Synthesis of 2-oxazolidinones from CO2 and 1,2-aminoalcohols catalyzed by n-Bu2SnO

Article abstract of DOI:10.1055/s-2002-19780

The dehydrative condensation of 1,2-aminoalcohols with CO₂ is found to proceed in NMP as solvent; 2-oxazolidinones are obtained in the yields of 53-94% when a commercially available tin compound, n-Bu₂SnO is used as catalyst.

Full text of DOI:10.1055/s-2002-19780

LETTER
307
Synthesis of 2-Oxazolidinones from CO2 and 1,2-Aminoalcohols Catalyzed by
n-Bu2SnO
S
ynthesis of 2-Oxa
e
zolidinone
n
s
fromCO
a
-
nd 1, 2-A
i
minoa
c
lcohols hi Tominaga, Yoshiyuki Sasaki*
2
Research Institute for Green Technology, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa,
Tsukuba, 305-8569, Japan
Fax +81(298)618175; E-mail: y.sasaki@aist.go.jp
Received 5 November 2001
R2
R3
Abstract: The dehydrative condensation of 1,2-aminoalcohols
with CO2 is found to proceed in NMP as solvent; 2-oxazolidinones
are obtained in the yields of 53–94% when a commercially avail-
able tin compound, n-Bu2SnO is used as catalyst.
R2
R3
n-Bu2SnO
R1HN
+ CO2
O
R1HN
OH
O
1a R1=Me, R2=R3=H
b R1=Et, R2=R3=H
c R1=R2=R3=H
d R1=R2=H, R3=Me
e R1=H, R2=R3=Me
2
Key words: carbon dioxide, aminoalcohols, oxazolidinone, tin, ca-
talysis
2-Oxazolidinones are useful intermediates for the synthe-
ses of polymers, agricultural chemicals, biologically ac-
tive compounds and so on. Since their preparation
generally uses highly toxic phosgene or isocyanates, and
therefore involves environmental and safety problems,
much effort has been directed toward the dehydrative con-
densation of 1,2-aminoalcohol with CO2. The reaction of
2-(methylamino)ethanol with CO2, however, gave only
1,4-dimethylpiperazine in water solvent and without any
catalyst,1 while 1-methylamino-2-propanol reacted with
CO2 to give 3,5-dimethyl-2-oxazolidinone in the yield of
58% under similar conditions.2 It was reported, on the oth-
er hand, that when triphenylstibine oxide was used as cat-
alyst even 2-(methylamino)ethanol reacted with CO2 to
give 3-methyl-2-oxazolidinone in the yield of 48%.3 Un-
fortunately, this catalyst failed to promote the reaction of
2-aminoethanols without N-substituent giving only small
amounts of 2-oxazolidinones. In order for this reaction to
proceed, it was necessary to add some dehydrating re-
agents such as phosphorus compounds4 or carbodiim-
ides.5 However, this method inevitably causes the
problems of increased costs and by-product formation.
The same can be applied to the utilization of aziridines,
the dehydrated form of 1,2-aminoalcohols, in their cyclo-
addition reactions with CO2 to 2-oxazolidinones.6 In the
course of our investigations to develop effective catalysts
for the synthesis of 2-oxazolidinones, we have found that
NMP is an excellent solvent and n-Bu2SnO can be used as
catalyst for the dehydrative condensation of 1,2-aminoet-
hanols with CO2 to give 2-oxazolidinones (Scheme 1). It
may be noteworthy that this catalyst is commercially
available in the form of powder and easy to handle be-
cause of its stability in the air.
Scheme 1
In a typical experiment, 1,2-aminoalcohols (10.0 mmol),
solvent (8.0 mL), and n-Bu2SnO (1.0 mmol) were charged
in a 50 mL-autoclave. After CO2 was introduced at an ini-
tial pressure of 5 MPa, the autoclave was heated at 180 °C
for 16 hours. The resulted reaction solutions were ana-
lyzed with GLC. The isolation of products was effected by
the fractional distillation of reaction solutions under re-
duced pressure. They were further purified with prepara-
tive GLC if necessary for identification. The products
1
were identified by comparing their FTIR, MS, and H
NMR spectra with those of the corresponding authentic
samples.
Figure 1 Effect of the amount of n-Bu2SnO. 2-(Methylamino)etha-
nol (10.0 mmol), NMP (8.0 mL), CO2 (5 MPa), 180 °C, 16 h.
= 3-methyl-2-oxazolidinone, = 2-(methylamino)ethanol.
Synlett 2002, No. 2, 01 02 2002. Article Identifier:
1437-2096,E;2002,0,02,0307,0309,ftx,en;Y22101ST.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0936-5214

308
K.-i. Tominaga, Y. Sasaki
LETTER
The effect of the amount of catalyst for the reaction of 2-
(methylamino)ethanol (1a) in N-methylpyrrolidone
(NMP) solvent is shown in Figure 1. All the reaction so-
lutions obtained are homogeneous and pale yellow in col-
or. While the reaction without a catalyst gives only 10%
of 3-methyl-2-oxazolidinone (2a) based on 1a introduced,
its yield increases up to 94% with increase in the amount
of n-Bu2SnO. The turnover numbers (TON) calculated
based on the differences between the amounts of 2a ob-
tained with catalyst and that without catalyst (0.95mmol)
were 8, 14 and 23 for the reactions with 1.0, 0.5 and
0.2mmol of the catalyst respectively.
The results with various 1,2-aminoalcohols and several
solvents are summarized in the Table. As for the choice
of solvent, NMP was much more effective than protic or
non-polar solvents (Runs 1, 3, and 4). The reaction with
2-(ethylamino)ethanol (1b) gave almost the same results
as that of 1a (Runs 5 and 6). On the other hand, the reac-
tivity of 1,2-aminoalcohols without N-substituent (1c–e)
towards CO2 was somewhat different; the corresponding
2-oxazolidinones were formed in fair yields even in the
absence of catalyst, but the addition of n-Bu2SnO still im-
proved their yields by more than 50% (Runs 1–12).
Figure 2 Electrospray mass spectra of the reaction solution of 1c:
(a) a calculated isotope distribution spectrum corresponding to
[C10H23ONSn + H]+ and (b) an observed spectrum7
The positive electrospray mass spectrum of the reaction
solution of 1c (Figure 2) shows the presence of stannaox-
azolidine 3, which may be derived from 1c and n-Bu2SnO.
Based on this observation, we propose the reaction mech-
anism as shown in Scheme 2. Since Sn-N bond is known
to be susceptible to CO2 insertion,8 a cyclic tin carbamate
4 may be formed through the insertion of CO2 into 3. Sub-
sequent intramolecular nucleophilic attack of alkoxy
group on a carbonyl carbon atom may cause the elimina-
tion of 2-oxazolidinone regenerating the starting tin oxide.
Table Synthesis of 2-Oxazolidinones from 1,2-Aminoalcohols and
CO2 catalyzed by n-Bu2SnOa
O
Run
Amino
alcohol
n-Bu2SnO Solvent
(mmol)
Conv. of 1 Yield of 2
n-Bu2Sn
(%)
98
24
89
97
83
24
87
67
90
63
100
75
(%)b
94
10
59
55
76
8
CO2
H2O
N
H
3
1
2
1a
1a
1a
1a
1b
1b
1c
1c
1d
1d
1e
1e
1.0
–
NMP
NMP
EtOH
toluene
NMP
NMP
NMP
NMP
NMP
NMP
NMP
NMP
H2N
OH
O
n-Bu2Sn
n-Bu2SnO
3
1.0
1.0
1.0
–
NH
O
4
4
O
O
NH
5
6
O
7
1.0
–
53
30
73
41
85
56
Scheme 2
8
9
1.0
–
References
10
11
12
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53, 10261c.
(2) Steele, A. B. U.S. Patent 2868801, 1959; Chem. Abstr. 1959,
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(3) Matsuda, H.; Baba, A.; Nomura, R.; Kori, M.; Ogawa, S.
Ind. Eng. Chem. Prod. Res. Dev. 1985, 24, 239.
(4) Akasaki, Y.; Hatano, S.; Fukuyama, M. Jpn. Kokai Tokkyo
Koho 78111062, 1979; Chem. Abstr., 1979, 90, 72191.
1.0
–
a Reaction conditions: 1,2-aminoalcohol (10.0 mmol), solvent (8.0
mL), CO2 (5 MPa), 180 °C, 16 h.
b GLC yield based on 1.
Synlett 2002, No. 2, 307–309 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Synthesis of 2-Oxazolidinones from CO2 and 1,2-Aminoalcohols
309
(5) Jpn. Kokai Tokkyo Koho 8242678, 1982; Chem. Abstr.,
1982, 97, 216155.
(6) Soga, K.; Hosoda, S.; Nakamura, H.; Ikeda, S. J. Chem. Soc.,
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(7) Positive ion ES mass spectra were recorded on a Waters ZQ-
2000 mass spectrometer. The needle voltage was 3 kV and
the drift voltage was 10 V. The CH3CN solution of the
reaction solution (50 ppm) was introduced into the ES probe
by syringe pomp.
(8) George, T. A.; Jones, K.; Lappert, M. F. J. Chem. Soc. 1965,
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Synlett 2002, No. 2, 307–309 ISSN 0936-5214 © Thieme Stuttgart · New York