Enantioselective Small Molecule Synthesis by Carbon Dioxide Fixation using a Dual Br?nsted Acid/Base Organocatalyst

Article abstract of DOI:10.1021/jacs.5b04425

Carbon dioxide exhibits many of the qualities of an ideal reagent: it is nontoxic, plentiful, and inexpensive. Unlike other gaseous reagents, however, it has found limited use in enantioselective synthesis. Moreover, unprecedented is a tool that merges on

Full text of DOI:10.1021/jacs.5b04425

Communication
pubs.acs.org/JACS
Enantioselective Small Molecule Synthesis by Carbon Dioxide
Fixation using a Dual Brønsted Acid/Base Organocatalyst
Brandon A. Vara, Thomas J. Struble, Weiwei Wang, Mark C. Dobish, and Jeffrey N. Johnston*
Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United
States
S
* Supporting Information
ABSTRACT: Carbon dioxide exhibits many of the
qualities of an ideal reagent: it is nontoxic, plentiful, and
inexpensive. Unlike other gaseous reagents, however, it has
found limited use in enantioselective synthesis. Moreover,
unprecedented is a tool that merges one of the simplest
biological approaches to catalysisBrønsted acid/base
activationwith this abundant reagent. We describe a
metal-free small molecule catalyst that achieves the three
component reaction between a homoallylic alcohol, carbon
dioxide, and an electrophilic source of iodine. Cyclic
carbonates are formed enantioselectively.
Figure 1. Enantioselective methods using CO2 as a reagent, contrasting
state-of-the-art metal-mediated reactions with this report of Brønsted
acid/base catalysis.
he current global economic and environmental landscape
has accelerated research into carbon dioxide (CO2) capture
T
and storage (CCS) technology across a broad range of chemical
disciplines. The most notable advancements have been made in
the areas of materials chemistry,1 carbon storage engineering,
and alkylamine-based “scrubbing” systems.2 The threat of CO2
accumulation as a greenhouse gas has motivated these
sequestration strategies, but this gaseous reagent holds immense
potential value as an abundant and nontoxic C1 building block3
for carbon−carbon bond formation and carbon−heteroatom
functionalization reactions in chemical synthesis.4,5 Unfortu-
nately, the underlying features that contribute to carbon dioxide’s
low general toxicity and ease of handling render it relatively inert
as a chemical reactant.6 This is punctuated by the contrasting
abundance of enantioselective chemical reactions using hydro-
gen (H2),7 oxygen (O2),8 and even carbon monoxide (CO).9
Chemical technologies that preferentially form one handedness
(enantiomer) of a chiral product have direct application to drug
development and new materials. Despite the virtues of high
temperature and/or pressure to address poor reactivity,
transformations employing CO2 as a reagent10 are typically
limited to either Lewis basic substrates with sufficient
carbon−oxygen bond formation. Metal-based systems include
CO2 insertion into activated epoxides generating almost
exclusively five-membered cyclic carbonates, including enantio-
selective kinetic resolutions (Figure 1A).13 Additionally, Yamada
has reported a silver(I)-based alcohol desymmetrization using
CO2 at high pressure to prepare five-membered cyclic
carbonates.14
We posited that a properly balanced Brønsted acid/base
bifunctional catalyst might lower the barrier to CO2 incorpo-
ration and/or assist in the stabilization of the resulting adduct15
as a prelude to its use as an oxygen nucleophile in a subsequent
enantioselective carbon−oxygen bond-forming step.16 If this
could be achieved using a metal-free catalystan organo-
catalystthe virtues of minimalism (symmetrical catalyst, low
temperature, atmospheric pressure, near-neutral pH) would
apply, suggesting broad impact. Here, we validate this design by
the development of a carboxylation/alkene functionalization
reaction of homoallylic alcohols to produce chiral cyclic
carbonates.
Homoallylic alcohol 1a became the basis for developing a
tandem alcohol carboxylation−alkene iodocarbonation reaction
due to the lower steric demand of a 1,1-disubstituted alkene. The
standard reaction to which others are compared involved chilling
(−20 °C) a toluene solution of homoallylic alcohol (1a, 0.4 M)
prior to addition of N-iodosuccinimide (Table 1, entry 1) and
CO2 (balloon). These catalyst-free conditions returned the
starting material following a 48 h reaction period. Compared to
3
nucleophilicity to react with the poorly electrophilic CO2 or
metal-based reagents to increase the rate of CO2 incorporation,
often through a metal carboxylate intermediate (Figure 1A).11,12
We sought a reagent, ideally a catalyst, that could both overcome
these barriers to reactivity and/or unfavorable equilibria while
simultaneously controlling stereoselection; in essence, a catalyst
that could stabilize a substrate-CO2 adduct but still activate this
adduct toward subsequent carbon−oxygen bond formation.
Unprecedented is the use of a metal-free catalyst to stabilize the
adduct of a weak nucleophile with CO2, such as a carbonic acid−
base complex, while effectively guiding it toward enantioselective
Received: April 28, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/jacs.5b04425
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Journal of the American Chemical Society
Communication
2a, however the carbonate was formed in a promising 39% ee
(Table 1, entry 9) at −20 °C. The analogous catalyst
incorporating trans-stilbene diamine (“StilbPBAM” (8)) instead
of trans-cyclohexane diamine provided the product in 33% yield
and similar ee (36% ee, Table 1, entry 10). It was noted in these
early experiments that the addition of molecular sieves (MS 4A)
resulted in more consistent reactions as judged by conversion
and/or yield (Table 1, entry 11). In reactions without sieves,
formation of a precipitate appeared to correlate with lower yields
and varying enantioselectivity (particularly with free base (7 or 8;
vide infra). Exploration of strong Brønsted acid additives (1:1
ligand:acid) led to moderate differences in enantioselection
(Table 1, entries 12−15), with catalyst complex 8·HNTf2
providing product with 91% ee (Table 1, entry 15). Some
sensitivity of both yield and selectivity to concentration was
noted,21 with lower concentrations leading to depressed yield
and selectivity (Table 1, entries 16−17). We reinvestigated
several achiral amine bases under these optimized conditions,
with only marginal improvement in yield (Table 1, entries 18−
21). Attempts were also made to simulate the Brønsted acid/base
character of catalyst 8·HNTf2 using monobasic amines in
combination with varying amounts of Brønsted acid (e.g.,
Table 1, entry 21), none resulting in significant improvement of
yield. Collectively, these results suggest an underlying order to
the hydrogen-bonding network in the key selectivity-determin-
ing step, if not unique reactivity associated with the proper
positioning of a Brønsted acid and base in the same molecule, in
this CO2-fixation reaction.
Application of conditions optimized for homoallylic alcohol 1a
to a range of similar substrates is outlined in Table 2. α-
Substituted styrene derivatives were scrutinized using the mild
conditions developed (2a−m, Table 2). Nominal substitution of
the aromatic ring led to equally positive outcomes, with 2a−c
formed in 91−95% ee and high chemical yield (82−96% yield)
(Table 2, entries 1, 3−5). Substitution near the alkene was not
tolerated, as no substrate conversion was observed to produce 2d
or 2e (Table 2, entries 6−7). Increasing the reaction temperature
to 0 °C led to complex mixtures suggestive of competing
intermolecular iodoetherification. However, a β-naphthyl-
substituted alkene led to good enantioselection and yield (2f,
90% ee, 88% yield) (Table 2, entry 8). Anisole derivatives (meta-
and para-substituted) provided generally good enantioselectivity
(80−90% ee) and higher chemical yield (97%, 2h), but lower
yield for 2g (Table 2, entries 9−10). Halogen-substituted arenes
led to a range of results, mostly related to reactivity, while
selectivity remained high; some reached only partial conversion
despite extended reaction times. Halogen substitution meta and
para to the alkene provided consistently good enantioselection
(87−90% ee) (Table 2, entries 11−14). Reactivity varied greatly
among 2i−l, however, and suggested that the alkene
nucleophilicity might be a key determinant of reactivity.
Carbonate 2m was produced in nearly quantitative yield and
91% ee (Table 2, entry 15).
Table 1. Development of an Enantioselective CO2 Capture
Reaction using a Homoallylic Alcohol
ee
(%)
a
b
c
d
entry ligand (base)
acid
notes
yield
1
2
3
4
5
6
7
8
9
none
−
−
−
−
−
−
−
−
−
−
−
−
NaH
0%
16%
25%
trace
trace
11%
6%
−
−
−
−
−
−
−
−
39
36
60
74
62
86
91
89
79
−
e
none
e
none
NaH (THF)
f
DMAP (5)
−
−
−
−
−
−
−
MS
MS
MS
f
DBU (6)
f
TBD (4)
f
TFA
f
3
4%
PBAM (7)
18%
33%
35%
62%
52%
70%
95%
51%
10%
trace
30%
13%
10 StilbPBAM (8)
11
12
13
14
15
16
17
18
19
20
21
8
8
8
8
8
8
8
5
4
6
6
HOTf
H2NTf
F6C3(SO2)2NH MS
g
HNTf2
HNTf2
HNTf2
−
−
−
MS, 0.4 M
MS, 0.2 M
MS, 0.1 M
−
f
f
f
f
MS
−
−
−
MS
1/2 HNTf2
MS
4%
b
a
Catalyst prepared as the 1:1 acid salt, except entry 21. MS denotes
molecular sieves 4A, employed at a concentration of 1 g/mmol relative
c
d
to the alcohol. Isolated yield. Enantiomeric excess (ee) determined
by HPLC using a chiral stationary phase. Reactions are 0.4 M toluene
e
unless otherwise noted. Reaction temp = 0 °C. 3-Methyl-3-buten-1-ol
f
was converted in 60% yield under identical conditions. 20 mol %
g
catalyst employed. 5 mol % catalyst employed, with results analogous
to those using 10 mol % catalyst.
an otherwise identical reaction, addition of a strong base (sodium
hydride, Table 1, entry 2) delivered the desired cyclic carbonate,
but in only 16% yield.17 Substitution of a more polar solvent (e.g.,
THF) for toluene increased the yield marginally (Table 1, entry
3). Based on precedence for Brønsted basic amines to react
directly with CO2 or CO2/H2O combined, several amine bases
were examined (Table 1, entries 4−5) as well as hydrogen-bond
donor/acceptor amines (e.g., TBD, Table 1, entry 6) in an
attempt to accelerate the desired reaction.18,19 These extensive
attempts generally provided three outcomes: (1) return of
unreacted homoallylic alcohol, (2) formation of apparent
iodoetherification products, or simply (3) low yields (<15%)
of the desired carbonate. Similarly, good hydrogen-bond donors,
such as TFA or thiourea 320 (Table 1, entries 7−8) failed to
deliver any significant amount of carbonate.
Alkenes bearing aliphatic substituents are often regarded as
challenging substrates in stereoselective difunctionalization
reactions.22 3-Alkyl butenols were prepared and converted to
carbonates 2n−p with promising levels of enantioselectivity (up
to 74% ee) (Table 2, entries 16−18). Iodocarbonate 2o, derived
from the sterically unencumbered 3-methyl-but-3-ene-1-ol, a
widely available isoprenyl feedstock, formed in a moderate 68%
ee. Although not a focus of these investigations, allylic alcohols
reacted sluggishly but exhibited good yield and lower
enantioselection. In an effort to probe the adaptation of this
Our ultimate goal was to explore the ability of a Brønsted acid/
base combination to promote the reaction. Use of pyrrolidine-
substituted bis(amidine) 7 (“PBAM”) resulted in an 18% yield of
B
DOI: 10.1021/jacs.5b04425
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Journal of the American Chemical Society
Communication
Table 2. Initial Scope of an Enantioselective CO2 Capture
a
Reaction using a Homoallylic Alcohol
Figure 2. Catalyst Inactivation Pathway and Its Recovery Using MS 4A.
appears reversible, reverting to active catalyst when a desiccant
(MS 4A) and dry gas (argon) are added. Although a noncovalent
complex is hypothesized in our work, some nucleophilic amines
can form a covalent adduct with CO2.24 When not in competition
with water, the alcohol substrate can entrain CO2, forming an
intermediate and transient alkyl carbonic acid salt with the
bifunctional catalyst. This intermediate, in reaction with NIS,
forms a complex which then collapses to the cyclic carbonate
either stepwise or directly.25
entry
1
R
product
time (h)
ee (%)
yield (%)
C6H5
C6H5
2a
2a
2b
2b
2c
2d
2e
2f
48
48
48
91
89
91
95
93
−
95
79
96
82
96
−
b
2
3
4
pMeC6H4
pMeC6H4
mMeC6H4
oMeC6H4
1Np
d
72
5
48
>96
>96
48
6
7
−
−
88
While cyclic carbonates are valuable in their own right26 and
are prepared here using CO2 as a phosgene surrogate, Scheme 2
8
2Np
90
80
90
90
87
89
90
91
67
68
74
e
9
pMeOC6H4
mMeOC6H4
pBrC6H4
mClC6H4
mFC6H4
pFC6H4
p((CH3)3C)C6H4
PhCH2CH2
Me
2g
2h
2i
48
26
10
11
48
97
65
44
40
54
99
71
72
76
a
Scheme 2. Conversions of Carbonate Products
48
c
12
2j
120
96
c
13
2k
2l
14
15
16
17
48
2m
2n
2o
2p
48
72
48
c
18
Cy
48
a
Enantiomeric excess (ee) determined by HPLC using a chiral
a
Conservation of ee observed in all cases.
stationary phase. Reactions are 0.4 M in toluene. Isolated yields are
listed. See SI for complete experimental details. Absolute configuration
for 2a assigned using X-ray analysis, remaining examples assigned by
b
analogy. 6.8 mmol (1.0 g) substrate was employed under the
details several notable transformations. First, reduction by
stannane provided carbonate 9 in 86% yield when applied to
iodocarbonate 2a. Straightforward carbonate hydrolysis with a
basic resin in methanol led to the versatile epoxide 10. This is
particularly significant from the viewpoint that CO2 is effectively
used as an equivalent to epoxidation, which normally requires an
electrophilic source of oxygen (e.g., a peracid or dioxirane). Full
reduction employing a stronger reducing agent (LiAlH4) leads to
tertiary alcohol 11 in 71% yield. This CO2 fixation method
therefore offers a simple two step equivalent to metal-free
oxidations of homoallylic alcohols,27 for which CO2 is converted
to either dialkyl carbonate or methanol.
optimized conditions (1 atm CO2) utilizing 3.0 mol % catalyst for 48
h. 10 mol % catalyst loading. Reaction temperature was −50 °C. It
was noted that purified 2g was prone to decomposition.
c
d
e
method to larger amounts, a gram-scale experiment using 3 mol
% catalyst led to the carbonate in 89% ee and 79% yield (Table 2,
entry 2). Finally, spirocyclic carbonate 2q was prepared from the
corresponding trisubstituted alkene in moderate yield (63%) and
encouraging enantioselection (69% ee) (Scheme 1).
Scheme 1. Iodocarbonation of a Trisubstituted Alkene
In summary, a mild and operationally straightforward CO2
fixation reaction has been developed using a dual Brønsted acid/
base catalyst that presents hydrogen-bond donor and acceptor
functionality to activate and orient substrates in an enantiose-
lective reaction. This metal-free method employs relatively weak
nucleophiles (homoallylic alcohols) in the CO2 fixation step,
generating transient acids that add to an alkene in combination
with N-iodosuccinimide. The catalysts deployed here use the
virtues of Brønsted acid/base activation alone to achieve highly
enantioselective carbonate synthesis.28 From a different view-
point, this CO2 fixation method circumvents approaches
dependent on phosgene29 as a source of carbonate protecting
group for 1,3-diol prepared through stereoselective synthesis.
Numerous enantioenriched small molecules might be prepared
using CO2 as a source for carbon−oxygen bond formation.
Several experimental observations are worth mentioning in
addition to the trends summarized above. Foremost among
these, use of a CO2 balloon attached to a degassed reaction
established that the steady-state CO2 concentration is significant
in chilled toluene and could be reached within 40 min; far shorter
than the time to complete conversion to carbonate (monitored
by in situ IR). The rate of CO2 absorption was affected
insignificantly by most every factor examined, including
temperature, the presence of MS 4A, and stirring rate. The
correlation between high chemical yield and molecular sieves can
be explained by the formation of a complex between the catalyst,
adventitious water, and CO2, which we hypothesize to be the
carbonic acid salt (Figure 2).23 This complex precipitates from
the reaction mixture when using 8·HNTf2, but its formation
ASSOCIATED CONTENT
* Supporting Information
Experimental procedures and spectroscopic data for all new
■
S
compounds, and X-ray data (cif) for 2a. The Supporting
C
DOI: 10.1021/jacs.5b04425
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

Journal of the American Chemical Society
Communication
(15) Direct spectroscopic identification of an alkyl carbonic acid is
limited by an equilibrium that generally favors free CO2 and the
corresponding organic alcohol: Gassensmith, J. J.; Furukawa, H.;
Smaldone, R. A.; Forgan, R. S.; Botros, Y. Y.; Yaghi, O. M.; Stoddart, J. F.
J. Am. Chem. Soc. 2011, 133, 15312. Formation of alkyl organic
carbonates is possible under supercritical CO2 conditions: West, K. N.;
Wheeler, C.; McCarney, J. P.; Griffith, K. N.; Bush, D.; Liotta, C. L.;
Eckert, C. A. J. Phys. Chem. A 2001, 105, 3947.
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/jacs.5b04425.
AUTHOR INFORMATION
Corresponding Author
*jeffrey.n.johnston@vanderbilt.edu
■
Notes
(16) Selected references: Dobish, M. C.; Johnston, J. N. J. Am. Chem.
Soc. 2012, 134, 6068. Davis, T. A.; Wilt, J. C.; Johnston, J. N. J. Am. Chem.
Soc. 2010, 132, 2880. Toda, Y.; Pink, M.; Johnston, J. N. J. Am. Chem.
Soc. 2014, 136, 14734. Denmark, S. E.; Kuester, W. E.; Burk, M. T.
Angew. Chem., Int. Ed. 2012, 51, 10938. Whitehead, D. C.; Yousefi, R.;
Jaganathan, A.; Borhan, B. J. Am. Chem. Soc. 2010, 132, 3298. Tan, C. K.;
Zhou, L.; Yeung, Y.-Y. Synlett 2011, 2011, 1335. Paull, D. H.; Fang, C.;
Donald, J. R.; Pansick, A. D.; Martin, S. F. J. Am. Chem. Soc. 2012, 134,
11128. Cheng, Y. A.; Yu, W. Z.; Yeung, Y.-Y. Org. Biomol. Chem. 2014,
12, 2333.
(17) This particular substrate (3-phenyl-3-butenol) has not been
reported with NaH in THF, but the analogous 3-methyl-3-butenol was
used under similar conditions: Bongini, A.; Cardillo, G.; Orena, M.;
Porzi, G.; Sandri, S. J. Org. Chem. 1982, 47, 4626.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Research reported in this publication was supported by the
National Institute of General Medical Sciences (NIH GM
084333). W.W.W. was supported by an HHMI Fellowship
(Kalamazoo College). We are grateful to Dr. Yasunori Toda and
Dr. Roozbeh Yousefi for the preparation of several alkene
substrates and insightful conversations and to Dr. Maren Pink
(Indiana University Molecular Structure Center) for X-ray
analysis.
REFERENCES
■
́
(18) Das Neves Gomes, C.; Jacquet, O.; Villiers, C.; Thuery, P.;
(1) Li, J.-R.; Kuppler, R. J.; Zhou, H.-C. Chem. Soc. Rev. 2009, 38, 1477.
Ramdin, M.; de Loos, T. W.; Vlugt, T. J. H. Ind. Eng. Chem. Res. 2012, 51,
8149. Gassensmith, J. J.; Furukawa, H.; Smaldone, R. A.; Forgan, R. S.;
Botros, Y. Y.; Yaghi, O. M.; Stoddart, J. F. J. Am. Chem. Soc. 2011, 133,
15312.
Ephritikhine, M.; Cantat, T. Angew. Chem., Int. Ed. 2012, 51, 187. Ma, J.;
Zhang, X.; Zhao, N.; Al-Arifi, A. S. N.; Aouak, T.; Al-Othman, Z. A.;
Xiao, F.; Wei, W.; Sun, Y. J. Mol. Catal. A: Chem. 2010, 315, 76.
(19) Hypoiodous acid: Minakata, S.; Sasaki, I.; Ide, T. Angew. Chem.,
Int. Ed. 2010, 49, 1309.
(2) Rochelle, G. T. Science 2009, 325, 1652.
(20) Okino, T.; Hoashi, Y.; Takemoto, Y. J. Am. Chem. Soc. 2003, 125,
(3) Sakakura, T.; Choi, J.-C.; Yasuda, H. Chem. Rev. 2007, 107, 2365.
Additional uses of CO2 as a feedstock: Lindsey, A. S.; Jeskey, H. Chem.
Rev. 1957, 57, 583. Greenhalgh, M. D.; Thomas, S. P. J. Am. Chem. Soc.
2012, 134, 11900. Luo, J.; Preciado, S.; Larrosa, I. J. Am. Chem. Soc.
2014, 136, 4109. Liu, Q.; Wu, L.; Jackstell, R.; Beller, M. Nat. Commun.
2015, 6. Reduction of CO2 for commodity-based chemical production:
Studt, F.; Sharafutdinov, I.; Abild-Pedersen, F.; Elkjær, C. F.;
Hummelshøj, J. S.; Dahl, S.; Chorkendorff, I.; Nørskov, J. K. Nat.
Chem. 2014, 6, 320. Graciani, J.; Mudiyanselage, K.; Xu, F.; Baber, A. E.;
Evans, J.; Senanayake, S. D.; Stacchiola, D. J.; Liu, P.; Hrbek, J.; Sanz, J.
F.; Rodriguez, J. A. Science 2014, 345, 546. For recent advances adapting
CO2 in continuous flow synthesis: Kozak, J. A.; Wu, J.; Su, X.; Simeon,
F.; Hatton, T. A.; Jamison, T. F. J. Am. Chem. Soc. 2013, 135, 18497. Wu,
J.; Kozak, J. A.; Simeon, F.; Hatton, T. A.; Jamison, T. F. Chem. Sci. 2014,
5, 1227.
12672.
(21) Interestingly, the electrophile NIS is sparingly soluble under the
optimized concentration in toluene (0.4 M), suggesting possible phase-
transfer-like activation of NIS by the soluble catalyst, as seen by
Jacobsen: Brindle, C. S.; Yeung, C. S.; Jacobsen, E. N. Chem. Sci. 2013, 4,
2100.
(22) Sakakura, A.; Ukai, A.; Ishihara, K. Nature 2007, 445, 900.
(23) Shaikh, A.-A. G.; Sivaram, S. Chem. Rev. 1996, 96, 951.
́
(24) Villiers, C.; Dognon, J.-P.; Pollet, R.; Thuery, P.; Ephritikhine, M.
Angew. Chem., Int. Ed. 2010, 49, 3465. Heldebrant, D. J.; Jessop, P. G.;
Thomas, C. A.; Eckert, C. A.; Liotta, C. L. J. Org. Chem. 2005, 70, 5335.
(25) Denmark, S. E.; Burk, M. T.; Hoover, A. J. J. Am. Chem. Soc. 2010,
132, 1232. Muller, C. H.; Rosner, C.; Hennecke, U. Chem. - Asian J.
̈
̈
2014, 9, 2162. Wu, J.; Wang, Y. M.; Drljevic, A.; Rauniyar, V.; Phipps, R.
J.; Toste, F. D. Proc. Natl. Acad. Sci. U. S. A. 2013, 110, 13729. Yousefi,
R.; Ashtekar, K. D.; Whitehead, D. C.; Jackson, J. E.; Borhan, B. J. Am.
Chem. Soc. 2013, 135, 14524.
(26) For recent advances in carbonate utilization: Chung, G.-C.; Kim,
H.-J.; Jun, S.-H.; Kim, M.-H. Electrochem. Commun. 1999, 1, 493.
Sanders, D. P.; Fukushima, K.; Coady, D. J.; Nelson, A.; Fujiwara, M.;
Yasumoto, M.; Hedrick, J. L. J. Am. Chem. Soc. 2010, 132, 14724.
Edward, J. A.; Kiesewetter, M. K.; Kim, H.; Flanagan, J. C. A.; Hedrick, J.
L.; Waymouth, R. M. Biomacromolecules 2012, 13, 2483.
(27) 1,1-Disubstituted olefins have generally been challenging for
asymmetric epoxidation: Wang, Z.-X.; Shi, Y. J. Org. Chem. 1997, 62,
8622. Xia, Q. H.; Ge, H. Q.; Ye, C. P.; Liu, Z. M.; Su, K. X. Chem. Rev.
2005, 105, 1603. Wang, B.; Wong, O. A.; Zhao, M.-X.; Shi, Y. J. Org.
Chem. 2008, 73, 9539.
(28) It is worth noting the magnesium-dependent enzyme ribulose-
1,5-bisphosphate carboxylase/oxygenase (RuBisCO). RuBisCO incor-
porates CO2 through carbon−carbon bond formation into glucose
precursors. Berry, J. A.; Lorimer, G. H.; Pierce, J.; Seemann, J. R.; Meek,
J.; Freas, S. Proc. Natl. Acad. Sci. U. S. A. 1987, 84, 734. Stec, B. Proc. Natl.
Acad. Sci. U. S. A. 2012, 109, 18785.
(4) Tsuji, Y.; Fujihara, T. Chem. Commun. 2012, 48, 9956.
(5) Cokoja, M.; Bruckmeier, C.; Rieger, B.; Herrmann, W. A.; Kuhn, F.
̈
E. Angew. Chem., Int. Ed. 2011, 50, 8510.
(6) Omae, I. Coord. Chem. Rev. 2012, 256, 1384.
(7) Cui, X.; Burgess, K. Chem. Rev. 2005, 105, 3272.
(8) Punniyamurthy, T.; Velusamy, S.; Iqbal, J. Chem. Rev. 2005, 105,
2329. For a metal-free example, see: Yang, Y.; Moinodeen, F.; Chin, W.;
Ma, T.; Jiang, Z.; Tan, C.-H. Org. Lett. 2012, 14, 4762.
(9) Nozaki, K.; Sato, N.; Takaya, H. J. Am. Chem. Soc. 1995, 117, 9911.
Brookhart, M.; Wagner, M. I.; Balavoine, G. G. A.; Haddou, H. A. J. Am.
Chem. Soc. 1994, 116, 3641. Reviews: Tietze, L. F.; Ila, H.; Bell, H. P.
Chem. Rev. 2004, 104, 3453. Bianchini, C.; Meli, A. Coord. Chem. Rev.
2002, 225, 35.
(10) Kielland, N.; Whiteoak, C. J.; Kleij, A. W. Adv. Synth. Catal. 2013,
355, 2115.
(11) Decortes, A.; Castilla, A. M.; Kleij, A. W. Angew. Chem., Int. Ed.
2010, 49, 9822.
(12) Maeda, C.; Miyazaki, Y.; Ema, T. Catal. Sci. Technol. 2014, 4, 1482.
(13) Paddock, R. L.; Nguyen, S. T. J. Am. Chem. Soc. 2001, 123, 11498.
Lu, X.-B.; Liang, B.; Zhang, Y.-J.; Tian, Y.-Z.; Wang, Y.-M.; Bai, C.-X.;
Wang, H.; Zhang, R. J. Am. Chem. Soc. 2004, 126, 3732. Berkessel, A.;
Brandenburg, M. Org. Lett. 2006, 8, 4401. Luinstra, G. A.; Haas, G. R.;
Molnar, F.; Bernhart, V.; Eberhardt, R.; Rieger, B. Chem.Eur. J. 2005,
11, 6298.
(29) McGhee, W.; Riley, D.; Christ, K.; Pan, Y.; Parnas, B. J. Org. Chem.
1995, 60, 2820. Fukuoka, S.; Kawamura, M.; Komiya, K.; Tojo, M.;
Hachiya, H.; Hasegawa, K.; Aminaka, M.; Okamoto, H.; Fukawa, I.;
Konno, S. Green Chem. 2003, 5, 497.
(14) Yoshida, S.; Fukui, K.; Kikuchi, S.; Yamada, T. J. Am. Chem. Soc.
2010, 132, 4072.
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DOI: 10.1021/jacs.5b04425
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