Conversion of oxiranes and CO2 to organic cyclic carbonates using a recyclable, bifunctional polystyrene-supported organocatalyst

Article abstract of DOI:10.1039/c3gc41919c

The development of a heterogeneous one-component bifunctional catalyst system able to catalyse the conversion of carbon dioxide and oxiranes to organic cyclic carbonates at low temperature (45 °C) is reported. The bifunctional system can be easily recycled and reactivated when required. When compared with other heterogeneous organocatalysts for the same transformation, the reported catalyst is active at much milder temperatures, thus emphasising the optimal sustainability profile of the new catalyst system.

Full text of DOI:10.1039/c3gc41919c

Green Chemistry
View Article Online
View Journal | View Issue
PAPER
Conversion of oxiranes and CO2 to organic cyclic
carbonates using a recyclable, bifunctional
polystyrene-supported organocatalyst†
Cite this: Green Chem., 2014, 16,
1552
Christopher J. Whiteoak,a Andrea H. Henseler,a Carles Ayats,a Arjan W. Kleij*a,b and
Miquel A. Pericàs*a,c
The development of a heterogeneous one-component bifunctional catalyst system able to catalyse the
conversion of carbon dioxide and oxiranes to organic cyclic carbonates at low temperature (45 °C) is
reported. The bifunctional system can be easily recycled and reactivated when required. When compared
with other heterogeneous organocatalysts for the same transformation, the reported catalyst is active at
much milder temperatures, thus emphasising the optimal sustainability profile of the new catalyst system.
Received 13th September 2013,
Accepted 10th December 2013
DOI: 10.1039/c3gc41919c
www.rsc.org/greenchem
Introduction
The use of carbon dioxide (CO2) in chemical synthesis is
attracting significant interest as a result of growing concerns
about the environmental impact of this greenhouse gas, but
also because CO2 as a potential carbon source is inexpensive,
widely available and non-toxic.1–4 The principal limitation to
the use of CO2 as a carbon source is its high kinetic stability
and therefore chemical processes utilising CO2 as feedstock
usually require elevated operating temperatures limiting
overall sustainability. An ideal CO2 utilising process should
emit less CO2 than it uses; hence there is a desire for the use
of lower reaction temperatures as energy generation required
for heating results in emissions of CO2. To date the develop-
ment of CO2 utilising processes which are operative at ambient
conditions is and continues to be a huge challenge. The com-
bination of CO2 and a reagent with high intrinsic energy can
facilitate the conversion of CO2 and indeed, one of the most
developed reactions for the conversion of CO2 into value-
added organic matter is the ring-expansion addition reaction
of CO2 to oxiranes (Scheme 1).
Scheme 1 Ring-expansion addition reaction of CO2 to oxiranes.
salt at 120 °C to yield the desired cyclic organic carbonates.5 In
addition to utilising a reagent with high intrinsic energy,
efficient catalytic systems can be employed to further enhance
the reaction kinetics and for the aforementioned ring-expan-
sion addition reaction of CO2 to oxiranes there have been
extensive reports of catalytic systems able to mediate this con-
version.6,7 The use of a Lewis acid catalyst in addition to a
nucleophilic co-catalyst permits the use of more sustainable
reaction conditions and in recent years several Lewis acidic
catalysts based on Al,8 Zn9 and Fe10 have been reported to be
active at ambient temperatures.
In contrast to the number of metal-based catalyst systems
reported, the number of organocatalyst systems reported is
relatively scarce and this is most probably due to their reduced
substrate activation potential. As a result, most of the reported
examples typically require the use of unfavourable elevated
temperatures (>100 °C) challenging the sustainability and
hence applicability of these catalysts. Previously, in our labora-
tory we have developed an organocatalyst system active at more
favourable temperatures (25–45 °C). We reported that commer-
cially available 1,2,3-tris-hydroxybenzene (pyrogallol) in combi-
nation with tetrabutylammonium iodide (TBAI) is able to
convert CO2 and a variety of oxiranes into the corresponding
organic cyclic carbonates at ambient temperature and pCO2 =
1.0 MPa.11 The mode of action of this catalyst system was eluci-
dated through DFT calculations and it was found that an
In the simplest case, this reaction proceeds in the presence
of only a catalytic amount of a tetrabutylammonium halide
aInstitute of Chemical Research of Catalonia (ICIQ), Av. Països Catalans 16, 43007 –
Tarragona, Spain. E-mail: mapericas@iciq.es, akleij@iciq.es; Fax: +34 977920224;
Tel: +34 977920247
bCatalan Institute for Research and Advanced Studies (ICREA), Pg. Lluís Companys
23, 08010 Barcelona, Spain
cDepartament de Química Orgànica, Universitat de Barcelona (UB),
08028 Barcelona, Spain
†Electronic supplementary information (ESI) available: Detailed experimental
procedures and copies of relevant NMR/IR spectra of known and new
compounds. See DOI: 10.1039/c3gc41919c
1552 | Green Chem., 2014, 16, 1552–1559
This journal is © The Royal Society of Chemistry 2014

View Article Online
Green Chemistry
Paper
extended hydrogen-bonding network is responsible for more
efficient stabilisation of reaction intermediates, making the
oxiranes more susceptible towards ring opening by the co-
catalytic halide nucleophile. This binary catalyst system showed
non-optimal recycling potential and in order to further increase
the sustainability of this catalyst system we decided to pursue
the possibility of developing a heterogenised system by anchor-
ing the pyrogallol unit onto a suitable support.
Immobilisation of catalysts allows facile separation from
the reaction mixture by simple filtration, avoiding tedious iso-
lation/purification steps, and as a result allows for catalyst
recycling. The main benefits of polystyrene (PS) as a support-
ing material include its high chemical, thermal, and mechan-
ical stability and the fact that the support allows for facile
chemical modification. Furthermore, heterogenised catalysts
combine the properties of their homogeneous analogues with
the key features of heterogeneous catalysts and are suitable for
continuous flow processes avoiding co-elution of the
catalyst.12–14 Recently, some of us had considerable success in
realising polystyrene supported organocatalyst systems for a
variety of catalytic applications15–18 and thus we decided to use
these favourable support features to develop a heterogenised
and more sustainable catalyst based on the aforementioned
pyrogallol.
Scheme 2 Synthesis of the PS-Cat 1. Reagents and conditions: (i) HBr,
AcOH, 16 h, reflux, 76%; (ii) NaHCO3 (2.4 eq.), propargyl bromide (2.0
eq.), DMF, 14 h, rt, 64%; (iii) azidomethyl polystyrene, Cu-cat (3 mol%),
DMF–THF (1 : 1), 1.5 h, 80 °C, 200 W.
Table 1 Conversion of 1,2-epoxyhexane 4 into its corresponding cyclic
carbonate 4a using PS-Cat 1a
There have been several reports of immobilised organocata-
lyst systems for the conversion of oxiranes and CO2 to organic
cyclic carbonates including immobilised ionic liquids,19 bio-
polymers20 and immobilised amino acids21 amongst others.
Unfortunately though, as mentioned earlier, most of these
catalyst systems require operating temperatures above 100 °C
which challenges their overall sustainability. Herein, we report
the synthesis and application of more sustainable and recycl-
able catalyst systems based on polystyrene supported pyrogal-
lol for the conversion of CO2 and oxiranes into cyclic organic
carbonates under attractive conditions.
Entry
PS-Cat
Run
Yieldb (%)
TONc
1
2
3
4
—
1
1
—
1
2
24
78
48
30
—
39
24
15
1
3
a Reaction conditions: 1,2-epoxyhexane (1.0 g, 9.98 mmol), PS-Cat 1
(2.0 mol%), TBAI (2.0 mol%), 45 °C, pCO2 = 1.0 MPa, 18 h. b Isolated
yield. c TON is defined as turnover per pyrogallol unit.
Results and discussion
subsequent filtration. After removal of the solvent and
unreacted substrate from the filtrate under reduced pressure,
pure organic cyclic carbonate was obtained. In comparison,
under these conditions TBAI alone at a loading of 2 mol%
allows for a much lower isolated yield of 24% (Table 1, entry 1).
The recovered catalyst system was then used in a second
run. Unfortunately, the activity of the catalyst system was
reduced in the second run, whereby only a 48% product yield
was obtained (Table 1, entry 3). The catalyst system was recov-
ered and used again in a third run in which a further
reduction in the isolated product was observed (30%, Table 1,
entry 4).
This reduction in catalytic activity was coupled with a
visible darkening of the PS-support as more runs were carried
out. In order to investigate this darkening we reacted pyrogal-
lol, TBAI and 1,2-epoxyhexane stoichiometrically using a
minimal amount of dichloromethane as a solvent. After
18 hours the darkened reaction mixture was analysed by
The synthesis of the initial PS-Cat 1 could be achieved in three
simple steps from commercially available starting materials
and is shown in Scheme 2. Demethylation of 3,4,5-trimethoxy-
phenylacetic acid 1 with hydrobromic acid afforded 3,4,5-tri-
hydroxyacetic acid 2, which was subsequently converted into
the corresponding propargylated product 3 by reaction with
propargyl bromide. PS-Cat 1 ( f = 1.0 mmol g−1) was then
obtained from the reaction of azidomethyl polystyrene and 3
via a copper-catalysed alkyne azide cycloaddition (CuAAC) reac-
tion (see ESI† for full procedures and details).22,23
When PS-Cat 1 was used as a catalyst for the conversion of
1,2-epoxyhexane, our benchmark substrate, at a loading of
2 mol% in the presence of TBAI (2 mol%) at 45 °C and a CO2
pressure of 1.0 MPa, we observed a conversion of 78% after
18 hours (Table 1, entry 2). The binary catalyst system could be
easily separated from the product by the addition of diethyl
ether (with NBu4I being rather insoluble in this solvent) and
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 1552–1559 | 1553

View Article Online
Paper
Green Chemistry
Table 2 Conversion of 1,2-epoxyhexane 4 into its corresponding cyclic
carbonate 4a using PS-Cat 2 and PS-Cat 4a
Scheme 3 Products arising from the reaction of pyrogallol, 1,2-epoxy-
hexane and TBAI.
1H NMR spectroscopy, where it was observed that the spec-
trum had changed from that of the initial one. Isolation of the
reaction products indicated that the pyrogallol had reacted
with TBAI to yield an ammonium phenolate salt and iodide
had reacted with the 1,2-epoxyhexane resulting in the for-
mation of a halohydrin species (see Scheme 3).
We propose that this reaction may be a catalyst deactivation
route as the hydrogen-bonding network decreases and halide
nucleophile concentration becomes depleted over successive
runs as a result. PS-Cat 1 contains a triazole linker as a result
of the CuAAC reaction involved in the PS functionalisation
step. It was envisaged that reaction of this triazole linker with
methyl iodide could result in a one-component bifunctional
catalyst system (cf., PS-Cat 2, Scheme 4) with a higher stability
than that of the binary catalyst system described above.
Entry
PS-Cat
Run
Yieldb (%)
TONc
1
2
3
4
5
4
2
2
2
2
—
1
2
3
4
20
84
76
62
48
5
21
19
16
12
a Reaction conditions: 1,2-epoxyhexane (1.0 g, 9.98 mmol), PS-Cat 2 or
PS-Cat 4 (4.0 mol%), 45 °C, pCO2 = 1.0 MPa, 18 h. b Isolated yield.
c TON is defined as turnover per pyrogallol unit.
activity observed is not the result of catalysis involving the
co-catalyst only.
As may be expected, the one-component PS-Cat 2 requires a
higher catalyst loading in order to attain a similar activity to
that of the binary system containing both but separate
PS-Cat 1 and TBAI (Table 1, entry 2 vs. Table 2, entry 2). The
bifunctional PS-Cat 2 shows a fourfold higher yield under
these conditions than PS-Cat 4, suggesting the involvement of
the 1,2,3-trihydroxybenzene moiety in the catalysis reaction
(Table 2, entries 1 and 2). It can also be seen that the decrease
in activity for bifunctional PS-Cat 2 is slower than that
observed for the binary catalyst system PS-Cat 1. A reduction in
the isolated product yield to 48% already occurs in run 2 using
the PS-Cat 1/TBAI binary catalyst system, while in the case of
the bifunctional PS-Cat 2 a similar decrease in the product
yield is noted in the fourth run and thus PS-Cat 2 retains
activity for a longer period of time. Elemental analysis
obtained for the PS-Cat 2 system before use (11.73% I) and after
4 runs (2.45% I) indicates that the loss of activity should be
ascribed to the reduction in the halide nucleophile that is
required for the ring opening of the oxirane during the conver-
sion into its carbonate. A similar iodine elemental analysis per-
formed on PS-Cat 4 showed that in this case no decrease in the
halide occurs with reuse, and this suggests that the adjacent
pyrogallol unit facilitates this process in PS-Cat 2 (e.g., through
a hydrogen-bond assisted Herzig–Meyer demethylation).
The remote position of a potential triazolium ion from the
1,2,3-trihydroxybenzene site is likely to make a one-component
bifunctional catalyst more stable toward the aforementioned
decomposition compared with the binary catalyst system.
Reaction of PS-Cat 1 with methyl iodide in acetonitrile resulted
in the formation of PS-Cat 2 (Scheme 4). A support material
terminated in a phenyl-triazole unit, PS-3, was also prepared
for comparison and reacted with methyl iodide in the same
manner to realise PS-Cat 4 which was used to ensure that any
In an attempt to realise a PS-supported catalyst system that
does not suffer from deactivation problems, we planned to
prepare a bifunctional resin where the triazolium and pyrogal-
lol units could be linked to distinct positions along the
polymer backbone. This could be easily brought into practice
as a result of the non-discriminating nature of CuAAC reac-
tions. Thus, even the relative proportions of the two desired
functional units could be in principle controlled by perform-
ing on the same azido-functionalized polymer two sequential
CuAAC reactions with the minor, limiting unit being
Scheme 4 Synthesis of PS-Cat 2 and PS-Cat 4. Reagents and con-
ditions: (i) MeI (5.0 eq.), CH3CN, 48 h, 75 °C.
1554 | Green Chem., 2014, 16, 1552–1559
This journal is © The Royal Society of Chemistry 2014

View Article Online
Green Chemistry
Paper
Scheme 5 Synthesis of PS-Cat 5. Reagents and conditions: (i) 3 (0.2
eq.), Cu-cat (3 mol%), DMF–THF (1 : 1), 1.5 h, 80 °C, 200 W; (ii) phenyl-
acetylene (1.2 eq.), Cu-cat (3 mol%), DMF–THF (1 : 1), 1.5 h, 80 °C, 200 W;
(iii) MeI (5 eq.), CH3CN, 48 h, 75 °C.
Fig. 1 Recycling of bifunctional PS-Cat 5 in the synthesis of 4a. Con-
ditions: 1,2-epoxyhexane (1.0 g, 9.98 mmol), PS-Cat 5 (4.0 mol%), 45 °C,
pCO2 = 1.0 MPa, 18 h. Note that 4 mol% of the “iodide” based PS sup-
ported catalyst only gives a 20% yield, cf. Table 2, entry 1. The catalyst
was reactivated after run 6.
introduced first. We accordingly devised a straightforward syn-
thetic protocol for the preparation of a resin where the PS-sup-
ported 1,2,3-trihydroxybenzene containing moieties and the
other units (cf., red and green parts in Scheme 5) existed in an
optimal 1 : 4 ratio. This could be brought into practice through
the sequence shown in Scheme 5, where a final treatment with
methyl iodide leads to PS-Cat 5. It is interesting to note that
higher than those that may be obtained with PS-Cat 1 or
PS-Cat 2.
The bifunctional PS-Cat 5 was also studied for the conver-
sion of other substrates.25 In these experiments the supported
catalyst was used to convert one substrate and then recycled in
this versatile methodology may have wider applicability as it order to convert further substrates. Table 3 summarises the
can be applied to the preparation of other types of bifunctional
heterogeneous catalyst systems whereby the inclusion of
results obtained from this study. Propylene oxide (5), epichloro-
hydrin (6) and 1,2-epoxy-5-hexene (7) could be successively
different catalytic moieties on the same PS support is required. converted (Table 3, entries 1–3) into their respective organic
Even in the case where the triazolium moieties linking the
1,2,3-trihydroxybenzene units to the polystyrene backbone
carbonates 5a–7a with excellent isolated yields. The catalyst
system was then further challenged by using styrene oxide 8
suffered a decomposition similar to the one observed in (Table 3, entry 4). This substrate was found to be more slug-
PS-Cat 2,24 the more abundant phenyltriazolium units should
remain stable with time (as observed with PS-Cat 4) and pre-
gish using the homogeneous version of the pyrogallol-based
catalyst system reported previously.11 The isolated yield of the
serve better the catalytic activity of PS-Cat 5. Indeed, PS-Cat 5 carbonate product 8a (53%) was lower in this case but in the
(4 mol%) maintains its activity levels for a longer period of
time than PS-Cat 2, whilst the reduction in the number of pyr-
same order of magnitude as for the homogeneously catalysed
reaction. To check if this reduced yield was a result of de-
ogallol units in PS-Cat 5 (from 4.0 to 0.8 mol%) only leads to a activation of the catalyst system PS-Cat 5, propylene oxide (5)
modest reduction in the overall activity, suggesting that the
amount of halide nucleophile present in PS-Cat 2 is indeed
was then tested again as a substrate and the isolated yield
proved to be only slightly lower (89%) than at the beginning of
limiting the overall activity. An appreciable reduction in the recycling experiment (Table 3, entry 1 versus entry 5).
activity of PS-Cat 5 only started to occur after five runs (Fig. 1).
As there was a small reduction in the yield it was decided to
reactivate the support by reaction with methyl iodide before
At this point, the support had slightly darkened in colour,
but less significantly than observed in the case of the binary further use (after run 5, Table 3). With the intention of increas-
couple PS-Cat 2/TBAI. Importantly, after a regenerative treat-
ment of PS-Cat 5 with methyl iodide, the initial activity was vir-
ing the obtained yield of the organic cyclic carbonate from
styrene oxide we decided to increase the operating temperature
tually recovered (Fig. 1, run 7) and the supported catalyst to 65 °C (entry 6), which is still significantly lower than the
regained a pale brown colour. The same sample of PS-Cat 5
was used in 11 consecutive runs giving a total of 938 turn-
temperatures reported for other heterogeneous organocatalyst
systems. At this higher temperature an almost quantitative
overs/1,2,3-trihydroxybenzene unit which is significantly yield of the organic cyclic carbonate product was obtained.
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 1552–1559 | 1555

View Article Online
Paper
Green Chemistry
Table 3 Reuse of bifunctional PS-Cat 5 with different substratesa
Table 3 (Contd.)
Yieldb (%)
89
Run
1
T (°C)
Substrate
Product
Yieldb (%)
96
Run
11
T (°C)
Substrate
Product
45
45
2
45
94
12
85
45
85
>99
72
3
4
45
45
91
53
13
14h
—
i
5c
45
65
65
89
98
8e
a Reaction conditions: substrate (10.0 mmol), PS-Cat 5 (8.0 mol%),
pCO2 = 1.0 MPa, 18 h. b Isolated yield. c Reactivation of PS-Cat 5 with
methyl iodide done after this run. d 42 h. e Traces of cis-product
present. f 66 h. g Product mixture contained 82% trans- and 18% cis-
carbonate by 1H NMR analysis. h The catalyst was reactivated with MeI
before this run was carried out. i A mixture of products was obtained;
for details see the ESI.
6
7d
This result prompted us to challenge the catalyst system still
further, by attempting to convert an internal oxirane (entries 7
and 8). Internal oxiranes have been shown to be difficult sub-
strates to convert and we chose the simplest example for our
study, trans-2,3-epoxybutane. At 65 °C a low yield of only 8%
was achieved, but upon increasing the temperature and time
of the reaction we were able to obtain up to 18% yield.
Although this yield may not appear significant, it should be
noted that most metal-based catalyst systems are unable to
mediate efficient conversion of this substrate. We also noted
that although the starting material was 100% pure trans-2,3-
epoxybutane, at the higher temperature there was a significant
loss of configuration in the product (up to 18% cis-carbonate
was obtained). This behaviour has been studied before using
an iron(III) amino-triphenolate based catalyst system and was
suggested to arise from different ring-closure mechanisms.26
We then also investigated the use of some more challenging
internal epoxides (Table 3, entries 9–14). The cyclic epoxides
of entries 9 and 10 were, as expected, only converted to a
minor extent (12 and 15% yields, respectively) in line with
8f
85
85
18g
12
9
10
85
15
1556 | Green Chem., 2014, 16, 1552–1559
This journal is © The Royal Society of Chemistry 2014

View Article Online
Green Chemistry
Paper
previous reports that internal epoxides generally require highly catalyst systems can be found in the ESI.† 1H and 13C NMR
potent (metal) catalysts and more harsh reaction con- spectra were recorded on a Bruker AV-400 or AV-500 spectro-
ditions.10,26,27 Hereafter, the benzyl glycidyl ether substrate meter and referenced to the residual deuterated solvent
(entry 11) could be cleanly converted in high yield (89%) and signals. IR spectra were obtained using a Bruker Alpha FT-IR.
also the rarely reported conversion of indene oxide28 pro- Elemental analysis was performed by MEDAC Ltd, United
ceeded smoothly (entry 12, >99% yield).
Kingdom.
In order to test whether the catalyst had lost some of its
Typical procedure for organic cyclic carbonate synthesis from
oxiranes and CO2
activity, propylene oxide was then used as
a substrate
(entry 13) and this afforded a 72% yield of the carbonate
product being lower than those reported in entries 1 and 1,2-Epoxyhexane (1.0 g, 9.98 mmol) was placed in a 30 mL
5. Therefore, before further use the PS-Cat 5 was first reacti- stainless steel autoclave with a PS-Cat (2.0 mol%) and TBAI
vated again using MeI.29 As a final substrate in the series, (2.0 mol%) (i.e.,
a binary catalyst system) or PS-Cat 5
phenyl glycidol (entry 14) was evaluated; unlike in the case of (4.0 mol%) (i.e., a bifunctional catalyst system). The autoclave
glycidol25 the product of this experiment could be isolated (see was then subjected to three cycles of pressurisation and
ESI† for details). However, by 1H NMR analysis and by com- depressurisation with carbon dioxide (5 MPa), before final
parison with authentic samples prepared individually it is stabilisation of the pressure to 10 MPa. The autoclave was
clear that the reaction proceeds with much lower selectivity, sealed and heated to 45 °C and left stirring. After 18 hours the
and indications were found for the formation of polyols, i.e. reaction mixture was suspended in diethyl ether (20 mL) and
ring-opening of this epoxide substrate by adventitious water filtered. The catalyst system was further washed with diethyl
had occurred.
ether (3 × 10 mL) and the solvent removed from the combined
Nonetheless, the results reported in Table 3 clearly demon- organic filtrates under reduced pressure to yield the organic
strate the unique potential of this supported, bifunctional cyclic carbonate product. The identity of the organic cyclic car-
catalyst PS-CAT 5 for the conversion of a variety of different bonate product was confirmed by comparison to literature
epoxides into their cyclic carbonates using a single catalyst data. The collected catalyst system was used again in sub-
1
batch.
sequent catalytic runs. H and 13C NMR and IR spectra of the
organic cyclic carbonate products can be found in the ESI.†
Below a listing of analytical data is presented of the obtained
cyclic carbonates 4a–13a.
Conclusions
4-Butyl-1,3-dioxolan-2-one (4a).30 1H NMR (400 MHz,
In summary, we have reported an efficient PS supported CDCl3) δ 4.79–4.62 (m, 1H), 4.52 (dd, JHH = 8.1 and JHH
2
3
=
2
3
organocatalyst system based on a pyrogallol (i.e., 1,2,3-trihy- 8.1 Hz, 1H), 4.08 (dd, JHH = 8.1 and JHH = 7.3 Hz, 1H),
3
droxybenzene) scaffold for the conversion of CO2 and oxiranes 1.90–1.58 (m, 2H), 1.53–1.25 (m, 4H), 0.92 (t, JHH = 7.0 Hz,
into organic cyclic carbonates which is active at significantly 3H). 13C NMR (101 MHz, CDCl3) δ 155.2 (CvO), 77.2, 69.5,
lower temperatures (45 °C) than those previously reported for 33.4, 26.4, 22.2, 13.7. IR (neat): ν = 1786 cm−1 (CvO).
other heterogeneous organocatalyst systems (>100 °C). This
catalyst system represents an improvement of our previously CDCl3) δ 4.93–4.79 (m, 1H), 4.56 (dd, JHH = 8.5 and JHH
4-Methyl-1,3-dioxolan-2-one (5a).30 1H NMR (400 MHz,
2
3
=
2
3
reported pyrogallol catalyst and is an example of how click- 7.6 Hz, 1H), 4.03 (dd, JHH = 8.5 and JHH = 7.2 Hz, 1H), 1.48
chemistry can be utilised for the immobilisation of an organo- (d, JHH = 6.3 Hz, 2H). 13C NMR (101 MHz, CDCl3) δ 155.1
3
catalyst onto functionalised-PS. The reported catalyst system (CvO), 73.6, 70.7, 19.4. IR (neat): ν = 1781 cm−1 (CvO).
(PS-Cat 5) can also be recycled and upon loss of activity can be
easily regenerated by reaction with methyl iodide. In addition, CDCl3) δ 5.09–4.83 (m, 1H), 4.60 (dd, JHH = 8.5 and JHH
4-Chloro-1,3-dioxolan-2-one (6a).31 1H NMR (400 MHz,
2
3
=
2
3
we have exemplified the potential for inclusion of different 8.5 Hz, 1H), 4.42 (dd, JHH = 8.5 and JHH = 5.8 Hz, 1H), 3.81
2
3
2
catalytic moieties on the same PS support, which may have (dd, JHH = 12.2 and JHH = 5.8 Hz, 1H), 3.75 (dd, JHH = 12.2
wider applicability for the realisation of other heterogeneous and JHH = 3.6 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ 154.4
3
catalysts which require multiple catalytic sites. It therefore (CvO), 74.4, 67.0, 43.90. IR (neat): ν = 1779 cm−1 (CvO).
marks this versatile catalyst preparation procedure as highly
4-(But-3-en-1-yl)-1,3-dioxolan-2-one
(7a).32 1H
NMR
attractive for optimising structure–reactivity features of new (500 MHz, CDCl3) δ 5.87–5.67 (m, 1H), 5.11–5.06 (m, 1H),
2
catalyst systems with an improved sustainability footprint.
5.06–5.01 (m, 1H), 4.78–4.66 (m, 1H), 4.52 (dd, JHH = 8.6 and
3JHH = 8.6 Hz, 1H), 4.06 (dd, JHH = 8.6 and JHH = 7.2 Hz, 1H),
2.32–2.12 (m, 2H), 1.99–1.86 (m, 1H), 1.84–1.69 (m, 1H). 13C
NMR (126 MHz, CDCl3) δ 155.0 (CvO), 136.2, 116.3, 76.4,
69.4, 33.0, 28.6. IR (neat): ν = 1783 cm−1 (CvO).
2
3
Experimental
All substrates and reagents are commercially available and
4-Phenyl-1,3-dioxolan-2-one (8a).30 1H NMR (400 MHz,
were used as received. Carbon dioxide (purchased from CDCl3) δ 7.52–7.40 (m, 3H), 7.40–7.32 (m, 2H), 5.69 (dd, 3JHH
=
2
3
PRAXAIR) was used without further purification or drying 8.5 and 8.0 Hz, 1H), 4.81 (dd, JHH = 8.5 and JHH = 8.5 Hz,
prior to use. Procedures for the synthesis of the PS supported 1H), 4.35 (dd, JHH = 8.5 and JHH = 8.0 Hz, 1H). 13C NMR
2
3
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 1552–1559 | 1557

View Article Online
Paper
Green Chemistry
(101 MHz, CDCl3) δ 154.8 (CvO), 135.8, 129.7, 129.2, 125.9,
78.0, 71.2. IR (neat): ν = 1774 cm−1 (CvO).
4 M. Cokoja, C. Bruckmeier, B. Reiger, W. A. Hermann and
F. E. Kühn, Angew. Chem., Int. Ed., 2011, 50, 8510.
5 V. Caló, A. Nacci, A. Monopoli and A. Fanizzi, Org. Lett.,
2002, 4, 2561.
6 M. North, R. Pasquale and C. Young, Green Chem., 2010,
12, 1514.
7 A. Decortes, A. M. Castilla and A. W. Kleij, Angew. Chem.,
Int. Ed., 2010, 49, 9822.
8 W. Clegg, R. W. Harrington, M. North and R. Pasquale,
Chem.–Eur. J., 2010, 16, 6828.
4,5-Dimethyl-1,3-dioxolan-2-one (9a).33 trans-Carbonate: 1H
3
NMR (400 MHz, CDCl3) δ 4.39–4.27 (m, 2H), 1.44 (d, JHH
=
5.9 Hz, 6H). 13C NMR (101 MHz, CDCl3) δ 154.33 (CvO), 79.9,
18.3. IR Neat: 1774 cm−1 (CvO). cis-Carbonate: 1H NMR
3
(400 MHz, CDCl3) δ 4.91–4.78 (m, 2H), 1.34 (d, JHH = 5.9 Hz,
6H). 13C NMR (101 MHz, CDCl3) δ 154.3 (CvO), 76.1, 14.3. IR
(neat): ν = 1774 cm−1 (CvO).
Hexahydrobenzo[d][1,3]dioxol-2-one
(10a).34 1H
NMR
(400 MHz, CDCl3) δ 4.71–4.66 (m, 2H), 1.94–1.82 (m, 4H),
1.66–1.55 (m, 2H), 1.46–1.37 (m, 2H). 13C NMR (101 MHz,
9 A. Decortes and A. W. Kleij, ChemCatChem, 2011, 3,
831.
CDCl3) δ 155.4 (CvO), 75.8, 26.7, 19.1. IR (neat): ν = 1784 cm−1 10 A. Buchard, M. R. Kember, K. G. Sandeman and
(CvO).
Tetrahydro-3aH-cyclopenta[d][1,3]dioxol-2-one
NMR (400 MHz, CDCl3) δ 5.12–5.08 (m, 2H), 2.15–2.06 (m, 2H),
C. K. Williams, Chem. Commun., 2011, 47, 212;
C. J. Whiteoak, E. Martin, M. Martínez Belmonte, J. Benet-
Buchholz and A. W. Kleij, Adv. Synth. Catal., 2012, 354, 469.
(11a).35 1H
1.83–1.61 (m, 4H). 13C NMR (101 MHz, CDCl3) δ 155.5 (CvO), 11 C. J. Whiteoak, A. Nova, F. Maseras and A. W. Kleij, Chem-
81.9, 33.1, 21.6. IR (neat): ν = 1780 cm−1 (CvO).
4-(Phenoxymethyl)-1,3-dioxolan-2-one (12a).36 1H NMR 12 C. A. McNamara, M. J. Dixon and M. Bradley, Chem. Rev.,
(400 MHz, CDCl3) δ 7.37–7.29 (m, 2H), 7.07–7.02 (m, 1H), 2002, 102, 3275.
6.96–6.91 (m, 2H), 5.08–5.01 (m, 1H), 4.63 (dd, JHH = 8.3, 13 J. Lu and P. H. Toy, Chem. Rev., 2009, 109, 815.
SusChem, 2012, 5, 2032.
2
2
3
3JHH = 8.3 Hz, 1H), 4.56 (dd, JHH = 8.3 Hz, JHH = 5.9 Hz, 1H), 14 Heterogenized Homogeneous Catalysts for Fine Chemical Pro-
2
3
2
4.25 (dd, JHH = 10.6, JHH = 4.2 Hz, 1H), 4.17 (dd, JHH
=
duction, ed. P. Barbaro and F. Liguori, Springer, Dordrecht,
10.6 Hz, JHH = 3.6 Hz, 1H). 13C NMR (101 MHz, CDCl3)
2010.
3
δ 157.8 (CvO), 129.7, 122.0, 114.6, 74.1, 66.9, 66.3. IR (neat): 15 X. Fan, S. Sayalero and M. A. Pericàs, Adv. Synth. Catal.,
ν = 1784 cm−1 (CvO).
2012, 354, 2971.
8,8a-Dihydro-3aH-indeno[1,2-d][1,3]dioxol-2-one (13a).34 1H 16 P. Kasaplar, P. Riente, C. Hartmann and M. A. Pericàs, Adv.
3
NMR (400 MHz, CDCl3) δ 7.55–7.29 (m, 4H), 6.02 (d, JHH
=
Synth. Catal., 2012, 354, 2905.
6.8 Hz, 1H), 5.49–5.43 (m, 1H), 3.43–3.39 (m, 2H). 13C NMR 17 L. Osorio-Planes, C. Rodríguez-Escrich and M. A. Pericàs,
(101 MHz, CDCl3) δ 155.8 (CvO), 140.1, 136.5, 131.1, 128.3,
126.5, 125.7, 83.6, 79.8, 38.0. IR (neat): ν = 1786 cm−1 (CvO).
Org. Lett., 2012, 14, 1816.
18 C. Ayats, A. H. Henseler and M. A. Pericàs, ChemSusChem,
2012, 5, 320.
19 For recent examples see: Y. Xie, K. Ding, Z. Liu, J. Li, G. An,
R. Tao, Z. Sun and Z. Yang, Chem.–Eur. J., 2010, 16, 6687;
L. Han, H-J. Choi, D-J. Kim, S-W. Park, B. Liu and
D-W. Park, J. Mol. Catal. A: Chem., 2011, 338, 58; L. Han,
H-J. Choi, S-J. Choi, B. Liu and D-W. Park, Green Chem.,
2011, 13, 1023; J. Sun, J. Wang, W. Cheng, J. Zhang, X. Li,
S. Zhang and Y. She, Green Chem., 2012, 14, 654; X. Chen,
J. Sun, J. Wang and W. Cheng, Tetrahedron Lett., 2012, 53,
2684; W. Cheng, X. Chen, J. Sun, J. Wang and S. Zhang,
Catal. Today, 2013, 200, 117.
Acknowledgements
We would like to acknowledge financial support from the ICIQ
Foundation, ICREA and the Spanish Ministerio de Economía y
Competitividad (MINECO) through projects CTQ2011-27385
(AWK), CTQ2008-00947/BQU (MAP) and CTQ2012-38594-C02-
01 (MAP), DEC 2009SGR623 (MAP). C. A. thanks MINECO for a
Juan de la Cierva postdoctoral fellowship. A. H. H. thanks the
MECD for an FPU fellowship. We thank Dr Alessandro Ferrali
for providing a sample of the indene oxide substrate.
20 K. R. Roshan, G. Mathai, J. Kim, J. Tharun, G-A. Park and
D-W. Park, Green Chem., 2012, 14, 2933; S. Liang, H. Liu,
T. Jiang, J. Song, G. Yang and B. Han, Chem. Commun.,
2011, 47, 2131.
21 C. Qi, J. Ye, W. Zeng and H. Juang, Adv. Synth. Catal., 2010,
352, 1925.
Notes and references
1 (a) Carbon Dioxide as Chemical Feedstock, ed. M. Aresta, 22 (a) H. C. Kolb, M. G. Finn and K. B. Sharpless, Angew.
Wiley-VCH, Weinheim, 2010; (b) M. Peters, B. Köhler,
W. Kuckshinrichs, W. Leitner, P. Markewitz and
Chem., Int. Ed., 2001, 40, 2004; (b) M. Meldal and
C. Wenzel Tornøe, Chem. Rev., 2008, 108, 2952.
T. E. Müller, ChemSusChem, 2011, 4, 1216; (c) W. Leitner, 23 For some early examples of CuAAC reactions for the immo-
Acc. Chem. Res., 2002, 35, 746.
2 T. Sakakura, J. C. Choi and H. Yasuda, Chem. Rev., 2007,
107, 2365.
bilisation of catalytic species, see: (a) D. Font, C. Jimeno
and M. A. Pericàs, Org. Lett., 2006, 8, 4653; (b) A. Bastero,
D. Font and M. A. Pericàs, J. Org. Chem., 2007, 72, 2460;
(c) E. Alza, X. C. Cambeiro, C. Jimeno and M. A. Pericàs,
3 R. Martin and A. W. Kleij, ChemSusChem, 2011, 4, 1259.
1558 | Green Chem., 2014, 16, 1552–1559
This journal is © The Royal Society of Chemistry 2014

View Article Online
Green Chemistry
Paper
Org. Lett., 2007, 9, 3717; (d) D. Font, S. Sayalero, A. Bastero,
C. Jimeno and M. A. Pericàs, Org. Lett., 2008, 10, 337.
24 Alternative deactivation routes for PS-Cat 2 or PS-Cat 5
(such as a Hoffman type elimination reaction resulting in
demethylation of the triazolium cation) cannot be ruled
out at this stage.
ratio 2.34), and after the second reactivation step
(cf., entry 13, Table 3: I/N ratio = 4.24). The relative
iodide content clearly decreases upon repeated use of
the catalyst but a close to initial iodide to nitrogen
ratio may be achieved upon reactivation using MeI.
This supports the view that indeed loss of iodide is
responsible for loss of activity, cf. demethylation may
occur of the triazole unit in PS-Cat 5.
25 The use of glycidol as a substrate was also investigated. In
this case, the high polarity of the carbonate product made
its separation difficult. In addition the catalyst darkened 30 J. Meléndez, M. North and R. Pasquale, Eur. J. Inorg. Chem.,
significantly, and this was accompanied by deactivation. 2007, 3323.
26 C. J. Whiteoak, E. Martin, E. Escudero-Adán and 31 J. Meléndez, M. North and P. Villuendas, Chem. Commun.,
A. W. Kleij, Adv. Synth. Catal., 2013, 355, 2233. 2009, 2577.
27 C. J. Whiteoak, N. Kielland, V. Laserna, E. C. Escudero- 32 Z. Zhu, A. G. Einset, C-Y. Yang, W-X. Chen and G. E. Wenk,
Adán, E. Martin and A. W. Kleij, J. Am. Chem. Soc., 2013, Macromolecules, 1994, 27, 4076.
135, 1228; F. Castro-Gómez, G. Salassa, A. W. Kleij and 33 K. Matsumoto, Y. Sato, M. Shimojo and M. Hatanaka, Tetra-
C. Bo, Chem.–Eur. J., 2013, 19, 6289. hedron: Asymmetry, 2000, 11, 965.
28 D. J. Darensbourg and S. J. Wilson, J. Am. Chem. Soc., 2011, 34 J.-L. Wang, J.-Q. Wang, L.-N. He, X.-Y. Dou and F. Wu,
133, 18610. Green Chem., 2008, 10, 1218.
29 In order to get more information on the deactivation 35 B. Gabriele, R. Mancuso, G. Salerno, L. Veltri, M. Costa and
of the PS-Cat 5, elemental analysis was performed on a A. DiBenedetto, ChemSusChem, 2011, 4, 1778.
catalyst sample before the first catalytic run (I/N 36 G. Rokicki, W. Kuran and B. Pogorzelska-Marciniak,
ratio = 4.57), after 13 runs (cf., entry 13, Table 3: I/N
Monatsh. Chem., 1984, 115, 205.
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 1552–1559 | 1559