Synthesis of natural fragrance jasminaldehyde using silica-immobilized piperazine as organocatalyst

Article abstract of DOI:10.1039/c3cy00313b

Jasminaldehyde (α-pentyl cinnamaldehyde) is a natural fragrance that can be produced via aldol-type C-C bond formation between heptanal and benzaldehyde. The use of bases like NaOH to form jasminaldehyde typically leads to significant waste and by-product formation. To provide sustainable options with diminished waste formation and high conversions and selectivities, herein a silica-immobilized piperazine is used as organocatalyst for the jasminaldehyde synthesis either in bio-based solvents (e.g. 2-methyltetrahydrofuran, 2-MeTHF) or in solvent-free conditions (using neat substrates as reaction media). Under reported conditions, a production of ～7 g jasminaldehyde L^-1 h^-1 is observed, delivering on-spec conversions and selectivities (>90% each). Selectivity remains unaltered during catalyst recycling, whereas a loss of conversion is significantly observed after reusing the catalyst for several cycles.

Full text of DOI:10.1039/c3cy00313b

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Page 1 of 18
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Synthesis of natural fragrance jasminaldehyde using silica-immobilized
piperazine as organocatalyst.
María PérezꢀSánchez, Pablo Domínguez de María*
Institut für Technische und Makromolekulare Chemie (ITMC),
RWTH Aachen University. Worringerweg 1. 52074 Aachen, Germany
Corresponding Author:
Dr. Pablo Domínguez de María.
Tel.: +49 241 8020468.
Fax: +49 241 8022177.
Eꢀmail: dominguez@itmc.rwthꢀaachen.de
1

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Abstract
Jasminaldehyde (αꢀpentyl cynnamaldehyde) is a natural fragrance that can be
produced via aldolꢀtype CꢀC bond formation between heptanal and benzaldehyde. The
use of bases like NaOH to form jasminaldehyde typically leads to significant waste
and byꢀproduct formation. To provide sustainable options with diminished waste
formation and high conversions and selectivities, herein a silicaꢀimmobilized
piperazine is used as organocatalyst for the jasminaldehyde synthesis either in bioꢀ
based solvents (e.g. 2ꢀmethyltetrahydrofuran, 2ꢀMeTHF), or in solventꢀfree (using
neat substrates as reaction media). Under reported conditions, a production of ~ 7 g
ꢀ1
ꢀ1
jasminaldehyde L h is observed, delivering on-spec conversions and selectivities (>
0 % each). Selectivity remains unaltered along catalyst recycling, whereas a loss of
conversion is significantly observed after reusing the catalyst for several cycles.
9
2

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1
.- Introduction.
Organocatalysis has flourished in the last years as a powerful tool to perform
highly selective chemical transformations, with CꢀC bond forming reactions (e.g.
1
ꢀ3
aldolꢀtype processes) representing a core step in this area. Initially envisaged for
asymmetric synthesis, the use of chiral organocatalysts from the natural pool (e.g.
proline and derivatives) emerged combining efficiency and bioꢀbased catalysis, with
outstanding cases of efficient chiral transfer processes. Based on that knowledge,
however, in recent years a number of applications of organocatalysis in the production
of less valuable (e.g. non chiral) products has started to appear, with several examples
4
5
6
using proline or DBU, chitosan, or other secondary amines such as piperidine, to
afford, for instance, biofuelꢀtype precursors. Albeit these reactions can be conducted
using more classic baseꢀcatalyzed concepts (e.g. using NaOH), the motivation of
using organocatalysis for these nonꢀchiral organic syntheses relies in the provision of
more sustainable chemistry, as less waste formation is expected from organocatalytic
processes, together with a more controllable catalysis to diminish the formation of byꢀ
products, often observed when baseꢀcatalyzed processes are conducted. Herein,
another important present trend for organocatalysis is the introduction of
heterogeneous catalysts to reduce the typically needed high organocatalyst loadings,
to enable simplified process setꢀups, and eventually to allow a straightforward catalyst
recovery and further reuse. Immobilized organocatalysts can be found in Nature, as in
5
the case of chitosan, or can be designed for tailored applications, e.g. by using ionic
7
,8
liquids as additives and “tag” molecules.
In another approach, the immobilization of organocatalyts in silica supports
may represent a costꢀeffective and useful approach to put forth novel heterogeneous
3

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organocatalysis to deliver efficient options for nonꢀasymmetric synthesis (e.g. in flow
9
ꢀ11
chemistry).
In this area, our research group has assessed silicaꢀimmobilized
12
TEMPO for the selective oxidation of 5ꢀHydroxymethylfurfural (HMF), as well as
silicaꢀimmobilized piperazine for aldolꢀ and Knoevenagelꢀlike condensations –
namely CꢀC bond formations – to afford either biofuelꢀtype precursors based on
1
3
furfural and acetone, or novel phosphonateꢀcontaining acyclic nucleosides with
potential antiviral activity, by using aldehydeꢀbearing nucleobases and different
14
ketones. Following these studies, herein the organocatalytic synthesis of
jasminaldehyde 3 using silicaꢀimmobilized piperazine is reported (Scheme 1).
Scheme 1. Synthesis of jasminaldehyde 3 via immobilized organocatalysis.
Jasminaldehyde 3 (αꢀpentyl cynnamaldehyde) is a natural fragrance that can be
synthetized by the selective crossed aldol condensation between heptanal 1 and
benzaldehyde 2 under basic conditions (e.g. NaOH), typically adding stoichiometric
15
amounts of base. In addition to the envisaged environmental problems that such a
synthesis may bring, reaction process lacks often the required selectivity, as selfꢀ
condensation of heptanal to afford 4 (Scheme 1) may occur as well. To overcome
these issues, apart from process design options (e.g. adding heptanal stepwise to
minimize secondary reactions), the use of heterogeneous catalysts such as solid acids,
4

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1
6ꢀ20
zeolites or aluminosilicates have been put forth.
However, the application of
organocatalysis for the synthesis of jasminaldehyde has been rather scarce, with some
21ꢀ23
few examples focusing on chitosan in different derivatized forms.
Aiming at
combining heterogeneous organocatalysis, sustainable chemistry and applicationꢀ
driven catalysis, herein the use of silicaꢀimmobilized piperazine for the
jasminaldehyde synthesis is reported for the first time.
2
.- Results & Discussion.
Focusing on the delivery of sustainable chemistry options, in a first set of
experiments, jasminaldehyde synthesis was organocatalytically conducted using
different solvents or directly in neat substrates (solventꢀfree), that is, in benzaldehyde
and heptanal as reaction media. As solvents, 2ꢀmethyltetrahydrofuran (2ꢀMeTHF) and
tertꢀbutanol were selected. The rationale behind these choices is that 2ꢀMeTHF can be
derived from biomass resources and shows promising biodegradability and valuable
preliminary toxicological data, thus conferring it an increasing interest as sustainable
24
organic solvent for future syntheses. Likewise, tertꢀbutanol is presently produced
from petroleumꢀbased isobutylene. However, recent fermentative routes to
biosynthesize isobutylene from sugars by means of genetically modified
microorganisms have been reported, and would certainly pave the way for the
provision of tertꢀbutanol as a future bioꢀbased solvent as well, within the soꢀcalled
25
biorefineries. Envisaging such potential importance in the future, our research group
has recently proposed the use of tertꢀbutanol as solvents for the biocatalystic selective
12,26
oxidation and / or esterifications of HMF and furfural.
5

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Results of jasminaldehyde 3 synthesis using silicaꢀimmobilized piperazine in
solventꢀfree, 2ꢀMeTHF and tertꢀbutanol as solvents are depicted in Figure 1.
Figure 1. Synthesis of jasminaldehyde 3 using silicaꢀimmobilized piperazine
as organocatalyst in different solvent conditions: Solventꢀfree, 2ꢀMeTHF and tertꢀ
butanol. Conditions: Heptanal 1, 0.42 mmol, benzaldehyde 2, 2.1 mmol, completed
ꢀ1
with 1 mL solvent; 100 mg catalyst (1.1 mmol g ), 60 °C, 18 h magnetic stirring.
1
Conversion and selectivity determined by HꢀNMR. Blank experiments either using
silica, nonꢀimmobilized piperazine, or catalystꢀfree did not show any conversion in
the reaction conditions applied.
As observed (Figure 1), reactions conducted in solventꢀfree (only substrates
were added) or in 2ꢀMeTHF led to analogous results in terms of selectivity (~ 60 %)
and conversion (~ 80 %) under these still nonꢀoptimized conditions, 60 °C, 18 h
reaction time. Conversely, the introduction of more polar solvents like tertꢀbutanol led
to unsatisfactory results, affording very low to negligible formation of jasminaldehyde
3
under the applied reaction conditions. A plausible reason for that might be the tertꢀ
6

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butylꢀalkylation of the active secondary amine of the immobilized piperazine. On the
other hand, the use of 2ꢀMeTHF for catalytic reactions in general, and for
organocatalytic reactions in particular, has been recently reported by several research
groups under different catalytic systems, representing a promising entry for efficient
5,13,14,24
sustainable chemistry.
Furthermore, the setꢀup of solventꢀfree reactions –
performed in neat substrates – is very valuable from a practical viewpoint, as high
substrate loadings can be combined with straightforward downstream processing and
a diminished waste formation. Since the jasminaldehyde synthesis was successful
under these neat conditions as well, the following studies focusing on processing
optimization were conducted in such solventꢀfree system, as higher product loadings
can be achieved.
Once the proofꢀofꢀprinciple with silicaꢀimmobilized piperazine was
successfully shown, in a next set of experiments the emphasis was put on optimizing
both the conversion and selectivity of the reaction. Especially, to reach on-spec values
for jasminaldehyde, a selectivity of 3 over byꢀproduct 4 (Scheme 1) must be higher
1
6ꢀ23
than 90 %,
and for obvious economic and technical reasons, a conversion higher
than 90 % is mandatory as well. Whereas for classic baseꢀcatalyzed processes
reaching these optimized figures is more challenging – due to the high reactivity of
such reaction systems –, the use of heterogeneous catalysts should provide more
controllable conditions. With these considerations in mind, the organocatalytic
reaction was studied by varying temperature and benzaldehyde–heptanal relationship.
Results regarding conversion and selectivity are depicted in Figure 2.
7

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Figure 2. Optimizations in conversion (above) and selectivity (below) by
changing temperature and benzaldehyde–heptanal ratio (mol:mol). Conditions: 0.42
mmol heptanal 1, variable amounts of benzaldehyde 2 as surplus (2.1, 4.2, and 8.4
ꢀ
mmol), and different temperatures (60ꢀ120 °C); 100 mg organocatalyst (1.1 mmol g
1
1
)
, 24 h, 8 h reaction, magnetic stirring. Conversion and selectivity determined by Hꢀ
NMR.
Gratifyingly, the optimization reaction parameters like temperature and
benzaldehyde–heptanal ratio led to largely improved results, both in conversion and
8

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selectivity, reaching in both cases ~ 90 % when conducted at 120 °C and at 20
benzaldehyde–heptanal ratios (Figure 2). Further improvements by setting a stepwise
addition of heptanal to benzaldehyde may be envisaged as well for future
improvements. Moreover, the setup of reactions in solventꢀfree conditions at 120 °C
led to these outstanding values in 8 h reaction time, thus showing a more optimized
process timing as well, with expected diminished waste formation, especially when
the process is compared with more classic homogeneous base catalysts (e.g. aqueous
13
NaOH). The formation of benzoic acid upon oxidation of benzaldehyde was
observed under this conditions (~ 5 % at 8 h compared to benzaldehyde), and could be
suppressed by performing the reactions under argon atmosphere. To further assess the
potential of the system the immobilized organocatalyst loading was subsequently
evaluated (Figure 3).
Figure 3. Influence of the catalyst loading in the jasminaldehyde synthesis
under optimized conditions. Conditions: Heptanal 1 0.42 mmol, benzaldehyde 2 8.4
mmol, 120 °C, solventꢀfree conditions, magnetic stirring, 8 h reaction time. Variable
ꢀ1
1
catalyst loadings from 50ꢀ400 mg (1.1 mmol g ). Conversion determined by Hꢀ
NMR.
9

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As observed (Figure 3), catalyst loadings of 100 mg almost led to full
conversion under the process timing reported (8 h). According to observed results, an
optimal catalyst–limiting substrate ratio (heptanal) of ~ 0.027 mmol of active catalytic
amino groups / mmol heptanal can be inferred for the jasminaldehyde synthesis.
ꢀ1
ꢀ1
Under those conditions, ~ 7 g jasminaldehyde L
solventꢀfree mild reaction conditions.
h
are produced under these
Finally, experiments aiming at assessing the catalyst recyclability were
conducted, studying the activity (based on conversion always at the same reaction
time) in jasminaldehyde 3. To this end, two approaches were followed. In the first one
the immobilized catalyst was washed with acetone and then with dichloromethane,
dried, and studied again in catalytic cycles (the soꢀcalled “organic washing” in Figure
4
). In the second approach, after such organic washing the catalyst was further washed
with water (starting with pH 9 to pH 7) until the pH of the solution remained neutral.
After drying the catalyst, it was assessed again in a new catalytic cycle. Results are
depicted in Figure 4.
Figure 4. Assessment of the reusability of the organocatalyst under several
cycles, based on activity (conversion). Conditions: Heptanal 1 0.42 mmol,
1
0

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benzaldehyde 2, 8.4 mmol, 120 °C, solventꢀfree conditions, 8 h reaction time, 100 mg
ꢀ1
1
organocatalyst (1.1 mmol g ). Activity determined by HꢀNMR.
In all cases the selectivity for jasminaldehyde remained always in excellent
values (on-spec, ~ 90 %, data not shown) along 4 consecutive cycles, under the
evaluated solventꢀfree reaction conditions. However, a lowering in the catalyst
activity over cycles was clearly observed when conversion was assessed, and the trend
turned out to be analogous in both washing systems. While the immobilized
piperazine could be virtually reused for two cycles maintaining its activity, a
significant loss of conversion was observed during the third and fourth rounds. Apart
from some expected physical losses of the catalyst under the nonꢀoptimized
conditions at lab scale, the formation of water during the reaction might break the
27ꢀ29
siloxane bridge that keeps the catalyst linked to the surface,
as well as chemical
28,30
losses of the catalyst.
Potential optimizations of the system might involve the use
of azeotropic distillation along the catalytic cycles, to avoid the accumulation of
water. Likewise, assessment of other chemical modifications derived from the
interaction of substrates (or products) with the catalysts should be further studied for
an inꢀdepth clarification of the reasons for catalyst deactivation. Looking beyond, the
combination of different organocatalysts has proven to be successful in enamine
31
catalysis, and may well fit in the design of future biꢀfunctional catalysts for more
sustainable and straightforward processes.
1
1

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3
.- Experimental
Chemicals. All compounds were purchased by SigmaꢀAldrich and were used
without further purification. Silicaꢀimmobilized piperazine was a kind gift of dichrom
®
GmbH (formerly SeQuant GmbH) – Silicycle Inc (Lot# 51343). Details: Catalyst
ꢀ1
ꢀ2
loading: 1.1 mmol g ; surface coverage based on molecular loading: > 1.91 ꢁmol m ;
particle size: 40ꢀ63 ꢁm; pore diameter: 60 Å, BJH; specific surface area (BET): 470ꢀ
2
ꢀ1
ꢀ1
5
30 m g ; specific pore volume: 0.70ꢀ0.85 mL g , BJH.
Organocatalytic reactions. 0.42 mmol of heptanal 1 were mixed with different
amounts of benzaldehyde 2 (2.1ꢀ8.4 mmol). Reactions took place mostly in solventꢀ
free conditions at 60ꢀ120 °C, with variable catalyst loadings (100ꢀ400 mg). Reaction
times were set from 8ꢀ18 h. For the workꢀup, suspended catalyst was filtered and the
reaction mixture analysed by 1HꢀNMR to assess conversion and selectivity. For
recycling experiments, the filtered catalyst was washed either with acetone and
dichloromethane (“washing with organic solvents”), or with acetone and
dichloromethane followed by water washing at pH 9, and subsequently with neutral
water at pH 7 until was neutral (“washing with oganic solvents + water”). After these
treatments, the immobilized catalyst was dried under vacuum (120 °C) under constant
weight, and added in a new reactor and fresh substrates were added.
1
HꢀNMR (300 MHz, CDCl ): (3): 9.53 (s, 1H); 7.53ꢀ7.38 (m, 5H); 7.21 (s,
3
1
1
H); 2.52 (t, 2H); 1ꢀ55ꢀ1.32 (m, 3H): 0.91 (t, 3H); (4) HꢀNMR (300 MHz, CDCl
3
):
9
.75 (s, 1H); 6.40 (t, 1H); 2.41 (t, 2H); 2.20 (t, 2H); 1.37 (m, 2H); 1.25 (m, 12H); 0.76
(
m, 6H). The conversion was measured comparing the substrate (1) and the product
3) and the selectivity by comparing products (3) and (4).
(
1
2

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4
.- Conclusions.
In summary, the use of silicaꢀimmobilized piperazine as organocatalyst for the
synthesis of jasminaldehyde 3 has been reported for the first time. Emphasis is given
to the increasing interest in using heterogeneous organocatalysis for nonꢀchiral
applications, in which a straightforward set up (immobilized catalysts) combined with
efficiency, high selectivity, and promising sustainable reaction conditions may be
envisaged. For this specific case, under optimized conditions on-spec high
conversions and selectivities (> 90%) can be achieved in solventꢀfree conditions
ꢀ1
ꢀ1
(
using neat substrates) enabling a production of jasminaldehyde of ~ 7 g L h . The
immobilized catalyst proved to be reusable, keeping such outstanding high selectivity
within all catalytic cycles, albeit a significant catalyst deactivation was observed
along these reuses. More research with this and other immobilized organocatalysts is
needed to further improve conditions for wasteꢀfree and efficient nonꢀchiral aldol
condensations like jasminaldehyde synthesis.
Acknowledgements.
Financial support from DFG training group 1166 “BioNoCo” (“Biocatalysis in
Nonꢀconventional Media”) is gratefully acknowledged. We thank Dr. Harald
®
Dibowski (dichrom GmbH (formerly SeQuant GmbH) – Silicycle Inc.) for kindly
donating a sample of the silicaꢀimmobilized piperazine.
1
3

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References
1
2
3
. M. Dondoni, A. Massi, Angew. Chem. Int. Ed. 2008, 47, 4638ꢀ4660
. P. Renzi, M. Bella, Chem. Commun. 2012, 48, 6881ꢀ6896
. P. Domínguez de María, P. Bracco, L.F. Castelhano, G. Bargeman, ACS
Catalysis 2011, 1, 70ꢀ75
4. A. Subrahmanyam, S. Thayumanavan, G.W. Huber, ChemSusChem 2010,
3
, 1158ꢀ1161.
5
. H. Kayser, C.R. Müller, C.A. GarcíaꢀGonzález, I. Smirnova, W. Leitner, P.
Domínguez de María, App. Catal. A: Gen. 2012, 445-446, 180ꢀ186.
. J.M. Keith, J.K. Kim, L. Alexander, R. Wu, R.L. Martin, E.R. Batista, R.
6
Michalczyk, B. Scott, S.K. Hanson, A.D. Sutton, J.C. Gordon, L.A.P. Silks, Curr.
Org. Chem. 2013. In press.
7. P. Domínguez de María (Ed). “Ionic Liquids in Biotransformations and
Organocatalysis: Solvents and Beyond”. Ed. John Wiley & Sons, Hoboken – US.
2
012.
8
9
1
. P. Domínguez de María. Angew. Chem. Int. Ed. 2008, 47, 6960ꢀ6968.
. A. Molnar, B. Rac, Curr. Org. Chem. 2006, 10, 1697ꢀ1726.
0. R. Maggi, G. Sartori, C. Oro, L. Soldi, Curr. Org. Chem. 2008, 12, 544ꢀ
5
63.
11. A. Sayari, S. Hamoudi, Chem. Mater. 2001, 13, 3151ꢀ3168.
12. M. Krystof, M. PérezꢀSánchez, P. Domínguez de María, ChemSusChem
2
013, 6, 826ꢀ830.
1
4

Page 15 of 18
Catalysis Science & Technology
View Article Online
DOI: 10.1039/C3CY00313B
®
®
1
3. Commercially available by Silicycle Inc. under the name of Siliabond : S.
Shanmuganathan, L. Greiner, P. Domínguez de María, Tetrahedron Lett. 2010, 51,
670ꢀ6672.
4. M. Palazzolo, M. PérezꢀSánchez, A.M. Iribarren, E.S. Lewkowicz, P.
Domínguez de María, Tetrahedron Lett. 2012, 53, 6797ꢀ6800.
6
1
1
1
5. L.S. Payne, EP0392579. 1990.
6. D. Abenhaim, C.P. Ngoc Son, A. Loupy, N. Ba Hiep, Synth. Commun.
1
994, 24, 1199ꢀ1205.
7. M.J. Climent, A. Corma, H. Garcia, R. GuilꢀLopez, S. Iborra, V. Fornés, J.
Catal. 2001, 197, 385ꢀ393.
1
18. M.J. Climent, A. Corma, R. GuilꢀLopez, S. Iborra, J. Primo, J. Catal.
1
998, 175, 70ꢀ79.
19. M.J. Climent, A. Corma, V. Fornés, R. GuilꢀLopez, S. Iborra, Adv. Synth.
Catal. 2002, 344, 1090ꢀ1096.
20. M. Hasni, J. Rouchaud, P. Grange, M. Devillers, S. Delsarte, Mat. Sci.
For. 2007, 554, 37ꢀ42.
21. N. Sudheesh, S.K. Sharma, R.S. Shukla, J. Mol. Cat. A: Chem. 2010, 321,
7
9
1
7ꢀ82.
2
2. A. El Kadib, K. Molvinger, M. Bousmina, D. Brunel, Org. Lett. 2010, 12,
3. A. El Kadib, K. Molvinger, M. Bousmina, D. Brunel, J. Catal. 2010, 273,
4. V. Pace, P. Hoyos, L. Castoldi, P. Domínguez de María, A.R. Alcántara,
48ꢀ951.
2
47ꢀ155.
2
ChemSusChem 2012, 5, 1369ꢀ1379.
5. P. Domínguez de María, ChemSusChem 2011, 4, 327ꢀ329.
2
1
5

Catalysis Science & Technology
Page 16 of 18
View Article Online
DOI: 10.1039/C3CY00313B
26. M. Krystof, M. PérezꢀSánchez, P. Domínguez de María, ChemSusChem
2
013, 6, 630ꢀ634.
2
2
2
7. D. Sachdev, A. Dubey, Catal. Lett. 2011, 141, 1548ꢀ1556.
8. M. Etienne, A. Walcarius, Talanta, 2003, 59, 1173ꢀ1188.
9. Q. Wang, E. Jordan, D.F. Shantz, J. Phys. Chem. C. 2009, 113, 18142ꢀ
1
8151.
30. Q. Wang, D.F. Shantz, J. Catal. 2010, 271, 170ꢀ177.
31. M. Wiesner, G. Upert, G. Angelici, H. Wennemers, J. Am. Chem. Soc.
2
010, 132, 6ꢀ7.
1
6

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Synthesis of natural fragrance jasminaldehyde using silica-immobilized
piperazine as organocatalyst.
María Pérez-Sánchez, Pablo Domínguez de María*
Table of Contents
Heterogeneous organocatalysis may contribute to the sustainable production of low-
to-medium added-value products under neat conditions.
1

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2