturated enals, dehydration takes place by removal of the more
acidic 3-H, an α-H of the aza-hemiacetal system, to form
product 4 (Table 3, entries 9–12).
1
2
3
4
5
6
7
8
H2O
6
9
9
7
9
7
9
8
87
10
30
80
—
50
—
60
CH3CN
EtOAc
CH2Cl2
THF
Dioxane
CH3OH
Toluene
a For experimental procedure, see Experimental section. b Yield of
isolated and purified product 3a.
of iodine (Table 1, entry 2). In the presence of 1 equivalent of
iodine the yield of azetine 3a did not change even when the reac-
tion time was extended up to 10 h. Next, we optimized the
amount of chloramine-T and found that the use of 1.5 equiva-
lents did not increase the yield of azetine 3a (Table 1, entry 4),
but its yield decreased on using 0.5 equivalent of chloramine-T
(Table 1, entry 5).
For comparison purposes, we also performed the reaction in
various solvents with 0.5 equivalent of iodine and 1 equivalent
of K2CO3 but we obtained significantly lower yield of 3a in rela-
tively longer reaction times (Table 2).
Of the solvents tested, water was the best in terms of the yield
and reaction time (Table 2, entry 1). This might be attributed to
the greater solubility of chloramine-T in water than in organic
solvents. Under the established optimized reaction conditions the
process was extended to a variety of α,β-unsaturated enals and
the results are summarised in Table 3.
We examined the substrate scope for different aromatic and
aliphatic α,β-unsaturated enals. It can be seen from Table 3 that
various aromatic α,β-unsaturated enals bearing functional groups
reacted successfully to give the corresponding 1-tosylazet-2-ols
Scheme 2 A plausible mechanism for the synthesis of azetines 3
and 4.
3326 | Green Chem., 2012, 14, 3325–3328
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1
Initially, chloramine-T 2 reacts readily with iodine to form the
active species N-chloro-N-iodo-p-toluenesulfonamide 5, which
acts as a source of iodonium ions and activates the carbonyl
group of enals 1 to induce the 1,4-addition of the nitrogen
nucleophile to form intermediate 6. The liberated NaI reduces
the intermediate 7 and the resulting species undergoes cycliza-
tion to afford 8. Intermediate 8 undergoes elimination of HI or
dehydration to afford products 3 or 4, respectively. The proposed
mechanism is in accordance with the earlier observations.11
770 cm−1. H NMR (400 MHz; CDCl3) δ = 2.45 (s, 3H), 6.98
(dd, J = 11.8, 9.4 Hz, 1H), 7.34 (d, J = 8.1 Hz, 2H), 7.41–7.45
(m, 3H), 7.49 (d, J = 11.8 Hz, 1H), 7.54–7.56 (m, 2H), 7.85 (d,
J = 8.1 Hz, 2H), 8.77 (d, J = 9.4 Hz, 1H). 13C NMR (100 MHz;
CDCl3) δ = 21.7, 77.4, 124.7, 128.0, 128.8, 129.2, 129.8, 131.2,
135.3, 144.6, 159.0, 171.0. EIMS (m/z): 301 (M+). Anal. Calcd
for C16H15NO3S: C, 63.77; H, 5.02; N, 4.65; Found: C, 63.52;
H, 5.14; N, 4.35.
Compound 3b. Yellow greasy solid, yield 85%. IR (KBr) νmax
3365, 3058, 2940, 1625, 1576, 1350, 1320, 1250, 1154, 1082,
1
977, 850, 765 cm−1. H NMR (400 MHz; CDCl3) δ = 2.43 (s,
Conclusions
3H), 3.85 (s, 3H), 6.86 (dd, J = 15.6, 9.5 Hz, 1H), 6.91–6.96 (m,
2H), 7.32 (d, J = 8.1 Hz, 2H), 7.43 (d, J = 15.6 Hz, 1H),
7.49–7.53 (m, 2H), 7.84 (d, J = 8.1 Hz, 2H), 8.73 (d, J =
9.5 Hz, 1H). 13C NMR (100 MHz; CDCl3) δ = 21.7, 55.8, 77.3,
115.1, 124.5, 126.3, 127.1, 128.1, 129.7, 143.8, 153.7, 159.2,
171.2. EIMS (m/z): 331 (M+). Anal. Calcd for C17H17NO4S: C,
61.61; H, 5.17; N, 4.23; Found: C, 61.58; H, 5.19; N, 4.41.
In conclusion, we have developed a novel, highly efficient and
ecofriendly one-pot procedure for the synthesis of 2-azetines
from α,β-unsaturated enals using chloramine-T as the nitrogen
source in the presence of iodine and K2CO3 in aqueous media.
Importantly, aromatic enals afforded azetinols, while aliphatic
enals furnished iodoazetes under the same reaction conditions.
Easily accessible substrates, operational simplicity, wide sub-
strate scope and ambient temperature are salient features of the
present investigation, which make it one of the most convenient
and efficient green methodologies for the synthesis of this rela-
tively inaccessible class of compounds.
Compound 3c. Brown greasy solid, yield 82%. IR (KBr) νmax
3367, 3070, 2932, 1623, 1572, 1348, 1328, 1148, 842,
1
764 cm−1. H NMR (400 MHz; CDCl3) δ = 2.37 (s, 3H), 2.44
(s, 3H), 6.87 (dd, J = 15.7, 9.6 Hz, 1H), 7.21–7.25 (m, 2H), 7.33
(d, J = 8.2 Hz, 2H), 7.45 (d, J = 15.7 Hz, 1H), 7.47–7.49 (m,
2H), 7.86 (d, J = 8.2 Hz, 2H), 8.76 (d, J = 9.6 Hz, 1H). 13C
NMR (100 MHz; CDCl3) δ = 21.6, 23.8, 77.2, 124.3, 126.8,
128.1, 129.0, 129.9, 133.5, 136.5, 145.1, 154.3, 169.9. EIMS
(m/z): 315 (M+). Anal. Calcd for C17H17NO3S: C, 64.74; H,
5.43; N, 4.44; Found: C, 64.86; H, 5.17; N, 4.76.
Experimental
General
IR spectra in KBr were recorded on a Perkin-Elmer 993 IR
1
spectrophotometer, H NMR spectra were recorded on a Bruker
Compound 3d. Yellow greasy solid, yield 95%. IR (KBr)
νmax 3360, 3062, 2960, 1628, 1580, 1520, 1347, 1332, 1318,
Avance II (400 MHz) FT spectrometer in CDCl3 using TMS as
an internal reference. 13C NMR spectra were recorded on the
same instrument at 100 MHz in CDCl3 and TMS was used as an
internal reference. Mass (EI) spectra were recorded on JEOL
D-300 mass spectrometer. Elemental analyses were carried out
in a Coleman automatic carbon, hydrogen and nitrogen analyser.
All chemicals used were reagent grade and were used as received
without further purification. All reactions were performed using
oven-dried glassware. Organic solutions were concentrated using
a Buchi rotary evaporator. Column chromatography was carried
out over silica gel (Merck 100–200 mesh) and TLC was per-
formed using silica gel GF254 (Merck) plates.
1
1150, 1094, 838, 759 cm−1. H NMR (400 MHz; CDCl3) δ =
2.45 (s, 3H), 7.02 (dd, J = 12.3, 9.8 Hz, 1H), 7.33 (d, J =
8.2 Hz, 2H), 7.52 (d, J = 12.3 Hz, 1H), 7.76–7.71 (m, 2H), 7.85
(d, J = 8.2 Hz, 2H), 8.23–8.28 (m, 2H), 8.80 (d, J = 9.8 Hz,
1H). 13C NMR (100 MHz; CDCl3) δ = 21.8, 77.5, 122.3, 124.4,
127.8, 129.7, 136.4, 141.4, 144.2, 148.6, 154.2, 169.7. EIMS
(m/z): 346 (M+). Anal. Calcd for C16H14N2O5S: C, 55.48; H,
4.07; N, 8.09; Found: C, 55.22; H, 4.28; N, 7.95.
Compound 3e. Yellow greasy solid, yield 91%. IR (KBr) νmax
3358, 3071, 2952, 1624, 1578, 1338, 1320, 1153, 1089, 856,
1
766 cm−1. H NMR (400 MHz; CDCl3) δ = 2.43 (s, 3H), 6.97
General procedure for the synthesis of azetines 3 and 4. A
mixture of α,β-unsaturated aldehyde 1 (1 mmol), chloramine-T 2
(1 mmol) and iodine (0.5 mmol) in water was stirred at room
temperature for 2 h with subsequent addition of K2CO3
(1 mmol). The reaction mixture was then stirred for another
4–7 h (Table 3). After completion of the reaction (monitored by
TLC), aqueous Na2S2O3 (0.2 M, 5 mL) was added to the reac-
tion mixture and the resulting solution was extracted with EtOAc
(3 × 5 mL). The combined organic phase was dried over anhyd.
Na2SO4, filtered and concentrated under reduced pressure. The
resulting crude product was purified by silica gel column
chromatography using a mixture of EtOAc–hexane (1 : 9) as
eluent to afford an analytically pure sample of 3 or 4.
(dd, J = 11.7, 9.4 Hz, 1H), 7.32 (d, J = 8.3 Hz, 2H), 7.39–7.43
(m, 2H), 7.46 (d, J = 11.7 Hz, 1H), 7.54–7.57 (m, 2H), 7.82 (d,
J = 8.3 Hz, 2H), 8.75 (d, J = 9.4 Hz, 1H). 13C NMR (100 MHz;
CDCl3) δ = 21.8, 77.3, 124.7, 127.0, 127.9, 128.8, 129.9, 132.8,
134.2, 144.0, 153.9, 170.2. EIMS (m/z): 335 (M+). Anal. Calcd
for C16H14ClNO3S: C, 57.23; H, 4.20; N, 4.17; Found: C,
57.41; H, 4.57; N, 4.08.
Compound 3f. Yellow greasy solid, yield 83%. IR (KBr) νmax
3366, 3038, 2930, 1621, 1576, 1363, 1324, 1274, 1153, 1089,
1
1045, 767 cm−1. H NMR (400 MHz; CDCl3) δ = 2.44 (s, 3H),
3.87 (s, 3H), 6.87 (dd, J = 15.5, 9.3 Hz, 1H), 6.99–7.04 (m, 1H),
7.10–7.13 (m, 1H), 7.17–7.21 (m, 1H), 7.31 (d, J = 8.2 Hz, 2H),
7.34–7.42 (m, 1H), 7.45 (d, J = 15.5 Hz, 1H), 7.83 (d, J =
8.2 Hz, 2H), 8.75 (d, J = 9.5 Hz, 1H). 13C NMR (100 MHz;
CDCl3) δ = 21.6, 55.4, 77.0, 111.5, 116.2, 121.3, 124.8, 126.8,
Compound 3a. Brown greasy solid, yield 87%. IR (KBr) νmax
3362, 3046, 2923, 1623, 1570, 1362, 1314, 1151, 1083, 859,
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129.4, 130.2, 136.1, 144.2, 154.0, 161.2, 170.7. EIMS (m/z):
331 (M+). Anal. Calcd for C17H17NO4S: C, 61.61; H, 5.17; N,
4.23; Found: C, 61.33; H, 5.26; N, 4.40.
99.9, 127.5, 129.1, 144.2, 151.2, 154.1. EIMS (m/z): 377 (M+).
Anal. Calcd for C13H16INO2S: C, 41.39; H, 4.27; N, 3.71;
Found: C, 41.26; H, 4.55; N, 4.03.
Compound 3g. Brown greasy solid, yield 80%. IR (KBr) νmax
Compound 4d. Brown greasy solid, yield 77%. IR (KBr) νmax
3372, 3062, 2935, 1627, 1569, 1340, 1326, 1146, 761 cm−1
.
3063, 2935, 1634, 1590, 1465, 1379, 1362, 1150, 866 cm−1
.
1H NMR (400 MHz; CDCl3) δ = 2.42 (s, 3H), 2.45 (s, 3H), 6.88
(dd, J = 15.6, 9.5 Hz, 1H), 7.26–7.30 (m, 1H), 7.34 (d, J =
8.3 Hz, 2H), 7.36–7.41 (m, 3H), 7.45 (d, J = 15.6 Hz, 1H), 7.88
(d, J = 8.3 Hz, 2H), 8.78 (d, J = 9.5 Hz, 1H). 13C NMR
(100 MHz; CDCl3) δ = 21.6, 23.7, 76.9, 122.6, 124.7, 125.8,
127.1, 128.0, 128.9, 129.8, 133.7, 136.9, 144.1, 153.9, 171.1.
EIMS (m/z): 315 (M+). Anal. Calcd for C17H17NO3S: C, 64.74;
H, 5.43; N, 4.44; Found: C, 64.98; H, 5.30; N, 4.11.
1H NMR (400 MHz; CDCl3) δ = 0.90 (t, J = 7.2 Hz, 3H),
1.32–1.54 (m, 4H), 1.71–1.95 (m, 2H), 2.40 (s, 3H), 3.16 (t, J =
5.0 Hz, 1H), 7.30 (d, J = 8.1 Hz, 2H), 7.76 (d, J = 8.1 Hz, 2H),
8.46 (s, 1H). 13C NMR (100 MHz; CDCl3) δ = 13.8, 21.6, 22.5,
25.6, 30.4, 58.4, 99.8, 127.2, 129.0, 144.2, 151.6, 154.0. EIMS
(m/z): 391 (M+). Anal. Calcd for C14H18INO2S: C, 42.98; H,
4.64; N, 3.58; Found: C, 42.88; H, 4.47; N, 3.75.
Compound 3h. Yellow greasy solid, yield 92%. IR (KBr)
νmax 3370, 3064, 2959, 1623, 1573, 1347, 1342, 1326, 1153,
Acknowledgements
1
1092, 851, 762 cm−1. H NMR (400 MHz; CDCl3) δ = 2.44 (s,
We sincerely thank SAIF, Punjab University, Chandigarh, for
providing microanalyses and spectra.
3H), 7.04 (dd, J = 12.5, 9.9 Hz, 1H), 7.34 (d, J = 8.3 Hz, 2H),
7.53 (d, J = 12.5 Hz, 1H), 7.72–7.74 (m, 1H), 7.87 (d, J =
8.3 Hz, 2H), 7.92–7.96 (m, 1H), 8.27–8.35 (m, 1H), 8.43–8.45
(m, 1H), 8.83 (d, J = 9.9 Hz, 1H). 13C NMR (100 MHz; CDCl3)
δ = 21.6, 77.4, 121.3, 122.8, 124.6, 127.6, 129.2, 130.1, 132.2,
136.1, 144.0, 149.1, 154.2, 171.2. EIMS (m/z): 346 (M+). Anal.
Calcd for C16H14N2O5S: C, 55.48; H, 4.07; N, 8.09; Found: C,
55.13; H, 4.23; N, 8.40.
References
1 (a) C.-J. Li and T.-H. Chan, Organic Reactions in Aqueous Media,
John Wiley and sons, New York, 1997; (b) Organic Synthesis in Water,
ed. P. A. Grieco, Blackie Academic and Professional, London, England,
1998.
2 P. R. Dave, R. Duddu, J. Li, R. Surapaneni and R. Gilardi, Tetrahedron
Lett., 1998, 39, 5481.
Compound 4a. Brown greasy solid, yield 85%. IR (KBr) νmax
3052, 2925, 1630, 1580, 1460, 1378, 1363, 1152, 869 cm−1. 1H
NMR (400 MHz; CDCl3) δ = 1.40 (d, J = 5.5 Hz, 3H), 2.40 (s,
3H), 3.22 (q, J = 5.5 Hz, 1H), 7.30 (d, J = 8.2 Hz, 2H), 7.75 (d,
J = 8.2 Hz, 2H), 8.47 (s, 1H). 13C NMR (100 MHz; CDCl3) δ =
19.7, 21.5, 57.2, 97.8, 127.6, 129.0, 144.1, 151.7, 154.2. EIMS
(m/z): 349 (M+). Anal. Calcd for C11H12INO2S: C, 37.84; H,
3.46; N, 4.01; Found: C, 37.55; H, 3.32; N, 4.37.
3 N. Legrand, B. Quiclet-Sire and S. Z. Zard, Tetrahedron Lett., 2000, 41,
9815.
4 (a) P. R. Dave, R. Duddu, J. Li, R. Surapaneni and R. Gilardi, Tetra-
hedron Lett., 1999, 40, 443; (b) D. Osborne and P. J. Stevenson, Tetra-
hedron Lett., 2002, 43, 5469; (c) P. J. Stevenson, M. Nieuwenhuyzen and
D. Osborne, Chem. Commun., 2002, 444; (d) P. J. Stevenson,
M. Nieuwenhuyzen and D. Osborne, ARKIVOC, 2007, xi, 129.
5 A. C. B. Burtoloso and C. R. D. Correia, Tetrahedron Lett., 2006, 47,
6377.
6 R. Bartnik, R. Faure and K. J. Gebicki, J. Chem. Crystallogr., 1998, 28,
119.
7 M. E. Jung and Y. M. Choi, J. Org. Chem., 1991, 56, 6729.
8 A. P. Marchand, R. Duddu, S. G. Bott and T. G. Archibald, J. Org.
Chem., 1994, 59, 1608.
9 N. De Kimpe, in Comprehensive Heterocyclic Chemistry II, ed.
A. Padwa, Elsevier, Oxford, 1996, vol. 1, ch. 1.21. Three- and four-mem-
bered rings, with all fused systems containing three- and four-membered
rings.
10 (a) M. M. Campbell and G. Johnson, Chem. Rev., 1978, 78, 65;
(b) D. H. Bremner, in Synthetic Reagents, ed. J. S. Pizey, Wiley,
New York, 1985, vol. 6, p. 9.
Compound 4b. Brown greasy solid, yield 82%. IR (KBr) νmax
3067, 2930, 1632, 1583, 1474, 1383, 1365, 1157, 878 cm−1
.
1H NMR (400 MHz; CDCl3) δ = 0.90 (t, J = 7.2 Hz, 3H),
1.70–1.93 (m, 2H), 2.42 (s, 3H), 3.11 (t, J = 5.2 Hz, 1H), 7.31
(d, J = 8.2 Hz, 2H), 7.76 (d, J = 8.2 Hz, 2H), 8.46 (s, 1H).
13C NMR (100 MHz; CDCl3) δ = 11.2, 21.6, 25.7, 59.1, 98.6,
127.4, 129.2, 143.9, 151.3, 154.3. EIMS (m/z): 363 (M+). Anal.
Calcd for C12H14INO2S: C, 39.68; H, 3.89; N, 3.86; Found: C,
39.99; H, 3.64; N, 3.78.
11 (a) S. Minakata, Acc. Chem. Res., 2009, 42, 1172; (b) S. Minakata and
J. Hayakawa, Chem. Commun., 2011, 47, 1905.
Compound 4c. Brown greasy solid, yield 78%. IR (KBr) νmax
12 (a) A. K. Singh, R. Chawla, A. Rai and L. D. S. Yadav, Chem. Commun.,
2012, 48, 3766; (b) R. Chawla, R. Kapoor, A. K. Singh and
L. D. S. Yadav, Green Chem., 2012, 14, 1308; (c) A. K. Singh and
L. D. S. Yadav, Synthesis, 2012, 591; (d) R. Chawla, A. K. Singh
and L. D. S. Yadav, Tetrahedron Lett., 2012, 53, 3382;
(e) A. K. Singh, R. Chawla and L. D. S. Yadav, Synthesis, 2012,
2353.
3058, 2932, 1637, 1585, 1469, 1380, 1364, 1154, 884 cm−1
.
1H NMR (400 MHz; CDCl3) δ = 0.91 (t, J = 7.1 Hz, 3H),
1.19–1.78 (m, 4H), 2.41 (s, 3H), 3.15 (t, J = 5.3 Hz, 1H), 7.32
(d, J = 8.2 Hz, 2H), 7.75 (d, J = 8.2 Hz, 2H), 8.45 (s, 1H).
13C NMR (100 MHz; CDCl3) δ = 13.5, 15.7, 21.7, 34.8, 58.1,
3328 | Green Chem., 2012, 14, 3325–3328
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