Highly efficient chemical process to convert mucic acid into adipic acid and DFT studies of the mechanism of the rhenium-catalyzed deoxydehydration

Article abstract of DOI:10.1002/anie.201310991

The production of bulk chemicals and fuels from renewable bio-based feedstocks is of significant importance for the sustainability of human society. Adipic acid, as one of the most-demanded drop-in chemicals from a bioresource, is used primarily for the large-volume production of nylon-6,6 polyamide. It is highly desirable to develop sustainable and environmentally friendly processes for the production of adipic acid from renewable feedstocks. However, currently there is no suitable bio-adipic acid synthesis process. Demonstrated herein is the highly efficient synthetic protocol for the conversion of mucic acid into adipic acid through the oxorhenium-complex-catalyzed deoxydehydration (DODH) reaction and subsequent Pt/C-catalyzed transfer hydrogenation. Quantitative yields (99 %) were achieved for the conversion of mucic acid into muconic acid and adipic acid either in separate sequences or in a one-step process. Taking a dip: A highly efficient synthetic protocol has been developed for the conversion of mucic acid into adipic acid by the oxorhenium-complex-catalyzed deoxydehydration reaction and subsequent Pt/C-catalyzed transfer hydrogenation. Quantitative yields were achieved for the conversion of mucic acid into muconic acid and adipic acid esters either through separate sequences or through a one-pot process.

Full text of DOI:10.1002/anie.201310991

Angewandte
Chemie
DOI: 10.1002/anie.201310991
Sustainable Chemistry
Highly Efficient Chemical Process To Convert Mucic Acid into Adipic
Acid and DFT Studies of the Mechanism of the Rhenium-Catalyzed
Deoxydehydration**
Xiukai Li, Di Wu, Ting Lu, Guangshun Yi, Haibin Su,* and Yugen Zhang*
Abstract: The production of bulk chemicals and fuels from
renewable bio-based feedstocks is of significant importance for
the sustainability of human society. Adipic acid, as one of the
most-demanded drop-in chemicals from a bioresource, is used
primarily for the large-volume production of nylon-6,6
polyamide. It is highly desirable to develop sustainable and
environmentally friendly processes for the production of adipic
acid from renewable feedstocks. However, currently there is no
suitable bio-adipic acid synthesis process. Demonstrated herein
is the highly efficient synthetic protocol for the conversion of
mucic acid into adipic acid through the oxorhenium-complex-
catalyzed deoxydehydration (DODH) reaction and subse-
quent Pt/C-catalyzed transfer hydrogenation. Quantitative
yields (99%) were achieved for the conversion of mucic acid
into muconic acid and adipic acid either in separate sequences
or in a one-step process.
Combined biocatalytic and chemocatalytic pathways have
been used to produce adipic acid from renewable precursors,
with cis,cis-muconic acid as the key intermediate.[6] In the
reported biocatalytic conversions of glucose into muconic
acid, the multiple-step fermentation processes invoke several
different kinds of enzymes, but the product yield and the
production efficiency are very low.[7,8] In contrast, the
conversion of muconic acid into adipic acid is rather
straightforward by using a hydrogenation reaction.[9] Adipic
acid preparations by chemocatalytic hydrogenations of furan-
2,5-dicarboxylic acid (FDCA)[10] and glucaric acid[11] have
been reported in patents. However, drastic reaction condi-
tions such as strong halogen acids and high pressure (more
than 50 bar) of H2 were employed. The step by step hydro-
genolysis of 5-hydroxymethylfurfural (HMF) can produce
1,6-hexanediol (a potential precursor for adipic acid) with
high selectivity, albeit with low HMF conversion.[12] The harsh
reaction conditions and low efficiency of these methods make
them unlikely to be industrialized.
The key challenge for the conversion of oxygen-rich
biocompounds (sugar, sugar acids, and sugar alcohols) into
industrial bulk chemicals is to develop highly efficient
catalytic deoxygenation systems which can selectively convert
a bioresource into the target chemicals. Recently, the well-
known deoxydehydration (DODH) reaction has been suc-
cessfully applied to the conversion of polyols, including sugar
alcohols, into conjugated alkenes.[13] Although the reaction
conditions for DODH reactions are rather mild, the substrate
scope is limited to polyols and the product selectivity is not
high enough.[13] Very recently, Shiramizu and Toste reported
the conversion of mucic acid into adipic acid ester, by using
a DODH and hydrogenation reaction, in moderate yields.[14]
In the present work, we report the highly efficient conversion
of mucic acid (1) into muconic acid (2) through a DODH
reaction catalyzed by an oxorhenium complex. Remarkably,
excellent yield (99%) is achieved for the DODH reaction of
this sugar acid substrate. By combining DODH with a trans-
fer-hydrogenation reaction, 1 is successfully converted into
adipic acid (3) with excellent yield in either one or two steps
(see Scheme S1 in the Supporting Information).
T
he production of bulk chemicals and fuels from renewable
bio-based feedstocks is of significant importance for the
sustainability of human society.[1] Adipic acid (hexanedioic
acid), as one of the most demanded drop in chemicals from
a bioresource, is used primarily for the large-volume produc-
tion of nylon-6,6 polyamide.[2] Currently, the commercial
adipic acid is mainly produced through the petroleum-based
cyclohexane route which involves a nitric acid oxidation
process.[3] Besides the nonrenewable feedstock source of
cyclohexane for this route, the emission of large amounts of
nitrous oxides (N2O, NO, and NO2) during the oxidation
process is also a major environmental concern.[4] It is highly
desirable to develop a sustainable and environmentally
friendly process for the production of adipic acid from
renewable feedstocks.[5]
[*] Dr. X. Li, Dr. T. Lu, Dr. G. Yi, Dr. Y. G. Zhang
Institute of Bioengineering and Nanotechnology
31 Biopolis Way, The Nanos, Singapore 138669 (Singapore)
E-mail: ygzhang@ibn.a-star.edu.sg
D. Wu, Prof. H. Su
School of Materials Science and Engineering, Nanyang Technolog-
ical University, N3-B4-W310, 50 Nanyang Avenue
Singapore 639798 (Singapore)
Mucic acid (1) is a C6 sugar acid which can be produced
from galactose on large scale by an established method.[15] In
our work, 1 was tested under typical DODH reaction
conditions with methyltrioxorhenium (MTO) as a catalyst.[13]
In the initial trial, 1 was heated in 3-octanol at 1808C for
2 hours. The reaction went very slowly and the selectivity was
low. The majority of 1 remained an insoluble solid throughout
the reaction. With 3-pentanol as the solvent at 1208C, the
reaction was still slow in the initial stage, probably because of
E-mail: hbsu@ntu.edu.sg
[**] This work was supported by the Institute of Bioengineering and
Nanotechnology (Biomedical Research Council, Agency for Science,
Technology and Research (A*STAR), Singapore), and Biomass-to-
Chemicals Program (Science and Engineering Research Council,
A*STAR, Singapore).
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201310991.
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
These are not the final page numbers!

.
Angewandte
Communications
the low solubility of 1, but showed excellent selectivity.
Kinetic studies showed that 1 was gradually converted into
the conjugated double-bond products in boiling 3-pentanol
(1208C) with 5 mol% MTO (Figure 1A). It was found that
the products were the monoester 4 and diester 5. The yield of
4 increased continuously and reached the maximum at
24 hours, and then decreased (Scheme 1). Meanwhile, the
yield of 5 kept increasing even after 24 hours. It was clear that
1 was first converted into 4 and then further converted into 5.
The full conversion into 4 and 5 was observed after 24 hours.
Compared with the DODH reactions of polyols,[13] the
reaction temperature of this system is lower, and the reaction
rate is also slower. This outcome could be due to the low
solubility of 1 or the interference of carboxylic acid groups. In
fact, higher reaction temperature led to lower selectivity, but
the reaction was sluggish at lower reaction temperature
(908C). To understand more about this reaction, the dieth-
ylmucate (6; Scheme 1) was prepared according to a reported
method[16] and was used as the starting material for the
DODH reaction. Under the same reaction conditions, full
conversion of 6 into 5 (30%) and 7 (70%) were achieved at
20 hours (see Figure S1 in the Supporting Information).
Apparently, the ester exchange reaction occurred and
65.0% of the ethyl groups were substituted by 3-pentanol.
Despite the fact that 6 has much better solubility than 1 in hot
alcohols,[16] the reaction of 6 proceeded only slightly faster
than that of 1. This result indicated that 1 was first subject to
esterification before undergoing the DODH reaction. The
reaction was generally conducted under N2 or air flow
(entry 3, Table S1). In contrast, a slower reaction was
observed in the sealed system (entry 4, Table S1) and much
faster reaction was achieved when a water separator was
employed (entry 5, Table S1).
To accelerate the reaction, Brønsted acids were added as
cocatalysts to promote the esterification step and enhance the
solubility of the starting material. As shown in Figure 1b, the
addition of para-toluene sulfonic acid (TsOH) remarkably
shortened the reaction time required to achieve full con-
version, and the product distribution and the trends of
products formation remained the same. Sulfuric acid also
showed the similar promoting effect (entry 7, Table S1). In
fact, the acid additives for the DODH reaction would assist
olefin extrusion by protonation of the rhenium diolate
intermediate,[17,18] and the extrusion of olefin from oxorhe-
nium complex is the key step in DODH reaction.[13a,19] With
the aid of an acid cocatalyst, the catalyst (MTO) loading can
be reduced to as low as 0.5 mol% (entries 8–11, Table S1).
Various Re catalysts have also been tested for the
reaction. [Re2(CO)10] is efficient for the DODH reaction of
a variety of vicinal diols.[13a,17] However, [Re2(CO)10] is
inactive for the DODH reaction of 1 (entry 12, Table S1),
probably because of the poor tolerance of [Re2(CO)10] to the
carboxylic acid group. In contrast, a high reaction rate was
observed for the Re2O7-catalyzed DODH reaction of 1 in 3-
pentanol (entries 13 and 14, Table S1). The reaction with the
Re2O7 catalyst is even faster than that catalyzed by MTO in
combination with TsOH. Re2O7 is hygroscopic and can react
easily with moisture to form HReO4,[20] which may promote
the esterification and olefin extrusion steps in the DODH
catalytic cycle. Addition of TsOH to the Re2O7 reaction
system did not additionally improve the reaction efficiency
(entries 15 and 16, Table S1).
Figure 1. a) DODH of mucic acid with an MTO catalyst. b) DODH of
mucic acid with MTO and TsOH catalysts. Reaction conditions: mucic
acid (1.0 mmol), catalysts (5.0 mol%), 3-pentanol (20.0 mL), 1208C.
As to the solvent for this reaction, 3-octanol is less active,
even though it can be used at a higher temperature, probably
because of the reduced polarity of 3-octanol (entry 1,
Table S2). 2-propanol is almost inactive, as the reaction is
carried out at a lower temperature given the lower boiling
point (entry 4, Table S2). The investigation on the viability of
using bioderived 1-butanol showed that the reaction effi-
ciency is similar to that of 3-pentanol, and almost quantitative
conversion of 1 into muconate was achieved in 12 hours with
Re2O7 as the catalyst (entry 3, Table S2). In the 1-butanol
system, only dibutyl muconate (8; Scheme 1) was observed,
probably because of the reduced steric effect of the primary
alcohol.
As the high yield of muconate from mucic acid was
achieved, a subsequent transfer-hydrogenation reaction was
demonstrated for the conversion of 2 or muconates into adipic
acid (3) or its esters (Scheme 2). Firstly, muconic acid (2)
Scheme 1. DODH of 1 and mucic acid diethyl ester to muconates.
2
www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
These are not the final page numbers!

Angewandte
Chemie
Scheme 2. Transfer-hydrogenation of trans,trans-muconic acid to adipic
acid and its ester.
could be quantitatively converted into 3 or the monoester 9 in
3-pentanol at 2008C in 12 to 24 hours. Similar results were
achieved when different catalysts (Ru/C, Pd/C, or Pt/C) were
used. Encouraged by this result, crude muconates, which were
obtained from the DODH reaction, were directly used as the
feedstock for the transfer-hydrogenation reaction. Remark-
ably, the muconates obtained from 1 by a DODH reaction
were fully converted into the adipic acid esters 9 and 10 (see
Table S3). The reaction was highly selective and no other by-
product was observed. Since both the DODH and transfer-
hydrogenation reaction could be conducted in 3-pentanol, the
one-step conversion of 1 into 3 or its esters was tested
(Scheme 3). In a closed reaction system with MTO, TsOH,
and Pt/C catalysts, 1 was converted into adipic acid esters in
75% yield within 48 hour at 2008C (entry 7,
Table S4). The moderate efficiency is due to
the low reaction rate for the DODH step in the
closed system, as mentioned above. Thus, when
the reaction was carried out in a one-pot, two-
step manner, that is, run at 1208C under air
flow for 12 h and subsequently in a sealed
system at elevated temperature (160–2008C)
for another 12 h, the reaction efficiency was
dramatically increased and a 99% yield of the
adipic acid esters (96% isolated yield) was
achieved directly from 1. The adipic acid esters
could be further hydrolyzed to give free adipic
acid (3) in 94% yield upon isolation. In a 5 g
scale experiment, a high yield (98%, isolated)
of adipic acid esters was also achieved (see the
Supporting Information). As mucic acid can be
obtained from renewable galactose on large
scale by the already established procedure,[15]
the method developed herein provides a highly
efficient synthetic protocol for the production
of renewable adipic acid (3).
Scheme 3. The conversion of 1 into adipic acid esters by a DODH/
transfer-hydrogenation process in one pot.
the MTO reduction reaction, our results showed that
reduction of MTO to MODH by a two-step hydrogen transfer
process is thermodynamically and kinetically favorable rela-
tive to MDO (Scheme 4). The energy barrier is 39.6 kcal
molÀ1 for MODH as compared to 47.5 kcalmolÀ1 for MDO,
while the relative energy is 7.8 kcalmolÀ1 for MODH as
compared to 19.4 kcalmolÀ1 for MDO. In the second step,
MODH was firstly applied in the DODH reaction of 1. In the
DODH cycle 1, a/b OH groups of 1 are activated and
Although the mechanism of the DODH
reaction for vicinal diols has been well dis-
cussed,[13,21] there are still some unclear points,
especially for the current mucic acid feedstock.
In the MTO catalyst case, Toste et al.[13a]
suggested the reaction sequence started from
the reduction of ReVII to ReV in the complex
methyldioxorhenium (MDO), with a subse-
quent MDO-catalyzed DODH reaction. How-
ever, Wang et al.[21] proposed a different active
species,
methyloxodihydroxyrhenium
(MODH), using density functional theory
(DFT) calculations. To resolve the controversy,
we performed detailed DFT calculations for
the mucic acid DODH process to understand
the reaction mechanism. For the first step of
Scheme 4. Energy diagram and proposed mechanism of MTO-catalyzed DODH
reaction for the conversion of mucic acid into muconic acid in alcohol.
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
3
These are not the final page numbers!

.
Angewandte
Communications
eliminated (Scheme 4). The process progressed through three
transition states (TS3, TS4, and TS5 in Scheme 4). Interest-
ingly, for the transition-state TS3, the hydrogen transferred
from an a-hydroxy group (OHa) is kinetically favorable, but
thermodynamically unfavorable as compared to TS3’ where
the hydrogen of the b-hydroxy group (OHb) is transferred.
However, the hydrogen transfer steps are not the rate-limiting
steps in the whole cycle. The highest energy barrier (21.1 kcal
molÀ1) in this process is associated with the third transition-
Experimental Section
Larger scale synthesis of adipic acid esters from mucic acid: A
mixture of mucic acid (25.0 mmol, 5.25 g), MTO (1.25 mmol, 300 mg),
TsOH (1.25 mmol, 215 mg), and 3-pentanol (250.0 mL) was charged
into a pressure flask. The reaction mixture was stirred at 1208C for
12 h. Awater separator was used to remove the produced water. After
that, 1.56 g of 5.0% Pt/C was added into the flask. The flask was
sealed and the reaction mixture was stirred at 1608C for another 12 h.
The reaction mixture was then cooled down to room temperature.
The catalysts were separated by filtration through Celite-545, the
solvent was removed by evaporation, and the obtained adipic acid
esters were purified by flash column chromatography (CHCl3/MeOH
10:1) to give colorless liquid (6.84 g, 98% yield, dipentyl ester/
monopentyl ester 93:7).
À
state TS5, which is accompanied with breaking C O bonds to
form the intermediate 11and to reform MTO. The second
DODH cycle from 11 to muconic acid (2) is similar to the first
cycle, but with a much lower energy barrier (17.6 kcalmolÀ1).
This result indicates that the second DODH cycle is much
faster than the first cycle, which is consistent with the fact that
11 was not observed experimentally. To provide a compre-
hensive comparison, the elimination of b- and g-hydroxy
groups in the first DODH cycle were also calculated, and the
results showed much higher energy barriers in the first cycle
Hydrolysis of adipic acid dipentyl ester: The separated adipic acid
dipentyl ester (286.0 mg, 1 mmol) was refluxed for 12 h in an EtOH/
H2O solution of sodium hydroxide (0.133 molLÀ1, 15.0 mL; EtOH/
H2O 1:2). After that, the reaction mixture was evaporated to dryness,
and the obtained solid was dissolved in 10.0 mL deionized water. The
pH value of the aqueous solution was adjusted to about 3.0 with 1m
HCl. The solution was again evaporated to dryness, and the obtained
solid was stirred in 10.0 mL methanol for 3 min. The mixture was then
filtered through Celite-545, and the filtrate was evaporated to afford
adipic acid as a white solid. The product was vacuum dried at 608C
overnight, and adipic acid was obtained at 94% yield (136.8 mg).
(29.5 kcalmolÀ1), as well as the second cycle (25.4 kcalmolÀ1
;
see Figures S2 and S3). Hence, the elimination of b- and g-
hydroxy groups in the first DODH cycle is unlikely to happen.
In addition, Tosteꢀs active species, MDO, has also been
calculated in the mucic acid DODH process. In this case, the
energy barrier of the first transition-state TS3D is 21.7 kcal
molÀ1, which is much higher than 9.9 kcalmolÀ1 of the MODH
process TS3 (see Figure S4). Interestingly, the energy barrier
of the first transition state in the second cycle (TS6D) is also
21.4 kcalmolÀ1, which is much higher than the 10.5 kcalmolÀ1
of the MODH process (TS6) as well (see Figure S5). In both
the DODH cycles 1 and 2, MDO and MODH exhibit the
same transition states, that is, TS4 and TS5, and TS7 and TS8.
The energy barrier of the entire processes (including MTO
reduction step) for the MDO pathway (47.5 kcalmolÀ1) is
much higher than that for the MODH one (39.6 kcalmolÀ1).
Therefore, MODH is the identified intermediate in the MTO-
catalyzed DODH reaction for 1. The reaction starts with the
a,b-positions first instead of the b,g-positions, thus resulting
from the activation of the a-hydroxy group by the carboxylic
acid group at the chain end.
In conclusion, we have demonstrated the highly efficient
synthetic protocol for the conversion of mucic acid (1) into
muconic acid (2) and then adipic acid (3) through the
oxorhenium-complex-catalyzed DODH and Pt/C-catalyzed
transfer-hydrogenation sequence. Quantitative yields were
achieved for conversion of 1 into 2 and adipic acid esters
either in separate sequences or in a one-pot process. The
mechanism of the MTO-catalyzed DODH reaction for 1 has
also been studied by DFT computations, which disclosed
a possible MODH intermediate. The DODH reaction occurs
preferentially at the a, b-positions rather than b, g-positions.
The results presented herein not only demonstrated a highly
efficient, simple, and green protocol for the production of
renewable adipic acid from sugar acid. More importantly, for
the first time, the mechanism of the MTO-catalyzed DODH
reaction for this useful aldaric acid transformation was
studied in detail. This work sheds light on the huge potential
of producing industrial chemicals from various sugar acids.
Received: December 19, 2013
Revised: January 16, 2014
Published online: && &&, &&&&
Keywords: density functional calculations ·
.
reaction mechanisms · renewable resources · rhenium ·
sustainable chemistry
[1] a) A. Corma, S. Iborra, A. Velty, Chem. Rev. 2007, 107, 2411;
b) P. Gallezot, Green Chem. 2007, 9, 295; c) C. H. Christensen, J.
Rass-Hansen, C. C. Marsden, E. Taarning, K. Egeblad, Renew-
able Chemicals Industry 2008, 1, 283; d) D. Tilman, R. Socolow,
J. A. Foley, J. Hill, E. Larson, L. Lynd, S. Pacala, J. Rrilly, T.
Searchinger, C. Somerville, R. Williams, Science 2009, 325, 270;
e) J. P. Holdren, Science 2007, 315, 737; f) B. Kamm, Angew.
Chem. 2007, 119, 5146; Angew. Chem. Int. Ed. 2007, 46, 5056;
g) F. W. Lichtenthaler, Biorefineries—Industrial Processes and
Products, Wiley-VCH, Weinheim, 2006; h) J. C. Serrano-Ruiz,
R. M. West, J. A. Dumesic, Annu. Rev. Chem. Biomol. Eng.
2010, 1, 79.
[2] a) T. Polen, M. Spelberg, M. Bott, J. Biotechnol. 2013, 167, 75 –
84; b) S. Van de Vyver, Y. Roman-Leshkov, Catal. Sci. Technol.
2013, 3, 1465 – 1479.
[3] A. Alshammari, A. Koeckritz, V. N. Kalevaru, A. Bagabas, A.
Martin, ChemCatChem 2012, 4, 1330 – 1336.
[4] S.-J. Lee, I.-S. Ryu, B.-M. Kim, S.-H. Moon, Int. J. Greenhouse
Gas Control 2011, 5, 167 – 176.
[5] a) S. Dutta, ChemSusChem 2012, 5, 2125 – 2127; b) J. O.
Metzger, ChemCatChem 2013, 5, 680 – 682.
[6] a) D. Schweitze, WO2012/82725A1, 2012; b) J. W. Frost, A.
Miermont, D. Schweitzer, V. Bui, US 20100314243A1, 2010;
c) V. Bui, J. W. Frost, WO2012/141993A1, 2012.
[7] a) K. M. Draths, J. W. Frost, J. Am. Chem. Soc. 1994, 116, 399 –
400; b) W. Niu, K. M. Draths, J. W. Frost, Biotechnol. Prog. 2002,
18, 201 – 211.
[8] X. Sun, Y. Lin, Q. Huang, Q. Yuan, Y. Yan, Appl. Environ.
Microbiol. 2013, 79, 4024 – 4030.
[9] a) J. M. Thomas, R. Raja, B. F. G. Johnson, T. J. OꢀConnell, G.
Sankar, T. Khimyak, Chem. Commun. 2003, 1126 – 1127; b) X.
4
www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
These are not the final page numbers!

Angewandte
Chemie
She, H. M. Brown, X. Zhang, B. K. Ahring, Y. Wang, Chem-
SusChem 2011, 4, 1071 – 1073.
[10] T. R. Boussie, E. L. Dias, Z. M. Fresco, V. J. Murphy, WO
2010144873, 2010.
[11] T. R. Boussie, E. L. Dias, Z. M. Fresco, V. J. Murphy,
WO2010144862, 2010.
[12] a) T. Buntara, S. Noel, P. H. Phua, I. Melian-Cabrera, J. G.
de Vries, H. J. Heeres, Angew. Chem. 2011, 123, 7221 – 7225;
Angew. Chem. Int. Ed. 2011, 50, 7083 – 7087; b) T. Buntara, S.
Noel, P. H. Phua, I. Melian-Cabrera, J. G. de Vries, H. J. Heeres,
Top. Catal. 2012, 55, 612 – 619.
[13] a) M. Shiramizu, F. D. Toste, Angew. Chem. 2012, 124, 8206 –
8210; Angew. Chem. Int. Ed. 2012, 51, 8082 – 8086; b) J. Yi, S.
Liu, M. M. Abu-Omar, ChemSusChem 2012, 5, 1401 – 1404; c) C.
Boucher-Jacobs, K. M. Nicholas, ChemSusChem 2013, 6, 597 –
599; d) A. L. Denning, H. Dang, Z. Liu, K. M. Nicholas, F. C.
Jentoft, ChemCatChem DOI: 10.1002/cctc.201300545.
[14] M. Shiramizu, F. D. Toste, Angew. Chem. Int. Ed. 2013, 52, 12905.
[15] M. Nabyl, M. B. James, B. Christian, US6498269B1, 2002.
[16] R. S. Tipson, M. A. Clapp, J. Org. Chem. 1953, 18, 952 – 963.
[17] E. Arceo, J. A. Ellman, R. G. Bergman, J. Am. Chem. Soc. 2010,
132, 11408 – 11409.
[18] Y. Amada, H. Watanabe, Y. Hirai, Y. Kajikawa, Y. Nakagawa, K.
Tomishige, ChemSusChem 2012, 5, 1991 – 1999.
[19] a) W. A. Herrmann, D. Marz, E. Herdtweck, A. Schafer, W.
Wagner, H. J. Kneuper, Angew. Chem. 1987, 99, 462 – 464;
Angew. Chem. Int. Ed. Engl. 1987, 26, 462 – 464; b) Z. L. Zhu,
A. M. Al-Ajlouni, J. H. Espenson, Inorg. Chem. 1996, 35, 1408 –
1409.
[20] I. R. Beattie, T. R. Gilson, P. J. Jones, Inorg. Chem. 1996, 35,
1301 – 1304.
[21] S. Qu, Y. Dang, M. Wen, Z.-X. Wang, Chem. Eur. J. 2013, 19,
3827 – 3832.
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5
These are not the final page numbers!

.
Angewandte
Communications
Communications
Sustainable Chemistry
X. Li, D. Wu, T. Lu, G. Yi, H. Su,*
Y. G. Zhang*
&&&& — &&&&
Highly Efficient Chemical Process To
Convert Mucic Acid into Adipic Acid and
DFT Studies of the Mechanism of the
Rhenium-Catalyzed Deoxydehydration
Taking a dip: A highly efficient synthetic
protocol has been developed for the
conversion of mucic acid into adipic acid
by the oxorhenium-complex-catalyzed
deoxydehydration reaction and subse-
quent Pt/C-catalyzed transfer hydrogena-
tion. Quantitative yields were achieved for
the conversion of mucic acid into
muconic acid and adipic acid esters
either through separate sequences or
through a one-pot process.
6
www.angewandte.org
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2014, 53, 1 – 6
These are not the final page numbers!