Hydrogen Gas-Mediated Deoxydehydration/Hydrogenation of Sugar Acids: Catalytic Conversion of Glucarates to Adipates

Article abstract of DOI:10.1021/jacs.7b07801

The development of a system for the operationally simple, scalable conversion of polyhydroxylated biomass into industrially relevant feedstock chemicals is described. This system includes a bimetallic Pd/Re catalyst in combination with hydrogen gas as a terminal reductant and enables the high-yielding reduction of sugar acids. This procedure has been applied to the synthesis of adipate esters, precursors for the production of Nylon-6,6, in excellent yield from biomass-derived sources.

Full text of DOI:10.1021/jacs.7b07801

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Hydrogen Gas-Mediated Deoxydehydration/Hydrogenation of Sugar
Acids: Catalytic Conversion of Glucarates to Adipates
Reed T. Larson,†,§ Andrew Samant,†,§ Jianbin Chen,†,§ Woojin Lee,† Martin A. Bohn,‡
Dominik M. Ohlmann,‡ Stephan J. Zuend,#,§ and F. Dean Toste*,†,§
†Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
§California Research Alliance (CARA), BASF Corporation, Berkeley, California 94720 United States
#BASF Corp., 46820 Fremont Boulevard, Fremont, California 94538, United States
‡BASF SE, Carl-Bosch-Straße 38, 67056 Ludwigshafen, Germany
S
* Supporting Information
ABSTRACT: The development of a system for the
operationally simple, scalable conversion of polyhydroxy-
lated biomass into industrially relevant feedstock chemicals
is described. This system includes a bimetallic Pd/Re
catalyst in combination with hydrogen gas as a terminal
reductant and enables the high-yielding reduction of sugar
acids. This procedure has been applied to the synthesis of
adipate esters, precursors for the production of Nylon-6,6,
in excellent yield from biomass-derived sources.
Figure 1. Methods for converting aldaric acids to adipic acid or adipate
esters.
he valorization of biomass is an ongoing challenge that has
Tsignificant implications for sustainability of processes in the
chemical industry.1 Most current commercial processes to utilize
biomass focus on chemically simple lipid-based sources.2 In
acid, an aldaric acid with two cis-diols in its open form, has been
converted into adipate esters in a two step process (Figure 1B),13
contrast, carbohydrate feedstocks such as cellulose and starch
have a high degree of chemical complexity and can potentially be
useful as precursors to complex, industrially relevant molecules.3
One attractive target that meets this criterion is adipic acid and its
derivatives.4 This C6 monomer is synthesized in quantities of 2.5
M tonnes per year in order to produce Nylon-6,6.5 Currently, its
production employs petroleum-derived starting materials and is
responsible for a significant proportion of anthropogenic N2O
emissions.6 As such, identification of economical routes for
adipic acid production from biomass would be a significant
development.7
Glucose is an attractive choice of starting material for this
route, as it is abundant and inexpensive.4,8 Additionally, it can be
readily oxidized to glucaric acid, which contains the carboxylic
acid functionality of adipic acid. While the conversion of glucaric
acid into adipic acid using hydrogen as the terminal reductant has
been reported, the reaction required stoichiometric hydrogen
bromide to promote the reaction, which is likely to lead to
challenges in reactor materials as well as issues involving removal
of brominated byproducts (Figure 1A).9 The deoxydehydration
(DODH) of diols to olefins is a promising alternative, as it offers
the possibility of achieving the desired transformation at near-
neutral pH without the need for any halogen promoters.10−12
However, traditional DODH chemistry is not without draw-
backs. First, the reaction generally shows a preference for cis-
diols, deriving from the requirement to form a rhenium diolate
intermediate. This constraint is highlighted by the fact that mucic
while the DODH reaction of glucaric acid gave only 25% of the
muconic ester. More importantly, most reported DODH
chemistry is mediated by expensive terminal reductants such as
triphenylphosphine or secondary alcohols. In recent years, there
have been several promising reports of hydrogen-mediated
DODH reactions on model systems.14,15 However, to date,
reports of applying such conditions to efficiently convert relevant
sugar acids into adipates are absent. Herein, we describe
discovery and development of a catalyst system that directly
provides adipates from glucose derivatives, in a single operation,
using hydrogen as a terminal reductant (Figure 1C).
We conducted initial studies to assess the viability of adipate
production via DODH using the ethyl ester of D-glucarate-6,3-
lactone 1, which can be derived from calcium glucarate. Direct
application of literature precedent using a secondary alcohol as
reductant/solvent and MTO as catalyst showed promising yields
of the initial DODH product 2-Et (Table 1, entry 1), but with a
significant degree of charring and precipitation of solid
byproducts.16 Changing the solvent to ethanol lowered the
yield of 2-Et somewhat, but also produced a homogeneous
solution at the end of the reaction. In subsequent experiments,
palladium on carbon and H2 were added with the aim of
achieving a one-pot reduction to the saturated lactone 3-Et.
Received: July 25, 2017
© XXXX American Chemical Society
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DOI: 10.1021/jacs.7b07801
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a
Table 1. Optimization of Reaction Conditions
H2
Reaction
Time
Entry
Catalyst(s)
10 mol % MeReO3
Additives
Pressure Solvent
Yield 2 Yield 3 Yield 4
Yield 5
b
c
c
c
c
1
-
-
-
-
-
-
-
-
-
-
3-octanol
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
MeOH
MeOH
MeOH
2 h
55%
-
-
-
-
-
-
-
-
-
2
10 mol % MeReO3
-
5 h
42%
-
-
3
10 mol % MeReO3, 2.5 mol % Pd/C
10 mol % MeReO3
-
5 h
40%
-
-
4
1 bar
1 bar
5 bar
5 bar
5 bar
5 bar
5 bar
5 bar
5 h
39%
-
-
5
10 mol % MeReO3, 2.5 mol % Pd/C
10 mol % MeReO3, 2.5 mol % Pd/C
10 mol % MeReO3, 2.5 mol % Pd/C
10 mol % KReO4, 2.5 mol % Pd/C
10 mol % KReO4, 2.5 mol % Pd/C
1 mol % KReO4, 0.75 mol % Pd/C
5 h
65%
trace
-
c
6
5 h
-
-
-
-
-
-
32%
-
c
c
7
18 h
18 h
18 h
18 h
18 h
28%
-
c
8
30%
-
22%
61%
71%
d
d
9
-
-
-
18%
de
,
10
11
27 wt % activated C
-
-
def
, ,
1 mol % KReO4, 0.75 mol % Pd/C
3 mol % H3PO4, 27 wt % activated C
88% (83%)
a
b
c
d
e
f
Reactions run at 0.75 mmol scale. 3-octyl ester. ethyl ester. methyl ester. Reaction run at 7.5 mmol scale and 1 M concentration. Isolated yield
of adipic acid from hydrolysis of crude product with 2 N HCl in parentheses.
Interestingly, while the yield of 2-Et improved under these
conditions, complete reduction to the saturated product was not
observed at 1 bar of hydrogen. However, both a hydrogen
atmosphere and Pd/C were necessary to observe an improve-
ment in yield, suggesting that in this system the palladium
facilitates the reduction of the rhenium catalyst by H2 (Table 1,
entries 2−5).
While several factors might result in formation of the fully
saturated ester using the combined Pd/Re/H2 system, we
posited the lack of alkene hydrogenation derived from the low
hydrogen pressure. Indeed, increasing the pressure of hydrogen
to 5 bar provided saturated 3-Et, but in significantly lower yield
(Table 1, entry 6) compared to the amount of 2-Et produced at 1
bar, even with prolonged reaction times (entry 7). This
observation supports a hypotheses the rhenium catalyst is
unstable to hydrogen and that the palladium catalyst is still active
at higher pressures. Thus, we posited the carbon−rhenium bond
in MTO might be problematic to its stability under the reactions
conditions, and sought alternative catalysts. Accordingly,
replacing MTO with potassium perrhenate resulted in reduction
to the saturated lactone 3-Et, as well as some production of 4-Et
due to ring-opening of this initial product followed by a second
DODH/hydrogenation sequence (entry 8).
reaction mixture further improved the process, affording
dimethyl adipate in 88% overall yield (entry 11). We propose
the Brønsted acid cocatalysts acts to facilitate the ring opening of
3-Et to the necessary open-form diol, which might increase the
rate of the desired reaction and that the activated carbon acts as a
scavenger for catalysts poisons or as a support for partially
reduced rhenium species.
With these optimized conditions in hand, we explored the
substrate scope of the reaction. A variety of polyhydroxylated
esters and lactones were competent substrates (Table 2).
a
Table 2. Substrate Scope
Spurred on by these promising results, conditions that
promoted the ring-opening reaction of 3-Et were explored in
order to improve the yield of the desired diethyl adipate. During
the synthesis of various potential substrates, we observed choice
of esterifying alcohol had a significant impact on the equilibrium
concentrations of various lactonized products based on glucaric
acid. In particular, while esterification with ethanol favored
a
Substrate left/product(s) right. Reaction conditions: 7.5 mmol
substrate, 1 mol % KReO4, 3 mol % H3PO4, 0.75 mol % Pd/C, 25
wt % activated carbon, 5 bar H2, 7.5 mL MeOH, 150 °C, 18 h.
isolation of 6,3-lactone 1, under similar conditions in methanol
the 1,4-lactone 6 was isolated almost exclusively.17 Given the
b
c
importance of the lactone/ester equilibrium on formation of the
Substrate prestirred at 120 °C in MeOH for 3 h. 48 h reaction time.
final adipate esters, methanol was examined as a solvent for the
tandem DODH/hydrogenation reaction, resulting in a good
yield of dimethyl adipate (5-Me) as well as some unsaturated
intermediate 4-Me (entry 9).
Studying various additives uncovered that addition of activated
carbon resulted in full conversion to 5-Me and allowed the
concentration of the reaction to be increased to 1 M.
Furthermore, addition of catalytic phosphoric acid to the
Interestingly, under these reaction conditions the DODH
reaction was completely selective for vicinal diols in the α,β
positions of carboxylic acids and esters; reaction of an equimolar
mixture of diethyl tartrate and 1,2-dodecanediol produced
diethyl succinate in 89% yield without a trace of dodecane (eq
1). This is in stark contrast to previously reported DODH
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Communication
protocols, where substrates primarily consist of electronically
neutral aliphatic diols.
Table 3. Metal Analysis of Residual Solids after DODH
Reaction
of rhenium species occurs to a significant extent over the course
of the reaction under typical conditions, the active catalyst is
likely a soluble species.
The divergent reactivity observed in this system prompted us
to investigate the possibility the reaction proceeds via a
mechanism that differs from the retro-[3+2]-cycloaddition
generally postulated for rhenium-catalyzed DODH reactions.18
One possibility is the ester moiety promotes a stepwise
dehydration19/ketone reduction pathway via either an α- or β-
ketoester, as palladium-catalyzed hydrogenations of both have
been reported previously.20 However, subjecting ethyl acetoace-
tate to the reaction conditions resulted in only trace reaction, and
while diethyl 2-oxoglutarate was fully decomposed on the time
scale of the reaction, only traces of the expected DODH/
hydrogenation product were observed (Figure 2A).21
Lastly, we recognized the importance of our catalytic system’s
reliance on hydrogen as a means of avoiding alcoholic solvents. In
contrast to previously reported DODH-based syntheses of
adipates, our system had the potential to directly produce adipic
acid in water. This would confer several advantages: reduction of
solvent cost, generation of the most industrially relevant nylon
precursor, and simplification of the purification process. Reaction
of glucarodilactone under analogous conditions did indeed
produce adipic acid, albeit in only 19% yield. Based on this
promising result, we examined strategies to stabilize the catalyst,
ultimately finding that prestirring the rhenium precatalyst with
DMAP23 and increasing the amount of activated charcoal used
resulted in a 72% yield of adipic acid (eq 2).
The combination of a rhenium(VII) catalyst and a palladium-
on-carbon cocatalyst has allowed for the development a catalytic
system to effect the high-yielding complete deoxygenation of 1,2-
diols using hydrogen gas as the terminal reductant. Key to the
success of this chemistry was the choice of a rhenium catalyst
sufficiently stable to the strongly reducing conditions, as well as
the addition of Pd/C, which acts both as a cocatalyst for the
DODH step and the catalyst for the reduction of the resulting
olefin. This catalyst system enabled the conversion of glucaric
acid into adipate esters, as well as direct conversion into adipic
acid using water as the solvent. In the future, we look forward to
further investigating and optimizing this system as a means to
affect the important goal of converting readily available biomass
into valuable chemical feedstocks that have, until now, been
derived from petroleum sources.
Figure 2. (A) Competence of diol dehydration products. (B) Impact of
electronic properties of styrene diols on reaction yield.
Having ruled out the intermediacy of ketonic dehydration
products, we reasoned the ester group might facilitate the
DODH reaction, either by serving as an electron-withdrawing
group or by coordinating to the rhenium catalyst. In order to
distinguish between these possibilities, ester-substituted styrene
glycol 7 and styrene glycol (8) were subjected to the standard
reaction conditions for 3 h, producing the fully hydrogenated
products in 53% and 15% yield, respectively (Figure 2B).
Additionally, a 1-h direct competition experiment between 7 and
8 produced the ester-containing product in 44% yield and only
traces of ethylbenzene. We therefore propose the ester (or other
electron withdrawing group) facilitates the reaction by accepting
electron density from the vicinal carbon−oxygen σ orbital into its
π* orbital. This effect lowers the energy of the transition state for
carbon−oxygen bond cleavage.18a,22
We also examined whether active rhenium catalyst was a
soluble species or if surface deposition was responsible for the
change in catalytic activity. SEM-EDS analysis indicated that use
of KReO4 in the DODH reaction was accompanied by significant
precipitation of rhenium-containing species onto the Pd-
containing solid support (Table 3). However, when tetrabuty-
lammonium perrhenate was used as precatalyst, essentially no Re
could be detected on the residual solids, while still performing at
a similar level to the potassium catalyst. Thus, while precipitation
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/jacs.7b07801.
■
S
Procedures and spectral data (PDF)
AUTHOR INFORMATION
Corresponding Author
*fdtoste@berkeley.edu
■
ORCID
F. Dean Toste: 0000-0001-8018-2198
Notes
The authors declare the following competing financial
interest(s): A provisional patent has been filed by UC Berkeley
and BASF.
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(12) Mo-catalyzed DODH: (a) Sandbrink, L.; Beckerle, K.; Meiners, I.;
Liffmann, R.; Rahimi, K.; Okuda, J.; Palkovits, R. ChemSusChem 2017,
10, 1375. (b) Dethlefsen, J. R.; Lupp, D.; Teshome, A.; Nielsen, L. B.;
Fristrup, P. ACS Catal. 2015, 5, 3638. (c) Hills, L.; Moyano, R.; Montilla,
ACKNOWLEDGMENTS
■
This work was financially supported by BASF Corporation
(Award Number 53093) and the NSF through the Center for
Sustainable Polymers (CHE-1413862). The authors thank Dr.
Selim Alayoglu for assistance with SEM/EDS measurements.
SEM/EDS work at the Molecular Foundry was supported by the
Office of Science, Office of Basic Energy Sciences, of the U.S.
Department of Energy under Contract No. DE-AC02-
05CH11231.
́
F.; Pastor, A.; Galindo, A.; Alvarez, E.; Marchetti, F.; Pettinari, C. Eur. J.
Inorg. Chem. 2013, 2013, 3352−3361. V-catalyzed DODH:
(d) Gopaladasu, T. V.; Nicholas, K. M. ACS Catal. 2016, 6, 1901.
(e) Nicholas, K. M.; Chapman, G., Jr Chem. Commun. 2013, 49, 8199.
(13) (a) Shiramizu, M.; Toste, F. D. Angew. Chem., Int. Ed. 2013, 52
(49), 12905. See also: (b) Li, X.; Wu, D.; Lu, T.; Yi, G.; Su, H.; Zhang, Y.
Angew. Chem., Int. Ed. 2014, 53, 4200.
(14) (a) Gopaladasu, T. V.; Nicholas, K. M. ACS Catal. 2016, 6, 1901.
(b) Ziegler, J. E.; Zdilla, M. J.; Evans, A. J.; Abu-Omar, M. M. Inorg.
Chem. 2009, 48, 9998.
REFERENCES
■
(1) (a) Shanks, B. H.; Keeling, P. L. Green Chem. 2017, 19, 3177.
(b) Sheldon, R. A. J. Mol. Catal. A: Chem. 2016, 422, 3. (c) Wu, L.;
Moteki, T.; Gokhale, A. A.; Flaherty, D. W.; Toste, F. D. Chem. 2016, 1,
32. (d) Deneyer, A.; Renders, T.; Van Aelst, J.; Van den Bosch, S.;
(15) A heterogeneous Re/Pd system gave excellent yields in the
DODH of simple diols, but only modest yields in the DODH of sugar
alcohols, see: (a) Ota, N.; Tamura, M.; Nakagawa, Y.; Okumura, K.;
Tomishige, K. Angew. Chem., Int. Ed. 2015, 54, 1897. (b) Ota, N.;
Tamura, M.; Nakagawa, Y.; Okumura, K.; Tomishige, K. ACS Catal.
2016, 6, 3213. (c) Tazawa, S.; Ota, N.; Tamura, M.; Nakagawa, Y.;
Okumura, K.; Tomishige, K. ACS Catal. 2016, 6, 6393. For an
additional example of H2/Pd/Re reduction with perchlorate anion as the
substrate, see: Hurley, K. D.; Shapley, J. R. Environ. Sci. Technol. 2007,
41, 2044. For a related example of polyol reduction using Re/Ir rather
than Re/Pd, see Tomishige, K.; Nakagawa, Y.; Tamura, M. Selective
Hydrogenolysis of C-O bonds Using the Interaction of the Catalyst
Surface and OH groups. In Selective Catalysis for Renewable Feedstocks
and Chemicals; Nicholas, K. M., Ed.; Topics in Current Chemistry Series
353; Springer International Publishing: Switzerland, 2014; pp 127−162.
(16) Previously reported DODH systems utilize solvents such as
benzenes, dioxane, or long chain alcohols, which tended to lead to
undesired condensation of 1 to 2, effectively eliminating the vicinal diol
functionality.
(17) The ratio of 1,4 vs 6,3 lactone is equal in the absence of catalysts in
both EtOH and MeOH. The isolation of 1 and 6 appears to result from a
dynamic crystallization process wherein 1 selectively crystallizes from
the mother liquor in EtOH, while the remaining soluble glucarate re-
equilibrates as 1 precipitates. The same holds true for 6 in MeOH. For
previous isolation of these lactones, see: Kiely, D. E.; Chen, L.; Lin, T. H.
J. Am. Chem. Soc. 1994, 116, 571.
(18) For DFT studies on the mechanism of: Recatalyzed DODH see:
(a) Gable, K. P.; Zhuravlev, F. A. J. Am. Chem. Soc. 2002, 124, 3970.
(b) Qu, S.; Dang, Y.; Wen, M.; Wang, Z.-W. Chem. - Eur. J. 2013, 19,
3827. (c) Dethlefsen, J. R.; Fristrup, P. ChemCatChem 2015, 7, 1184.
(d) Wu, D.; Zhang, Y.; Su, H. Chem. - Asian J. 2016, 11, 1565. (e) V-
catalyzed DODH: Galindo, A. Inorg. Chem. 2016, 55, 2284.
(19) Korstanje, T. J.; Jastrzebski, J. T. B. H.; Gebbink, R. J. M. K. Chem.
- Eur. J. 2013, 19, 13224.
Gabriels, D.; Sels, B. F. Curr. Opin. Chem. Biol. 2015, 29, 40. (e) Tuck, C.
̈
́ ́
O.; Perez, E.; Horvath, I. T.; Sheldon, R.; Poliakoff, M. Science 2012, 337,
695.
(2) (a) Thakur, D. S.; Kundu, A. J. Am. Oil Chem. Soc. 2016, 93, 1575.
(b) Marshall, A.-L.; Alaimo, P. J. Chem. - Eur. J. 2010, 16, 4970. (c) Behr,
A.; Westfechtel, A.; Gomes, J. P. Chem. Eng. Technol. 2008, 31, 700.
(d) Wittcoff, H. A.; Reuben, B. G.; Plotkin, J. S. In Industrial Organic
Chemicals; John Wiley & Sons, Inc.: Hoboken, NJ, 2012; pp 493−521.
(3) (a) Dusselier, M.; Mascal, M.; Sels, B. F. Top. Curr. Chem. 2014,
353, 1. (b) Tong, X.; Ma, Y.; Li, Y. Appl. Catal., A 2010, 385, 1.
(4) (a) Kruyer, N. S.; Peralta-Yahya, P. Curr. Opin. Biotechnol. 2017, 45,
136. (b) Bart, J. C. J.; Cavallaro, S. Ind. Eng. Chem. Res. 2015, 54, 567.
(c) Van de Vyver, S.; Roman-Leshkov, Y. Catal. Sci. Technol. 2013, 3,
1465.
(5) (a) Bart, J. C. J.; Cavallaro, S. Ind. Eng. Chem. Res. 2015, 54, 1.
(b) Hermans, I.; Jacobs, P. A.; Peeters, J. Chem. - Eur. J. 2006, 12, 4229.
(c) Lichtenthaler, F. W. In Ullmann’s Encyclopedia of Industrial
Chemistry; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, 2000.
(d) Musser, M. T. In Ullmann’s Encyclopedia of Industrial Chemistry;
Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, 2000.
(6) (a) Thiemens, M. H.; Trogler, W. C. Science 1991, 251 (4996), 932.
(b) Reimer, R. A.; Slaten, C. S.; Seapan, M.; Lower, M. W.; Tomlinson,
P. E. Environ. Prog. 1994, 13, 134.
(7) (a) Llevot, A.; Dannecker, P.-K.; von Czapiewski, M.; Over, L. C.;
Soyler, Z.; Meier, M. A. R. Chem. - Eur. J. 2016, 22, 11510. (b) Harmsen,
̈
P. F. H.; Hackmann, M. M.; Bos, H. L. Biofuels, Bioprod. Biorefin. 2014, 8,
306.
(8) Draths, K. M.; Frost, J. W. J. Am. Chem. Soc. 1994, 116, 399.
(9) Boussie, T. R.; Dias, E. L.; Fresco, Z. M.; Murphy, V. J.; Shoemaker,
J.; Archer, R.; Jiang, H. US8669397B2, March 11, 2014.
(20) (a) Krebs, A.; Bolm, C. Synlett 2011, 2011, 671. (b) Marrodan, C.
M.; Berti, D.; Liguori, F.; Barbaro, P. Catal. Sci. Technol. 2012, 2, 2279.
(c) Hattori, K.; Sajiki, H.; Hirota, K. Tetrahedron 2001, 57, 4817.
(21) Additionally, α,β-dideuterated substrates showed washing out of
deuterium at the β position but not the α position. Since formation of
either of these intermediates should result in deuterium exchange at the
α-position (by direct reduction of that position for the α-ketoester and
by facile enolization of the β-ketoester), this observation further
supports the idea that ketoester intermediates are not involved in
product formation (see SI for details).
(22) Theoretical studies have shown the exact nature of the transition
state for deoxydehydration and dihydroxylation can vary significantly
depending on the ligand set of the catalytic species. As such, any insight
into the specifics of the relevant transition state is challenging to derive
from analogy to known catalytic systems. For experimental demon-
stration of an asynchronous transition state in the [3+2] cycloreversion,
see 18a. For a theoretical analysis of the favored dihydroxylation/
deoxydehydration transition states for various simple rhenium
complexes, see: Deubel, D. V.; Frenking, G. J. Am. Chem. Soc. 1999,
121, 2021.
(10) For a general reviews of deoxygenation of biomass, see:
(a) Rogers, K. A.; Zheng, Y. ChemSusChem 2016, 9, 1750. (b) Raju,
S.; Moret, M.-E.; Gebbinik, R. J. M. K. ACS Catal. 2015, 5, 281.
(c) Boucher-Jacobs, C.; Nicholas, K. M. Top. Curr. Chem. 2014, 353,
163.
(11) (a) Cook, G. K.; Andrews, M. A. J. Am. Chem. Soc. 1996, 118,
9448. (b) Vkuturi, S.; Chapman, G.; Ahmad, I.; Nicholas, K. M. Inorg.
Chem. 2010, 49, 4744. (c) Arceo, E.; Ellman, J. A.; Bergman, R. G. J. Am.
Chem. Soc. 2010, 132, 11408. (d) Shiramizu, M.; Toste, F. D. Angew.
Chem., Int. Ed. 2012, 51, 8082. (e) Yi, J.; Liu, S.; Abu-Omar, M. M.
ChemSusChem 2012, 5, 1401. (f) Liu, P.; Nicholas, K. M. Organo-
metallics 2013, 32, 1821. (g) Raju, S.; Jastrzebski, J. T. B. H.; Lutz, M.;
Gebbink, R. J. M. K. ChemSusChem 2013, 6, 1673. (h) Denning, A. L.;
Dang, H.; Liu, Z.; Nicholas, K. M.; Jentoft, F. C. ChemCatChem 2013, 5,
3567. (i) Boucher-Jacobs, C.; Nicholas, K. M. ChemSusChem 2013, 6,
597. (j) Dethlefsen, J. R.; Fristrup, P. ChemSusChem 2015, 8, 767.
(k) Sandbrink, L.; Klindtworth, E.; Islam, H.-U.; Beale, A. M.; Palkovits,
R. ACS Catal. 2016, 6, 677. (l) Raju, S.; van Slagmaat, C. A. M. R.; Li, J.;
Lutz, M.; Jastrzebski, J. T. B. H.; Moret, M.-E.; Gebbink, R. J. M. K.
Organometallics 2016, 35, 2178. (m) Shin, N.; Kwon, S.; Moon, S.;
Hong, C. H.; Kim, Y. G. Tetrahedron 2017, 73, 4758.
(23) Li, X.; Zhang, Y. ChemSusChem 2016, 9, 2774.
D
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