Carbonylative ring opening of terminal epoxides at atmospheric pressure

Article abstract of DOI:10.1021/jo7014455

(Chemical Equation Presented) The carbonylative opening of terminal epoxides under mild conditions has been developed using Co₂-(CO) ₈ as the catalyst. Under 1 atm of carbon monoxide and at room temperature in methanol, propylene oxide is converted to methyl 3-hydroxybutanoate in up to 89% yield. This transformation is general for many terminal epoxides bearing alkyl, alkenyl, aryl, alkoxy, chloromethyl, phthalimido, and acetal functional groups. The opening takes place without epimerization at the secondary stereocenter.

Full text of DOI:10.1021/jo7014455

Carbonylative Ring Opening of Terminal Epoxides at Atmospheric
Pressure
Scott E. Denmark* and Moballigh Ahmad
Roger Adams Laboratory, Department of Chemistry, UniVersity of Illinois, Urbana, Illinois 61801
denmark@scs.uiuc.edu
ReceiVed August 23, 2007
The carbonylative opening of terminal epoxides under mild conditions has been developed using Co2-
(CO)8 as the catalyst. Under 1 atm of carbon monoxide and at room temperature in methanol, propylene
oxide is converted to methyl 3-hydroxybutanoate in up to 89% yield. This transformation is general for
many terminal epoxides bearing alkyl, alkenyl, aryl, alkoxy, chloromethyl, phthalimido, and acetal
functional groups. The opening takes place without epimerization at the secondary stereocenter.
Introduction
double carbonylation), whereas carbonylative ring opening with
N- or O-nucleophiles affords â-hydroxyl amides6 or esters,
respectively (Scheme 1).7
Given the environmental concerns in modern society, catalytic
reactions that minimize waste and increase efficiency are in great
demand. Accordingly, the development of atom-economic1 and
atom-efficient2 reactions is of great interest. Obviously, the most
atom-efficient processes are either molecular rearrangements or
addition reactions that incorporate all of the starting materials
into the products without generating a waste stream. Among
the latter processes, those reactions that incorporate new
functional groups and stereocenters are particularly useful.
Catalytic carbonylative ring opening or ring expansion of
epoxides represents an extremely efficient reaction, that affords
high value-added products.3 The carbonylative ring expansion
of epoxides produces lactones4 or succinic anhydrides5 (by
Carbonylation chemistry is used extensively in industry as
illustrated by the bulk production of carbonylation intermedi-
ates.8 Of particular note is the industrial process for the synthesis
of propane-1,3-diol, a useful pharmaceutical intermediate and
polyester component.9 The production of this diol from ethylene
oxide (by hydroformylation followed by hydrogenation) has
been studied intensively.10 Landmark reports from Heck11 and
others12 on the application of homonuclear ion pairs (HNIP’s),
(6) (a) Goodman, S. N.; Jacobsen, E. N Angew. Chem., Int. Ed. 2002,
41, 4703-4705. (b) Watanabe, Y.; Nishiyama, K.; Zhang, K.; Okuda, F.;
Kondo, T.; Tsuji, Y. Bull. Chem. Soc. Jpn. 1994, 67, 879-882. (c) Suji,
Y.; Nishiyama, K.; Kobayashi, M.; Okuda, F.; Watanabe, Y. J. Chem. Soc.,
Chem. Commun. 1989, 1253-1254.
(7) (a) Hinterding, K.; Jacobsen, E. N. J. Org. Chem. 1999, 64, 2164-
2165. (b) Kim, H. S.; Bae, J. Y.; Lee, J. S.; Jeong. C., II; Choi, D. K.;
Kang, S. O.; Cheong, M. Appl. Catal., A 2006, 301, 75-78. (c) Liu, J.;
Chen, J.; Xia, C. J. Mol. Catal. A: Chem. 2006, 250, 232-236. (d)
Eisenmann. J. L.; Yamartino, R. L.; Howard, J. F. J. Org. Chem. 1961, 26,
2102-2104.
(1) (a) Trost, B. M. Science 1991, 254, 1471-1477. (b) Trost, B. M.
Angew. Chem., Int. Ed. 1995, 34, 259-281.
(2) Sheldon, R. A. Pure Appl. Chem. 2000, 72, 1233-1246.
(3) (a) Church, T. L.; Getzler, Y. D. Y. L.; Byrn, C. M.; Coates, G. W.
Chem. Commun. 2007, 657-674. (b) Nakano, K.; Nozaki, K. Top.
Organomet. Chem. 2006, 18, 223-238.
(4) (a) Drent, E.; Kragtwijk, E. Shell Internation Research, European
Patent Application EP 577206; Chem. Abstr. 1994, 120, 191517c. (b) Lee,
J. T.; Thomas, P. J.; Alper, H. J. Org. Chem. 2001, 66, 5424-5426. (c)
Allmendinger, M.; Eberhardt, R.; Luinstra, G. A.; Molnar, F.; Rieger, B.
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M.; Eberhardt, R.; Luinstra, G. A.; Molnar, F.; Rieger, B. Z. J. Organomet.
Chem. 2004, 689, 971-979. (e) Getzler, Y. D. Y. L.; Mahadevan, V.;
Lobkovsky, E. B.; Coates, G. W. J. Am. Chem. Soc. 2002, 124, 1174-
1175. (f) Mahadevan, V.; Getzler, Y. D. Y. L.; Coates, G. W. Angew. Chem.,
Int. Ed. 2002, 41, 2781-2784. (g) Schmidt, J. A. R.; Mahadevan, V.;
Getzler, Y. D. Y. L.; Coates, G. W. Org. Lett. 2004, 6, 373-376. (h)
Schmidt, J. A. R.; Lobkovsky, E. B.; Coates, G. W. J. Am. Chem. Soc.
2005, 127, 11426-11435.
(8) (a) Yoneda, N.; Kusano, M.; Yasui, P.; Pujado, S.; Wilcher Appl.
Catal., A 2001, 301, 253-254. (b) Maitlis, P.M.; Haynes, A; Sunely, G. J.;
Howard, M. J. J. Chem. Soc., Dalton Trans 1996, 2187-2178. (c) Beller,
M.; Cornils, B.; Frohing, C.; Kohlpainter, C. W. J. Mol. Catal. A: Chem.
1995, 105, 17-74. (d) Howard. M. J.; Jones, M. D.; Roberts, M. S.; Taylor,
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Mol. Catal. A: Chem. 1982, 17, 299-303.
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10.1021/jo7014455 CCC: $37.00 © 2007 American Chemical Society
Published on Web 11/08/2007
9630
J. Org. Chem. 2007, 72, 9630-9634

CarbonylatiVe Ring Opening of Terminal Epoxides
SCHEME 1
shown that zinc Lewis acids such as ZnBr2(NC5H5) accelerate
the carbonylative ring opening of ethylene oxide with Co2-
(CO)8.18 Finally, Coates has developed a highly efficient
bimetallic catalyst that allows the carbonylative ring expansion
of epoxides under atmospheric pressure of CO and at room
temperature.19
Although high-pressure reactions often provide interesting
products, the need for specialized equipment represents a
limitation for synthetic organic chemists. Thus, we have
embarked on a program to develop novel Lewis bases to
efficiently catalyze the formation of reactive HNIP’s that are
effective at opening epoxides and aziridines under mild condi-
tions (1 atm of CO and room temperature). We targeted the
carbonylation of epoxides because the â-hydroxy ester products
are useful intermediates in organic and polymer chemistry4e,20
and thus initiated studies on the carbonylative ring opening of
propylene oxide (1a) in methanol as the test reaction. Much to
our surprise we observed through preliminary control experi-
ments that this reaction proceeded readily at atmospheric
pressure of CO and room temperature in the absence of a Lewis
basic catalyst! Because this unexpected observation contradicted
the general practice for this important process we have
extensively investigated the reaction and describe our results
in full below.
for carbonylative carbon-carbon bond forming reactions, set a
milestone in carbonylation chemistry. Mechanistic studies by
Marko and Faschinetti showed that HNIP’s are generated from
the disproportionation of Co2(CO)8 by Lewis bases.13 The
preparative advantages of HNIP’s are clear, as this catalyst
system requires only one metal. Upon interaction with a Lewis
base the Co2(CO)8 disproportionates into an ionic species,
[LB2Co(CO)3]+ [Co(CO)4]-. The Lewis acidic cationic portion
[LB2Co(CO)3]+ is known to coordinate and activate the epoxide
and the anionic [Co(CO)4]- will attack the epoxide to make an
organocobalt ate complex. Insertion of carbon monoxide to this
cobalt ate species results in a cobalt acyl complex, which is
intercepted by nucleophiles to give â-lactones or â-hydroxy
esters and amides. In the early 1990s Drent and Kragtwijk
reported an efficient HNIP catalytic system based on Co2(CO)8
and 3-hydroxypyridine (3) for the carbonylative ring opening
of terminal aliphatic epoxides.14 Hinterding and Jacobsen7a
successfully exploited this transformation in the production of
enantiopure â-hydroxy esters starting from enantiopure epoxides
that are, in turn, easily prepared by hydrolytic kinetic resolu-
tion.15 Although the reported carbonylation conditions are milder
than those reported by Eisenmann,16 they still required 40 bar
of carbon monoxide and 65-70 °C.17
Results and Discussion
1. Initial Discovery. The carbonylation of 1a in MeOH/THF
under CO pressure was selected as the model system. Initial
studies involved a survey of CO pressure, temperature, time,
solvent, and catalyst. Orienting experiments employed the
conditions developed by Drent: 5 mol % of Co2(CO)8, 10 mol
% of 3 in a 1:1 mixture of MeOH and THF under 41 bar of CO
at 72 °C for 12 h. Under these conditions an 85% yield of
methyl-3-hydroxybutyrate (2a) was obtained (Table 1, entry 1).
As part of a series of standard, systematic control experiments,
we performed the carbonylation of 1a, in MeOH/THF (1:1),
with 10 mol % of Co2(CO)8 and 20 mol % of 3 under
atmospheric pressure of CO and at room temperature. Much to
our surprise, 2a was isolated in 40% yield (Table 1, entry 2).
2. Optimization and Control Experiments. This striking
observation encouraged further investigation of this reaction.
Remarkably, by lowering the loading of both Co2(CO)8 (to 5
mol %) and 3 (to 10 mol %) at atmospheric pressure of CO
and room temperature, the yield of 2a improved from 40% to
80% (Table 1, entries 2 and 3).21 The next two controls showed
that no reaction occurs without Co2(CO)8, but surprisingly, an
85% yield of 2a was obtained in an experiment without 3 (Table
1, entries 4 and 5). Apparently, methanol alone is able to
The disproportionation of Co2(CO)8 with other nucleophiles,
for example, silyl amides, has been used for the carbonylative
ring opening of epoxides to produce â-hydroxy amides under
atmospheric pressure of carbon monoxide.6 Moreover, Kim has
(10) (a) Brossmer, C.; Arntz, D. U.S. Patent 6,140,543, 2000. (b) Smith,
C. W.; Schrauzer, G. N.; Windgassen, R. J.; Koetiz, K. F. U.S. Patent 3,-
463,819, 1969. (c) Bieble, H.; Marten, H.; Hippe, H.; Deckwer, W. D. Appl.
Microbiol. Biotechnol. 1992, 36, 592-600. (d) Powell, J. B.; Slaugh, L.;
Forschner, T. B.; Thomson, T. B.; Semple, T. C.; Achanetcet, J. P. U.S.
Patent 5,463,144, 1995. (e) Knifton, J. F.; Slaugh, L.; Weider, P. R.; James,
T. R. U.S. Patent 6,468,940, 2002. (f) Han, Y. Z. U.S. Patent 6,323,374,
2001. (g) Storu, Y.; Hiroshi, K. Japan Patent Appl. 2002.332, 250.
(11) (a) Heck, R. F. J. Am. Chem. Soc. 1960, 82, 4438-4439. (b) Heck,
R. F.; Breslow, D. S. J. Am. Chem. Soc. 1960, 82, 750-751. (c) Heck, R.
F.; Breslow, D. S. J. Am. Chem. Soc. 1962, 84, 2499-2502. (d) Heck, R.
F.; Breslow, D. S. J. Am. Chem. Soc. 1962, 84, 2499-2502. (e) Heck, R.
F. J. Am. Chem. Soc. 1963, 85, 651-654, 655-657, 657-661.
(12) (a) Roelen, O. Ger. Patent 849548, 1938; DE2, 327, 066, 1943. (b)
Khand, I. U.; Knox, G. R.; Pausen, P. L.; Watts, W. E.; Foreman, M. I. J.
Chem. Soc., Parkin Trans. 1973, 977-981.
(13) (a) Sisak, A.; Ungvary, F.; Marko, L. Organometallics 1983, 2,
1244-1246. (b) Sisak, A.; Marko, L. J. Organomet. Chem. 1987, 330, 201-
206. (c) Fachinetti, G.; Del Cima, F. J. Organomet. Chem. 1985, 287, C23-
C24. (d) Fachinetti, G.; Fochi, G.; Funaioli, T. J. Organomet. Chem. 1986,
301, 91-97.
(14) Drent, E.; Kragtwijk, E. Shell International Research, European
Patent Appl. EP 577206; Chem. Abstr. 1994, 120, 191517c.
(15) (a) Tokunaga, M.; Larrow, J. F.; Kakiuchi, F.; Jacobsen, E. N.
Science 1997, 277, 936-938. (b) Schaus, S. E.; Barnes, B. D.; Larrow, J.
F.; Tokunaga, M.; Hansen, K. B.; Gould, A. E.; Furrow, M. E.; Jacobsen,
E. N. J. Am. Chem. Soc. 2002, 124, 1307-1310.
(18) Kim, H. S.; Bae, J. Y.; Lee, J. S.; Jeong. C., II; Choi, D. K.; Kang,
S. O.; Cheong, M. Appl. Catal., A 2006, 301, 75-78.
(19) Kramer, J. W.; Lobkovsky, E. B.; Coates, G. W. Org. Lett. 2006,
8, 3709-3712.
(20) (a) Brossmer, C.; Arntz, D. U.S. Patent 6,140,543, 2000. (b) Smith,
C. W.; Schrauzer, G. N.; Windgassen, R. J.; Koetiz, K. F. U.S. Patent 3,-
463,819, 1969. (c) Bieble, H.; Marten, H.; Hippe, H.; Deckwer, W. D. Appl.
Microbiol. Biotechnol. 1992, 36, 592-600. (d) Powell, J. B.; Slaugh, L.;
Forschner, T. B.; Thomson, T. B.; Semple, T. C.; Achanetcet, J. P. U.S.
Patent 5,463,144, 1995. (e) Knifton, J. F.; Slaugh, L.; Weider, P. R.; James,
T. R. U.S. Patent 6,468,940, 2002. (f) Han, Y. Z. U.S Patent 6,323,374,
2001. (g) Storu, Y.; Hiroshi, K. Japan Patent Appl. 332,250, 2002.
(21) The adverse effect of high carbon monoxide pressure and reaction
temperature has been observed on the outcome of the cobalt-catalyzed
carbonylation of cyclic ethers using N-silylamines by Watanabe et al. See:
Watanabe, Y.; Nishiyama, K.; Zhang, K.; Okuda, F.; Kondo, T.; Tsuji, Y.
Bull. Chem. Soc. Jpn. 1994, 67, 879-882.
(16) Eisenmann. J. L.; Yamartino, R. L.; Howard, J. F. J. Org. Chem.
1961, 26, 2102-2104.
(17) Liu, J.; Chen, J.; Xia, C. J. Mol. Catal. A: Chem. 2006, 250, 232-
236.
J. Org. Chem, Vol. 72, No. 25, 2007 9631

Denmark and Ahmad
TABLE 1. Optimization of Carbonylative Ring Opening of
Propylene Oxidea
Having ruled out adventitious contaminants in the starting
materials and the solvent as the source of accelerated reactions,
we next investigated if the workup and purification were
responsible for the carbonylation reaction. To exclude this
possibility, a standard reaction was run for 24 h and then was
filtered through a sintered glass frit. Careful evaporation of the
solvent gave a pink oil that by 1H NMR analysis (broad peaks
observed because of cobalt present) confirmed the formation
of 2a (Table 1, entry 12).
In another series of control experiments, a survey of MeOH
or THF alone as the solvent revealed that the carbonylative
ring opening of 1a runs smoothly in MeOH to afford an
89% yield of 2a, whereas in THF, only â-lactone formation
was observed (1H NMR analysis) in extremely poor yield
(Table 1, entries 13 and 14). Next, to test if the (arbitrarily
chosen) 24 h reaction time was indeed necessary, a series of
experiments under standard conditions were set up and quenched
at 0.5, 1, 3, 6, and 12 h. After workup, the 0.5-h run afford a
37% yield of 2a, whereas the reactions run for 1, 3, 6, and
12 h gave 55%, 75%, 76%, and 89% yield of 2a, respectively
(Table 1, entries 15-19). Thus, on the basis of all the con-
trol experiments and foregoing studies, we conclude that the
Co2(CO)8-catalyzed, carbonylatiVe ring opening of 1a in
methanol/THF takes place at 1 atm of CO and room temper-
ature.
3. Demonstration of Scope. The ready carbonylative ring
opening of 1a with Co2(CO)8 in methanol under atmospheric
pressure at room temperature stimulated a study of the general
scope of this catalytic process for the synthesis of â-hydroxy
esters. Thus, a wide range of functionalized, terminal epoxides
bearing alkyl, alkenyl, alkyl-aryl, glycidyl, and carbonyl groups
were subjected to the carbonylation conditions. In general, very
good yields of â-hydroxy esters were obtained. Not surprisingly,
simple aliphatic and olefinic terminal epoxides reacted well
(Table 2, entries 1, 2, and 3). Terminal epoxides bearing
aromatic residues are known to react slowly thus affording lower
yields. Thus, 3-phenylpropylene oxide and 4-phenylbutene 1,2-
oxide gave moderate yields with minor amounts of a methyl
ketone side product (Table 2, entries 4 and 5). Ketone formation
(particularly at lower CO pressure) finds ample precedent in
related studies and arises from the non-carbonylative rearrange-
ment of ring-open epoxide intermediate as proposed by Coates
et al.25 Heteroatom functionalized epoxides such as epichloro-
hydrin afforded a 73% yield of methyl 4-chloro-3-hydroxybu-
tyrate (Table 2, entry 6). In addition, various glycidol ethers
also reacted well to afford the â-hydroxy esters in good yields
together with the minor amounts of a methyl ketone byproduct
(Table 2, entries 7-9). Surprisingly, the TBS-protected glycidol
1j did not react cleanly and gave an equivalent amount of the
methyl ketone with lower conversion, whereas N-(2,3-epoxypro-
pyl)pthalimide afforded the corresponding â-hydroxy ester in
good yield (Table 2, entries 10 and 11). Functionally more
diverse epoxides such as acetal, ester, and ketone-bearing
oxiranes gave poor yields for the desired product (Table 2,
entries 12-15). Presumably, carbonyl functional groups are not
compatible with the HNIP generated from Co2(CO)8 and
methanol. In a preliminary experiment with an internal epoxide,
cyclohexane oxide 1p, the â-hydroxy ester 2p was formed in
20% yield.
Co2(CO)8
entry (mol %) (mol %)
3b
CO temp time yield
solvent
(bar) (°C) (h) (%)c
1
2
3
4
5
6f
7f
8
9
5
10
5
10
20
10
10
-
MeOH/THF (1:1)d 41
72 12
85
40
80
0
85
79
90
72
80
71
81
NDk
l
MeOH/THF (1:1)e
MeOH/THF (1:1)
MeOH/THF (1:1)
MeOH/THF (1:1)
MeOH/THF (1:1)
MeOH/THF (1:1)
MeOH/THF (1:1)
MeOH/THF (1:1)
MeOH/THF (1:1)i
MeOH/THF (1:1)
MeOH/THF (1:1)
THF
1
1
1
1
1
1
1
1
1
1j
1
1
1
1
1
1
1
1
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
24
24
24
24
24
24
24
24
24
24
24
24
24
-
5
5g
-
5g
5h
5h
5g
5g
5g
5g
5g
5g
5g
5g
5g
5g
-
10
-
10
10
10
-
11
12
13
14
15
16
17
18
19
-
-
MeOH
MeOH
89
-
0.5 37
1
3
6
12
-
MeOH
MeOH
55
76
83
90
-
-
MeOH
MeOH
-
a 5 mmol of epoxide, 1 M. b 3-Hydroxypyridine. c Isolated yield. d 0.5
M. e 2 M. f Distilled 1a (from CaH2) was used. g Sublimed Co2(CO)8 was
used. h Different bottle of Co2(CO)8. i THF and MeOH from freshly opened
ACS Grade bottle. j New tank of CO. k No ethereal workup and passing
through plug of silica gel. l â-Lactone formation in low yield by 1H NMR
analysis.
disproportionate the Co2(CO)8 to produce the HNIP that
catalyzed the carbonylative ring opening of 1a.22
Because of the dramatic differences between the conditions
employed herein and those described in the literature for opening
of 1a, we suspected that a spurious contaminant could be
catalyzing the formation of the HNIP’s. Accordingly, we
checked the source and purity of 1a, Co2(CO)8, the sol-
vents, and carbon monoxide. Thus, 1a was redistilled, the Co2-
(CO)8 was sublimed,23 and both were employed in the carbo-
nylative ring opening with and without 3. We were delighted
to find that both reactions were reproducible: in the presence
of 3 the yield of 2a was 79% (compare entries 3 and 6 in Table
1) whereas in the absence of 3 the yield of 2a was 90%
(compare entries 5 and 7 in Table 1). To eliminate all possibility
of adventitious catalysts, Co2(CO)8 from a different bottle
was employed both with and without 3. Once again, both
reactions afforded 2a in similar yields as before (compare
entries 8 and 3, and entries 9 and 5 in Table 1). The next con-
trol experiment targeted the source of MeOH and THF (ACS
grade). In these experiments, freshly opened bottles of solvent
were used instead of the freshly purified MeOH (distilled
from Mg(OMe)2) or THF (dried through Al2O3). Under
these conditions, a 71% yield of 2a was obtained (Table 1, entry
10). The reaction also worked well with CO from a dif-
ferent cylinder,24 affording and 81% yield of 2a (Table 1,
entry 11).
(22) Evidence for the existence of [Co(CO)4(ROH)]+[Co(CO)4]- com-
plexes from Co2(CO)8 and methanol at >25 °C has been provided; see:
Tucci, E. R.; Gwynn, B. H. J. Am. Chem. Soc. 1964, 86, 4838-4841.
(23) Propylene oxide (Fischer Scientific) was heated at reflux over
calcium hydride for 12 h, distilled, and stored in a Schlenk flask. Dicobalt
octacarbonyl (Strem Chemicals) was sublimed in a 100 mL glass sublimation
chamber at 35 °C (0.5 mmHg), using an acetone/dry ice cold finger.
(24) Compressed carbon monoxide from Matheson TRI.GAS, CP grade
(CP ) Chemically pure). Lot no. 1046405663B9
(25) Eisenmann. J. L. J. Org. Chem. 1962, 27, 2706.
9632 J. Org. Chem., Vol. 72, No. 25, 2007

CarbonylatiVe Ring Opening of Terminal Epoxides
TABLE 2. Cobalt-Catalyzed Carbonylation of Epoxidesa
a Reactions run with 5 mmol of epoxide. b Yield of isolated, purified products. c Based on the yield of isolated products.
The catalytic, ring-opening carbonylation of terminal epoxides
is known to proceed with retention of configuration.7a Under
the mild conditions described in this report, (S)-1a (98.4/1.6
er) provided (S)-2a (>99/1 er) as well (Scheme 2).
Although the scope of the carbonylative ring opening under
these conditions is somewhat limited, and therefore may not
be of general preparative significance, we are nonetheless struck
by the use of high pressure and temperature for simple terminal
epoxides in the literature. Most importantly, we are encouraged
in our pursuit to identify Lewis basic activators of the formation
of HNIPs for the ligand-accelerated, catalytic carbonylation of
epoxides of diverse structure.
J. Org. Chem, Vol. 72, No. 25, 2007 9633

Denmark and Ahmad
SCHEME 2
Conclusion
(5.0 mL) was added and the mixture was stirred for 2 min before
1a (350 µL, 5.0 mmol) was added in one portion and the reaction
was allowed to stir at room temperature for 24 h. The carbon
monoxide balloon was removed carefully and vented in a fume
hood. The reaction mixture was diluted with ether (50 mL) and
stirred for 30-60 min to precipitate the cobalt complex. The mixture
was filtered through a plug of silica gel (5 g), using ether as the
eluent, and upon careful removal of solvent under reduced pressure,
525 mg (89%) of 2a was obtained as a clear colorless oil.26 Data
for 2a: 1H NMR (500 MHz, CDCl3) δ 4.21-4.17 (m, 1 H), 3.70
(s, 3 H), 2.96 (d, 1 H), 2.49 (dd, J ) 16.0, 3.5 Hz, 1 H), 2.42 (dd,
J ) 16.2, 8.7 Hz, 1 H), 1.22 (d, 3 H); 13C NMR (125 MHz, CDCl3)
173.3, 64.2, 51.7, 42.5, 22.4.
We have demonstrated that carbonylative ring opening of
terminal epoxides can be performed at atmospheric pressure of
CO and room temperature under catalysis by Co2(CO)8. Modest
to good yields are obtained with simple as well as functionalized
epoxides and glycidols, but epoxides bearing carbonyl groups
give lower yields. Enantiopure propylene oxide is opened with
complete retention of configuration. Further studies on HNIP-
based catalytic ring opening of aziridines and epoxides are in
progress, and will be reported in due course.
Acknowledgment. We are grateful to the National Science
Foundation for generous financial support (NSF CHE 0414440
and 0717989). Dr. Son T. Nguyen is thanked for the preparation
of Jacobsen’s catalyst.
Supporting Information Available: Full experimental proce-
dures and characterization data for all carbomethoxylation products.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Experimental Section
General Experimental Procedures. See the Supporting Infor-
mation.
Ring Opening Carbonylation of Propylene Oxide: Prepara-
tion of Methyl 3-Hydroxybutanoate (2a) [Table 2, Entry 1]. In
a glovebox, Co2(CO)8 (84.5 mg, 0.25 mmol, 0.05 equiv) was placed
in a 100-mL Schlenk flask equipped with a magnetic stir bar. The
flask was sealed with a rubber septum and was removed from the
drybox. The flask was purged three times for 2 s with carbon
monoxide (filled in a 5 in. latex balloon). Freshly distilled methanol
JO7014455
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9634 J. Org. Chem., Vol. 72, No. 25, 2007