Biomass-Based and Oxidant-Free Preparation of Hydroquinone from Quinic Acid

Article abstract of DOI:10.1002/ejoc.201600616

A biomass-based route to the preparation of hydroquinone starting from the renewable starting material quinic acid is described. Amberlyst-15 in the dry form promoted the one-step formation of hydroquinone from quinic acid in toluene without any oxidants or metal catalysts in 72 % yield. Several acidic polymer-based resins and organic acids as promoters as well as a variety of reaction conditions were screened including temperature, concentration and low- and high-boiling-point solvents. A 1:4 (w/w) ratio of quinic acid/Amberlyst-15 was determined to be optimal to promote hydroquinone formation with only traces of a dimeric side-product. A mechanism has been proposed based on the decarbonylation of protonated quino-1,5-lactone that is supported by experimental and computational calculation data.

Full text of DOI:10.1002/ejoc.201600616

DOI: 10.1002/ejoc.201600616
Full Paper
Hydroquinone Synthesis
Biomass-Based and Oxidant-Free Preparation of Hydroquinone
from Quinic Acid
[a]
[b]
[c]
[a]
Benedicta Assoah, Luis F. Veiros, Carlos A. M. Afonso, and Nuno R. Candeias*
Abstract: A biomass-based route to the preparation of hydro- ing temperature, concentration and low- and high-boiling-point
quinone starting from the renewable starting material quinic solvents. A 1:4 (w/w) ratio of quinic acid/Amberlyst-15 was de-
acid is described. Amberlyst-15 in the dry form promoted the termined to be optimal to promote hydroquinone formation
one-step formation of hydroquinone from quinic acid in tolu- with only traces of a dimeric side-product. A mechanism has
ene without any oxidants or metal catalysts in 72 % yield. Sev- been proposed based on the decarbonylation of protonated
eral acidic polymer-based resins and organic acids as promoters quino-1,5-lactone that is supported by experimental and com-
as well as a variety of reaction conditions were screened includ- putational calculation data.
Introduction
sidering that sugars and polyol platforms can be highly ex-
ploited. However, the production of aromatic compounds
[
4]
The chemical industry has made enormous efforts in the last continues to be highly dependent on non-renewable fossil
decades to minimise waste and use less toxic and/or hazardous feedstocks. Despite the enormous achievements in the
reagents to develop safer and greener processes. However, depolymerisation of lignin, the only renewable source of high-
[
5]
most of the raw materials used in the chemical industry are volume aromatic compounds, the industrial application of any
generally obtained from fossil resources totalling 10 % of the of the reported methods has not yet been achieved.
[
1]
crude oil consumption. To accomplish sustainable methods
for the production of commodity chemicals and liquid fuels,
non-renewable fossil resources (crude oil, coal and natural gas)
should be replaced by sustainable feedstocks. Despite the in-
tense interest and the methods developed for the large-scale
industrial conversion of biomass into chemicals and materials
in the second half of the 19th century, such investments
declined in the 20th century due to the much cheaper products
synthesised by the now conventional routes from abundantly
Hydroquinone is prepared industrially by the hydroperoxid-
ation of p-diisopropylbenzene, the hydroxylation of phenol and
the oxidation of aniline. The world production of hydroquinone
is 40000–50000 tons a year and it is mainly used in the rubber
industry, as monomer inhibitors, dyes and pigments and anti-
oxidants as well as in agricultural and photographic applica-
[6]
tions. It is mostly used as a water-soluble reducing agent in
photography film development and in the rubber industry for
the production of anti-oxidants and anti-ozonants. It is also
used as an inhibitor of acrylic acid, methyl methacrylate, cyano-
acrylate and other monomers commonly used in adhesives,
glue and other types of bonding applications and in cosmetic
applications in skin-whitening compositions.
[
2]
available fossil resources. Fossil raw materials are irrevocably
decreasing and the environmental consciousness of the chemi-
cal industry and the regulatory authorities has led to enormous
research activity in the last decade to progressively shift to
[
3]
renewable feedstocks. The selective defunctionalisation of
highly functionalised molecules derived from renewable feed-
stocks is probably the biggest challenge in such a shift, con-
The preparation of hydroquinone from non-fossil sources has
been reported by Frost and co-workers since the seminal work
[
7]
of Woskresensky on the isolation of hydroquinone by the dry
distillation of quinic acid (1, Scheme 1). Frost reported the prep-
aration of hydroquinone from glucose in two enzyme-catalysed
steps and two chemical steps via 2-deoxy-scyllo-inosose syn-
[
a] Department of Chemistry and Bioengineering, Tampere University of
Technology,
Korkeakoulunkatu 8, 33101 Tampere, Finland
E-mail: nuno.rafaelcandeias@tut.fi
[8]
thase. The construction of a transgenic Escherichia coli strain
able to synthesise quinic acid from glucose under shake-flask
conditions was coupled with the oxidation of the obtained
http://www.tut.fi/en/about-tut/departments/chemistry-and-bioengineering/
b] Centro de Química Estrutural, Instituto Superior Técnico, Universidade de
Lisboa,
Av. Rovisco Pais No. 1, 1049-001 Lisboa, Portugal
c] The Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy,
University of Lisbon,
[
[
quinic acid with stoichiometric amounts of MnO
one. Other oxidative systems such as NaOCl, (NH ) Ce (SO ) ,
to hydroquin-
2
[
9]
4
2
2
4 3
V O and K S O in the presence of catalytic amounts of Ag PO
4
2
5
2
2
8
3
have been reported to induce the same transformation in up
Av. Prof. Gama Pinto, Lisboa, Portugal
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under http://dx.doi.org/10.1002/ejoc.201600616.
[
10]
[11]
to 91 % yield. Quinic acid is readily available from the bark
[
12]
of the cinchona tree as a side-product during the extraction
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of cinchona alkaloids and is the principal constituent in coffee higher activity of the powder resin should be associated with
[
13]
[18]
beans and other plant products.
the exposed external surface of the resin.
Despite the 71 %
yield of hydroquinone (2), use of the ground Amberlyst led to
considerable formation of the ether side-product 3 (entry 13).
Table 1. Screening of acid promoters for the formation of hydroquinone from
quinic acid.[
a]
Scheme 1. Fossil-based route and the alternative biomass-based route to hy-
droquinone.
Yield [%][b]
Entry
Acid
2
3
Taking the dry distillation of quinic acid for the preparation
1
2
3
4
5
6
7
8
9
Amberlyst-15 (dry)
Amberlyst-15 (wet)
Amberlyst-16 (wet)
Amberlyst-36 (wet)
Amberlite IRC86
62
6
4
5
n.d.
6
3
[
7]
of hydroquinone, it was hypothesised that the same transfor-
mation could be achieved under aerobic, strongly acidic condi-
tions. Besides the formation of hydroquinone, other products
expected in the acid-promoted decomposition of quinic acid
n.d.[
c]
n.d.
n.d.
n.d.
n.d.
<3
[
14]
[15]
Amberlite IR120/H
are bicyclic quino-1,5-lactone,
one.
benzoic acid
and quin-
Dowex 50WX4
12
<3
[
10]
[d]
pTSA·H
2
O
n.d.
[d]
[e]
pTSA, 4 Å MS
n.r.
<3
[f]
1
11
0
H
2
SO
4
n.d.
n.d.
[g]
Results and Discussion
Acetic acid
none
n.d.
n.r.
71
1
2
Versatile and robust polymer-based resins were screened as
13
Amberlyst-15 (dry), ground
7
promoters for the conversion of quinic acid (1) into hydroquin-
[
a] Reagents and conditions: Unless otherwise stated, the reaction was carried
[
16]
one (2). Preliminary reactions of quinic acid were carried out
with different forms of polystyrene macro-reticular Amberlyst
resins: Amberlyst-15 (dry and wet), Amberlyst-16 and Amber-
lyst-36 in toluene at 100 °C (Table 1). Amberlyst-15 in the dry
form resulted in the formation of hydroquinone (2) in 62 %
yield accompanied by ether 3, which results from the condensa-
tion of hydroquinone (entry 1). Despite the presence of quino-
out with quinic acid (0.5 mmol), resin (0.3 g), and toluene (15 mL) at 100 °C
for 17 h in an open vessel. [b] Determined by analysis of the H NMR spectra
of the reaction mixtures using bromobenzene as internal standard. [c] n.d.:
not detected. [d] 0.5 mmol of pTSA in 7 mL of toluene heated for 24 h. [e]
n.r.: no reaction. [f] 1.5 mL of H
as solvent.
1
2 4
SO in 15 mL of toluene. [g] 3 mL of AcOH
In an attempt to optimise the reaction conditions and to
1
,5-lactone in the reaction mixture, a likely reaction intermedi- allow the dissolution of quinic acid into the reaction solvent,
ate, benzoquinone formation was not observed. Amberlyst-15 other solvents were screened. Using Amberlyst-15 as the reac-
has been reported in many instances as a mild and selective tion promoter in THF, 1,4-dioxane, CH Cl , 1,2-dichloroethane,
heterogeneous polymeric material for routine acid-catalysed CCl , chlorobenzene and methanol at reflux temperature or in
Other Amberlyst resins glycerol, sulfolane and poly(ethylene glycol) at 125 °C for 24 h
2
2
4
[
17]
transformations in organic synthesis.
tested showed inferior activity, leading to only traces of the did not improve the selectivity towards hydroquinone forma-
desired hydroquinone (entries 2–4). Acidic ion-exchange resins tion. Besides toluene, hydroquinone (2) was detected in the
Amberlite IRC86, IR120/H and Dowex 50WX4 also failed to pro- crude reaction mixtures of only chlorinated solvents. Of the
vide hydroquinone (2) in decent yields (entries 5–7). Despite above-mentioned solvents, chlorobenzene gave the highest
the high moisture content (64–72 %), Dowex 50WX4 proved to formation of hydroquinone when the reaction was performed
be superior to the other ion-exchange resins, providing 12 % of in a sealed tube, with 2 and 3 obtained in a 4:3 ratio (68 %
hydroquinone after 17 h (entry 7). After identification of Amber- conversion).
lyst-15 in the dry form as the best reaction promoter amongst
Taking toluene as the reaction solvent for this two-phase
those tested, and being a polymer-supported sulfonic acid reaction, the influence of temperature on the reaction outcome
resin, we tested p-toluenesulfonic acid (pTSA, entries 8 and 9) was assessed (Figure 1). Very low conversions were achieved
and sulfuric acid (entry 10) as reaction promoters. Although below 100 °C, hydroquinone was formed in higher yields in
sulfuric acid and monohydrate pTSA resulted in traces of hydro- the range 100–110 °C, and higher temperatures induced the
quinone (entries 8 and 10), use of molecular sieves and anhy- dimerisation of 2 into ether 3. This process was verified by the
drous pTSA resulted in recovery of the starting materials after exclusive formation of 3 in 48 % isolated yield after heating
1
7 h (entry 9). Better conversions of the starting quinic acid hydroquinone 2 in toluene in the presence of Amberlyst-15 for
were achieved by employing ground Amberlyst-15, sieved 6 days.
through a 106 μm sieve. Previous studies on the acid-site acces-
With these optimised conditions, we shifted our attention to
sibility of Amberlyst-15 showed similar strengths of acid sites the effect of the Amberlyst/quinic acid ratio on the reaction
for both the bead and powder forms of Amberlyst-15 and the (Table 2). It was observed that the yield of hydroquinone
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salts[19] were effective catalysts in the putative aerobic oxidation
process.
Table 3. Effect of oxidation conditions on the reaction.[a]
Entry
Reaction conditions
open vessel
Yield [%][b]
Figure 1. Effect of temperature on hydroquinone formation. Reagents and
conditions: Quinic acid (0.5 mmol), Amberlyst-15 (0.3 g), toluene (15 mL),
2
3
1
2
3
4
5
6
7
8
72
64
46
62
58
51
43
47
5
6
<3
3
4
4
1
00 °C, 17 h.
O
2
atmosphere
argon atmosphere
1.5 equiv. of H
5 mol-% CuBr
5 mol-% CuI
2
O
increased with only trace formation of ether 3, or none at all,
as the Amberlyst/quinic acid ratio (w/w) was increased from 0.5
to 4 (entries 1–7). Further increasing the amount of Amberlyst
did not show any considerable improvement when performing
the reaction at 100 °C for 17 h (entries 7–9). Tuning the reaction
conditions further, namely the amount of solvent and reaction
time (see the Supporting Information), resulted in the formation
of the desired hydroquinone in a yield of 71 % together with
5 mol-% CuBr
5 mol-% CuCl
2
3
4
2
·H
2
O
[
a] Reagents and conditions: Quinic acid (0.5 mmol), Amberlyst-15 (1:4 ratio,
w/w) in toluene (10 mL) at 100 °C for 24 h in an open vessel, except entries 2
and 3. [b] Determined by analysis of H NMR spectra of the reaction mixtures
using bromobenzene as internal standard.
1
To gain further insight into the reaction mechanism, two
possible reaction intermediates, 4 and 5, were prepared and
allowed to react under similar reaction conditions (Scheme 2).
Lactone 4 was converted into hydroquinone (2) in 52 % yield,
as observed for the reaction of quinic acid. As previously dem-
5
% of ether 3 after 25 h (entry 10) and isolation by chromatog-
raphy. Extension of the reaction time to 48 h proved beneficial
for ether 3 formation, but the yield of hydroquinone remained
the same (entry 11).
[
10]
onstrated by Frost and co-workers,
ketone 5 was converted
Table 2. Effect of amberlyst/quinic acid ratio on reaction.[a]
into the hydroquinone via the two possible enone intermedi-
ates. In such a strongly acidic medium, the dehydration of 5 is
a very fast process and such intermediates are not visible in the
NMR spectrum of the quinic acid dehydration reaction mixture.
It was nevertheless possible to detect and isolate a mixture of
the enones 7 in 25 % yield when the reaction was performed
in dioxane.
Entry
Amberlyst-15/1
Time [h]
Yield [%][b]
Adding (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), but-
ylated hydroxytoluene (BHT), styrene and azodicarboxylates to
the reaction mixture did not allow the isolation of any interme-
diates derived from a single-electron-transfer pathway. Curi-
ously, TEMPO inhibited the formation of the hydroquinone (2)
and only starting material and lactone 4 were detected. Addi-
tionally, the use of tert-butyl peroxide as radical initiator did not
improve hydroquinone formation or reduce the reaction rate.
The carbon atom lost in the conversion of quinic acid (1) into
hydroquinone (2) occurs through the liberation of carbon mon-
oxide. Such an event was confirmed by the reduction of palla-
dium chloride to palladium when a filter paper soaked in PdCl2
aqueous solution (1:500, w/v) was placed on the top of the
ratio (w/w)
2
3
1
2
3
4
5
6
7
8
0.5
1
2
17
17
17
17
17
17
17
17
17
25
48
9
17
29
43
48
56
55
55
59
n.d.[c]
n.d.
n.d.
<3
<3
<3
<3
<3
<3
5
3
3.125
3.5
4
5
10
4
9
1
1
0[
1
d]
72 (71)
72
[e]
[d]
4
9
[
a] Reagents and conditions: Unless otherwise stated, the reaction was carried
out with quinic acid (0.5 mmol), Amberlyst-15 (dry) in toluene (15 mL) at
00 °C in an open vessel. [b] Yield calculated from the H NMR spectra of
reaction mixtures using bromobenzene as internal standard. [c] n.d.: not de-
tected. [d] 10 mL of toluene as solvent. [e] Isolated yield after flash chroma-
tography.
1
1
[
20]
reaction condenser (see the Supporting Information).
[
21]
DFT calculations
were performed to compare ionic and
radical mechanisms through the optimisation of likely interme-
diates. The free-energy values obtained for the diradical inter-
Being a formal oxidation, the influence of oxygen and other mediates considered in single-electron-transfer processes
oxidative conditions were also investigated (Table 3). The clearly preclude a radical pathway for the reaction (ΔG = 80–
absence of air or the presence of water had a detrimental effect 84 kcal/mol, see the Supporting Information for details). Fur-
on hydroquinone formation and neither oxygen nor copper thermore, the high acidity of Amberlyst should favour an ionic
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protonated lactone over the pericyclic process (Scheme 4): A
large energy barrier of 72.9 kcal/mol needs to be overcome
for the pericyclic process, whereas the energy barrier for the
H
decarbonylation of 4 is only 1.2 kcal/mol. Under the highly
acidic reaction conditions, 9 should be formed after the double
protonation and dehydration of 5 to form the more stable hy-
droquinone. The overall reaction from quinic acid (1) to hydro-
quinone (2) is a thermodynamically favourable process with
ΔG = –15 kcal/mol.
Scheme 2. Reactivity of reaction intermediates 4 and 5.
mechanism by the favourable protonation of the starting mate-
rial and reaction intermediates. Two ionic mechanisms were
considered for the decarbonylation step, both having lactone 4
as the starting point: 1) Pericyclic decarbonylation of the
lactone with concomitant formation of the enol aldehyde 8 and
b) ring-opening of protonated lactone 4H (Scheme 3). From a
thermodynamic point of view, the formation of enol aldehyde
Scheme 4. Energy profiles calculated for two alternative decarbonylation
steps. The free energies of the intermediates and transition states are indi-
cated in italics [kcal/mol].
8
seems to be unlikely due to its high free energy (ΔG =
2
2.9 kcal/mol) whereas the decarbonylation of protonated lact-
H
one 4 should be a spontaneous process towards the formation
of protonated ketone 5H (ΔG = –15.8 kcal/mol). This is further
confirmed by the energy barriers calculated for both processes,
Conclusions
which clearly indicate a preference for the ring-opening of the A mild and efficient method for the conversion of naturally
available quinic acid (1) into hydroquinone (2) has been dis-
closed herein. By using Amberlyst-15 in its dry form as an acid
promoter it is possible to obtain the hydroquinone in up to
7
2 % yield with only small amounts of the dimeric ether com-
pound formed after 24 h. This method does not rely on the
use of any oxidants or high temperatures unlike the previously
reported methods. An ionic decarbonylation mechanism has
been proposed, supported by experimental and computational
calculation data.
Experimental Section
General Methods: Polymer-based resins were used as received
from suppliers: Amberlyst-15 (dry), 20–50 mesh from Fluka (06423)
and Aldrich (216380), Amberlyst-15 (wet) from Aldrich (216399),
Amberlyst-16 (wet) from Aldrich (86317), Amberlyst-36 (wet) from
Fluka (06455), Amberlite IRC86 from Aldrich (10322), Amberlite
IR120/H from Aldrich (216534) and Dowex 50WX4 from Aldrich
(422096). Quinic acid was obtained from Sigma–Aldrich and sieved
through a 106 μm sieve prior to use. Retsch ZM200 and Retsch
AS200 were used as grinder and sieve, respectively. Other reagents
were used as obtained from the suppliers (Sigma–Aldrich and
Scheme 3. Proposed ionic reaction mechanisms. Calculated free energies of
the intermediates are indicated in italics [kcal/mol].
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Fluka). The reactions were monitored by TLC carried out on pre-
coated (Merck TLC silica gel 60 F254) aluminium plates by using UV
light as visualising agent and cerium molybdate solution as devel-
tion and solvent removal under reduced pressure, the residue ob-
tained was purified by flash chromatography with an eluent gradi-
ent from ethyl acetate/hexane (9:1) to methanol/ethyl acetate (1:9).
oping agent. Flash column chromatography was performed on sil- The desired ketone 5 was obtained in 75 % yield (1.03 g) with simi-
[
10] 1
ica gel 60 (Merck, 0.040–0.063 mm). NMR spectra were recorded lar spectroscopic data as previously reported.
H NMR (D O,
2
with a Varian Mercury 300 MHz spectrometer using CDCl3,
300 MHz): δ = 4.83 (s, 3 H), 4.29 (ddd, J = 6.3, 3.7, 2.9 Hz, 1 H), 4.15
(td, J = 8.2, 5.3 Hz, 1 H), 3.97 (dd, J = 7.8, 2.8 Hz, 1 H), 2.83–2.80 (m,
[
D ]DMSO or D O as solvent and calibrated by using tetramethyl-
6 2
silane as internal standard. Chemical shifts are reported in ppm 1 H), 2.78–2.75 (m, 1 H), 2.65–2.50 (m, 2 H) ppm. 13C NMR (D O,
2
1
relative to TMS and coupling constants are reported in Hz. H NMR
yields were determined by adding a known amount of bromo-
benzene to the reaction mixture after work-up.
75 MHz): δ = 212.8, 73.0, 68.7, 45.7 ppm.
4-Methoxyphenol (6): Ketone 5 (0.5 mmol) was dissolved in meth-
anol (1 mL) and dispersed in toluene (10 mL) in a round-bottomed
flask equipped with a magnetic stirrer bar. Amberlyst 15 (dry,
384 mg) was added and the mixture stirred at 100 °C until disap-
pearance of the starting material, as judged by TLC (1.5 h). After
Hydroquinone (2): Quinic acid (0.5 mmol) was added to a suspen-
sion of Amberlyst-15 (dry, 0.38 g) in toluene (10 mL) in a round-
bottomed flask equipped with a magnetic stirrer bar and condenser
open to the air. The mixture was heated at 100 °C for 24 h. After cooling to room temperature, methanol (5 mL) was added, the mix-
cooling to room temperature methanol (5 mL) was added and the
mixture stirred vigorously for 5 min. The mixture was filtered and
the solid residue re-suspended in methanol (20 mL) and stirred for
an additional 5 min. After filtration and washing with more meth-
ture filtered and the solvent removed under reduced pressure. The
residue was purified by flash chromatography with gradient elution
with ethyl acetate/hexane (1:9 to 1:1), to afford 42 % (23 mg) of
hydroquinone (2) and 37 % (23 mg) of 6 with similar spectroscopic
[
24] 1
anol (10 mL), the solvents were removed under reduced pressure.
data as previously reported.
H NMR (CDCl , 300 MHz): δ = 6.78
3
1
13
The residue was either dissolved in [D ]DMSO for H NMR yield
(d, J = 1.8 Hz, 4 H), 4.93 (br. s., 1 H), 3.77 (s, 3 H) ppm. C NMR
6
determination (72 %) or purified by flash chromatography with tolu-
(CDCl , 75 MHz): δ = 153.6, 149.4, 116.0, 114.8, 55.8 ppm.
3
ene/ethyl acetate (3:1) to afford pure hydroquinone (39 mg, 71 %
4
,5-Dihydroxycyclohex-2-en-1-one (7): Amberlyst-15 (dry, 0.38 g)
was added to a solution of ketone 5 (1 mmol) in 1,4-dioxane
10 mL) and the mixture stirred at 100 °C for 5 min. After cooling
1
yield) with similar spectroscopic data as commercial samples.
H
C
13
NMR ([D ]DMSO, 300 MHz): δ = 8.64 (s, 2 H), 6.55 (s, 4 H) ppm.
6
(
NMR ([D ]DMSO, 75 MHz): δ = 149.8, 115.8 ppm.
6
to room temperature the mixture was filtered and the solvent re-
moved under reduced pressure. The residue was purified by flash
chromatography with eluent gradient from ethyl acetate/hexane
(4:1) to methanol/ethyl acetate (1:9) to afford 20 % (20 mg) of hy-
Bis(4-hydroxyphenyl) Ether (3): Hydroquinone (1.0 mmol) was
added to a suspension of Amberlyst-15 (dry, 0.77 g) in toluene
(20 mL) in a round-bottomed flask equipped with a magnetic stirrer
bar and condenser. The mixture was heated at 100 °C for 6 d. After droquinone (2) and 25 % (31 mg) of 7 in a cis/trans ratio of 1:4, as
1
cooling to room temperature, methanol (10 mL) was added and the
mixture stirred vigorously for 5 min. The mixture was filtered and
the solid residue re-suspended in methanol (40 mL) and stirred for
determined by H NMR spectroscopy and comparison with previous
[
10] 1
reports.
H NMR (D O, 300 MHz): δ = 6.96 (dd, J = 10.1, 2.2 Hz,
1 H), 6.92–6.87 (m, 0.2 H), 6.73–6.72 (m, 0.2 H), 6.06 (dd, J = 2.2,
2
an additional 5 min. After filtration and washing with more meth- 1.0 Hz, 0.2 H), 6.03–5.98 (m, 1 H), 4.64–4.61 (m, 0.2 H), 4.39–4.30 (m,
anol (20 mL), the solvents were removed under reduced pressure.
The residue was purified by preparative TLC with toluene/ethyl
1.2 H), 3.99–3.91 (m, 1 H), 2.78–2.76 (m, 0.5 H), 2.73–2.71 (m, 1 H),
2.68 (dd, J = 5.1, 1.0 Hz, 0.2 H), 2.55–2.46 (m, 1.3 H) ppm. C NMR
1
3
acetate (3:1) to afford pure 3 (49 mg, 48 %) with similar spectro- (D O, 75 MHz): δ = 204.8, 204.4, 156.2, 154.2, 151.8, 131.6, 131.5,
2
[22] 1
scopic data as previously reported.
H NMR (CDCl , 300 MHz):
119.2, 74.4, 74.3, 72.5, 70.3, 68.8, 63.3, 57.8, 46.5, 45.7 ppm.
3
1
3
δ = 6.70–6.83 (m, 8 H) ppm. C NMR (CDCl , 75 MHz): δ = 151.9,
3
1
50.8, 120.1, 119.4, 115.9 ppm.
Acknowledgments
N. R. C. acknowledges the Academy of Finland for an academy
Quino-1,5-lactone (4): Amberlyst-15 (dry, 0.69 g) was added to a
suspension of quinic acid (3 mmol) in acetonitrile (150 mL) and the
mixture stirred at 50 °C for 24 h. After cooling, the reaction mixture research fellowship (decision number 287954). Dr. Alexandre Ef-
was filtered through Celite and washed with methanol. Solvent re- imov is acknowledged for valuable discussions of the NMR
moval under reduced pressure yielded the desired lactone 4 in spectra and Dr. Henrik Tolvanen for facilitating the use of the
quantitative yield (0.52 g) with similar spectroscopic data as previ-
grinder and sieve.
ously reported.[
23] 1
H NMR ([D ]DMSO, 300 MHz): δ = 5.90 (s, 1 H),
6
5
1
2
1
6
.24 (d, J = 3.8 Hz, 1 H), 4.84 (d, J = 6.7 Hz, 1 H), 4.61 (t, J = 5.3 Hz,
H), 3.81 (d, J = 4.1 Hz, 1 H), 3.49 (dd, J = 11.0, 4.8 Hz, 1 H), 2.27–
Keywords: Sustainable chemistry · Heterogeneous
catalysis · Natural products · Cyclitols
.24 (m, 1 H), 2.13–2.07 (m, 1 H), 1.87–1.82 (m, 1 H), 1.75–1.66 (m,
H) ppm. 13C NMR ([D ]DMSO, 75 MHz): δ = 177.8, 76.0, 71.6, 65.6,
6
5.3, 39.4, 36.8 ppm.
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to a previously reported procedure. A 14 % aqueous NaOCl solu-
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[
2
4
stirred solution of quinic acid (10 mmol) in water (7 mL) over
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[
[
[
3
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Published Online: ■
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Full Paper
Hydroquinone Synthesis
B. Assoah, L. F. Veiros, C. A. M. Afonso,
N. R. Candeias* ................................... 1–7
Biomass-Based and Oxidant-Free
Preparation of Hydroquinone from
Quinic Acid
Hydroquinone from
a
non-fossil in the dry form promoted the conver-
source: Hydroquinone has been pre- sion of quinic acid into hydroquinone
pared from a biomass-based starting under mild conditions, whereas unca-
material by a metal- and oxidant-free talysed processes demanded unpracti-
process. Polymer-based Amberlyst-15 cal reaction conditions.
DOI: 10.1002/ejoc.201600616
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim