Synthesis of 2-oxazolines and 2-thiazolines using lanthanide amino alkoxide

Article abstract of DOI:10.1080/00397910701545098

New 2-oxazolines and 2-thiazolines are prepared from phenacysulfonylacetic acid methyl ester using lanthanide amino alkoxide. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701545098

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Synthesis of 2‐Oxazolines and 2‐Thiazolines
using Lanthanide Amino Alkoxide
V. Padmavathi a , B. Chandra Obula Reddy a , P. Thriveni a & A.V. Nagendra
Mohan a
a Department of Chemistry , Sri Venkateswara University , Tirupati, India
Published online: 10 Sep 2007.
To cite this article: V. Padmavathi , B. Chandra Obula Reddy , P. Thriveni & A.V. Nagendra Mohan (2007)
Synthesis of 2‐Oxazolines and 2‐Thiazolines using Lanthanide Amino Alkoxide, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry, 37:18, 3127-3142, DOI:
10.1080/00397910701545098
To link to this article: http://dx.doi.org/10.1080/00397910701545098
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Synthetic Communicationsw, 37: 3127–3142, 2007
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701545098
Synthesis of 2-Oxazolines and 2-Thiazolines
using Lanthanide Amino Alkoxide
V. Padmavathi, B. Chandra Obula Reddy, P. Thriveni, and
A.V. Nagendra Mohan
Department of Chemistry, Sri Venkateswara University, Tirupati, India
Abstract: New 2-oxazolines and 2-thiazolines are prepared from phenacysulfonylacetic
acid methyl ester using lanthanide amino alkoxide.
Keywords: b-cyclodextrin, 2-oxazolines, SmCl3, 2-thiazolines
INTRODUCTION
Oxazoline and thiazoline rings are important constituents of bioactive natural
products and pharmaceuticals.[1] In fact, the use of oxazoline and thiazoline
rings as building blocks in pharmaceutical drug discovery is continually
increasing. A variety of methods have been reported for the synthesis of oxa-
zolines, viz., cyclodehydration of amidoalcohols,[2] condensation of imidate
hydrochlorides,[3] carboxylic acids,[4] ortho esters,[5] imino ether hydrochlo-
rides,[6] and nitriles[7] with aminoalcohols. Similarly, syntheses of thiazolines
have been reported by the coupling of imidates and esters with 2-ami-
nothiols,[8] cyclodehydration of hydroxy thioamides,[9] and heterocyclic inter-
conversions from oxazolines[10] or oxazolidines.[11] Although lanthanide
triflates, alkoxides, and amides have been extensively used, use of lanthanide
amino alkoxide complexes as reagents for a similar purpose is sparsely
reported.[12] Herein, we report our results pertaining to the synthesis of 2-oxa-
zolines and 2-thiazolines from carboxylic esters and lanthanide 2-amino
alkoxide complexes.
Received January 29, 2007
Address correspondence to V. Padmavathi, Department of Chemistry, Sri
Venkateswara University, Tirupati 517502, India. E-mail: vkpuram2001@yahoo.com
3127

3128
V. Padmavathi et al.
RESULTS AND DISCUSSION
Earlier, we reported the synthesis of 2-arylsulfonylmethyloxazolines (3) and
2-arylmethanesulfonylmethyloxazolines (4) by the traditional four-step,
three-intermediate route from arylsulfonylacetic acid methyl ester (1)/aryl-
methanesulfonylacetic acid methyl ester (2) via hydroxyethylacetamide
followed by treatment with thionyl chloride and cyclocondensation in the
presence of base.[13] However, 3/4 is prepared in a one-pot reaction by
treating 1/2 with 2-aminoethanol and n-butyllithium complexed with a sus-
pension of 5–10% mol. equiv. of anhydrous SmCl3 in toluene (Scheme 1).
Thus, this method provides a simple and elegant route to prepare oxazolines
and thiazolines directly from carboxylic esters.
Adopting a similar methodology, the reaction of 1/2 is carried out with
2-aminoethanethiol and n-butylithium in the presence of anhydrous SmCl3
in toluene. The compounds obtained are 2-arylsulfonylmethylthiazolines
(5)/2-arylmethane sulfonylmethylthiazoline (6). In our continued efforts to
develop simple and efficient routes for five-membered heterocycles, we
thought to extend this methodology to exploit phenacylsulfonylacetic
esters. When phenacylsulfonylacetic ester 7 is treated with 2-aminoethanol
in the presence of n-butyllithium and SmCl3, instead of the expected 2-(4,5-
dihydrooxazol-2-ylmethanesulfonyl)-1-phenylethanone (8), 2-phenyl-4,5-
dihydrooxazole (9) is obtained. Similarly, the reaction of 7 with 2-aminoetha-
nethiol under identical conditions gave 2-phenyl-4,5-dihydrothiazole (11)
instead of 2-(4,5-dihydrothiazol-2-ylmethanesulfonyl)-1-phenylethanone
1
(10) (Scheme 2). The H NMR spectra of 9 and 11 displayed two triplets at
d 3.97, 4.41 and 4.36, 3.32 for C4-H and C5-H of 2-oxazoline and 2-thiazoline
rings, respectively.
To obtain the desired product 8/10, the carbonyl group in 7 is protected
by treatment with hydroxylamine hydrochloride. The oxime derivative 12 is
treated with 2-aminoethanol and SmCl3 in the presence of n-butyllithium,
where 2-(4,5-dihydrooxazol-2-ylmethanesulfonyl)-1-phenylethanone oxime
(13) is obtained (Scheme 3). Similarly, 2-(4,5-dihydrothiazol-2-ylmethanesul-
fonyl)-1-phenylethanone oxime (14) is prepared by the reaction of 12 with
2-aminoethanethiol under identical conditions. The compounds 13 and 14 in
1
their H NMR spectra displayed triplets at d 4.01, 4.40 and 4.43, 3.34 for
C4-H and C5-H respectively. In addition, two singlets are observed at d
4.82, 4.78 and 3.72, 3.68, due to methylene protons flanked between
Scheme 1. i) NH2CH2CH2OH, Sm(III)Cl3, n-BuLi, toluene, ii) NH2CH2CH2SH,
Sm(III)Cl3, n-BuLi, toluene. n ¼ 0 (1,3,5), n ¼ 1 (2, 4, 6). R ¼ a) H, b) Me, c) Cl.

2-Oxazolines and 2-Thiazolines
3129
Scheme 2. i) NH2CH2CH2OH, Sm(III)Cl3, n-BuLi, toluene, ii) NH2CH2CH2SH,
Sm(III)Cl3, n-BuLi, toluene. R ¼ a) H, b) Me, c) Cl.
C55NOH and SO2 and heterocyclic ring and SO2 groups. The structure of the
compounds is further ascertained by 13C NMR spectra.
There are different methods for the deoximation of oxime group, viz.,
acid catalyzed hydrolysis,[14] oxidative deprotection,[15] reductive deprotec-
tion,[16] clay-supported ferric nitrite,[17] trimethylsilyl chlorochromate,[18]
pyridinium chlorochromate,[19] pyridinium chlorochromate/H2O2,[16] 2-iodoxy-
benzoic acid/dimethylsulfoxide-tetrahydrofuran (DMSO-THF),[20] trimethyl-
ammonium chlorochromate,[21] chromium trioxide/chlorotrimethylsilane,[22]
photochemical deprotection,[23] and b-cyclodextrin.[24] We have adopted the
Scheme 3. i) NH2OH, HCl, MeOH, pyridine, ii) NH2CH2CH2OH, Sm(III)Cl3,
n-BuLi, toluene, iii) NH2CH2CH2SH, Sm(III)Cl3, n-BuLi, tolune, iv) b-CD, H2O, r, t.
R ¼ a) H, b) Me, c) Cl.

3130
V. Padmavathi et al.
deoximation of oxime using a mild oxidizing agent, 2-iodoxybenzoic acid,
catalyzed by b-cyclodextrin using water as solvent at room temperature.
After work up of the reaction mixture, the compounds 8/10 are obtained
1
in good yield (Scheme 3). The H NMR spectra of 8 and 10 showed triplets
for C4-H and C5-H at d 4.03, 4.41 and 4.46, 3.32. The 13C NMR spectra
showed signal at d 190, which indicates deoximation indeed takes place.
The use of SmCl3 thus provides a direct and an efficient synthetic pathway
for the synthesis of 2-oxazolines and 2-thiazolines apart from the traditional
four-step, three-intermediate route. Further, protection of carbonyl group by
oximation and deoximation using b-cyclodextrin in the presence of an
oxidizing agent provides a simple, elegant, and efficient methodology for pro-
tection and deprotection reactions.
EXPERIMENTAL
General
Melting points were determined in open capillaries on a Mel-Temp
apparatus and are uncorrected. The purity of the compounds was checked
by thin-layer chromatography (TLC; silica gel H, BDH, ethyl acetate–
hexane, 1:3). The IR spectra were recorded on a Thermo Nicolet IR 200
FT-IR in KBr pellets. The 1H NMR spectra were recorded at 300 MHz
on a Varian EM-360 spectrometer, and 13C NMR spectra were run on a
Varian VXR spectrometer operating at 75.5 MHz. All chemical shifts are
reported in parts per million (ppm) from TMS as an internal standard.
Elemental analyses were performed using a Perkin-Elmer 240C elemental
analyzer.
The benzenesulfonylacetic acid methyl ester (1)/phenylmethanesulfony-
lacetic acid methyl ester (2) and phenacylsulfonylacetic acid methyl ester (7)
were prepared by standard procedures.[25,26]
General Procedure for the Synthesis of 2-Arylsulfonylmethyl-
4,5-dihydrooxazole (3)
Dry toluene (10 mL) and aminoalcohol (2 mmol) were added to a flask
charged with anhydrous SmCl3 (0.1 mmol). n-BuLi (2.2 mmol) was added
to this suspension at 08C and stirred for 15 min. Then, the flask was heated
to reflux (1008C). Arylsulfonylacetic acid methyl ester (1) (1 mmol) was
added to the contents and refluxed for an additional 6–8 h. The suspension
was cooled to room temperature, filtered, and washed with chloroform. The
filtrate was extracted with chloroform and washed with water, and the
solvent was removed in vacuo. The solid was purified by recrystallization
from methanol.

2-Oxazolines and 2-Thiazolines
Data
3131
3a: Colorless solid; yield 0.153 g (68%); mp 184–1858C. IR (KBr): 1132, 1340
(SO2), 1570 (C55N) cm21. 1H NMR (CDCl3): d ¼ 3.75 (s, 2H, SO2-CH2), 4.03
(t, J ¼ 5.7 Hz, 2H, H-4), 4.45 (t, J ¼ 5.7 Hz, 2H, H-5), 7.28–7.45 (m, 5H, Ar-
H). 13C NMR (CDCl3): d ¼ 52.4 (C-4), 52.6 (SO2-CH2), 54.6 (C-5), 157.1 (C-
2), 126.5, 127.4, 129.3, 132.7 (aromatic carbons). Anal. calcd. for C10H11NO3S:
C, 53.32; H, 4.92; N, 6.22. Found: C, 53.46; H, 4.89; N, 6.31.
3b: Colorless solid; yield 0.172 g (72%); mp 198–2008C. IR (KBr): 1145,
1
1325 (SO2), 1580 (C55N) cm21. H NMR (CDCl3): d ¼ 2.38 (s, 3H, Ar-
CH3), 3.81 (s, 2H, SO2-CH2), 4.01 (t, J ¼ 5.9 Hz, 2H, H-4), 4.41
(t, J ¼ 5.9 Hz, 2H, H-5), 7.20–7.42 (m, 4H, Ar-H). 13C NMR (CDCl3):
d ¼ 21.2 (Ar-CH3), 49.3 (C-4), 54.9 (SO2-CH2), 58.8 (C-5), 158.3 (C-2),
124.7, 129.7, 130.9, 139.2 (aromatic carbons). Anal. calcd. for
C11H13NO3S: C, 55.21; H, 5.48; N, 5.85. Found: C, 55.17; H, 5.43; N, 5.94.
3c: Colorless solid; yield 0.192 g (74%); mp 208–2108C. IR (KBr): 1135, 1342
(SO2), 1575 (C55N) cm21. 1H NMR (CDCl3): d ¼ 3.79 (s, 2H, SO2-CH2), 4.08
(t, J ¼ 5.8 Hz, 2H, H-4), 4.44 (t, J ¼ 5.8 Hz, 2H, H-5), 7.31–7.52 (m, 4H,
Ar-H). 13C NMR (CDCl3): d ¼ 49.5 (C-4), 53.9 (SO2-CH2), 54.7 (C-5),
158.2 (C-2), 126.0, 129.2, 132.3, 135.7 (aromatic carbons). Anal. calcd. for
C10H10ClNO3S: C, 46.25; H, 3.88; N, 5.39. Found: C, 46.31; H, 3.93; N, 5.47.
General Procedure for the Synthesis of 2-Arylmethanesulfonyl
methyl-4,5-dihydrooxazole (4)
Dry toluene (10 mL) and aminoalcohol (2 mmol) were added to a flask
charged with anhydrous SmCl3 (0.1 mmol). To this, n-BuLi (2.2 mmol) was
added at 08C and stirred at the same temperature for 15 min. Then, the flask
was heated to reflux (1008C). Arylmethanesulfonylaceticacid methyl ester
(2) (1 mmol) was added to the contents and refluxed for an additional 9–
10 h. The suspension was cooled to room temperature, filtered, and washed
with chloroform. The filtrate was extracted with chloroform and washed
with water, and the solvent was removed in vacuo. The solid was purified
by recrystallization from methanol.
Data
4a: Colorless solid; yield 0.167 g (70%); mp 228–2298C. IR (KBr): 1141,
1
1325 (SO2), 1572 (C55N) cm21. H NMR (CDCl3): d ¼ 3.80 (s, 2H, SO2-
CH2), 4.00 (t, J¼ 5.7 Hz, 2H, H-4), 4.40 (t, J ¼ 5.7 Hz, 2H, H-5), 4.51
(s, 2H, Ar-CH2-SO2), 7.39–7.53 (m, 5H, Ar-H). 13C NMR (CDCl3):
d ¼ 52.5 (C-4), 55.4 (SO2-CH2), 56.6 (C-5), 66.6 (Ar-CH2-SO2), 158.3

3132
V. Padmavathi et al.
(C-2), 128.4, 128.7, 129.1, 130.6 (aromatic carbons). Anal. calcd. for
C11H13NO3S: C, 55.21; H, 5.48; N, 5.85. Found: C, 55.27; H, 5.52; N, 5.90.
4b: Colorless solid; yield 0.18 g (71%); mp 232–2338C. IR (KBr): 1138, 1335
(SO2), 1574 (C55N) cm21. 1H NMR (CDCl3): d ¼ 2.21 (s, 3H, Ar-CH3), 3.79
(s, 2H, SO2-CH2), 4.04 (t, J ¼ 5.9 Hz, 2H, C4-H), 4.39 (t, J ¼ 5.9 Hz, 2H,
H-5), 4.53 (s, 2H, Ar-CH2-SO2), 7.17–7.42 (m, 4H, Ar-H). 13C NMR
(CDCl3): d ¼ 20.2 (Ar-CH3), 52.2 (C-4), 55.1 (SO2-CH2), 55.9 (C-5), 63.8
(Ar-CH2-SO2), 157.2 (C-2), 125.4, 129.8, 130.5, 139.2 (aromatic carbons).
Anal. calcd. for C12H15NO3S: C, 56.90; H, 5.97; N, 5.53. Found: C, 56.82;
H, 5.89; N, 5.62.
4c: Pale yellow solid; yield 0.202 g (74%); mp 239–2408C. IR (KBr): 1132,
1
1335 (SO2), 1568 (C55N) cm21. H NMR (CDCl3): d ¼ 3.76 (s, 2H, SO2-
CH2), 3.99 (t, J ¼ 5.8 Hz, 2H, H-4), 4.39 (s, 2H, Ar-CH2-SO2), 4.42
(t, J ¼ 5.8 Hz, 2H, H-5), 7.37–7.50 (m, 4H, Ar-H). 13C NMR (CDCl3):
d ¼ 49.5 (C-4), 54.9 (SO2-CH2), 58.1 (C-5), 68.4 (Ar-CH2-SO2), 158.2
(C-2), 126.3, 129.3, 132.4, 135.8 (aromatic carbons). Anal. calcd. for
C11H12ClNO3S: C, 48.26; H, 4.42; N, 5.12. Found: C, 48.32; H, 4.38; N, 5.20.
General Procedure for the Synthesis of 2-Arylsulfonylmethyl-4,5-
dihydrothiazole (5)
Anhydrous SmCl3 (0.1 mmol) dry toluene (10 mL), and aminothiol
(2 mmol) were taken into a flask and kept at ice-bath temperature. To
this, n-BuLi (2.2 mmol) was added. After the reaction mixture was stirred
at 08C for 15 min, the flask was heated to reflux (1008C). Then arylsulfo-
nylacetic acid methyl ester (1) (1 mmol) was added, and the reaction
mixture was refluxed for an additional 6–7 h. The suspension was cooled
to room temperature and filtered. The filtrate was extracted with chloroform
and washed with water, and the solvent was removed. The solid was
purified by column chromatography (silica gel (60–120 mesh), EtOAc–
hexane, 3:1.5].
Data
5a: Colorless solid; yield 0.157 g (65%); mp 179–1818C. IR (KBr): 1130,
1
1336 (SO2), 1559 (C55N) cm21. H NMR (CDCl3): d ¼ 3.52 (s, 2H, SO2-
CH2), 3.98 (t, J ¼ 7.9 Hz, 2H, H-5), 4.42 (t, J ¼ 7.9 Hz, 2H, H-4), 7.30–
7.73 (m, 5H, Ar-H). 13C NMR (CDCl3): d ¼ 27.5 (C-5), 52.7 (C-4), 53.6
(SO2-CH2), 155.6 (C-2), 126.5, 127.4, 130.2, 133.5 (aromatic carbons).
Anal. calcd. for C10H11NO2S2: C, 49.77; H, 4.59; N, 5.80. Found: C, 49.69;
H, 4.55; N, 5.74.

2-Oxazolines and 2-Thiazolines
3133
5b: Yellow solid; yield 0.179 g (70%); mp 202–2048C. IR (KBr): 1141, 1325
(SO2), 1560 (C55N) cm21. 1H NMR (CDCl3): d ¼ 2.20 (s, 3H, Ar-CH3), 3.56
(s, 2H, SO2-CH2), 3.89 (t, J ¼ 8.2 Hz, 2H, H-5), 4.47 (t, J ¼ 8.2 Hz, 2H, H-4),
7.23–7.79 (m, 4H, Ar-H); 13C NMR (CDCl3): d ¼ 20.8 (Ar-CH3), 28.5 (C-5),
53.2 (C-4), 54.2 (SO2-CH2), 156.3 (C-2), 128.4, 132.2, 133.5, 136.7 (aromatic
carbons). Anal. calcd. for C11H13NO2S2: C, 51.74; H, 5.13; N, 5.49. Found: C,
51.69; H, 5.16; N, 5.48.
5c: Pale yellow solid; yield 0.187 g (68%); mp 165–1678C. IR (KBr): 1138,
1
1335 (SO2), 1563 (C55N) cm21. H NMR (CDCl3): d ¼ 3.48 (s, 2H, SO2-
CH2), 3.94 (t, J ¼ 8.1 Hz, 2H, H-5), 4.46 (t, J ¼ 8.1 Hz, 2H, H-4), 7.39–
7.68 (m, 4H, Ar-H). 13C NMR (CDCl3): d ¼ 26.1 (C-5), 53.7 (C-4), 54.6
(SO2-CH2), 157.2 (C-2), 128.4, 130.2, 132.7, 136.8 (aromatic carbons).
Anal. calcd. for C10H10ClNO2S2: C, 43.55; H, 3.65; N, 5.08. Found: C,
43.62; H, 3.59; N, 5.14.
General Procedure for the Synthesis of 2-Arylmethanesulfonyl
methyl-4,5-dihydrothiazole (6)
Dry toluene (10 mL) and aminothiol (2 mmol) were added to a flask charged
with anhydrous SmCl3 (0.1 mmol). To this, n-BuLi (2.2 mmol) was added at
08C and stirred at the same temperature for 15 min. Then, arylmethanesulfo-
nylacetic acid methyl ester (2) (1 mmol) was added, and the reaction mixture
was refluxed for 9–10 h. The suspension was cooled to room temperature and
filtered. The filtrate was extracted with chloroform and washed with water,
and the solvent was removed. The solid was purified by column chromato-
graphy [silica gel (60–120 mesh), EtOAc–hexane, 3:1.5].
Data
6a: Colorless solid; yield 0.171 g (67%); mp 214–2168C. IR (KBr): 1130,
1
1340 (SO2), 1573 (C55N) cm21. H NMR (CDCl3): d ¼ 3.57 (s, 2H, SO2-
CH2), 4.01 (t, J ¼7.8 Hz, 2H, H-5), 4.45 (t, J ¼ 7.8 Hz, 2H, H-4), 4.68
(s, 2H, Ar-CH2-SO2), 7.25–7.67 (m, 5H, Ar-H). 13C NMR (CDCl3):
d ¼ 29.4 (C-5), 52.9 (C-4), 54.7 (SO2-CH2), 58.3 (Ar-CH2-SO2), 158.6
(C-2), 126.2, 127.9, 128.9, 130.6 (aromatic carbons). Anal. calcd. for
C11H13NO2S2: C, 51.74; H, 5.13; N, 5.49. Found: C, 51.83; H, 5.16; N, 5.57.
6b: Colorless solid; yield 0.175 g (65%); mp 221–2238C. IR (KBr): 1122,
1
1330 (SO2), 1572 (C55N) cm21. H NMR (CDCl3): d ¼ 2.34 (s, 3 H, Ar-
CH3), 3.58 (s, 2H, SO2-CH2), 3.98 (t, J ¼ 8.1 Hz, 2H, H-5), 4.42
(t, J ¼ 8.1 Hz, 2H, H-4), 4.64 (s, 2H, Ar-CH2-SO2), 7.23–7.69 (m, 4H, Ar-
H). 13C NMR (CDCl3): d ¼ 21.0 (Ar-CH3), 29.8 (C-5), 53.4 (C-4), 55.9
(SO2-CH2), 59.3 (Ar-CH2-SO2), 156.3 (C-2), 125.4, 129.8, 130.5, 132.3

3134
V. Padmavathi et al.
(aromatic carbons). Anal. calcd. for C12H15NO2S2: C, 53.50; H, 5.61; N, 5.20.
Found: C, 53.58; H, 5.57; N, 5.25.
6c: Pale yellow solid; yield 0.206 g (71%); mp 229–2308C. IR (KBr): 1134,
1
1328 (SO2), 1569 (C55N) cm21. H NMR (CDCl3): d ¼ 3.79 (s, 2H, SO2-
CH2), 4.02 (t, J ¼ 8.3 Hz, 2H, H-5), 4.43 (t, J ¼ 8.3 Hz, 2H, H-4), 4.49
(s, 2H, Ar-CH2-SO2), 7.36–7.50 (m, 4H, Ar-H). 13C NMR (CDCl3):
d ¼ 29.6 (C-5), 53.2 (C-4), 55.2 (SO2-CH2), 58.4 (Ar-CH2-SO2), 158.8 (C-
2), 126.3, 129.5, 130.2, 131.5 (aromatic carbons). Anal. calcd. for
C11H12ClNO2S2: C, 45.59; H, 4.17; N, 4.83. Found: C, 45.65; H, 4.21; N, 4.90.
General Procedure for the Synthesis of 2-Aryl-4,5-dihydrooxazole (9)
Anhydrous SmCl3 (0.1 mmol), dry toluene (10 mL), and aminoalcohol
(2 mmol) were taken into a flask, and n-BuLi (2.2 mmol) was added to this
at 08C. After the reaction mixture was stirred at 08C for 15 min, the flask
was heated to reflux (1008C). To this, phenacylsulfonylacetic acid methyl
ester (7) (1 mmol) was added and refluxed for an additional 10–12 h. The sus-
pension was cooled to room temperature and filtered. The filtrate was
extracted with chloroform and washed with water, and the solvent was
removed. The product was purified by column chromatography [silica gel
(60–120 mesh), EtOAc-hexane, 3:1].
Data
9a: Yellow liquid; yield 0.101 g (69%); bp 245–2488C (Lit.[9a] bp 242-
2438C). IR (KBr): 1569 (C55N) cm21
.
1H NMR (CDCl3): d ¼ 3.97
(t, J ¼ 5.5, Hz, 2H, H-4), 4.36 (t, J ¼ 5.5 Hz, 2H, H-5), 7.28-7.45 (m, 5H,
Ar-H). 13C NMR (CDCl3): d ¼ 52.3 (C-4), 56.5 (C-5), 158.1 (C-2), 128.6,
129.0, 130.8, 137.3 (aromatic carbons). Anal. calcd. for C9H9NO: C, 73.45;
H, 6.16; N, 9.52. Found: C, 73.49; H, 6.21; N, 9.57.
9b: Colorless solid; yield 0.108 g (67%); mp 68–708C (lit.[27] mp 69–718C).
IR (KBr): 1570 (C55N) cm21. 1H NMR (CDCl3): d ¼ 2.35 (s, 3H, Ar-CH3),
3.92 (t, J ¼ 5.7 Hz, 2H, H-4), 4.34 (t, J ¼ 5.7 Hz, 2H, H-5), 7.08–7.50
(m, 4H, Ar-H). 13C NMR (CDCl3): d ¼ 21.2 (Ar-CH3), 52.8 (C-4), 57.0 (C-
5), 159.6 (C-2), 128.9, 129.3, 134.2, 140.0 (aromatic carbons). Anal. calcd.
for C10H11NO: C, 74.51; H, 6.88; N, 8.69. Found: C, 74.45; H, 6.91; N, 8.79.
9c: Pale yellow solid; yield 0.132 g (73%); mp 76-788C (lit.[27] mp 77–798C).
IR (KBr): 1572 (C55N) cm21. 1H NMR (CDCl3): d ¼ 3.88 (t, J ¼ 5.9 Hz, 2H,
H-4), 4.29 (t, J ¼ 5.9 Hz, 2H, H-5), 7.30–7.56 (m, 4H, Ar-H). 13C NMR
(CDCl3): d ¼ 52.4 (C-4), 56.8 (C-5), 159.3 (C-2), 129.0, 130.4, 135.4,

2-Oxazolines and 2-Thiazolines
3135
136.1 (aromatic carbons). Anal. calcd. for C9H8ClNO: C, 59.52; H, 4.44; N,
7.71. Found: C, 59.64; H, 4.48; N, 7.79.
GeneralProcedurefortheSynthesisof2-Aryl-4,5-dihydrothiazole(11)
Dry toluene (10 mL) and aminothiol (2 mmol) were added to a flask charged
with anhydrous SmCl3 (0.1 mmol), followed by n-BuLi (2.2 mmol) at 08C.
After the reaction mixture was stirred at 08C for 15 min, the flask was
heated to reflux (1008C). Then phenacylsulfonylacetic acid methyl ester (7)
(1 mmol) was added and refluxed for an additional 10–12 h. The suspension
was cooled to room temperature and filtered. The filtrate was extracted with
chloroform and washed with water, and the solvent was removed. The
product was purified by column chromatography [silica gel (60–120 mesh),
EtOAc-hexane, 3:1].
Data
11a: Colorless thick gummy substance; yield 0.117 g (72%); IR (KBr): 1568
1
(C55N) cm21. H NMR (CDCl3): d ¼ 3.30 (t, J ¼ 8.0 Hz, 2H, H-5), 4.43
(t, J ¼ 8.0 Hz, 2H, H-4), 7.29–7.54 (m, 5H, Ar-H). 13C NMR (CDCl3):
d ¼ 32.8 (C-5), 64.2 (C-4), 163.7 (C-2), 128.5, 129.0, 130.8, 137.3
(aromatic carbons). Anal. calcd. for C9H9NS: C, 66.22; H, 5.56; N, 8.58.
Found: C, 66.28; H, 5.53; N, 8.65.
11b: Colorless solid; yield 0.122 g (69%); mp 47–498C. IR (KBr): 1569
(C55N) cm21
.
1H NMR (CDCl3): d ¼ 2.34 (s, 3H, Ar-CH3), 3.34
(t, J ¼ 8.2 Hz, 2H, H-5), 4.38 (t, J ¼ 8.2 Hz, 2H, H-4), 7.09–7.50 (m, 4H,
Ar-H). 13C NMR (CDCl3): d ¼ 20.5 (Ar-CH3), 33.6 (C-5), 63.8 (C-4),
162.8 (C-2), 128.9, 129.3, 134.3, 140.0 (aromatic carbons). Anal. calcd. for
C10H11NS: C, 67.75; H, 6.25; N, 7.90. Found: C, 67.85; H, 6.21; N, 7.99.
11c: Yellow solid; yield 0.148 g (75%); mp 53–548C (lit.[28] mp 50–528C).
1
IR (KBr): 1567 (C55N) cm21. H NMR (CDCl3): d ¼ 3.34 (t, J ¼ 8.4 Hz,
2H, H-5), 4.42 (t, J ¼ 8.4 Hz, 2H, H-4), 7.09–7.50 (m, 4H, Ar-H). 13C
NMR (CDCl3): d ¼ 32.4 (C-5), 61.8 (C-4), 163.5 (C-2), 128.4, 128.7,
132.4, 137.9 (aromatic carbons). Anal. calcd. for C9H8ClNS: C, 54.68; H,
4.08; N, 7.09. Found: C, 54.55; H, 4.12; N, 7.02.
General Procedure for the Synthesis of (Hydroximino-aryl-
methanesulfonyl)-acetic Acid Methyl Ester (12)
Hydroxylamine hydrochloride (5 mmol) and pyridine (0.2 mL) were added to
a mixture of phenacylsulfonylacetic acid methyl ester (7) (1 mmol) in

3136
V. Padmavathi et al.
methanol and refluxed for 7–8 h on a water bath. It was poured onto crushed
ice, and the resultant solid was purified by recrystallization from methanol.
Data
12a: Colorless solid; yield 0.228 g (84%); mp 113–1158C. IR (KBr): 1148,
1325 (SO2), 1625 (C55N), 1721 (C55O), 3338 (OH) cm21 1H NMR
.
(CDCl3): d ¼ 3.67 (s, 3H, OCH3), 4.35 (s, 2H, SO2-CH2), 4.92 (s, 2H, CH2-
SO2), 7.32–7.61 (m, 5H, Ar-H), 12.15 (s, 1H, NOH). 13C NMR (CDCl3):
d ¼ 53.3 (OCH3), 56.5 (SO2-CH2), 57.3 (CH2-SO2), 166.3 (C55NOH),
169.2 (CO), 128.2, 129.4, 131.2, 132.4 (aromatic carbons).
12b: Colorless solid; yield 0.251 g (88%); mp 122–1238C. IR (KBr): 1146,
1335 (SO2), 1628 (C55N), 1720 (C55O), 3335 (OH) cm21 1H NMR
.
(CDCl3): d ¼ 2.31 (s, 3H, Ar-CH3), 3.65 (s, 3H, OCH3), 4.33 (s, 2H, SO2-
CH2), 4.89 (s, 2H, CH2-SO2), 7.11–7.31 (m, 4H, Ar-H), 11.93 (s, 1H,
NOH). 13C NMR (CDCl3): d ¼ 20.4 (Ar-CH3), 53.6 (OCH3), 56.2 (SO2-
CH2), 58.1 (CH2-SO2), 164.9 (C55NOH), 168.6 (COOCH3), 128.7, 130.1,
131.5, 132.2 (aromatic carbons).
12c: Colorless solid; yield: 0.275 g (90%); mp 98–1008C. IR (KBr): 1150,
1327 (SO2), 1632 (C55N), 1722 (C55O), 3339 (OH) cm21 1H NMR
.
(CDCl3): d ¼ 3.69 (s, 3H, OCH3), 4.38 (s, 2H, SO2-CH2), 4.95 (s, 2H, CH2-
SO2), 7.22–7.41 (m, 4H, Ar-H), 12.26 (s, 1H, OH). 13C NMR (CDCl3):
d ¼ 54.0 (OCH3), 56.9 (SO2-CH2), 58.6 (CH2-SO2), 166.9 (C55NOH),
169.6 (COOCH3), 129.2, 131.0, 133.4, 136.0 (aromatic carbons).
General Procedure for the Synthesis of 2-(4,5-Dihydrooxazol-
2-ylmethanesulfonyl)-1-aryl-ethanone Oxime (13)
Anhydrous SmCl3 (0.1 mmol), dry toluene (10 mL), and aminoalcohol
(2 mmol) were taken into a flask, and n-BuLi (2.2 mmol) was added to this
at 08C. The contents of the flask was heated to 1008C, and then (hydroxi-
mino-aryl-methanesulfonyl)-acetic acid methyl ester (12) (1 mmol) was
added. The reaction mixture was refluxed for an additional 10–12 h. The sus-
pension was cooled to room temperature and filtered. The filtrate was
extracted with chloroform and washed with water and the solvent was
removed. The solid obtained was purified by column chromatography [silica
gel (60–120 mesh), EtOAc–hexane, 3:1.5].
Data
13a: Colorless solid; yield 0.175 g (62%); mp 165–1678C. IR (KBr): 1128,
1
1334 (SO2), 1570 (C55N), 3368 (OH) cm21. H NMR (CDCl3): d ¼ 3.72

2-Oxazolines and 2-Thiazolines
3137
(s, 2H, SO2-CH2), 4.01 (t, J ¼ 5.6 Hz, 2H, H-4), 4.43 (t, J ¼ 5.6 Hz, 2H, H-5),
4.82 (s, 2H, CH2-SO2), 7.30–7.62 (m, 5H, Ar-H), 12.23 (s, 1H, NOH). 13C
NMR (CDCl3): d ¼ 52.1 (C-4), 53.0 (SO2-CH2), 54.8 (C-5), 59.1 (CH2-
SO2), 157.2 (C-2), 163.7 (C55N), 128.6, 129.0, 130.8, 131.2 (aromatic
carbons).
13b: Colorless solid; yield 0.201 g (68%); mp 159–1618C. IR (KBr):
1121, 1328 (SO2), 1568 (C55N), 3370 (OH) cm21 1H NMR (CDCl3):
.
d ¼ 2.19 (s, 3 H, Ar-CH3), 3.73 (s, 2H, SO2-CH2), 4.05 (t, J ¼ 5.8 Hz,
2H, H-4), 4.49 (t, J ¼ 5.8 Hz, 2H, H-5), 4.78 (s, 2H, CH2-SO2), 7.25–
7.56 (m, 4H, Ar-H), 12.25 (s, 1H, NOH). 13C NMR (CDCl3): d ¼ 20.8
(Ar-CH3), 52.3 (C-4), 52.9 (SO2-CH2), 54.5 (C-5), 59.6 (CH2-SO2),
159.2 (C-2), 164.2 (C55N), 128.2, 128.9, 129.3, 134.2 (aromatic carbons).
13c: Colorless solid; yield 0.209 g (67%); mp 173–1758C. IR (KBr): 1126,
1
1330 (SO2), 1572 (C55N), 3374 (OH) cm21. H NMR (CDCl3): d ¼ 3.67
(s, 2H, SO2-CH2), 4.04 (t, J ¼ 5.9 Hz, 2H, H-4), 4.44 (t, J ¼ 5.9 Hz, 2H,
H-5), 4.80 (s, 2H, CH2-SO2), 7.32–7.60 (m, 4H, Ar-H), 12.20 (s, 1H,
NOH). 13C NMR (CDCl3): d ¼ 52.4 (C-4), 52.6 (SO2-CH2), 54.2 (C-5),
59.4 (CH2-SO2), 157.8 (C-2) 162.8 (C55N), 129.0, 129.4, 130.4, 131.6
(aromatic carbons).
General Procedure for the Synthesis of 2-(4,5-Dihydrothiazol-
2-ylmethanesulfonyl)-1-aryl-ethanone Oxime (14)
A mixture of anhydrous SmCl3 (0.1 mmol), dry toluene (10 mL), and ami-
nothiol (2 mmol) was taken into a flask. To this, n-BuLi (2.2 mmol) was
added at 08C and stirred for 15 min. The flask was heated to 1008C, and
(hydroximino-aryl-methanesulfonyl)-acetic acid methyl ester (12) (1 mmol)
was added. The reaction mixture was refluxed for an additional 12–13 h.
The suspension was cooled to room temperature and filtered. The filtrate
was extracted with chloroform and washed with water, and the solvent was
removed. The solid obtained was purified by column chromatography [silica
gel (60–120 mesh), EtOAc–hexane, 3:1.5].
Data
14a: Colorless solid; yield 0.209 g (68%); mp 149–1518C. IR (KBr): 1129, 1334
(SO2), 1574 (C55N), 3368 (OH) cm21
.
1H NMR (CDCl3): d ¼ 3.34
(t, J ¼ 7.9 Hz, 2H, H-5), 3.68 (s, 2H, SO2-CH2), 4.40 (t, J ¼ 7.9 Hz, 2H,
H-4), 4.78 (s, 2H, CH2-SO2), 7.29–7.62 (m, 5H, Ar-H), 12.26 (s, 1 H, NOH).
13C NMR (CDCl3): d ¼ 34.5 (C-5), 57.8 (SO2-CH2), 64.8 (C-4), 68.9 (CH2-
SO2), 156.8 (C-2), 163.7 (C55N), 128.6, 129.0, 130.8, 131.2 (aromatic carbons).

3138
V. Padmavathi et al.
14b: Colorless solid; yield 0.209 g (67%); mp 173–1758C. IR (KBr): 1135,
1
1338 (SO2), 1569 (C55N), 3362 (OH) cm21. H NMR (CDCl3): d ¼ 2.40
(s, 3 H, Ar-CH3), 3.39 (t, J ¼ 8.1 Hz, 2H, H-5), 3.72 (s, 2H, SO2-CH2),
4.39 (t, J ¼ 8.1 Hz, 2H, H-4), 4.82 (s, 2H, CH2-SO2), 7.26–7.70 (m, 4H,
Ar-H), 12.19 (s, 1 H, NOH). 13C NMR (CDCl3): d ¼ 20.9 (Ar-CH3), 36.2
(C-5), 57.2 (SO2-CH2), 65.2 (C-4), 67.9 (CH2-SO2), 159.4(C-2), 164.0
(C55N), 128.2, 128.9, 129.3, 140.0 (aromatic carbons).
14c: Colorless solid; yield 0.239 g (72%); mp 167–1698C. IR (KBr): 1144,
1
1339 (SO2), 1574 (C55N), 3370 (OH) cm21. H NMR (CDCl3): d ¼ 3.34
(t, J ¼ 8.2 Hz, 2H, H-5), 3.81 (s, 2H, SO2-CH2), 4.45 (t, J ¼ 8.2 Hz, 2H,
H-4), 4.90 (s, 2H, CH2-SO2), 7.39–7.71 (m, 4H, Ar-H), 12.25 (s, 1 H,
NOH). 13C NMR (CDCl3): d ¼ 37.3 (C-5), 57.4 (SO2-CH2), 66.1 (C-4),
68.3 (CH2-SO2), 157.8 (C-2) 164.6 (C55N), 129.0, 129.3, 130.4, 136.1
(aromatic carbons).
General Procedure for the Synthesis of 2-(4,5-Dihydrooxazol-
2-ylmethanesulfonyl)-1-aryl-ethanone(8)
To a solution of b-cyclodextrin (0.1 mmol) in distilled H2O (15 mL), 2-(4,5-
dihydro-oxazol-2-ylmethanesulfonyl)-1-aryl-ethanoneoxime (13) dissolved in
acetone (2 mL) followed by 2-iodoxybenzoic acid (280 mg, 1 mmol) were
added and stirred at room temperature for 12–14 h. The reaction mixture
was extracted with EtOAc, dried (anhyd. Na2SO4) and concentrated under
vacuum. The crude product thus obtained was purified by column chromato-
graphy [silica gel (60–120 mesh), EtOAc–hexane, 9:1].
Data
8a: Pale yellow solid; yield 0.176 g (66%); mp 176–1788C. IR (KBr): 1125,
1
1336 (SO2), 1559 (C55N), 1674 (C55O) cm21. H NMR (CDCl3): d ¼ 3.75
(s, 2H, SO2-CH2), 4.03 (t, J ¼ 5.7 Hz, 2H, H-4), 4.46 (t, J ¼ 5.7 Hz, 2H, H-5),
4.76 (s, 2H, CO-CH2), 7.37–7.86 (m, 5H, Ar-H). 13C NMR (CDCl3): d ¼ 52.4
(C-4), 54.3 (SO2-CH2), 54.9 (C-5), 61.5 (CO-CH2), 160.4 (C-2), 196.6
(C55O), 128.3, 128.6, 130.9, 132.4 (aromatic carbons). Anal. calcd. for
C12H13NO4S: C, 53.92; H, 4.90; N, 5.24. Found: C, 53.97; H, 4.83; N, 5.29.
8b: Pale yellow solid; yield 0.194 g (69%); mp 194–1968C. IR (KBr): 1134,
1
1328 (SO2), 1558 (C55N), 1671 (C55O) cm21. H NMR (CDCl3): d ¼ 2.20
(s, 3H, Ar-CH3), 3.72 (s, 2H, SO2-CH2), 4.04 (t, J ¼ 5.6 Hz, 2H, H-4), 4.45
(t, J ¼ 5.6 Hz, 2H, H-5), 4.70 (s, 2H, CO-CH2), 7.17–7.72 (m, 4H, Ar-H).
13C NMR (CDCl3): d ¼ 21.0 (Ar-CH3), 51.8 (C-4), 54.8 (SO2-CH2), 55.3
(C-5), 61.2 (CO-CH2), 157.8 (C-2), 196.9 (C55O), 128.5, 128.9, 129.1,

2-Oxazolines and 2-Thiazolines
3139
134.4, (aromatic carbons). Anal. calcd. for C13H15NO4S: C, 55.50; H, 5.37; N,
4.98. Found: C, 55.42; H, 5.34; N, 5.10.
8c: Colorless solid; yield 0.199 g (66%); mp 185–1878C. IR (KBr): 1122, 1330
(SO2), 1559 (C55N), 1680 (C55O) cm21. 1H NMR (CDCl3): d ¼ 3.79 (s, 2H,
SO2-CH2), 4.08 (t, J ¼ 5.9 Hz, 2H, H-4), 4.47 (t, J ¼ 5.9 Hz, 2H, H-5), 4.72
(s, 2H, CO-CH2), 7.26–7.65 (m, 4H, Ar-H). 13C NMR (CDCl3): d ¼ 52.6
(C-4), 54.6 (SO2-CH2), 55.8 (C-5), 60.3 (CO-CH2), 158.7 (C-2), 193.6
(C55O), 128.8, 130.0, 134.5, 135.2 (aromatic carbons). Anal. calcd. for
C12H12ClNO4S: C, 47.76; H, 4.01; N, 4.64. Found: C, 47.85; H, 4.04; N, 4.69.
General Procedure for the Synthesis of 2-(4,5-Dihydrothiazol-2-
ylmethanesulfonyl)-1-aryl-ethanone (10)
A solution of b-cyclodextrin (0.1 mmol) in distilled H2O (15 mL) and 2-(4,5-
dihydro-thiazol-2-ylmethane-sulfonyl)-1-aryl-ethanone oxime (14) (1 mmol)
in acetone (2 mL) were taken. To this, 2-iodoxybenzoic acid (1 mmol) was
added and stirred at room temperature for 10–11 h. The reaction mixture
was extracted with EtOAc, washed with water, and concentrated under
vacuum. The crude product thus obtained was purified by column chromato-
graphy [silica gel (60–120 mesh), EtOAc-hexane, 9:1].
Data
10a: Colorless solid; yield 0.201 g (71%); mp 157–1598C. IR (KBr): 1144,
1
1320 (SO2), 1557 (C55N), 1678 (C55O) cm21. H NMR (CDCl3): d ¼ 3.32
(t, 2H, J ¼ 8.0 Hz, H-5), 3.65 (s, 2H, SO2-CH2), 4.41 (t, J ¼ 8.0 Hz, 2H,
H-4), 4.74 (s, 2H, CO-CH2), 7.37–7.86 (m, 5H, Ar-H). 13C NMR (CDCl3):
d ¼ 35.3 (C-5), 56.6 (SO2-CH2), 60.8 (CO-CH2), 63.9 (C-4), 160.7 (C-2),
196.4 (C55O), 128.4, 128.6, 132.7, 137.4 (aromatic carbons). Anal. calcd. for
C12 H13NO3S2: C, 50.86; H, 4.62; N, 4.94. Found: C, 50.91; H, 4.64; N, 4.90.
10b: Colorless solid; yield 0.205 g (69%); mp 165–1678C. IR (KBr): 1136,
1
1321 (SO2), 1559 (C55N), 1676 (C55O) cm21. H NMR (CDCl3): d ¼ 2.34
(s, 3 H, Ar-CH3), 3.36 (t, J ¼ 8.1 Hz, 2H, H-5), 3.62 (s, 2H, SO2-CH2),
4.43 (t, J ¼ 8.1 Hz, 2H, H-4), 4.76 (s, 2H, CO-CH2), 7.17–7.74 (m, 4H,
Ar-H). 13C NMR (CDCl3): d ¼ 20.1 (Ar-CH3), 34.9 (C-5), 57.0 (SO2-CH2),
61.0 (CO-CH2), 64.8 (C-4), 162.0 (C-2), 197.0 (C55O), 128.5, 129.1, 134.4,
142.1 (aromatic carbons). Anal. calcd. for C13H15NO3S2: C, 52.50; H, 5.08;
N, 4.71. Found: C, 52.55; H, 5.05; N, 4.76.
10c: Pale yellow solid; yield 0.234 g (74%); mp 184–1868C. IR (KBr): 1124,
1
1322 (SO2), 1560 (C55N), 1681 (C55O) cm21. H NMR (CDCl3): d ¼ 3.34

3140
V. Padmavathi et al.
(t, J ¼ 8.4 Hz, 2H, H-5), 3.56 (s, 2H, SO2-CH2), 4.45 (t, J ¼ 8.4 Hz, 2H, H-4),
4.73 (s, 2H, CO-CH2), 7.52–7.98 (m, 4H, Ar-H). 13C NMR (CDCl3): d ¼ 34.5
(C-5), 58.6 (SO2-CH2), 59.9 (CO-CH2), 64.5 (C-4), 162.1 (C-2), 198.5
(C55O), 128.9, 130.8, 134.5, 139.3 (aromatic carbons). Anal. calcd. for
C12H12ClNO3S2: C, 45.35; H, 3.81; N, 4.41. Found: C, 45.41; H, 3.83; N, 4.47.
ACKNOWLEDGMENT
The authors are thankful to UGC, New Delhi, India, for the financial support.
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