A novel way to chiral 2-oxazolidinones: selenium-catalyzed cyclocarbonylation of 2-aminoethanols

Article abstract of DOI:10.1016/j.tet.2007.09.037

Selenium-catalyzed cyclocarbonylation of 2-aminoethanols with CO under atmospheric pressure at 30 °C afforded 2-oxazolidinones in excellent yields without any other co-catalyst. The method was then applied to the syntheses of chiral 2-oxazolidinones and no racemization was detected.

Full text of DOI:10.1016/j.tet.2007.09.037

Tetrahedron 63 (2007) 12419–12423
A novel way to chiral 2-oxazolidinones: selenium-catalyzed
cyclocarbonylation of 2-aminoethanols
Peng Li,a,b Xiaohua Yuan,a Shudong Wanga and Shiwei Lua,
*
aNational Engineering Research Center for Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences,
161 Zhongshan Road, Dalian, Liaoning 116011, PR China
bGraduate University of Chinese Academy of Sciences, Beijing 100049, PR China
Received 8 May 2007; revised 16 September 2007; accepted 18 September 2007
Available online 22 September 2007
Abstract—Selenium-catalyzed cyclocarbonylation of 2-aminoethanols with CO under atmospheric pressure at 30 ꢀC afforded 2-oxazolidi-
nones in excellent yields without any other co-catalyst. The method was then applied to the syntheses of chiral 2-oxazolidinones and no
racemization was detected.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
knowledge, catalytic carbonylation reactions of chiral
2-aminoethanols with carbon monoxide to obtain chiral
2-oxazolidinones have not been investigated.
2-Oxazolidinones are a very important class of heterocyclic
compounds. Some molecules containing the 2-oxazolidinone
moiety have shown antibacterial activity,1 and the chiral
2-oxazolidinones have been used as chiral auxiliaries in
a wide range of asymmetric reactions.2–10 A variety of
conventional syntheses of 2-oxazolidinones have been devel-
oped from 2-aminoethanols as starting materials. Syntheses of
2-oxazolidinones were carried out by cyclization of alkyl or
aryl carbamates under either acidic11 or basic12,13 conditions,
cyclization of triphenylphosphonium salts14 or N-nitroso
compounds,15 and carbonylation of 2-aminoethanols with
phosgene,16,17 diphosgene,18,19 triphosgene,20,21 urea,22 or
cyanates.17,23 Most of these preparative methods need drastic
conditions (high temperature or strong acid or base) or toxic
compounds such as phosgene or phosgene derivatives.
Selenium-catalyzed carbonylation reaction of 2-aminoetha-
nols has been proved to be an excellent method for the cheap
and easily available catalyst, mild reaction conditions, and
reaction process phase transfer property.33 This method
was first reported by Koch and Perrotti in 1974,34 and then
improved by Sonoda, in whose works the reaction proceeded
under atmospheric pressure at room temperature but suf-
fered from large amounts of strong base.35 In the course of
our ongoing studies on the selenium-catalyzed carbonyl-
ation reactions using CO, we had investigated the influence
of the oxidants to the cyclocarbonylation reaction of ethanol-
amine under pressurized conditions at 150–160 ꢀC and
found that molecular oxygen served as the best oxidants.36
Most recently, we are surprised to find that 2-oxazolidinones
can be obtained in excellent yields in the absence of any ba-
sic compound under mild conditions (1 atm, 30 ꢀC). No ra-
cemization has been detected when we apply this method to
the syntheses of chiral 2-oxazolidinones. Herein we report
a first synthesis of both racemic and chiral 2-oxazolidinones
using the selenium-catalyzed carbonylation of correspond-
ing 2-aminoethanols with bubbling CO in CH3CN under
atmospheric pressure at 30 ꢀC for the first time.
Nowadays, as an alternative, direct carbonylation of 2-
aminoethanols with carbon monoxide is an attractive and ef-
fective way to prepare these heterocyclic compounds in view
of environmental concerns. Recently, many efforts have
been addressed to the transition metal catalyzed intramolec-
ular cyclocarbonylation of 2-aminoethanols.24–30 Although
some advancement has been achieved, the reaction condi-
tions are still stern and the catalysts used are usually expen-
sive. The cyclocarbonylation reactions in the presence of
elemental sulfur have also been investigated, but equivalent
moles of sulfur and base or otherwise relatively stern reac-
tion conditions are required.31,32 Furthermore, to our best
2. Results and discussion
2.1. Carbonylation of ethanolamine under various
conditions
Keywords: Chiral 2-oxazolidinones; 2-Aminoethanols; Carbon monoxide;
Selenium.
Ethanolamine (1a) was treated with bubbling mixed gas of
carbon monoxide and oxygen in the presence of 5 mol %
* Corresponding author. Tel.: +86 411 83699167; fax: +86 411 83698749;
e-mail: lusw@dicp.ac.cn
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.09.037

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P. Li et al. / Tetrahedron 63 (2007) 12419–12423
of selenium in acetonitrile at 30 ꢀC for 8 h. Oxidative car-
bonylation of 1a proceeded efficiently to give 2-oxazolidi-
none (2a) in 93% yield (Table 2, entry 1). Reaction
conditions of 1a were examined at atmospheric pressure
(Table 1). When protic solvents such as CH3CH2OH and
H2O were used as solvents at 30 ꢀC, the selenium did not dis-
solve during the bubbling of CO through the media and so,
no carbonylation of 1a occurred (Table 1, entries 1 and 2).
The reaction proceeded to some extent in aprotic solvents
such as tetrahydrofuran (THF), acetone, and ethylene glycol
diethyl ether (EGDE) (Table 1, entries 3–5). When CH3CN
and N,N-dimethylformamide (DMF) were used as the car-
bonylation solvents, the reaction went smoothly and gave
excellent yields of 2-oxazolidinone (Table 1, entries 6 and
7). It is noteworthy that elemental selenium dissolved
much more slowly in ethylene glycol diethyl ether than in
THF or in acetone, but the subsequent oxidation carbonyla-
tion process was faster. An increase of the concentration of
the substrate by three times in the reaction system decreased
the yield of 2-oxazolidinone, but not severely (Table 1, entry
8). Elevated temperature at 50 ꢀC was favorable to the car-
bonylation process on account of the shortened reaction
time (Table 1, entry 9). However, a further elevation of the
temperature to 70 ꢀC decreased the yield of 2a (Table 1, en-
try 10). Oxygen was an excellent oxidant to the current car-
bonylation. Although both hydrogen peroxide and DMSO
(CH3SOCH3) were effective oxidants in our previous tri-
als,36 they showed poor, or even in the worst, and no activity
under current reaction conditions (Table 1, entries 11 and 12,
respectively). Despite the fact that the cyclocarbonylation
reaction went smoothly without any other additional bases
as co-catalyst, it was proved that tertiary amines such as tri-
ethylamine could promote the present reaction to some
extent. For example, carbonylation process in DMF gave
only 52% yield of 2-oxazolidinone at 18 ꢀC in 8 h while
84% yield of 2-oxazolidinone was produced in the presence
of 1 equiv of triethylamine (Table 1, entries 13 and 14, re-
spectively). Moreover, the carbonylation reaction at 30 ꢀC
finished in 5 h in the presence of 1 equiv triethylamine
(3 h faster than that without triethylamine) and gave 95%
yield of 2-oxazolidinone (Table 1, entry 15). On the one
hand, triethylamine promoted the present carbonylation
reactions. On the other hand, it brought other problems to
the process besides economic considerations. Due to the sta-
bilization effect of triethylamine to the selenium-containing
intermediates and active species generated in the reaction
system, it became more difficult to precipitate selenium
thoroughly by oxygen oxidation, and usually, the sele-
nium-containing intermediates left in the mother liquid
consequently brought an bothersome color to the products.
The selenium catalyst remained its activity when it was
recycled (Table 1, entries 16 and 17 for the first recycling
and the second recycling of the catalyst, respectively).
2.2. Carbonylation of substituted 2-aminoethanols
Various substituted 2-aminoethanols including chiral 2-
aminoethanols were treated in the similar way as ethanol-
amine and some representative results are listed in Table 2.
2-Oxazolidinones were consistently obtained in excellent
yields (90–96%) within 8–9 h. Despite of the generality of
the present catalytic system, reaction times revealed that
2,2-dimethyl ethanolamine and phenylglycinol were a little
less reactive (Table 2, entries 2 and 5, respectively) than
other substrates employed. This phenomenon may be attrib-
uted to the steric effect of the relatively large substituents
contained in these two molecules. For 2e, 2g, and 2j, the
enantiomeric excess was analyzed by HPLC37 and as ex-
pected, no racemization of the products was detected
(>99% ee). This made our present method a powerful tool
to obtain useful chiral auxiliaries of this kind. Presently, their
synthesis needs two steps: the acylation of amino group and
the intramolecular cyclization.38 Usually, the reaction condi-
tions are stern and the atom economy is low. Among the
compounds synthesized, 2g and 2h are well known as Evans
Reagents and widely used in asymmetric synthesis. No reac-
tion occurred when the present methodology was applied to
the carbonylation reaction of 2-aminophenol.
Table 1. Carbonylation of ethanolamine (1a) to 2-oxazolidinone (2a)
Entrya Solvent
Oxidant Temp (ꢀC) Time (h) Yield (%)
2.3. Proposed pathway of the carbonylation reaction
1
2
3
EtOH
H2O
THF
O2
O2
O2
30
30
30
30
30
30
30
30
50
70
30
30
18
18
30
30
30
8
8
8
0
0
A reaction process involving a phase transfer phenomenon
of the catalyst33 was presented during the above-discussed
reactions. Prior to the introduction of CO into the reaction
mixture, the catalytic system was heterogeneous and the cat-
alyst selenium was observed as a powder. As the reaction
proceeded the selenium was completely dissolved and the
system became homogeneous. When the reaction was
quenched by stopping the bubbling of CO but continuing
the introduction of O2, the light-yellowish selenium species
was oxidized to form a gray selenium precipitate which can
be easily recovered. These results suggested that the present
catalytic system was bestowed with advantages of both ho-
mogeneous and heterogeneous catalysis. The reason for
the dissolvation of elemental selenium during the reaction
process could be the in situ formation of SeCO, a key inter-
mediate in selenium-catalyzed carbonylation and/or reduc-
tion reactions.39,40 Ethanolamine could attack SeCO to
form the ammonium intermediate I (Scheme 1), which could
subsequently undergo intramolecular nucleophilic replace-
ment to give 2-oxazolidinone and salt of hydrogen selenide
63
57
78
93
93
86
94
56
11
0
4
5
6
Acetone O2
O2
8
8
EGDEb
DMFc
O2
O2
8
8
7
CH3CN
DMF
8d
9
O2
O2
15
6
CH3CN
CH3CN
CH3CN
CH3CN
DMF
10
11
12
13
14e
15e
16f
17g
O2
8
H2O2
DMSO
O2
O2
O2
10
8
8
8
5
52
84
95
92
93
DMF
CH3CN
CH3CN
CH3CN
O2
O2
8
8
a
Reaction conditions: ethanolamine, 10 mmol; Se, 0.5 mmol; solvent,
10 ml; bubbling CO and O2 (v/v¼8:1), 1 atm.
EGDE¼ethylene glycol diethyl ether.
b
c
d
e
f
DMF¼N,N-dimethylformamide.
Ethanolamine of 40 mmol was delivered.
Triethylamine of 10 mmol was added.
Recycled catalyst for the first time.
g
Recycled catalyst for the second time.

P. Li et al. / Tetrahedron 63 (2007) 12419–12423
Table 2. Carbonylation of aminoethanols to 2-oxazolidinones
12421
Entrya
Config
Reactant
Cyclic product
Isolated yield (%)
Product’s mp (ꢀC) (references)
H
N
O
O
HO
1
—
93
91–92 (88–8926
)
NH2
(1a)
(2a)
O
O
2b
—
DL
DL
D
93
96
96
90
93
93
53–55 (55.6–56.442
)
N
H2N
(1b)
OH
NH2
NH2
H
(2b)
H
N
O
O
HO
3
Oil
Oil
(1c)
(2c)
H
N
O
O
HO
4
(1d)
(2d)
H
Ph
Ph
*
N
*
5b
132–133 (132–13343
)
O
H2N
OH
OH
O
(1e)
(2e)
H
N
*
*
6
D
58–60 (oil26
)
O
H2N
O
(1f)
(2f)
H
N
Ph
*
*
Ph
87–88 (87–8826
)
O
7
L
H2N
OH
O
(1g)
(2g)
H
*
N
*
O
8
9
L
L
L
95
96
96
73 (69–7026
)
H2N
OH
O
(2h)
(1h)
H
N
*
*
O
Oil
Oil
H2N
OH
O
(2i)
(1i)
H3CS
H
N
H3CS
*
*
O
10
H2N
OH
O
(2j)
(1j)
a
Reaction conditions: aminoethanols, 10 mmol; Se, 0.5 mmol; CH3CN, 10 ml; bubbling CO and O2 (v/v¼10:1), 1 atm; 30 ꢀC; 8 h.
b
Reaction for 9 h.
III. Further oxidation of III could recover the elemental
3. Conclusion
selenium and release a molecule of water. We do not believe
that triethylamine is essential to the present reaction and eth-
anolamine alone could be basic enough to stabilize the in situ
generated selenium-containing species. In this respect, we
propose that the present selenium-catalyzed carbonylation
process could be self-promoted.
In summary, we have developed an efficient synthetic
method for 2-oxazolidinones especially for chiral 2-oxazoli-
dinones from 2-aminoethanols under very mild conditions.
The catalytic system is simple. Both the catalyst and the
solvent used can be easily recycled.

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P. Li et al. / Tetrahedron 63 (2007) 12419–12423
1H), 4.64 (m, 1H), 7.38 (br, 1H). 13C NMR (DMSO-d6)
d 20.5, 46.5, 72.3, 159.0.
HO
NH2
.
SeCO H2N
OH
4.2.3. 4-Ethyl-2-oxazolidinone (2d). Purified by short-
column chromatography (petroleum ether/AcOEt, 5:3); H
1
CO
NMR (CDCl3) d 0.93 (t, 3H), 1.58 (m, 2H), 3.84 (m, 1H),
4.01 (t, 1H), 4.48 (t, 1H), 7.33 (br, 1H). 13C NMR (CDCl3)
d 8.4, 27.4, 53.1, 69.3, 159.9.
NHCOSe- +NH3CH2CH2OH
I
HO
O
.
Se H2N
OH
H2O
4.2.4. 4-Phenyl-2-oxazolidinone (2e). Purified by recrystal-
lization from petroleum ether and acetone; 1H NMR
(DMSO-d6) d 4.00 (t, 1H), 4.67 (t, 1H), 4.94 (t, 1H), 7.31–
7.42 (m, 5H), 8.23 (br, 1H). 13C NMR (DMSO-d6) d 55.3,
71.6, 126.2, 128.2, 128.9, 141.1, 159.2; (>99% ee).
O2
OH
HSe- +NH3CH2CH2OH
III
Se- +NH3CH2CH2OH
II
N
H
4.2.5. 4-Methyl-2-oxazolidinone (2f). Purified by short-
column chromatography (petroleum ether/AcOEt, 1:1); H
NMR (DMSO-d6) d 1.17 (q, 3H), 3.83–3.94 (m, 2H), 4.41
(m, 1H), 7.68 (br, 1H). 13C NMR (DMSO-d6) d 20.2, 47.1,
70.2, 158.4.
O
1
O
NH
Scheme 1. Proposed pathway of the carbonylation reaction.
4.2.6. 4-Benzyl-2-oxazolidinone (2g). Purified by short-
column chromatography (petroleum ether/AcOEt); 1H NMR
(DMSO-d6) d 2.72–2.85 (m, 2H), 3.97–4.05 (m, 2H), 4.25
(t, 1H), 7.24–7.33 (m, 5H), 7.82 (br, 1H). 13C NMR
(DMSO-d6) d 40.3, 52.5, 52.6, 68.1, 126.7, 128.5, 129.5,
136.6, 158.8; (>99% ee).
4. Experimental
4.1. General
2-Aminoethanols 1a–f, elemental selenium (99.95%), car-
bon monoxide (99.9%), and all the organic solvents were
all reagent grade and were used as received without further
purification. 2-Aminoethanols 1h–j were reduced from the
corresponding amino acids according to the literature.41
Melting points were determined on a Taike X-4 apparatus
(Beijing, China) and were uncorrected.
4.2.7. 4-Isopropyl-2-oxazolidinone (2h). Purified by short-
column chromatography (petroleum ether/AcOEt, 5:3) fol-
lowed by recrystallization from petroleum ether; H NMR
1
(DMSO-d6) d 0.80–0.86 (dd, 6H), 1.60 (m, 1H), 3.52 (m,
1H), 3.98 (q, 1H), 4.31 (t, 1H), 7.79 (br, 1H). 13C NMR
(DMSO-d6) d 18.2, 18.3, 32.8, 57.9, 67.9, 159.7.
4.2. A typical procedure for the synthesis of 2-oxazoli-
dinone from ethanolamine and carbon monoxide
catalyzed by selenium
4.2.8. 4-Isobutyl-2-oxazolidinone (2i). Purified by short-
column chromatography (petroleum ether/AcOEt, 5:1); H
NMR (DMSO-d6) d 0.92 (m, 6H), 1.31 (m, 1H), 1.43 (m,
1H), 1.67 (m, 1H), 3.83–3.92 (m, 2H), 4.42 (m, 1H), 7.78
(br, 1H). 13C NMR (DMSO-d6) d 21.6, 22.6, 23.8, 43.9,
49.6, 69.2, 158.4.
1
Ethanolamine (10 mmol, 0.61 g) was dissolved in 10 ml of
CH3CN to which was added 0.5 mmol (0.0395 g) of elemen-
tal selenium, and carbon monoxide was bubbled into the
solution at a rate of 12 ml/min for about 15 min at 30 ꢀC
(ambient temperature) until the gray selenium was dissolved
completely. Then oxygen gas was passed through the solu-
tion in about 12% volume of carbon monoxide for 8 h.
Finally the carbon monoxide stream was stopped while
oxygen was continued to recover the selenium. Filtration of
the selenium followed by removal the solvent gave the crude
2-oxazolidinone stoichiometrically. Further purification by
short-column chromatography (silica gel, AcOEt) afforded
2a in 93% (0.81 g) yield as a white solid; 1H NMR
(DMSO-d6) d 3.45 (q, 2H), 4.30 (t, 2H), 7.45 (br, 1H).
13C NMR (DMSO-d6) d 39.9, 64.2, 159.7.
4.2.9. 4-(2-Methylsulfanyl-ethyl)-2-oxazolidinone (2j).
Purified by short-column chromatography (petroleum
ether/AcOEt, 5:3); H NMR (DMSO-d6) d 1.71 (m, 2H),
1
2.01 (s, 3H), 2.46 (m, 2H), 3.81–3.96 (m, 2H), 4.38 (t,
1H), 7.79 (br, 1H). 13C NMR (DMSO-d6) d 15.3, 29.6,
35.1, 51.6, 69.6, 159.4; (>99% ee).
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