Ionic liquid as an efficient promoting medium for fixation of carbon dioxide: A clean method for the synthesis of 5-methylene-1,3-oxazolidin-2-ones from propargylic alcohols, amines, and carbon dioxide catalyzed by Cu(I) under mild conditions

Article abstract of DOI:10.1021/jo050802i

The reactions of propargylic alcohols, aliphatic primary amines, and CO₂ were conducted in CuCl/ [BMIm]BF₄ system to produce the corresponding 5-methylene-1,3-oxazolidin-2-ones under relatively mild conditions. The products could be

Full text of DOI:10.1021/jo050802i

Ionic Liquid as an Efficient Promoting Medium for Fixation of
Carbon Dioxide: A Clean Method for the Synthesis of
5-Methylene-1,3-oxazolidin-2-ones from Propargylic Alcohols,
Amines, and Carbon Dioxide Catalyzed by Cu(I) under Mild
Conditions
Yanlong Gu,†,‡ Qinghua Zhang,† Zhiying Duan,† Juan Zhang,† Shiguo Zhang,† and
Youquan Deng*,†
Center for Green Chemistry, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences,
Lanzhou 730000, China, and State Key Laboratory of Applied Organic Chemistry,
Lanzhou University, Lanzhou 730000, China
ydeng@ns.lzb.ac.cn
Received April 20, 2005
The reactions of propargylic alcohols, aliphatic primary amines, and CO2 were conducted in CuCl/
[BMIm]BF4 system to produce the corresponding 5-methylene-1,3-oxazolidin-2-ones under relatively
mild conditions. The products could be conveniently isolated by means of liquid-liquid extraction.
The solvent ionic liquid as well as CuCl catalyst can be recovered and reused three times without
appreciable loss of activity. By this green approach, several new 5-methylene-1,3-oxazolidin-2-
ones were prepared in excellent yields and purity and were well-characterized.
Introduction
exocyclic double bond (5-methylene-1,3-oxazolidin-2-ones
or R-methylene oxazolidinones) allow the further trans-
formation of the 1,3-oxazolin-2-one and the preparation
of synthetically useful derivatives. 5-Methylene-1,3-ox-
azolidin-2-ones could be prepared from propynyl carbam-
ates through an intramolecular nucleophilic cyclization
in the presence of a base.5 Alternatively, propargylic
amines can react with carbon dioxide, leading to the
formation of 5-methylene-1,3-oxazolidin-2-ones in the
presence of catalysts, such as copper salts,6 ruthenium
or palladium complexes,7 and strong organic bases.8
Analogous synthetic reactions could also be conducted in
an aprotic solvent using tetraethylammonium carbonate
or tetraethylammonium hydrogen carbonate instead of
carbon dioxide as the carbonyl contributor.9 Moreover,
R-methylene cyclic carbonates have also been used as
substrates to react with amines to give 5-methylene-1,3-
Cyclic carbamates 1,3-oxazolidin-2-ones are useful
substrates in organic synthesis.1 In their optically active
form, they are frequently used as chiral auxiliaries in a
wide range of asymmetric synthesis such as alkylation,
acylation and Diels-Alder reactions, and aldolic conden-
sations.2 Moreover, the cyclic carbamate nucleus consti-
tutes the core unit of many therapeutic agents, including
antibacterial drugs.3 Thus, synthesis of this heterocyclic
system is of much interest, and a number of procedures
have been developed.4 1,3-Oxazolidin-2-ones with an
* Corresponding author. Fax: +86-931-4968116.
† Chinese Academy of Sciences.
‡ Lanzhou University.
(1) (a) Sugiyama, S.; Arai, S.; Ishii, K. Heterocycles 2005, 65, 149.
(b) Xu, X.; Kotti, S. R. S. S.; Liu, J. Y.; Cannon, J. F.; Headley, A. D.;
Li, G. G. Org. Lett. 2004, 6, 4881. (c) Me´nand, M.; Dalla, V. Synlett
2005, 95.
(2) Ager, D. J.; Prakash, I.; Schaad, D. R. Chem. Rev. 1996, 96, 835
and references therein.
(5) Shachat, N.; Bagnell, J. J. J. Org. Chem. 1963, 28, 991.
(6) Dimroth, P.; Pasedach, H. German Patent 1164411, 1964.
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dron Lett. 1987, 28, 4417. (b) Shi, M.; Shen, Y. M. J. Org. Chem. 2002,
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Choi, E. C. Bioorg. Med. Chem. 2004, 12, 5904. (b) Das, J.; Rao, C. V.
L.; Sastry, T. V. R. S.; Roshaiah, M.; Sankar, P. G.; Khadeer, A. K.;
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10.1021/jo050802i CCC: $30.25 © 2005 American Chemical Society
Published on Web 08/12/2005
7376
J. Org. Chem. 2005, 70, 7376-7380

Ionic Liquid as Promoting Medium for Fixation of CO2
oxazolidin-2-ones under mild conditions.10 However, pro-
pynyl carbamates, propargylic amines, and R-methylene
cyclic carbonates are not easily available and are expen-
sive; their preparations are also hard tasks. Regarding
the availability and the economic viability, the most
attractive method for the synthesis of 5-methylene-1,3-
oxazolidin-2-ones should be the three-component reac-
tions of propargylic alcohols, primary amines, and carbon
dioxide, which are usually catalyzed by copper salts or
tributylphosphine.11,12 However, most of the synthetic
protocols for 5-methylene-1,3-oxazolidin-2-ones reported
thus far suffer from harsh conditions (5.0 MPa of CO2
pressure and 110-140 °C), poor yields (38-72%), pro-
longed time period (20 h), and use of hazardous and often
expensive catalysts.12 Moreover, the synthesis of these
heterocycles has been usually carried out in polar sol-
vents such as acetonitrile, DMF, and DMSO, leading to
complex isolation and recovery procedures. These pro-
cesses also generate waste-containing solvent and cata-
lyst, which have to be recovered, treated, and disposed
of. With increasing environmental concerns, it is impera-
tive that new “environment friendly” approaches for the
synthesis of 5-methylene-1,3-oxazolidin-2-ones be devel-
oped and used.
In recent years, studies of low waste routes and
reusable reaction media for enhanced selectivity and
energy minimization have been the key interests of
synthetic organic chemists the world over.13 In this
context, the use of room-temperature ionic liquids as
“green” solvents in organic synthetic processes has gained
considerable importance due to their solvating ability,
negligible vapor pressure, and easy recyclability.14 They
have the potential to be highly polar yet noncoordinating.
In addition to the above-mentioned salient features of
ionic liquids as reaction media, we have also recently
shown that they can act as promoting media for the
chemical fixation of carbon dioxide. The reactions inves-
tigated by us are cyclic addition of epoxide to CO2,15
electrochemical synthesis of cyclic carbonates,16 and
direct synthesis of symmetrical dialkylurea from CO2 and
aliphatic amines,17 which proceed in significantly en-
hanced reaction rates, high selectivity, and excellent
isolated yields. In particular, we have recently reported
the atom-economic reactions of propargylic alcohols with
CO2 in the CuCl/[BMIm][PhSO3] system to afford R-me-
SCHEME 1. General Reaction
TABLE 1. Three-Component Reaction of 1a, 2a, and
a
Carbon Dioxide in [BMIm]BF4
amount of catalyst
(mol %)
yield
entry
catalyst
solvent
(%)
1
CuCl
CuBr
CuI
CuCl2
-
CuCl
CuCl
CuCl
CuCl
CuCl
CuCl
2
2
2
2
0
2
2
2
2
2
2
[BMIm]BF4
[BMIm]BF4
[BMIm]BF4
[BMIm]BF4
[BMIm]BF4
[BPy]BF4
[BMIm]PF6
DMF
92
84
85
66
9
59
67
42
4
2
3
4
5b
6
7
8
9b
10b
11c
ClCH2CH2Cl
toluene
DMF
3
50
a Reaction conditions: ionic liquid, 3.0 mL, 2a, 10 mmol; 1a,
10 mmol; carbon dioxide, 2.5 MPa, temperature, 100 °C, reaction
time, 10 h. b Reaction time is 20 h, and the result was recorded
as GC yield. c 5.0 MPa CO2 and 20 h, and the result was recorded
as GC yield.
thylene cyclic carbonates in excellent isolated yields
under mild conditions.18
Proceeding along the same lines, we chose to evolve
an efficient and ecofriendly process for the preparation
of 5-methylene-1,3-oxazolidin-2-ones based on the prop-
argylic alcohols/amines/CO2 protocol using the “green”
ionic liquids as reaction media as well as promoters.
Herein we disclose the successful outcome of this en-
deavor in which propargylic alcohols, primary aliphatic
amines, and CO2 afforded excellent yields of the products
in CuCl/[BMIm]BF4 system. Scheme 1 shows the general
reaction.
(10) Shi, M.; Shen, Y. M.; Shen, Y. J. Heterocycles 2002, 57, 245.
(11) (a) Fournier, J.; Bruneau, C.; Dixneuf, P. H. Tetrahedron Lett.
1989, 30, 3981. (b) Dimroth, P.; Pasedach, H.; Schefczik, E. German
Patent 1151507, 1964.
Results and Discussion
Initial experimentation was undertaken in 1-butyl-3-
methylimidazolium tetrafluoroborate ([BMIm]BF4) using
1-ethynyl-1-cyclohexanol (1a) and cyclohexylamine (2a)
as substrates under 2.5 MPa of CO2, the mixture being
heated at 100 °C for 10 h (Table 1, entry 1). After a simple
treatment as described in the Experimental Section, a
white solid was obtained. The structure was confirmed
as 4,4-pentamethylene-N-cyclohexyl-5-methylene-1,3-ox-
azolidin-2-one (3a) from the spectroscopic data and
elemental analysis. The GC-MS analysis revealed that
the peak at m/z 249 is the best choice for the molecular
ion. This implies that the nitrogen number contained in
this molecule should be odd. The base peak in the
spectrum occurs at m/z ) 168. It represents loss of m/z
(12) Fournier, J.; Bruneau, C.; Dixneuf, P. H. Tetrahedron Lett.
1990, 31, 1721.
(13) (a) Olivier-Bourbigou, H.; Magan, L. J. Mol. Catal. 2002, 182-
183, 419. (b) Dyson, P. J. Appl. Organomet. Chem. 2002, 16, 495. (c)
Dzyuba, S. V.; Bartsch, R. A. Angew. Chem., Int. Ed. 2003, 42, 148.
(d) Seddon, K. R. J. Chem. Technol. Biotechnol. 1997, 68, 351. (e)
Wilkes, J. S. Green Chem. 2002, 4, 73. (f) Zhao, D.; Wu, M.; Kou, Y.;
Min, E. Catal. Today 2002, 74, 157.
(14) (a) Welton, T. Chem. Rev. 1999, 99, 2071. (b) Gordon, C. Appl.
Catal. A 2001, 222, 101. (c) Wasserscheid, P.; Keim, W. Angew. Chem.,
Int. Ed. 2000, 39, 3772. (d) Sheldon, R. Chem. Commun. 2001, 2399.
(e) Earle, M. J.; Seddon, K. R. Pure Appl. Chem. 2000, 72, 1391. (f)
Dupont, J.; de Souza, R. F.; Suarez, P. A. Z. Chem. Rev. 2002, 102,
3667.
(15) (a) Shi, F.; Zhang, Q.; Ma, Y.; He, Y.; Deng, Y. J. Am. Chem.
Soc. 2005, 127, 4182. (b) Peng, J.; Deng, Y. New J. Chem. 2001, 25,
639.
(16) Yang, H.; Gu, Y.; Deng, Y. Chem. Commun. 2002, 274.
(17) Shi, F.; Deng, Y.; Sima T. L.; Peng, J.; Gu, Y.; Qiao, B. Angew.
Chem., Int. Ed. 2003, 42, 3257.
(18) Gu, Y.; Shi, F.; Deng, Y. J. Org. Chem. 2004, 69, 391.
J. Org. Chem, Vol. 70, No. 18, 2005 7377

Gu et al.
TABLE 2. Three-Component Reaction of 1a, 2a, and
Carbon Dioxide in CuCl/[BMIm]BF4 Systema
) 81 from the molecular ion, suggesting the presence of
cyclohexyl group. The IR spectra exhibited a sharp band
1
at 1711 cm-1 (CdO). The H NMR spectra showed the
entry
time (h)
temp (°C)
pressure(MPa)
yield (%)
absence of -NH2 and -OH proton and the presence of
two protons at 3.95 and 4.21 (s, 1H, and s, 1H), indicating
the presence of the methylene group. UV-vis spectra
exhibited a sharp band at 223 nm. This observation
implies that a conjugate action between CdO and the
methylene group may occur in this molecule. The el-
emental analysis was also in conformity with the struc-
ture 3a.
A preliminary screening of commercially available
cuprous salts as promoters for the three-component
reaction of 1a, 2a, and carbon dioxide in [BMIm]BF4 is
summarized in Table 1. As depicted, 3a was formed in
ca. 92% yield over CuCl/[BMIm]BF4 after 10 h. In this
reaction, the only identified byproduct is N-cyclohexyl-
formamide (<1%, tested by GC-MS analysis). R-Meth-
ylene cyclic carbonate, which could be formed by addition
reaction of carbon dioxide to propargylic alcohol,18 was
not detected in the present condition. CuBr and CuI also
efficiently promoted the reaction as did CuCl (entries
1-3). CuCl2 is also capable of catalyzing the synthesis
of R-methylene oxazolidinone, but the efficiency seems
to be slightly inferior as compared with that of CuCl
(entry 4). In the absence of CuCl catalyst, the reaction
seems to be sluggish, and only 9% yield of 3a was
obtained even after prolonged time (entry 5).
1
2
3
4
10
10
6
100
80
100
100
2.5
2.5
2.5
1.5
92
24
26
9b
10
a Reaction conditions: ionic liquid, 3 mL, 1a, 10 mmol; 2a, 10
mmol; CuCl, 0.2 mmol. b Conversion of 2a.
TABLE 3. Three-Component Reactions of Propargylic
Alcohols, 1a, and Carbon Dioxide in CuCl/[BMIm]BF4
Systema
To determine whether [BMIm]BF4 was an essential
factor to realize the high yield of the present three-
component reaction, the same reaction was carried out
in other ionic or molecular solvents, and the results are
presented in Table 1. [BMIm]BF4 has proved to be an
excellent medium for the synthesis of 3a. Some other
ionic liquids, such as 1-butyl-3-methylimidazolium hexa-
fluorophosphate ([BMIm]PF6) and N-butylpyridinium
tetrafluoroborate ([BPy]BF4), also worked well, but the
yields of 3a were slightly inferior (entries 6 and 7). It is
quite noteworthy that the produced 3a could be obtained
as a white solid in the [BMIm]BF4 system because all
nongaseous substrates were completely consumed after
10 h reaction. In the case of DMF, a mixture of product,
unreacted starting substrates, and solvent was obtained
after reaction; therefore the separation of product has to
be performed using column chromatography (entry 8). In
toluene and 1,2-dichloroethane, the three-component
reaction afforded no 3a and the unreacted amine 1a and
propargylic alcohol 2a were recovered, although the
reaction time was prolonged to 20 h (entries 9 and 10).
In contrast to organic solvents, enhanced reaction rates,
improved yields, and mild conditions are the features
obtained in ionic liquids. For example, the treatment of
1a and 2a with 2.5 MPa carbon dioxide in [BMIm]BF4
ionic liquid for 10 h afforded the corresponding 3a in 92%
yield, whereas the same reaction in DMF after 20 h under
5.0 MPa of carbon dioxide gave the product in 50% GC
yield (entry 11). It should be pointed out here that the
yield obtained over CuCl/[BMIm]BF4 system is much
higher than those hitherto reported for 3a.12 The use of
ionic liquids as reaction media for this transformation
avoids the use of toxic reagents or high CO2 pressure
reaction conditions to affect the reaction. This clearly
indicates the efficiency of ionic liquids for this transfor-
mation.
a Reaction conditions: ionic liquid, 3.0 mL; CuCl, 0.2 mmol;
propargylic alcohol, 10 mmol; 1a, 10 mmol; carbon dioxide, 2.5
MPa, temperature, 100 °C. b Reused in the fourth time.
We then focused our attention on investigating the
optimization of reaction conditions in CuCl/[BMIm]BF4
system, and the results are listed in Table 2. It was found
that 2.5 MPa of carbon dioxide, 100 °C, and 10 h should
be an optimum condition for the synthesis of 3a (entry
1). Under lower temperature (80 °C) and shortened time
(6 h), the substrate cannot be completely consumed, and
thus the yields were decreased (entries 2 and 3). It should
be noted that CO2 pressure appeared to considerably
affect the reaction. Low pressure (1.5 MPa) led to poor
conversion level (entry 4). By contrast, the desired
product 3a could be obtained with good yield at 2.5 MPa.
In addition to the high yield of product, our optimized
conditions are milder and more attractive compared with
that of literature,12 in which 5.0 MPa, 110 °C, and 20 h
were required to affect reaction.
To prove the general utility of the above protocol, a
variety of propargylic alcohols were used to react with
7378 J. Org. Chem., Vol. 70, No. 18, 2005

Ionic Liquid as Promoting Medium for Fixation of CO2
TABLE 4. Three-Component Reactions of 2a, Amines,
and Carbon Dioxide in CuCl/[BMIm]BF4 Systema
subsequent reaction, [BMIm]BF4 as well as CuCl catalyst
were reused intact simply after evacuation under reduced
pressure to remove the resulting water in the previous
run. In the reaction of 1a, 2a, and carbon dioxide, the
[BMIm]BF4/CuCl system can be reused up to four times,
although with some loss of activity (Table 3, entry 6).
Conclusion
In summary, we have demonstrated that the three-
component reactions between propargylic alcohols, ali-
phatic amines, and CO2 can be successfully conducted
in [BMIm]BF4/CuCl system under relatively mild condi-
tions. By this green approach, several new 5-methylene-
1,3-oxazolidin-2-ones were prepared in excellent yields
and purity and were well-characterized. The solvent ionic
liquid as well as CuCl catalyst can be recovered and
reused three times without appreciable loss of activity.
Moreover, this methodology offers significant improve-
ments with regard to yield of products, simplicity in
operation, cost efficiency, and green aspects avoiding toxic
or expensive reagents.
Experimental Section
Synthesis of 5-Methylene-1,3-oxazolidin-2-ones and
Analysis. All reactions were conducted in a 100-mL autoclave
with glass tube inside equipped with magnetic stirring. In each
reaction, ionic liquid, 3 mL, propargylic alcohol (10 mmol),
amine (10 mmol), catalyst (0.2 mmol), and CO2 (1.5-2.5 MPa)
were successively introduced and reacted at 100 °C for the
desired period. After reaction, the reaction vessel was cooled
to room temperature, and the resulting mixture was extracted
with diethyl ether (4 mL × 3). To determine the substrate
conversion, the combined organic phase was then analyzed
with GC-MS (qualitative analysis) and GC equipped with a
FID detector (quantitative analysis). Then, the combined
organic phase was evaporated and dried in a vacuum to afford
the primary product. A pure product was obtained by further
recrystallization of the primary product with a solution
containing water and ethanol.
a Reaction conditions: ionic liquid, 3.0 mL; CuCl, 0.2 mmol; 2a,
10 mmol; amine, 10 mmol; carbon dioxide, 2.5 MPa; temperature,
100 °C, reaction time, 10 h.
Spectroscopic Data for Products. 4,4-Pentamethylene-
N-cyclohexyl-5-methylene-1,3-oxazolidin-2-one (3a): White
solid (yield: 92%, 2.29 g) mp 120-123 °C; δH (400; CCl3D)
1.00-1.92 (20 H, m), 3.48 (1H, m), 3.93 (1H, d, J ) 2.8 Hz),
and 4.21 (1H, d, J ) 2.8 Hz) ν/cm-1 1711 (CdO); λmax/nm 223,
GC-MS: m/z ) 249 (M+), 168, 124, 112, 91, 79, 67, 55, 41;
C15H23NO2 (249.352) Calcd: C, 72.25; H, 9.30; N, 5.62.
Found: C, 71.98; H, 9.55; N, 5.77.
1a and CO2 under conditions identical to those of 3a over
10-15 h. As indicated in Table 3, various commercially
available propargylic alcohols, including 3,4-dimethyl-1-
pentyn-3-ol (2b), 1-ethynyl-1-cyclopentanol (2c), and
2-phenyl-3-butyn-2-ol (2d), have been successfully used.
The corresponding 5-methylene-1,3-oxazolidin-2-one 3b,
3c, and 3d could be obtained in 84-95% yields (entries
1-3). As to secondary and primary propargylic alcohols,
even no desired products were detected which showed
that such a reaction seems to be specific for tertiary
alcohols (entries 4 and 5).
Variation of amines was also examined, and the results
are listed in Table 4. In the presence of 2a, the reactions
of benzylamine (1e), allylamine (1f), n-butylamine (1g),
and n-heptylamine (1h) were found to proceed smoothly
with yields in the range of 78-89% (entries 1-4). As to
aniline, only unreacted amine and 2a were recovered
(entry 5). An aliphatic diamine, hexamethylenediamine
(1i), also underwent the three-component reaction to give
the double nucleus compound 3i in 82% isolated yield
(entry 6).
4-Methyl-4-isopropyl-N-cyclohexyl-5-methylene-1,3-
oxazolidin-2-one (3b): White solid (yield: 84%, 1.99 g) mp
99-101 °C; δH (400; CCl3D) 0.89 (1H, d, J ) 6.4), 0.96-1.17
(7H, m), 1.20-1.36 (4H, m), 1.44 (3H, s), 1.63-1.78 (3H, m),
1.79-1.86 (2H, m), 3.59 (1H, t, J ) 12.0 Hz), 3.94 (1H, d, J )
2.8 Hz), and 4.25 (1H, d, J ) 2.4 Hz) ν/cm-1 1762 (CdO); λmax
/
nm 224, GC-MS: m/z ) 237 (M+), 195, 194, 178, 156, 113,
112, 83, 67, 55, 41; C14H23NO2 (237.341) Calcd: C, 70.85; H,
9.77; N, 5.90. Found: C, 70.64; H, 9.91; N, 5.99.
4,4-Tetramethylene-N-cyclohexyl-5-methylene-1,3-ox-
azolidin-2-one (3c): White solid (yield: 87%, 2.05 g) mp 73-
75 °C; δH (400; CCl3D) 1.00-2.07 (18 H, m), 3.59 (1H, m), 4.01
(1H, d, J ) 2.8 Hz), and 4.22 (1H, d, J ) 2.8 Hz) ν/cm-1 1711
(CdO); λmax/nm 224, GC-MS: m/z ) 235 (M+), 154, 112, 93,
77, 67, 55, 41; C14H21NO2 (235.325) Calcd: C, 71.46; H, 8.99;
N, 5.95. Found: C, 71.74; H, 9.23; N, 6.11.
4-Methyl-4-phenyl-N-cyclohexyl-5-methylene-1,3-ox-
azolidin-2-one (3d): White solid (yield: 95%, 2.57 g) mp 109-
110 °C; δH (400; CCl3D) 0.95-1.88 (13 H, m), 3.35 (1H, m),
4.11 (1H, s), 4.36 (1H, s), and 7.27-7.48 (4 H, m), ν/cm-1 1709
(CdO); λmax/nm 221 and 263, GC-MS: m/z ) 271 (M+), 190,
In these synthetic reactions of 5-methylene-1,3-oxazo-
lidin-2-ones, the products could be conveniently isolated
by means of liquid-liquid extraction, thus allowing the
recycling of both catalyst and ionic liquid. For the
J. Org. Chem, Vol. 70, No. 18, 2005 7379

Gu et al.
146, 130, 118, 103, 91, 77, 67, 55, 41; C17H21NO2 (271.358)
Calcd: C, 75.25; H, 7.80; N, 5.16. Found: C, 75.39; H, 7.62;
N, 5.27.
4,4-Pentamethylene-N-heptyl-5-methylene-1,3-oxazo-
lidin-2-one (3h): White solid (yield: 89%, 2.36 g) mp 41-43
°C; δH (400; CCl3D) 0.88 (3H, t, J ) 6.8 Hz), 1.27-1.87 (20 H,
m), 3.43 (2H, t, J ) 7.4 Hz), 3.96 (1H, d, J ) 2.4 Hz), and 4.07
(1H, d, J ) 2.8 Hz) ν/cm-1 1766 (CdO); λmax/nm 225, GC-MS:
m/z ) 265 (M+), 210, 192, 181, 168, 151, 136, 122, 79, 67, 55,
41; C16H27NO2 (265.395) Calcd: C, 72.41; H, 10.25; N, 5.28.
Found: C, 72.59; H, 10.01; N, 5.14.
N,N′-Hexamethylene-bis(4,4-pentamethylene-5-meth-
ylene-1,3-oxazolidin-2-one) (3i): White solid (yield: 82%,
3.41 g) mp 139-140 °C; δH (400; CCl3D) 1.25-1.87 (28 H, m),
3.43 (4H, t, J ) 7.2 Hz), 3.96 (2H, d, J ) 2.8 Hz), and 4.06
(2H, d, J ) 2.8 Hz) ν/cm-1 1755 (CdO); λmax/nm 227, MS: m/z
) 416 (M+), 375, 331, 250, 236, 206, 192, 181, 159, 150, 136,
122, 108, 94, 79, 67, 55, 41; C24H36N2O4 (416.560) Calcd: C,
69.20; H, 8.71; N, 6.72. Found: C, 69.47; H, 8.62; N, 6.53.
4,4-Pentamethylene-N-benzyl-5-methylene-1,3-oxazo-
lidin-2-one (3e): White solid (yield: 88%, 2.26 g) mp 174-
177 °C; δH (400; CCl3D) 1.19-1.76 (9 H, m), 1.88 (1H, s), 3.93
(1H, d, J ) 2.4, Hz), 4.11 (1H, d, J ) 2.8, Hz), 4.65 (2 H, s),
and 7.24-7.35 (5 H, m) ν/cm-1 1708 (CdO); λmax/nm 219 and
252, GC-MS: m/z ) 257 (M+), 215, 202, 170, 122, 91, 77, 65,
55, 41; C16H19NO2 (257.332) Calcd: C, 74.68; H, 7.44; N, 5.44.
Found: C, 74.82; H, 7.25; N, 5.57.
4,4-Pentamethylene-N-allyl-5-methylene-1,3-oxazolidin-
2-one (3f): White solid (yield: 78%, 1.61 g) mp 46-47 °C; δH
(400; CCl3D) 1.22-1.77 (10 H, m), 3.98 (1H, d, J ) 2.4 Hz),
4.04 (2H, s), 4.07 (1H, d, J ) 1.6 Hz), 5.13-5.27 (2 H, m), and
5.70-5.79 (1 H, m) ν/cm-1 1768 (CdO); λmax/nm 221, GC-MS:
m/z ) 207 (M+), 162, 152, 134, 120, 106, 94, 81, 67, 55, 41;
C12H17NO2 (207.272) Calcd: C, 69.54; H, 8.27; N, 6.76.
Found: C, 69.81; H, 8.25; N, 6.69.
4,4-Pentamethylene-N-butyl-5-methylene-1,3-oxazoli-
din-2-one (3g): White solid (yield: 80%, 1.78 g) mp 61-63
°C; δH (400; CCl3D) 0.944 (3H, m), 1.23-1.68 (14 H, m), 3.44
(2H, t, J ) 5.6 Hz), 3.96 (1H, d, J ) 2.8 Hz), and 4.00 (1H, d,
J ) 3.2 Hz) ν/cm-1 1768 (CdO); λmax/nm 221, GC-MS: m/z )
223 (M+), 208, 181, 168, 137, 122, 112, 106, 94, 79, 67, 55, 41;
C13H21NO2 (223.314) Calcd: C, 69.92; H, 9.48; N, 6.27.
Found: C, 69.80; H, 9.59; N, 6.50.
Acknowledgment. This work was financially sup-
ported by the National Natural Science Foundation of
China (No. 20225309).
Supporting Information Available: General experimen-
tal methods, 1H NMR, UV-vis, MS, and IR spectra of
compounds a-i (PDF). This material is available free of charge
via the Internet at http://pubs.acs.org.
JO050802I
7380 J. Org. Chem., Vol. 70, No. 18, 2005