Towards the efficient development of homogeneous catalytic transformation to γ-valerolactone from biomass-derived platform chemicals

Article abstract of DOI:10.1002/cctc.201402548

Recent efforts focused on the production of selected chemicals from biomass as an effective approach to replace fossil feedstocks. Among them, transformation of the biogenic platform molecule levulinic acid to γ-valerolactone has been an extensively studied reaction. Although this transformation can be achieved by heterogeneous catalysis, there exists also a strong interest for effective homogeneous catalysis that can operate selectively under milder and sustainable conditions. Herein, we report the utilization of various triphos-analogue ligands that in the presence of Ru(acac)₃ (acac=acetylacetonate) lead to highly efficient γ-valerolactone production (yield up to 95 %). Excellent catalyst turnover numbers (up to 75 855) and turnover frequencies (up to 1382 h^-1) were accomplished. Practically sustainable in every way: The practical production of γ-valerolactone (GVL) is described from the biomass-derived platform chemicals methyl levulinate and levulinic acid using three different ruthenium-triphos-based catalyst systems under optimized reaction conditions. acac=Acetylacetonate, TON=turnover number, TOF=turnover frequency.

Full text of DOI:10.1002/cctc.201402548

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DOI: 10.1002/cctc.201402548
Towards the Efficient Development of Homogeneous
Catalytic Transformation to g-Valerolactone from Biomass-
Derived Platform Chemicals
Abhishek Dutta Chowdhury, Ralf Jackstell, and Matthias Beller*[a]
Recent efforts focused on the production of selected chemicals
from biomass as an effective approach to replace fossil feed-
stocks. Among them, transformation of the biogenic platform
molecule levulinic acid to g-valerolactone has been an exten-
sively studied reaction. Although this transformation can be
achieved by heterogeneous catalysis, there exists also a strong
interest for effective homogeneous catalysis that can operate
selectively under milder and sustainable conditions. Herein, we
report the utilization of various triphos-analogue ligands that
in the presence of Ru(acac)3 (acac=acetylacetonate) lead to
highly efficient g-valerolactone production (yield up to 95%).
Excellent catalyst turnover numbers (up to 75855) and turn-
over frequencies (up to 1382 hÀ1) were accomplished.
Introduction
The depletion of fossil fuels with increasing amount of atmos-
pheric carbon dioxide over the last century encourages chemi-
cal researchers in academia and industry to look for more
benign transformations of viable renewable resources.[1–3] In
this aspect, plant biomass is considered as economical and
energy-efficient resource for the sustainable production of bio-
fuels and various utility chemicals.[1,3] In general, such transfor-
mations generate significantly less greenhouse-gas emission
than their fossil-fuel counterpart.[2] The carbohydrates resulting
from lignocellulosic biomass consist of the largest fraction of
global biomass feedstocks. Here, catalysis is playing a crucial
role in the development of new technologies for producing
energy, alternative fuel, as well as basic and fine chemicals
from biomass.[1,4–5]
Although the first-generation biofuels, which are usually de-
rived from starch, vegetable oil, or animal fat, have been suc-
cessfully implemented, still more efficient processes need to
be developed to reduce the current world’s dependence on
petroleum. In this respect, especially new technologies using
(nonedible) lignocellulosic biomass must be developed, and g-
valerolactone (GVL) has been acknowledged as an interesting
renewable platform molecule with potential impact for the
production of both energy or carbon-based consumer prod-
ucts (Scheme 1).[6]
GVL can easily be stored and moved globally in large quanti-
ties because of its low melting point, high boiling/flash point
and water miscibility to assist biodegradation. The emission
characteristics can simply be minimized by the low vapor pres-
sure of GVL.[6] The sweet “nontoxic” smell can be utilized for
Scheme 1. Lignocellulosic biomass roadmap for the production and applica-
tion of GVL. 2MTHF=2-methyltetrahydrofuran
[a] Dr. A. Dutta Chowdhury, Dr. R. Jackstell, Prof. Dr. M. Beller
Leibniz-Institut fꢀr Katalyse an der Universitꢁt Rostock
Albert-Einstein-Strasse 29a, 18059 Rostock (Germany)
E-mail: matthias.beller@catalysis.de
easy recognition of leaks and spills. Owing to such attractive
physical and chemical properties, GVL is considered as a sus-
tainable liquid for global storage and transportation.
Hence, a cost-effective and environmentally benign synthe-
sis of GVL from levulinic acid/ester has attracted substantial at-
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201402548.
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Results and Discussion
tention both in homogeneous and heterogeneous catal-
ysis.[4a,7–8] Levulinic acid is now considered amongst the top 12
chemical building blocks from biomass because of the versatile
applications and synthetic utility of GVL as depicted in
Scheme 1.[3a,b] So far, the hydrogenation of levulinic acid to
GVL was accomplished by heterogeneous catalysts (e.g., ruthe-
nium or platinum catalysts supported on carbon, aluminum
oxide, or titanium dioxide).[7] Although this approach offers the
advantage of easy catalyst recycling, high pressure and/or tem-
peratures are necessary to obtain high conversion. Moreover,
such processes are usually associated with the formation of
over-hydrogenated 2-methyltetrahydrofuran, which has safety
issues as the latter product can readily be converted into the
corresponding hazardous peroxide.[8f] These problems prompt-
ed researchers to look into analogous homogeneous catalytic
pathways.[4a,8] Already in 1982, Yoshikawa et al. reported the
catalytic hydrogenation of levulinic acid using RuCl2(PPh3)2 as
the catalyst at 1808C.[8a] Almost 25 years later in 2008, Horvꢁth
et al. observed that Ru(acac)3 (acac=acetylacetonate) ligated
with PBu3, tris(3-sulfonatophenylphosphine) (TPPTS) provides
good to moderate yields of GVL at 80 bar hydrogen pressure
and high temperature (2008C).[8b] More recently, Guo and Fu
et al. developed a RuCl3/PPh3-based catalytic system for levu-
linic acid hydrogenation using formic acid as hydrogen source
(no external hydrogen gas applied). Again, high temperature
(2008C) and 10 mol% base were necessary to obtain sufficient
conversion to achieve high yield of GVL.[8c] In 2010, Leitner and
co-workers improved these earlier methods by using Ru(acac)3
as the catalyst, PnOct3 as the ligand and NH4PF6 as an additive
at 100 bar hydrogen pressure and 1608C.[8d] The following year,
a biphasic RuCl3–TPPTS system was developed by Heeres et al.
in which the catalytic system can be recycled but the product
yield dropped by approximately 30% after the first catalytic
run.[8e] Although these catalysts (see below) allowed for high
yields of the desired product, still the turnover numbers (TON,
moles of products/moles of catalyst) need to be improved. The
maximum TON does not exceed 1560 if using the reported ho-
mogeneous ruthenium-based catalyst (Supporting Information,
Scheme S1).[8a–e] In this aspect, the work of Zhou et al. is note-
worthy. By using sophisticated iridium pincer complexes, excel-
lent catalyst TONs (71000) were achieved at 1008C. However,
addition of 120 mol% of base eventually limits its practical po-
tential.[8f] In 2013, a high TON of 78000 was achieved by using
half-sandwich iridium complex at 1208C; reported again by
Guo and Fu et al. (Scheme S1).[8g]
The initial optimizations were performed in the presence of
Ru(acac)3 as the catalyst and p-toluenesulfonic acid (PTSA) as
an additive by using methyl levulinate as the model substrate.
Unlike most of the relevant reports under homogeneous con-
ditions (Scheme S1),[4a,8] here only a catalytic amount of the ad-
ditive (1.75 equivalents with respect to the catalyst) was used.
In the absence of both acid and ligand, only 19% yield of GVL
was obtained. The addition of PTSA increased the yield merely
to 21% (Figure 1, Table S1).
Figure 1. Hydrogenation reaction of methyl levulinate under variation of li-
gands (reaction conditions: 0.08 mol% Ru(acac)3, 0.08 mol% ligand,
0.14 mol% additive, substrate, 24 mmol, 50 bar H2, solvent: THF, 1408C,
22 h). For details, see Table S1.
Next, various mono-, bi-, and tridentate phosphine-based li-
gands were added to the model reaction (Scheme 2, Figure 1).
The product yield was slightly improved (up to 27%) in the
presence of monodentate PPh3 (L1) but only traces of activity
was noted in the case of bidentate Xantphos (L2) as the
ligand. To our delight, the commercially available triphos,
bis(2-diphenylphosphinoethyl)phenylphosphine (L3) led to
82% yield under identical reaction conditions. Notably, another
commercially available tridentate ligand (tris[2-(diphenylphos-
phino)ethyl]phosphine, L4) gave rise to 35% of GVL. Next, ac-
cording to the literature we prepared tris((diphenylphosphino)-
methyl)amine (L5); however, subsequent catalytic tests re-
vealed low activity (24% of GVL). These initial results prompted
us to explore the structural aspects of the triphos backbone of
L3 in more detail (Figure 1, Scheme 2). Hence, three newly de-
signed triphos analogue ligands {[(phenylphosphinediyl)bis-
(2,1-phenylene)]bis(methylene)}bis-(diphenylphosphine) (L6),
{[(phenylphosphinediyl)bis(2,1-phenylene)]bis(methylene)}bis-
(di-tert-butylphosphine) (L7) and {[(phenylphosphinediyl)bis-
Herein, we report three ruthenium–triphos-based efficient
catalytic systems, which yielded GVL in excellent yield (up to
95%) with very high TON (75855) under relatively mild reac-
tion conditions (1408C) on a preparative scale (substrate load-
ing as high as 185 mmol) and under solvent-free (neat) condi-
tions. In essence, we believe these catalyst systems constitute
an important step towards a practical GVL production in a sus-
tainable manner under homogeneous conditions (Scheme S1).
(methylene)]bis(2,1-phenylene)}bis-(diphenylphosphine)
(L8)
were prepared and fully characterized. The synthetic routes of
these ligands (L6–L8) are depicted in Scheme 3 and the de-
tailed procedures are described in the Supporting Information.
Interestingly, L6 and L7 revealed significantly different cata-
lytic performances. In the presence of L6, 81% of GVL was ob-
tained, but L7 gave only 7% of the desired product under
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ingly, the commercially available
triphos derivative, 1,1,1-tris(di-
phenylphosphinomethyl)ethane
(L12) gave 52% of GVL under
identical conditions. Such a posi-
tive influence of methylenic di-
phenylphosphino (ÀCH2ÀPPh2)
moiety of L3, L4, and L6 could
be attributed to the stable cata-
lytically active species formation
during the reaction, because
ruthenium nanoparticles were
observed at the end of the reac-
tions using L5, L7–L9 as the li-
gands (entries 18–20, Table S1)
under such reducing environ-
ment.[8a–e,9]
Next, we explored the influ-
ence of additives as it was ra-
tionalized in earlier reports.[8] For
this study, the combination of
ligand L3 with Ru(acac)3 was
considered. In the absence of
any acid as an additive, only
30% of GVL was obtained. To
our surprise, very poor activity
(6% yield) was observed in the
presence of the similar Brønsted
acid, methanesulfonic acid (MSA)
as an additive. Addition of inor-
ganic acids such as phosphoric
acid (H3PO4) and phosphotungs-
tic acid (H3PW12O40) yielded 58
and 15% of GVL, respectively,
under optimized reaction condi-
tions. Interestingly, substantial
yield of GVL (62%) was achieved
by using scandium triflate. How-
ever, only traces of activity
(ꢀ<1%) were observed by using
sodium triflate. This implies the
necessity of either acid or a suita-
ble cation in this process. In con-
clusion, the initially tested PTSA
Scheme 2. List of ligands utilized during initial optimization of the reaction conditions.
Scheme 3. Synthetic routes for ligands L6–L8. TMEDA=N,N,N’,N’-Tetramethylethylenediamine.
identical reaction conditions (Figure 1). This clearly indicates
the positive influence of the phenyl-substituted phosphine
ligand. To our surprise, the ligand L8, which contains analo-
gous features to L6, exhibited very poor reactivity (only 3%
GVL yield). Similarly, [(phenylphosphinediyl)di-2,1-phenylene]-
bis(diphenylphosphine) (L9), 1,2-bis(diphenylphosphinome-
thyl)benzene (L10), and 2,2’-bis[(diphenylphosphino)methyl]-
1,1’-binaphthalene (L11) yielded only 4–5% of GVL, respective-
ly (Figure 1, Scheme 2, Table S1). The reactivity comparison be-
tween the positive catalytic influence of L3 and L6 and the
negative influence of L7–L9 indicates a constructive role of
the “methylenic diphenylphosphino” (ÀCH2ÀPPh2) moiety at
the triphos backbone in this hydrogenation chemistry. Interest-
was established as the best additive in the presence of ligand
L3.
Nevertheless, the strong influence of the additive encour-
aged us to further optimize the catalytic system with L4,
which contains a methylenic diphenylphosphino (ÀCH2ÀPPh2)
moiety at the triphos backbone. If 5 equivalents of PTSA were
used (instead of the usual 1.75 equiv.) with L4, the GVL yield
increased drastically to 77% from 35%. Finally, the yield with
L4 as the ligand rose to 82% if using scandium triflate as an
additive. However, the use of other additive/ligand combina-
tions usually resulted in the formation of black ruthenium
nanoparticles after the reaction and, hence, lower activity was
detected (entries 1–20, Table S1). Thus, PTSA was found to be
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temperature and 50 bar H2 pressure were found to have
a most pronounced effect on the reactivity and selectivity (en-
tries 24–28, Table S1) in this catalysis.
Next, we performed the benchmark reaction under solvent-
free conditions to showcase the efficacy of our catalytic sys-
tems. Using 0.012 mol% of catalyst, the catalyst TON with L3,
L4, and L6 were 6000, 5100 and 6600, respectively (Table 1,
entries 4–6). Here again, the L6 ligand operated very fast (6 h)
that is, with high turnover frequency (TOF) of 1100 hÀ1, relative
to L3 (TOF=273 hÀ1) and L4 (TOF=232 hÀ1, Figure 3). The re-
spective gas consumption profile reveals that the reaction with
L6 was even faster (almost completed) during the initial 3 h
(Supporting Information, Figure S1).[10] These results encour-
aged us to decrease the catalyst loading furthermore to
0.003 mol%. Gratifyingly, catalyst TON of 23000, 20600, and
30400 were obtained by using L3, L4, and L6-based catalytic
systems, respectively (Figure 3, Table 1, entries 7–9). Notably,
95% yield with TON=30400 was achieved after 22 h using the
L6-based catalytic system. Moreover, the ligand L6 operated
much faster with very high catalyst TOF of 1382 hÀ1, whereas
L3 and L4 exhibited TOFs of 548 hÀ1 (42 h reaction time) and
936 hÀ1 (22 h reaction time), respectively.[11] Finally, we per-
formed the hydrogenation reaction in the presence of only
0.001 mol% catalyst, at which loading, interestingly, all three
catalytic systems needed longer time to proceed. Here, L3 and
L4 yielded catalyst TONs of 66666 (TOF=694 hÀ1) and 61866
(TOF=644 hÀ1) after 4 days, however, very high catalyst TON
of 75855 (TOF=452 hÀ1) was accomplished using L6
after 7 days (Figure 3, Table 1, entries 10–12). To the
best of our knowledge, such high TONs using ruthe-
nium-based catalytic systems have not been reported
yet.
Figure 2. Influence of additives in the hydrogenation of methyl levulinate
using L3 and L4 (reaction conditions: 0.08 mol% Ru(acac)3, 0.08 mol%
ligand, 0.14 mol% additive, substrate 24 mmol, 50 bar, 22 h). For details see
Table S1.
the only additive that commonly operates for L3, L4, and L6.
In essence, these studies demonstrate the crucial role of acids
in this catalysis. Similar critical influences of acids in relation to
the hydrogenation chemistry has also earlier been mentioned
in the literature.[8a–e,9] (Figure 2)
After initial optimization, similar overall catalyst productivi-
ties (TON) of 980, 983, and 970 were measured by using L3,
L4, and L6, respectively, if using 0.08 mol% of catalyst and
methyl levulinate as the substrate (Figure 3). However, at lower
To our surprise, though L6 was able to provide
highest catalyst TON using 0.001 mol% of catalyst,
the corresponding TOF was affected by the longer re-
action time. Likewise, adding two equivalents of
ligand failed to realize a faster reaction as only 24%
GVL yield was obtained (Table 1, entry 13); presuma-
bly as a result of blocking of active catalytic sites. As
shown in Figure 3, only the catalyst system consisting
of ligand L3 was completely stable irrespective of
the catalyst loading as TOF always has an increasing
trend.[12]
Levulinic acid was finally tested as the substrate by
Figure 3. Respective catalyst TONs and turnover frequencies (TOF) of ligands L3, L4, and
L6 versus catalyst concentration.
using these three optimized catalytic systems (using
0.001 mol% of catalyst) under similar reaction condi-
tions (Table 1, entries 11–13). Interestingly, ligand L4
catalyst loadings these ligands behave differently. For example,
catalyst TONs of 3650, 2850, and 3050 were obtained at
0.025 mol% catalyst systems with L3, L4, and L6, respectively
(Figure 3, Table 1, entries 1–3). Here, the ligand L6 appeared to
significantly accelerate the reaction (only 6 h reaction time) rel-
ative to the other two ligands (reaction time 22 h for L3 and
L4) under identical reaction conditions. At this stage, further
influence of temperature and pressure on this catalytic system
was assessed by using 0.025 mol% of catalyst and L3 as the
ligand. However, the combination of earlier observed 1408C
(TON=73142) was found to be highly active here compared
to L3 (TON=59265) and L6 (TON=12000). The unexpected
lower activity of L6 can be attributed to its bad solubility in
levulinic acid, which was also reflected by its poor yield and
ruthenium black formation after the reaction.
Interestingly, we observe that TOFs increase at lower catalyst
loadings, attributed to the inhibition of THF solvent at higher
catalyst loadings (Figure 3). This result prompted us to explore
the further solvent effects on our system because TOFs were
increased on exclusion of solvent. Thus we performed the fol-
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(72%), and 875 hÀ1 (87%) were observed if using THF as the
solvent, under neat conditions, and g-butyrolactone as the sol-
vent, respectively (Table S2, Figure S2). To our surprise, these
reactions now proceeded with quantitative yields and at lesser
time (i.e., even higher TOF) with g-butyrolactone as the solvent
(Figure S2). These results were also reflected by the corre-
sponding TOFs and gas consumption profile (Figure S3). There-
fore, these control experiments provided further evidence for
the inhibition effect by THF (presumably by blocking of active
catalytic sites through coordination) and the higher TOF under
solvent-free conditions.
Table 1. Hydrogenation of methyl levulinate and levulinic acid.[a]
Entry
1[b]
R
Ru(acac)3 Ligand Additive Time Yield [%]
(substrate [mmol]) [mol%] [h] (TON)
Conclusion
Me (80)
0.025
L3
PTSA
22 91 (3650)
88 (3530)[c]
The present report demonstrates the facile production of g-va-
lerolactone from a most popular and versatile biogenic plat-
form chemical, methyl levulinate and levulinic acid. Excellent
yields (up to 95%), high catalyst turnover numbers (up to
75855), and high turnover frequencies (up to 1382 hÀ1) were
obtained by using three different highly selective and flexible
multifunctional ruthenium-based catalytic systems. Herein,
three different analogous triphos ligands have been identified
to be highly effective in this transformation and the newly syn-
thesized ligand L6 led to highest catalyst turnover numbers
and catalyst turnover frequencies in the present study. The ad-
vantages of these processes include utilization and very low
loading of ruthenium catalyst, use of catalytic amounts of addi-
tive, solvent-free conditions, practical substrate scale under
comparatively low hydrogen pressure. This report also includes
the design and syntheses of three new triphos-analogue
ligand structures, which demonstrate the influential role of
“methylenic diphenylphosphino” (ÀCH2ÀPPh2) moiety at tri-
phos backbone in hydrogenation chemistry. In essence, these
reactions constitute a further step towards a practical g-valero-
lactone production using homogeneous catalysis.
2[b]
3[b]
4
5
6
7
8
9
Me (80)
Me (80)
0.025
0.025
0.012
0.012
0.012
0.003
0.003
0.003
L4
L6
L3
L4
L6
L3
L4
L6
Sc(OTf)3 22 71 (2850)
PTSA
PTSA
6
76 (3050)
Me (160)
Me (160)
Me (160)
Me (160)
Me (160)
Me (160)
22 75 (6000)
Sc(OTf)3 22 65 (5100)
PTSA
PTSA
6
82 (6600)
42 72 (23000)
Sc(OTf)3 22 65 (20600)
PTSA
22 95 (30400)
89 (28478)[c]
10
11
12
Me (185)
Me (185)
Me (185)
0.001
0.001
0.001
L3
L4
L6
PTSA
96 67 (66666)
Sc(OTf)3 96 62 (61866)
PTSA
168 76 (75855)
74 (74000)[c]
13[d] Me (185)
14
15
0.001
0.001
0.001
L6
L3
L4
PTSA
PTSA
168 24 (24000)
96 59 (59265)
H (68)
H (68)
Sc(OTf)3 96 73 (73142)
71 (71111)[c]
16[e] H (68)
0.001
L6
PTSA
168 12 (12000)
[a] Reaction conditions:
A 100 mL stainless-steel autoclave or 25 mL
Hastelloy-c autoclave was charged with the catalyst Ru(acac)3, the ligand
L3, L4, or L6 (1 mole equivalent with respect to catalyst) and the addi-
tive (1.75 mole equivalent with respect to catalyst) under argon atmos-
phere, unless noted otherwise. The required amount of substrate and/or
THF was then added under argon atmosphere, unless noted otherwise.
The reaction was then performed at 1408C after the addition of hydrogen
at 80 bar. Finally, yield and TON were determined by GC with respect to
isooctane as an internal standard against authenticated samples. TON is
expressed in [mmolGLV mmolcatalystÀ1]. All the reactions were repeated at
least twice to ensure reproducibility and yields or TONs reported in this
study are averages of at least two runs. See Table S1 and the Experimen-
tal Section in the Supporting Information for more details. [b] Performed
in THF (20 mL) under 50 bar of H2. [c] Yield and TON of isolated GVL.
[d] 2 Equivalents of L6. [e] Ruthenium black was observed after the reac-
tion.
Experimental Section
Catalytic reactions
General procedure: An autoclave (100 mL stainless-steel or 25 mL
Hastelloy-c) was charged with equimolar amounts of catalyst, Ru-
(acac)3 and respective phosphine-based ligands along with addi-
tives, unless noted otherwise. Then, the autoclave was evacuated
and back-filled with argon three times. Under high stream of
argon, the substrate (methyl levulinate or levulinic acid) and/or
THF were added. Then, the autoclave was pressured with H2 (50 or
80 bar) and heated at 1408C for the specified reaction time. After-
wards, the autoclave was cooled to RT, the pressure was released,
and the reaction mixture was stirred with isooctane as an internal
standard. The mixture was then filtered through Celite and subject
to GC analysis for the determination of yield and conversion. GVL
was isolated by vacuum distillation and subsequently characterized
by NMR spectroscopy. The very detailed experimental procedures
are also described in the Supporting Information.
lowing control experiments with L3 as the ligand: 1) Using sol-
vent-free conditions at higher catalyst loadings, and 2) using
THF as the solvent at lower catalyst loadings.[12,13] Additionally,
these reactions were also performed by using g-butyrolactone
as the solvent.[14] At a higher catalyst loading (0.025 mol%),
TOFs of 166, 223, and 234 hÀ1 were observed using THF as the
solvent, under neat conditions, and g-butyrolactone as the sol-
vent, respectively, (Table S2, Figure S2). However, the THF in-
hibition effect was more pronounced at lower catalyst loadings
(0.003 mol%). Here, TOFs (yields) of 119 hÀ1 (15%), 548 hÀ1
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[10] The gas consumption profile also reveals that the ligand L3 has a slow
but steady reaction rate throughout the reaction time, whereas the
rate decreases after 8 h in the case of L4 after a good start. For details
see Figure S1.
[11] The longer reaction time (42 h) only in the case of L3 can be attributed
to the initial slow rate of the reaction.
[12] The (always) steady reaction rate in the case of L3 is reflected in its
constant increasing trend of TOFs. See Figure 3 and Figure S1.
[13] The ligand L3 was selected for this study because of its always increas-
ing trend of TOF; see Figure 3.
Acknowledgements
This research was funded by the Bundesministerium fꢀr Bildung
und Forschung (BMBF), the State of Mecklenburg-Vorpommern
and the Deutsche Forschungsgemeinschaft (Leibniz-prize to M.B.).
We thank Dr. Wolfgang Baumann, Dr. Christine Fischer, Susann
Buchholz, Susanne Schareina, Andreas Koch, and Sigrun Ross-
meisl (all at LIKAT) for their excellent technical and analytical
support.
Keywords: biomass · homogeneous catalysis · ligand effects ·
ruthenium · oxygen heterocycles
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[14] g-Butyrolactone was selected as an additional solvent because of its
similarity of chemical and physical properties with the product, g-
valerolactone.
Received: July 18, 2014
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Revised: August 28, 2014
Published online on && &&, 0000
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 7
&
6
&
ÞÞ
These are not the final page numbers!

FULL PAPERS
A. Dutta Chowdhury, R. Jackstell,
M. Beller*
&& – &&
Towards the Efficient Development of
Homogeneous Catalytic
Transformation to g-Valerolactone
from Biomass-Derived Platform
Chemicals
Practically sustainable in every way:
The practical production of g-valerolac-
tone (GVL) is described from the bio-
mass-derived platform chemicals methyl
levulinate and levulinic acid using three
different ruthenium–triphos-based cata-
lyst systems under optimized reaction
conditions. acac=Acetylacetonate,
TON=turnover number, TOF=turnover
frequency.
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 7
&
7
&
ÞÞ
These are not the final page numbers!