Copper (I) catalyzed synthesis of 1,3-oxazolidin-2-ones from alkynes, amines, and carbon dioxide under solvent-free conditions

Article abstract of DOI:10.1016/j.tetlet.2012.10.073

It was described that 1,3-oxazolidin-2-ones could be produced from alkynes, amines, and CO₂ catalyzed by copper (I) iodide under the solvent-free conditions. Terminal aryl alkynes and aliphatic primary amine are good substances for the transfor

Full text of DOI:10.1016/j.tetlet.2012.10.073

Tetrahedron Letters 53 (2012) 6999–7002
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Tetrahedron Letters
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Copper (I) catalyzed synthesis of 1,3-oxazolidin-2-ones from alkynes, amines,
and carbon dioxide under solvent-free conditions
Jinwu Zhao a,b, Huanfeng Jiang a,
⇑
a School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640, PR China
b School of Pharmacy, Guangdong Medical College, Songshan Lake Sci. & Tech. Industry Park, Dongguan 523808, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
It was described that 1,3-oxazolidin-2-ones could be produced from alkynes, amines, and CO2 catalyzed
by copper (I) iodide under the solvent-free conditions. Terminal aryl alkynes and aliphatic primary amine
are good substances for the transformation of CO2 into the target oxazolidinones in good yields.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 19 May 2012
Revised 12 October 2012
Accepted 18 October 2012
Available online 24 October 2012
Keywords:
Carbon dioxide
Oxazolidinone
Solvent-free
Copper-catalyzed
The 1,3-oxazolidin-2-ones constitute a very important class of
heterocyclic compounds which could be used not only as multipur-
pose chiral synthons in asymmetric syntheses of biologically active
compounds or their synthetic intermediates,1 but also as chiral
auxiliaries in many asymmetric transformations such as alkylation,
acylation, and Diels–Alder reactions, and aldolic condensations.2
Moreover, some oxazolidinones such as DUP-105, DUP-721, and
linezolid (Zyvox) have drawn interest as monodrug- or multidrug-
resistant antibacterial agents.3 The importance of these heterocy-
clic derivatives justifies the continuous endeavors to develop novel
routes to their synthesis and a number of procedures to synthesize
1,3-oxazolidin-2-ones have been developed.4
The use of industrially produced CO2 as a chemical feedstock is
attracting growing attention. CO2 is a major contributor to the
greenhouse effect, and a number of strategies have been developed
to reduce its concentration in the atmosphere. Although the
employment of CO2 in chemical synthesis contributes relatively lit-
tle to mitigation of the CO2 concentration in the atmosphere, sev-
eral other factors render CO2 an interesting chemical feedstock,
such as low cost, relative nontoxicity, nonflammability, and
renewal.5
from propargylic alcohols, and secondary amines.10 As a part of
our works in this field, we recently developed an efficient approach
to synthesize oxazolin-2-ones via the cycloaddition of terminal al-
kynes, primary amines, and CO2 under the catalysis of copper (I) io-
dide (Scheme 1). Compared to the reported starting materials for
chemical fixation of CO2 to 1,3-oxazolidin-2-ones, alkynes is much
cheaper than aziridines,11 propargylic amines,12 or propargylic
alcohols.13
In order to explore the optimum reaction conditions, the interac-
tion of CO2, phenylacetylene, and n-butylamine was selected as the
model reaction. The experimental data are collected in Table 1. On
the basis of our experience on using supercritical carbon dioxide
as the reaction medium,14 we initially carried out the reaction in
supercritical carbon dioxide catalyzed by CuBr under CO2 pressure
of 7.5 MPa at 110 °C for 24 h. It was found that the desired (Z)-4-
benzyl-5-benzylidene-3-butyloxazolidin-2-one was obtained in
71% yield (Table 1, entry 1). The target compound was formed in
86% in the above reaction system catalyzed by CuI instead (Table
1, entry 2). Other cuprous salts, for instance, CuCl and CuOTf, gave
inferior results (Table 1, entries 3 and 4). Although monovalent sil-
ver and gold reagents are usually employed to activate alkynes,
In our continuing efforts to chemical fixation of CO2, we have
developed a number of protocols to transform CO2 into value-
added products, such as 1,3-oxazolidin-2-ones from propargylic
alcohols, and primary amines or aziridines,6,7 cyclic carbonates
from epoxides or propargylic alcohols,8,9 b-oxopropylcarbamates
O
R2
CuI
+ R2 NH2
R1
CO2
+
O
N
2
solvent-free
R1
R1
⇑
Corresponding author. Tel./fax: +86 20 8711 2906.
E-mail address: jianghf@scut.edu.cn (H. Jiang).
Scheme 1. Synthesis of 1,3-oxazolidin-2-ones from alkynes, amines, and CO2
catalyzed by copper (I) iodide.
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.10.073

7000
J. Zhao, H. Jiang / Tetrahedron Letters 53 (2012) 6999–7002
Table 1
AgBr and AgOTf had no ability to drive the transformation (Table 1,
entries 5 and 6). Aurous chloride and Chloro(triphenylphos-
phine)gold (I) exhibited extremely weak activity (Table 1, entries
7 and 8). The effect of CO2 pressure was then investigated. As the
experimental results had shown, when CO2 pressure was gradually
tuned from 7.5 MPa to 2 MPa, the yield of target oxazolidinone had
no significant change (Table 1, entries 9 and 10). This result was
beyond our expectation because our original destination was to
develop a transformation in supercritical carbon dioxide. The
following study suggested that further reduction of the pressure
resulted in a decline of the yield (Table 1, entry 11). When CO2 pres-
sure was set at 0.5 MPa, the yield of the desired product plunged to
29% (Table 1, entry 12) The influence of the reaction temperature
was finally examined and it was found that the yield had not been
impacted when the temperature was regulated from 110 °C to
90 °C (Table 1, entry 13). The reaction temperature decreased to
70 °C or increased to 130 °C led to a lower yield (Table 1, entries
14 and 15).
With the optimized reaction conditions in hand, we next evalu-
ated the generality and scope of the methodology for the synthesis
of 1,3-oxazolidin-2-ones via the cycloaddition of alkynes, primary
amines, and CO2. And the results are summarized in Table 2. A vari-
ety of amines were firstly subjected to the cycloaddition reaction
with phenyl acetylene and CO2. As the results showed, sec-butyl
amine gave a lower yield compared with n-butylamine(Table 2,
entries 1 and 2),15 The reaction of phenyl acetylene with ethyl
Optimizing the reaction conditions for the synthesis of 1,3-oxazolidin-2-one from
alkynes, amines, and CO2
a
O
cat.
n-Bu
2 Ph
n-Bu NH2 CO2
O
N
+
+
Ph
Ph
Yieldb (%)
Entry
Cat.
P (MPa)
T. (oC)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
CuBr
CuI
CuCl
7.5
7.5
7.5
7.5
7.5
7.5
7.5
7.5
5
2
1
0.5
2
2
2
110
110
110
110
110
110
110
110
110
110
110
110
90
71
86
35
27
0
CuOTf
AgBr
AgOTf
AuCl
0
Trace
9
Ph3PAuCl
CuI
86
86
77
29
86
72
85
CuI
CuI
CuI
CuI
CuI
CuI
70
130
a
Reagents and conditions: phenyl acetylene (2 mmol), butylamine (2 mmol),
catalyst (0.1 mmol).
b
Determined by 1H NMR.
Table 2
Synthesis of 1,3-oxazolidin-2-ones from alkynes, amines, and CO2 catalyzed by CuI under solvent-free conditionsa
O
R2
CuI
R2 NH2
O
N
2 R1
CO2
+
+
solvent-free
R1
R1
Entry
1
Alkyne
Amine
Product no.
Yieldb (%)
84
NH2
2a
3aa
1a
1a
2
3ab
80
2b
NH2
NH2
2c
3
4
5
3ac
3ad
3ae
86
73
87
1a
1a
1a
1a
NH2
2d
NH2
2e
2f
NH2
6
3af
69
NH2
NH2
NH2
2a
2a
2a
Et
7
8
3ba
3ca
86
89
1b
1c
Me
Me
9
3da
3ea
79
58
1d
Me
NH2
2a
10
1e
NH2
NH2
NH2
2a
2a
2a
F
11
12
13
3fa
83
81
52
1f
1g
3ga
3ha
Cl
1h

J. Zhao, H. Jiang / Tetrahedron Letters 53 (2012) 6999–7002
7001
Table 2 (continued)
Entry
Alkyne
Amine
Product no.
Yieldb (%)
NH2
2a
14
3ia
3ja
0
0
O2N
1i
NH2
15
1j
2a
a
Reagents and conditions: alkyne (2 mmol), amine (2 mmol), CuI (0.1 mmol), P = 2 MPa, 90 °C.
Isolated yields.
b
2. (a) Matsunaga, H.; Ishizuka, T.; Kunieda, T. Tetrahedron 2005, 61, 8073; (b)
Vicario, J. L.; Badia, D.; Carrillo, L.; Reyes, E.; Etxebarria, J. Curr. Org. Chem. 2005,
9, 219.
3. (a) Mukhtar, T. A.; Wright, G. D. Chem. Rev. 2005, 105, 529; (b) Renslo, A. R.;
Luehr, G. W.; Gordeev, M. F. Bioorg. Med. Chem. Lett. 2006, 14, 4227; (c) Osa, Y.;
Hikima, Y.; Sato, Y.; Takino, K.; Ida, Y.; Hirono, S.; Nagase, H. J. Org. Chem. 2005,
70, 5737.
R2
O
HN
R2
NH2
R2
CO2
CuI
Cu I
R1
O
N
+
R1
R1
R1
R1
4. (a) Paz, J.; Perez-Balado, C.; Iglesias, B.; Munoz, L. J. Org. Chem. 2010, 75, 3037;
(b) Schindler, C. S.; Forster, P. M.; Carreira, E. M. Org. Lett. 2010, 12, 4102; (c)
Kojima, N.; Nishijima, S.; Tanaka, T. Synlett 2009, 3171; (d) Liu, J. M.; Peng, X.
G.; Liu, J. H.; Zheng, S. Z.; Sun, W.; Xia, C. G. Tetrahedron Lett. 2007, 48, 929.
5. (a) Huang, K.; Sun, C. L.; Shi, Z. J. Chem. Soc. Rev. 2011, 40, 2435; (b) Riduan, S.
N.; Zhang, Y. G. Dalton T 2010, 39, 3347; (c) Sakakura, T.; Sakakura, J. C.; Yasuda,
H. Chem. Rev. 2007, 107, 2365.
Scheme 2. The probable pathway of the formation of 1,3-oxazolidin-2-ones from
alkynes, amines, and CO2 catalyzed by copper (I) iodide.
amine and n-hexyl amine proceeded smoothly with 3ac and 3ad
obtained in yields of 86% and 73%, respectively (Table 2, entries 3
and 4). Cyclohexylamine and benzylamine gave the corresponding
products 3ae and 3af in yields of 87% and 69%, respectively
(Table 2, entries 5 and 6). Various terminal alkynes were treated
with n-butyl amine and our studying results indicated that alkyl
substituted aryl terminal alkynes could all go across the reaction
despite the alkyl groups in para-, meta-, or ortho-position of aryl
rings (Table 2, entries 7–10), the transformation could also tolerate
halogen groups (Table 2, entries 11 and 12). Substrate 1 h, bearing
a bulky substituent, could also undergo the cycloaddition (Table 2,
entry 13). Our experimental results indicated that substrate 1i,
bearing a strongly electron-withdrawing nitro group failed to
furnish the desired 1,3-oxazolidin-2-one and aliphatic alkyne that
appeared less reactive (Table 2, entries 14 and 15).
6. (a) Jiang, H. F.; Zhao, J. W. Tetrahedron Lett. 2009, 50, 60; (b) Jiang, H. F.; Zhao, J.
W.; Wang, A. Z. Synthesis 2008, 763.
7. (a) Qi, C. R.; Ye, J. W.; Zeng, W.; Jiang, H. F. Adv. Synth. Catal. 2010, 325, 1925; (b)
Jiang, H. F.; Ye, J. W.; Qi, C. R.; Huang, L. B. Tetrahedron Lett. 2010, 51, 928.
8. (a) Qi, C. R.; Jiang, H. F.; Wang, Z. Y.; Zou, B.; Yang, S. R. Synlett 2007, 255; (b) Qi,
C. R.; Jiang, H. F.; Wang, Z. Y.; Zou, B. Chin. J. Chem. 2007, 1051, 25; (c) Qi, C. R.;
Jiang, H. F.; Liu, H. L.; Yang, S. R.; Zou, B. Chem. J. Chin. Univ. 2007, 28, 1084.
9. Jiang, H. F.; Wang, A. Z.; Liu, H. L.; Qi, C. R. Eur. J. Org. Chem. 2008, 2309.
10. (a) Qi, C. R.; Jiang, H. F. Green Chem. 2007, 9, 1284; (b) Qi, C. R.; Huang, L. B.;
Jiang, H. F. Synthesis 2010, 1433.
11. (a) Yang, Z. Z.; Li, Y. N.; Wei, Y. Y.; He, L. N. Green Chem. 2011, 13, 2351; (b)
Fontana, F.; Chen, C. C.; Aggarwal, V. K. Org. Lett. 2011, 13, 3454; (c) Zhou, H.;
Wang, Y. M.; Zhang, W. Z.; Qu, J. P.; Lu, X. B. Green Chem. 2011, 13, 644.
12. (a) Maggi, R.; Bertolotti, C.; Orlandini, E.; Oro, C.; Sartori, G.; Selva, M.
Tetrahedron Lett. 2007, 48, 2131; (b) Kayaki, Y.; Yamamoto, M.; Suzuki, T.;
Ikariya, T. Green Chem. 2006, 8, 1019; (c) Feroci, M.; Orsini, M.; Sotgiu, G.; Rossi,
L.; Inesi, A. J. Org. Chem. 2005, 70, 7795; (d) Shi, M.; Shen, Y. M. J. Org. Chem.
2002, 67, 16.
The probable pathway of the cycloaddition of terminal alkynes,
primary amines, and CO2 is described in Scheme 2. Alkyne inter-
acted with amine via a copper-catalyzed tandem anti-markovnikov
hydroamination and alkyne addition to furnish propargylamine
which then went across the cycloadditon with CO2 to afford 5-ary-
lidene-1,3-oxazolidin-2-one.16,12
13. (a) Fournier, J.; Bruneau, C.; Dixneuf, P. H. Tetrahedron Lett. 1990, 31, 1721; (b)
Gu, Y. L.; Zhang, Q. H.; Duan, Z. Y.; Zhang, J.; Zhang, S. G.; Deng, Y. Q. J. Org.
Chem. 2005, 70, 7376; (c) Zhang, Q. H.; Shi, F.; Gu, Y. L.; Yang, J.; Deng, Y. Q.
Tetrahedron Lett. 2005, 46, 5907.
14. Jiang, H. F. Curr. Org. Chem. 2005, 9, 289.
15. Typical experimental procedure for the copper (I) catalyzed synthesis of 1, 3-
oxazolidin-2-ones from alkynes, amines, and carbon dioxide under solvent-free
conditions. A 15 mL polytetrafluoroethylene (PTFE) reaction vessel was charged
with CuI (0.1 mmol), alkyne (2 mmol), and amine (2 mmol). The vessel was
fixed into a stainless steel autoclave with a pressure-regulating system. The
autoclave was sealed and CO2 was introduced from a cylinder. The autoclave
was heated by an oil bath. The reaction continued under magnetic stirring for
24 h. When the reaction was complete, the vessel was cooled with an ice bath
and the pressure was released slowly to atmospheric pressure. The residue was
extracted with ethyl acetate (10 mL). The collected filtrate was concentrated
under reduced pressure. The product was purified by chromatography on a
silica gel column using light petroleum ether/ethyl acetate as eluent. (Z)-4-
Benzyl-5-benzylidene-3-butyloxazolidin-2-one (3aa) 1H NMR (400 MHz,
CDCl3) d 7.46 (d, J = 7.4 Hz, 2H), 7.44–7.13 (m, 8H), 5.19 (d, J = 1.5 Hz, 1H),
4.71–4.62 (m, 1H), 3.68–3.55 (m, 1H), 3.19–2.92 (m, 3H), 1.62–1.46 (m, 2H),
1.31 (m, 2H), 0.92 (t, J = 7.3 Hz, 1H). 13C NMR (101 MHz, CDCl3) d 155, 146, 135,
133, 130, 129, 128, 128, 127, 127, 104, 59, 42, 40, 29, 20, 14. IR (KBr): 2959,
1775, 1410. MS (EI, 70 eV): m/z (%) = 230 (100), 174 (35), 103 (10). HRMS Calcd
for C21H23NO2: 321.1729, Found: 321.1721. (Z)-4-Benzyl-5-benzylidene-3-sec-
butyloxazolidin-2-one (3ab) 1H NMR (400 MHz, CDCl3) d 7.46–7.16 (m, 10H),
4.83 (d, J = 3.8 Hz, 1H), 4.62 (td, J = 8.7, 4.0 Hz, 1H), 3.67–3.48 (m, 1H), 3.33 (m,
1H), 2.90 (m, 1H), 2.00–1.77 (m, 2H), 1.42 (dd, J = 16.8, 6.9 Hz, 3H), 0.98 (dd,
J = 17.1, 7.5 Hz, 3H). 13C NMR (101 MHz, CDCl3) d 155, 146, 135, 133, 130, 129,
128, 127, 104, 62, 53, 42, 28, 19, 11. MS (EI, 70 eV): m/z (%) = 230(72), 175(10),
174(100), 103(20). IR (KBr): 2978, 1780, 1420, 698. HRMS Calcd for C21H23NO2:
321.1729, Found: 321. 1725. (Z)-4-Benzyl-5-benzylidene-3-ethyloxazolidin-2-
one (3ac) 1H NMR (400 MHz, CDCl3) d 7.50 (d, J = 7.6 Hz, 2H), 7.33 (t, J = 7.2 Hz,
5H), 7.26–7.20 (m, 3H), 5.22 (s, 1H), 4.72 (t, J = 5.5 Hz, 1H), 3.71 (m, 1H), 3.22–
3.13 (m, 2H), 3.00 (dd, J = 14.0, 6.6 Hz, 1H), 1.22 (t, J = 7.2 Hz, 3H). 13C NMR
(101 MHz, CDCl3) d 155, 146, 135, 133, 130, 129, 128, 127. 104, 59, 40, 37, 13.
MS (EI, 70 eV): m/z (%) = 202(100), 174(9), 103(9), 91(11), 56(22). IR (KBr):
2970, 1775, 1376, 699. HRMS Calcd for C19H19NO2: 293.1416, Found: 293.
1427. (Z)-4-Benzyl-5-benzylidene-3-hexyloxazolidin-2-one (3ad) 1H NMR
(400 MHz, CDCl3) d 7.46 (d, J = 7.5 Hz, 2H), 7.32–7.25 (m, 5H), 7.22–7.14 (m,
3H), 5.19 (d, J = 1.1 Hz, 1H), 4.66 (t, J = 5.0 Hz, 1H), 3.64–3.55 (m, 1H), 3.17–2.94
In conclusion, we have disclosed that copper (I) iodide could
catalyze the chemical fixation of CO2 into 1,3-oxazolidin-2-ones
with alkynes and amines under solvent-free conditions. This proce-
dure supplies an alternative route to 1,3-oxazolidin-2-ones from
relatively low-cost alkynes and amines.
Acknowledgments
We thank the National Natural Science Foundation of China
(20932002 and 21172076), the National Basic Research Program
of China (973 Program) (2010CB-732206), the Doctoral Fund of
the Ministry of Education of China (20090172110014), the Guang-
dong Natural Science Foundation (10351064101000000), and the
Fundamental Research Funds for the Central Universities
(2011ZZ007) for financial support.
Supplementary data
Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.tetlet.2012.10.
073.
References and notes
1. (a) Ager, D. J.; Prakash, I.; Schaad, D. R. Chem. Rev. 1996, 96, 835; (b) Dyen, M. E.;
Swern, D. Chem. Rev. 1967, 67, 197.

7002
J. Zhao, H. Jiang / Tetrahedron Letters 53 (2012) 6999–7002
(m, 3H), 1.27 (s, 6H), 0.88 (t, J = 6.6 Hz, 3H). 13C NMR (101 MHz, CDCl3) d 155,
6H), 1.62–1.53 (m, 2H), 1.39–1.27 (m, 2H), 0.95 (t, J = 7.4 Hz, 3H). 13C NMR
(101 MHz, CDCl3) d 155, 146, 138, 135, 133, 130, 129, 128, 127, 126, 104, 60,
43, 40, 29, 21, 20, 14. MS (EI, 70 eV): m/z (%) = 244(100), 188(31), 117(11),
105(8). IR (KBr): 2924, 1779, 1417, 1045. HRMS Calcd for C23H27NO2: 349.2042,
Found: 349. 2045. (Z)-3-Butyl-4-(2-methylbenzyl)-5-(2-methylbenzylid
ene)oxazolidin-2-one (3ea) 1H NMR (400 MHz, CDCl3) d 7.37 (d, J = 8.1 Hz,
2H), 7.14–7.04 (m, 6H), 5.21 (d, J = 1.4 Hz, 1H), 4.64 (t, J = 4.7 Hz, 1H), 3.61 (m,
1H), 3.11–3.01 (m, 2H), 2.95 (m, 1H), 2.32 (s, 6H), 1.59–1.51 (m, 2H), 1.36–1.24
(m, 2H), 0.92 (t, J = 7.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) d 155, 145, 1376,
132, 131, 129, 128, 104, 59, 42, 39, 29, 21, 20, 14. MS (EI, 70 eV): m/z
(%) = 244(100), 188(25), 117(11), 105(11). IR (KBr): 2926, 1780, 1417, 1049.
146, 135, 133, 130, 129, 128, 127, 104, 59, 42, 40, 31, 27, 26, 23, 14. MS (EI,
70 eV): m/z (%) = 258(100), 174(44), 103(12), 43(11) IR (KBr): 2924, 1771,
1410, 695. HRMS Calcd for C23H27NO2: 349.2042, Found: 349.2037. (Z)-4-
Benzyl-5-benzylidene-3-cyclohexyloxazolidin-2-one (3ae) 1H NMR (400 MHz,
CDCl3) d 7.39 (d, J = 7.5 Hz, 2H), 7.33–7.23 (m, 5H), 7.22–7.13 (m, 3H), 4.85 (s,
1H), 4.64–4.57 (m, 1H), 3.41–3.31 (m, 1H), 3.27 (m, 1H), 2.87 (m, 1H), 2.01–
1.62 (m, 6H), 1.35–1.12 (m, 4H). 13C NMR (101 MHz, CDCl3) d 154, 146, 135,
134, 130, 129, 128, 127, 104, 60, 55, 42, 31, 30, 26. MS (EI, 70 eV): m/z
(%) = 256(63), 174(100), 103(19), 55(17) IR (KBr): 2931, 1775, 1376, 696. HRMS
Calcd for
C
23H25NO2: 347.1885, Found: 347. 1879. (Z)-3,4-Dibenzyl-5-
benzylideneoxazolidin-2-one (3af) 1H NMR (400 MHz, CDCl3)
d
7.45 (d,
HRMS Calcd for C23H27NO2: 349.2042, Found: 349.2041. (Z)-3-Butyl-4-(4-
J = 7.4 Hz, 2H), 7.35–7.24 (m, 8H), 7.17 (dd, J = 10.3, 4.3 Hz, 3H), 7.13–7.08
(m, 2H), 5.13 (d, J = 1.5 Hz, 1H), 4.96 (d, J = 15.2 Hz, 1H), 4.10 (m, 1H), 4.05 (s,
1H), 4.02 (s, 1H), 3.15–2.91 (m, 1H) 13C NMR (101 MHz, CDCl3) d 155, 146, 135,
135, 133, 130, 129, 128, 127, 104, 59, 46, 40. MS (EI, 70 eV): m/z (%) = 264(53),
91(100). IR (KBr): 3029, 1783, 1416, 1054, 670. HRMS Calcd for C24H21NO2:
355.1572, Found: 355.1572. (Z)-3-Butyl-4-(4-ethylbenzyl)-5-(4-ethylbenzylid
ene)oxazolidin-2-one (3ba) 1H NMR (400 MHz, CDCl3) d 7.39 (d, J = 8.2 Hz, 2H),
7.17–7.08 (m, 6H), 5.20 (d, J = 1.3 Hz, 1H), 4.64 (dd, J = 5.5, 4.0 Hz, 1H), 3.66–
3.54 (m, 2H), 3.13–2.90 (m, 2H), 2.67–2.55 (m, 4H), 1.23 (m, 10H), 0.90 (dd,
J = 12.8, 5.5 Hz, 3H). 13C NMR (101 MHz, CDCl3) d 155, 145, 143, 132, 131, 130,
129, 128, 104, 59, 42, 39, 29, 28, 20, 16, 14. MS (EI, 70 eV): m/z (%) = 258(100),
202(21), 131(13). IR (KBr): 2963, 1773, 1411, 1957. HRMS Calcd for C25H31NO2:
377.2355, Found: 377, 2357. (Z)-3-Butyl-4-(4-methylbenzyl)-5-(4-methylben
zylidene)oxazolidin-2-one (3ca) 1H NMR (400 MHz, CDCl3) d 7.37 (d, J = 8.0 Hz,
2H), 7.14–7.04 (m, 6H), 5.21 (s, 1H), 4.63 (t, J = 5.0 Hz, 1H), 3.67–3.57 (m, 1H),
3.12–3.00 (m, 2H), 2.94 (m, 1H), 2.33 (s, 6H), 1.62–1.49 (m, 2H), 1.37–1.24 (m,
2H), 0.92 (t, J = 7.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) d 155, 145, 137, 132,
131, 129, 128, 104, 59, 42, 39, 29, 21, 20, 14. MS (EI, 70 eV): m/z (%) = 244(100),
207(17), 188(28), 117(11), 105(12), 32(12). IR (KBr): 2929, 1738, 1407, 757.
HRMS Calcd for C23H27NO2: 349.2042, Found: 349, 2041. (Z)-3-Butyl-4-(3-
methylbenzyl)-5-(3-methylbenzylidene)oxazolidin-2-one (3da) 1H NMR (400
MHz, CDCl3) d 7.34–7.00 (m, 8H), 5.19 (d, J = 1.2 Hz, 1H), 4.68 (t, J = 5.0 Hz, 1H),
3.68–3.58 (m, 1H), 3.18–3.03 (m, 2H), 2.95 (m, 1H), 2.42–2.30 (d, J = 3.8 Hz,
fluorobenzyl)-5-(4-fluorobenzylidene)oxazolidin-2-one (3fa) 1H NMR (400
MHz, CDCl3) d 7.43 (dd, J = 8.6, 5.5 Hz, 2H), 7.14 (dd, J = 8.3, 5.5 Hz, 2H), 6.99
(td, J = 8.6, 6.4 Hz, 4H), 5.18 (s, 1H), 4.64 (t, J = 5.0 Hz, 1H), 3.69–3.59 (m, 1H),
3.13–3.02 (m, 2H), 2.97 (m, 1H), 1.57 (m, 2H), 1.34 (m, 2H), 0.94 (t, J = 7.3 Hz,
3H) 13C NMR (101 MHz, CDCl3) d 163, 161, 155, 145, 131, 130, 129, 116, 115,
103, 59, 42, 39, 29, 20, 14. MS (EI, 70 eV): m/z (%) = 248(100), 192(51), 121(17),
109(16). IR (KBr): 2928, 1778, 1508, 1227, 830. HRMS Calcd for C21H21F2NO2:
357.1540, Found: 357.1550. (Z)-3-Butyl-4-(4-chlorobenzyl)-5-(4-chlorobenzyl
idene)oxazolidin-2-one (3ga) 1H NMR (400 MHz, CDCl3) d 7.39 (d, J = 8.5 Hz,
2H), 7.27 (dd, J = 10.3, 5.1 Hz, 4H), 7.10 (d, J = 8.2 Hz, 2H), 5.19 (s, 1H), 4.65 (t,
J = 4.9 Hz, 1H), 3.69–3.59 (m, 1H), 3.13–3.02 (m, 2H), 2.98 (m, 1H), 1.57 (m,
2H), 1.34 (m, 2H), 0.94 (t, J = 7.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) d 155, 146,
131, 130, 129, 103, 59, 42, 39, 29, 20, 14. MS (EI, 70 eV): m/z (%) = 266(32),
264(100), 210(12), 208(40) IR (KBr): 2930, 1684, 1406, 1091, 761. HRMS Calcd
for C21H21Cl2NO2: 389.0949, Found: 389. 0948. (Z)-3-Butyl-4-((40-propylbiphe
nyl-4-yl)methyl)-5-((40-propylbiphenyl-4-yl)methylene)oxazolidin-2-one (3h
a) 1H NMR (400 MHz, CDCl3) d 7.59–7.46 (m, 10H), 7.25 (m, 6H), 5.27 (s, 1H),
4.72 (s, 1H), 3.71–3.61 (m, 1H), 3.23–2.99 (m, 3H), 2.64 (m, 4H), 1.68 (m, 4H),
1.58 (m, 2H), 1.33 (m, 2H), 1.02–0.89 (m, 9H). 13C NMR (101 MHz, CDCl3) d 155,
146, 142, 140, 139, 138, 134, 132, 130, 129, 127, 103, 60, 42, 40, 38, 29, 25, 20,
14. IR (KBr): 2957, 1914, 1395, 808. HRMS Calcd for C39H43NO2: 557.3294,
Found: 557.3289.
16. Zhou, L.; Bohle, D. S.; Jiang, H. F.; Li, C. J. Synlett 2009, 937.