FULL PAPER
“This is the peer reviewed version of the following article: ChemSusChem 2016, 9, 1304-1311, which has been published in final form
at DOI: 10.1002/cssc.201600238. This article may be used for non-commercial purposes in accordance with Wiley Terms and
Conditions for Self-Archiving published at http://olabout.wiley.com/WileyCDA/Section/id-820227.html."

FULL PAPER
Catalytic Coupling of Carbon Dioxide with Terpene Scaffolds:
Access to Challenging Bio-Based Organic Carbonates
Giulia Fiorani,*[a] Moritz Stuck,[a] Carmen Martín,[a] Marta Martínez Belmonte,[a] Eddy Martin,[a] Eduardo
C. Escudero-Adán[a] and Arjan W. Kleij*[a][b]

Abstract: The challenging coupling of highly substituted terpene
oxides and carbon dioxide into bio-based cyclic organic carbonates
catalyzed by Al(aminotriphenolate) complexes, is reported herein.
Both acyclic as well as cyclic terpene oxides were used as coupling
partners, showing distinct reactivity/selectivity behavior. Whereas
cyclic terpene oxides showed excellent chemo-selectivity towards the
organic carbonate product, acyclic substrates exhibited poorer
selectivities due to concomitant epoxide rearrangement reactions and
the formation of undesired oligo/polyether side products. Considering
the challenging nature of these coupling reactions, the isolated yields
of the targeted bio-carbonates are reasonable and in most cases in
the range 5060%. The first crystal structures of tri-substituted
terpene based cyclic carbonates are reported and their stereoconnectivity suggests that their formation proceeds through a double
inversion pathway.

challenges associated to this process, including enhanced
reactivity/selectivity,[6] improved overall sustainability,[7] and the
development of commercially attractive, recyclable catalysts.[8]
However, there are still important open challenges in this specific
area of research, including the limited number of substrates that
can be used due to the lack of efficient catalytic strategies for their
coupling. Highly substituted epoxides (1,3-dioxolan-2-ones)
including those with a 4,5-disubstitution[9] and 4,4´,5trisubstitution[10] remain challenging reaction partners despite the
presence of such patterns in many naturally occurring plant based
organic carbonates (Figure 1).[11]

Introduction
The conversion of carbon dioxide (CO2) into useful organic
products is a prominent strategy towards the valorization of this
renewable carbon-based feed stock.[1] Despite the exciting
progress in the area of catalytic conversion of CO 2 into various
products such as polymers,[2] synthetic fuels[3] and finechemicals,[4] a remaining challenge in the area of CO2 conversion
is represented by the limited number of chemical functionalities
that can be derived from this C1 building block. So far, most efforts
have been devoted to CO2 conversion via reductive and nonreductive coupling chemistry. Within the latter category, CO2 is
incorporated into an organic substrate without affecting the
oxidation state of the carbon center, and the most prominent
among this type of transformations is the formation of organic
carbonates using epoxides as reaction partners. [5]
The catalytic coupling of epoxides and CO 2 is an atomefficient reaction that has been well-studied and ditto developed
over the years, with important contributions to solve key

[a]

[b]

Dr. G. Fiorani, M. Stuck, Dr. C. Martín, Dr. M. Martínez Belmonte,
Dr. E. Martin, E. C. Escudero-Adán, Prof. Dr. A. W. Kleij
Institute of Chemical Research of Catalonia (ICIQ)
The Barcelona Institute of Science and Technology
Av. Països Catalans 16, 43007 Tarragona (Spain)
E-mail: akleij@iciq.es; gfiorani@iciq.es
Prof. Dr. A. W. Kleij
Catalan Institute of Research and Advanced Studies (ICREA)
Pg. Lluís Companys 23, 08010 Barcelona (Spain)
Supporting information for this article is given via a link at the end of
the document.

Figure 1. Top: naturally occurring organic carbonates based on complex
scaffolds. The carbonate unit is marked in blue. Below: some representative
terpene scaffolds with similar di- and tri-substituted alkene units highlighted in
yellow.

We have recently become interested in the use of renewable
feed stocks such as terpenes as substrates for CO2 conversion.[12]
Terpenes, including limonene (Figure 1),[10,13a] have increasingly
found applications in polymer science and sustainable
materials.[13b] The formation of cyclic organic carbonates from
terpene scaffolds ultimately results in 100% bio-derived
compounds with relatively unexplored potential,[14] and we thus
set out to develop an efficient catalytic process for their formation.
Here we describe the Al(III) catalysed coupling between CO2 and

FULL PAPER
both cyclic and acyclic terpene oxides affording new bio-based
carbonates. The first crystal structures of terpene derived
carbonates are also presented and the observed stereoconnectivity is linked to a double inversion pathway in the coupling
between the oxirane precursors and CO2.

Results and Discussion
Terpene Carbonates with bicyclic structures. We first devoted
our attention to the conversion of 1-methylcyclohexene oxide 1a
to the corresponding cyclic carbonate product 1b via CO2
insertion. Up to 70ºC we were unable to detect any formation of
cyclic carbonate 1b. This is in line with a previously reported
density functional theory analysis of the coupling between
limonene oxide (LO, a structurally related trisubstituted oxirane)
and CO2, showing that the kinetic barrier towards cyclic carbonate
formation (via backbiting) is comparatively high to the one
associated to chain propagation.
Table 1. Screening of reaction conditions in the coupling
methylcyclohexene oxide 1a and CO2 to afford cyclic carbonate 1b.[a]

of

Entry

Cat
[mol%]

PPNCl
[mol%]

T
[ºC]

t
[h]



3.0

85

24

18

2



3.0

85

48

19

3



3.0

85

66

31

4

A, 1.0



85

24

0

5

A, 1.0

3.0

85

24

26

6

B, 1.0

3.0

85

24

7

7

C, 1.0

3.0

85

24

22

8

D, 1.0

3.0

85

24

17

9

A, 1.0

3.0

85

48

40

10

A, 1.0

3.0

85

66

49[c]

11

A, 1.0

3.0

85

66

1[d]

12

B, 1.0

3.0

85

66

34

13

A, 1.0

1.0

85

66

14

Indeed, when coupling LO and CO2 at lower temperatures
(4070ºC)
the
only
product
observed
was
the
poly(limonene)carbonate.[12a]
Hence,
higher
reaction
temperatures were probed in order to direct the chemo-selectivity
towards the cyclic carbonate product when using 1methylcyclohexene oxide 1a. The substrate 1-methylcyclohexene
oxide 1a was taken as a representative terpene model substrate
(Table 1). Al(III) aminotriphenolate complexes AD were used as
catalysts together with bis(triphenylphosphine)iminium chloride
(PPNCl) as the nucleophilic additive. Although in the presence of
the nucleophile only (entries 1-3, Table 1) conversion to 1b is
noted, the addition of a Lewis acid (AD) substantially improves
the overall kinetics, most noteworthy when complex A is used
(entries 5, 9 and 10). As expected, in the absence of PPNCl (entry
4) no conversion was noted. A lower loading of PPNCl (entry 13,
1 mol%) reduced the yield of 1b to only 14% showing the
requirement for a higher loading of the nucleophile. In the
absence of solvent (MEK) virtually no conversion was obtained
(see entry 11) underlining the crucial role of this solvent to
accommodate appropriate mixing of all reactants. The structure
of 1b was confirmed by X-ray analysis and is depicted in Figure
2.

Yield 1b
[%][b]

1

the NMR yield was 75%, in the absence of complex A the NMR and isolated
yield were both 31% (see entry 3). [d] No MEK used.

[a] Reaction conditions: 1-methylcyclohexene oxide 1a (5 mmol), MEK
(methylethyl ketone, 1.0 mL), p(CO2) = 1.0 MPa (10 bar). [b] Isolated yield,
selectivity for 1b was >99% in all cases determined by 1H NMR. [c] Note that

Figure 2. X-ray molecular structure for 1b. Selected bond lengths (Å) and
angles (º) for 1b: C(1)-O(1) = 1.1988(18), C(1)-O(2) = 1.3442(19), C(1)-O(3) =
1.3487(18); O(2)-C(1)-O(3) = 111.47(12), O(1)-C(1)-O(2) = 124.23(14).

With these optimal conditions in hand we decided to
investigate a wider scope of trisubstituted carbonates derived
from cyclic epoxides based on terpene scaffolds (see Figure 3).
Due to the challenging nature of these coupling reactions,
conversion of the respective terpene epoxides proceeds slowly
and reaction times of 66 h are typically required (Figure 3). Longer
reaction times at 85ºC did not improve the conversion levels and
neither did higher reaction temperatures. [15] We first examined
limonene oxide (LO) as a substrate using the best conditions
probed for the synthesis of 1b. Whereas pure trans-LO was
converted into limonene carbonate 2b in appreciable conversion
(73%) and yield (57%), the use of the pure cis isomer only led to
4% yield of cis-3b (by NMR) of its respective carbonate. The
extreme sluggish outcome observed for CO2 coupling with the

FULL PAPER
above mentioned cis-isomer was confirmed using commercially
available LO (a 60:40 trans/cis mixture)

FULL PAPER

Figure 3. Investigated scope for the formation of trisubstituted bicyclic terpene carbonates. Reaction conditions (unless state otherwise): 1.0 mol% [AltBu], 3.0 mol%
PPNCl, 1.0 mL MEK, 66 h, 85ºC, p(CO2)º = 1.0 MPa. The diastereo-isomeric ratios (dr values, major isomer indicated) and selectivity towards the carbonate
products were also determined by 1H NMR; note that the dr relates to the relative position of both substituents on the cyclohexyl ring. [a] Conversion relates to total
amount of epoxide groups converted to cyclic carbonate ones determined by 1H NMR (CDCl3) integration, NMR yield of 6b was 74%. [b] The NMR yield of 7b was
27% with 24% of 6b being present along with polyether by-product. [c] Reaction performed at 120ºC. [d] The major stereo-isomer assignment was not possible by
1D/2D NMR due to a combination of complex patterns.

5b

2b

6b

7b

Figure 4. X-ray molecular structures for terpene carbonates trans-2b, cis-5b, 6b and trans-7b with the adopted numbering scheme. Selected bond lengths (Å) and
angles (º) for 2b: C(2)-O(2) = 1.221(8), C(2)-O(1) = 1.326(8), C(2)-O(3) = 1.344(7); O(2)-C(2)-O(3) = 123.1(7), O(1)-C(2)-O(3) = 112.8(5); Selected data for 5b:
C(1)-O(1) = 1.200(2), C(1)-O(2) = 1.350(2), C(1)-O(3) = 1.338(2); O(2)-C(1)-O(3) = 111.73(14), O(1)-C(1)-O(2) = 123.53(17); Selected data for 6b: C(1)-O(1) =
1.330(7), C(1)-O(2) = 1.197(7), C(1)-O(3) = 1.333(8), C(6)-O(4) = 1.448(9); O(1)-C(1)-O(3) = 112.6(5), O(1)-C(1)-O(2) = 124.5(7); Selected data for 7b: C(1)-O(1)
= 1.336(7), C(1)-O(2) = 1.474(6), C(1)-O(3) = 1.354(7), C(11)-O(4) = 1.362(7), C(11)-O(5) = 1.182(8), C(11)-O(6) = 1.332(7); O(1)-C(1)-O(3) = 111.3(5), O(1)-C(1)O(2) = 124.6(5), O(4)-C(11)-O(6) = 110.7(6), O(4)-C(11)-O(5) = 124.0(6).

FULL PAPER
Table 2. Screening and optimization of reaction conditions in the coupling of acyclic terpene-based epoxides 9a14a and CO2 to afford their cyclic carbonate
products 9b14b.[a] Note that the commercial olefinic, terpene precursors are drawn together with their epoxidized derivatives.

Entry

Substrate

Cat
[mol%]

PPNCl
[mol%]

p(CO2)
[MPa]

T
[ºC]

t
[h]

Epoxide
[%][b]

AA
[%][b]

K
[%][b]

CC
[%][b]

PE
[%][b]

1

9a

AlCl, 1.0

3.0

1.0

70

66

7

6

9

31

21

2

9a



3.0

1.0

70

66

57

2

<1

17

8

3

9a

AlCl, 1.0

3.0

1.0

85

66

22

5

3

20

35

4[c]

9a

AlCl, 1.0

3.0

1.0

85

66

<1

12

14

52

24

5

9a



3.0

1.0

85

66

17

19

7

19

2

6

9a

AlCl, 1.0

3.0

3.0

70

66

16

<1

<1

45

22

7

9a

AlCl, 1.0

3.0

4.0

70

66

23

<1

<1

36

36

8

9a



3.0

4.0

70

66

27

2

<1

15

23

9[c]

9a

AlCl, 1.0

3.0

4.0

85

66

3

7

7

56

28

10

14a

AltBu, 1.0

3.0

1.0

85

24

23

2

6

51

13

11

14a

AlCl, 1.0

3.0

1.0

85

24

40

2

9

31

16

12[c]

10a

AlCl, 1.0

3.0

4.0

85

66

8

2

8

47

35

13[c]

11a

AlCl, 1.0

3.0

4.0

85

66

5

5

7

61

16

14[c]

12a

AlCl, 1.0

3.0

4.0

85

66

3

4

3

71

9

15[d]

13a

AlCl, 1.0

3.0

1.0

85

66

<1

15

16

19

30

[a] Reactions conditions: substrates 9a14a (2.5 mmol), MEK (methylethyl ketone, 0.5 mL), pressure/time/temperature and catalyst/co-catalyst loadings indicated.
[b] NMR yields from 1H NMR analysis using mesitylene as internal standard; for the use of 9a: allylic alcohol (AA) peak at  = 4.93 ppm (septet) and 4.84 ppm
(quintet), ketone (K) peak at  = 2.61 ppm (quintet), epoxide at  = 2.68 ppm (triplet), cyclic carbonate (CC) peak at  = 4.20 ppm (multiplet) and oligo/polyether
peak in the region  = 3.33.8 ppm. [c] Substrate amount was 5.0 mmol. [d] The 1H NMR spectrum of the crude mixture showed apart from the CC product 13b a
number of peaks in the region 5.0-5.5 ppm attributed to unknown olefin-containing by-products.

resulting in the almost exclusive formation of trans-4b from transLO in 43% isolated yield. The proposed trans-connectivity pattern
in 2b was confirmed by NMR analysis and further substantiated
by X-ray diffraction (see Figure 4). As far as we know, Figure 4
represents the first structurally characterized terpene based

carbonates. The trans nature of carbonate 2b enforces the idea
that these conversions occur with complete retention of
configuration as would be expected from a double inversion
pathway.[9b,12c] Interestingly, we previously observed that cis-LO
reacts faster than its trans isomer in copolymerization reactions

FULL PAPER
resulting in an almost exclusive formation of a trans configured
copolymer (i.e. a formal inversion occurred). Conversely, at
higher temperatures (85ºC) cyclic carbonate formation starting
from the trans isomer seems to be the favoured process (cf.,
formation of trans-2b and trans-4b, Figure 3). The observed
requisite for higher reaction temperatures in the case of cyclic
carbonate formation from LO is in agreement with the higher
computed kinetic barriers compared with the corresponding
copolymerization process.[12a]
Coupling between CO2 and other (bi)cyclic terpene oxides
(including carvone oxide, limonene diepoxide and menthene
oxide) exhibited a similar reactivity giving the respective terpene
(mono)carbonates 5b, 6b and 8b in 4552% yield and high
chemo-selectivity.[16] We also attempted to optimize the synthesis
of limonene bis-carbonate 7b (27%) using more forcing reaction
conditions (120ºC) but at the cost of the chemo-selectivity. This is
likely due to an observed increase of the viscosity of the reaction
mixture during the reaction of limonene diepoxide, limiting the
diffusion of CO2 towards the reactive centre; the presence of
significant amounts of oligo/polyether product as determined by
1
H NMR is in line with this assumption (see Supporting
Information for details). The molecular structures of terpene
(bis)carbonates 2b, 5b, 6b and 7b were determined by X-ray
crystallography and confirmed in all cases their proposed
formulations. Notably, as far as we know, these X-ray analyses
represent the first ones reported for this family of bio-based
carbonates, and bis-carbonate 7b was for the first time isolated
and fully characterized.[10c]
Formation of Acyclic Terpene Carbonates. We next turned
our focus on the formation of terpene carbonates based on acyclic
scaffolds. Our investigation started with the epoxide derived from
citronellyl acetate 9a (Table 2) using the optimal conditions
developed for the synthesis of most of the bicyclic terpene
carbonates (i.e., 85ºC, 1.0 MPa, 66 h; 3.0 mol% PPNCl) but using
AlCl (1 mol%) as the Lewis acid.[17] Whereas the conversion of 9a
already proceeds at 70ºC (entry 1) with a 31% NMR yield for the
corresponding cyclic carbonate 9b, at 85ºC (entry 3) we
unexpectedly observed a poorer outcome in terms of chemoselectivity. Increasing the scale of the reaction (entry 4) did result
in further improvement, but a combination of the latter with a
higher applied CO2 pressure (entries 6, 7 and 9; 3.04.0 MPa)
gave slightly more satisfactory results observing formation of the
corresponding cyclic carbonate in 56% NMR yield (51% isolated,
Figure 5) while further suppressing by-product formation. Notably,
the reaction performed with only the nucleophilic additive (PPNCl)
proceeded with significantly lower efficiency (cf., entries 2 and 8).
It should be noted that the overall chemo-selectivity towards
the carbonate 9b was much poorer than the ones observed
starting from the aforementioned bicyclic terpene oxides.[18]
Beside the formation of substantial amount of oligo/polyether
(Table 2, entry 9, 28%; 9e),[19] the formation of two other sideproducts was noted. These side-products were isolated and fully
characterized for the citronellyl acetate case (see Experimental
Section and Supporting Information for details), and were
unambiguously identified as an allylic alcohol (9c) and a ketone
(9d), both arising from the rearrangement of the starting epoxide
9a (see Figure 6). The allylic alcohol 9c may arise from a

phenolate-assisted rearrangement of the epoxide 9a; such
conversions have precedence though are typically carried out
with strong bases.[20] Additionally, Lewis acid induced Meinwald
type rearrangement of epoxides to ketones has been wellestablished.[21]

Figure 5. Schematic structures of the terpene derived carbonates 9b14b, their
isolated yields after chromatographic purification and diastereo-isomeric ratios
(dr) for 9b and 11b. For terpene carbonates 10b and 12b the amount of (E) and
(Z) isomers, respectively, was >98%.

MEK

Figure 6. 1H NMR trace (CDCl3, region 2.05.1 ppm) for the crude product
obtained in the conversion of terpene oxide 9a and the assigned peaks, MEK
stands for methylethyl ketone. Note that the R group in the schematic figures
represents a –CH2CH2CH(Me)CH2CH2OAc side chain. For a full NMR trace see
the Supporting Information.

In order to rule out the possibility that the terpene scaffold
itself induces the aforementioned side-product formation, we
carried out the synthesis of the non-functionalized, tri-substituted
cyclic carbonate 14b derived from trimethyloxirane 14a: in
essence the same product distribution was observed (Table 2,
entries 10 and 11, Figure 5) confirming that side-product
formation does not depend on the nature of the terpene scaffold.
Furthermore, the less polar and more volatile nature of 14a seem

FULL PAPER
to influence the course of the coupling reaction as for this
substrate the use of the [AltBu] complex gave better results (Table
2, entries 10 and 11).
Having determined the optimized conditions for the
preparation of acyclic terpene carbonates (Table 2, entry 9) we
then extended the scope of these transformations to terpene
oxides 10a13a which were converted into the respective cyclic
carbonate products 10b13b (entries 12-15). In general, apart
from the desired carbonate products, similar distributions of sideproducts (allylic alcohol, ketone and oligo/polyether) were
observed, together with small amounts of the starting material.
The desired cyclic carbonate products were conveniently isolated
by column purification of the crude mixtures in yields of up to 61%
(for 11b and 12b; Figure 5). Notably, using a myrcene based
scaffold (13b) led to the formation of a complex reaction mixture
as other side reactions involving the conjugated double bonds
occurred. Indeed, we were not able to isolate a pure sample of
13b using chromatographic separation as further degradation
occurred during the purification step. It is well-known that
isoprenes show good polymerization potential in the presence of
Lewis acids[22] and this subunit is also present in 13b (highlighted
in green). Thus, it seems reasonable to assume that further
impurities to the ones reported in Table 2 (entry 15) may also be
ascribed to oligo-myrcene species (see Supporting Information
for details) resulting from diene activation catalysed by complex
B.
The significant by-product formation generally observed for
the synthesis of acyclic terpene carbonates 9b14b as opposed
to the chemo-selective formation of bicyclic carbonate structures
1b5b and 8b can be explained taking into account the different
transformations involving the metal-alkoxide intermediate formed
after nucleophilic ring-opening of the epoxide group.[23] In
particular, it should be noted that polyether formation remains a
competitive process even for CO2 coupling reactions with acyclic
substrates carried out at higher pressure (4.0 MPa, cf. entry 4 and
9, Table 2). This observation suggests that, after initial
coordination of the epoxide to the Lewis acid catalyst and
subsequent nucleophile-assisted ring opening, acyclic substrates
favour the insertion of an additional epoxide molecule rather than
CO2 insertion. This behaviour can be ascribed to the nature of the
Lewis acid catalyst employed: in particular, a chloride-substituted
Al(aminotriphenolate) complex (i.e., AlCl) was used with acyclic
substrates 9a14a. Previous studies have shown that this AlCl
complex combined with NBu4I is a highly active binary catalyst for
terminal epoxide/CO2 conversion into cyclic carbonates. Detailed
computational and kinetic studies supported the view that CO2
insertion into the initially formed Al-alkoxide bond is the ratelimiting step.[6d] Thus, the higher Lewis acidity of AlCl, when
compared to AltBu, results in a relatively more stable Al-alkoxide
intermediate with a lower nucleophilic character, thus making the
CO2 insertion step slower. This former observation seems to
corroborate with the modest chemo-selectivities attained in the
synthesis of acyclic terpene carbonates 9b and 11b14b. As a
result substantial oligo/polyether formation is noted.
In order to qualitatively assess the influence of the structure
of the Al-complex on the overall selectivity, we decided to prepare
terpene carbonate 9b (based on citronellyl acetate) using the

AltBu complex under the same conditions as reported in entry 9
(Table 2). Whereas the use of AlCl gives rise to virtually full
conversion of the starting epoxide 9a (97%), significant formation
of oligo/polyether 9e (28%) is also noted with a calculated chemoselectivity towards the carbonate 9b of 57% (56% NMR yield).
Notably, the presence of AltBu results in lower conversion of
epoxide 9a (71%) alongside with formation of a much lower
amount of oligo/polyether (8%) with an overall chemo-selectivity
of 67% for carbonate 9b (46% NMR yield).
In contrast, the use of AltBu with bicyclic terpene oxides led to
the chemo-selective formation of the respective terpene
carbonates (Figure 3). This is in agreement with our former notion
that this Lewis acidic complex is primarily involved at the initial
stage of the coupling between the epoxide and CO2, as previously
proposed for oxetane/CO2 coupling reactions promoted by
AltBu.[24] Upon formation of a metal hemi-carbonate intermediate,
the metal-mediated formation of the cyclic carbonate is sterically
disfavoured. This causes to release the hemi-carbonate from the
coordination sphere of the metal following fast outer-sphere
cyclization. The combined observed differences in chemoselectivity underline the importance of matching the reactivity and
product selectivity features in the formation of terpene based
cyclic carbonates.

Conclusions
In summary, we have developed the first general and effective
route towards bio-based, cyclic carbonates derived from various
terpene scaffolds. A binary catalyst comprising a Lewis acidic
Al(III) complex and a nucleophilic additive (PPNCl) is able to
mediate these challenging conversions with different degrees of
chemo-selectivity: bicyclic terpene oxides were converted with
high selectivity whereas the acyclic substrates showed inferior
chemo-selectivity under comparable temperature/pressure
conditions. The highly challenging nature of these conversions
limit to some extend the isolated yields of the terpene carbonates
(typically between 5060%), though the results shown herein offer
a reference point for catalyst development to further optimize the
reactivity/selectivity features of such processes. Our future
activities therefore aim at improving these aspects by carefully
designing suitable (aminophenolate) ligand scaffolds and
selection of appropriate Lewis acid metals favouring CO2 insertion
into the metal-alkoxide bond after nucleophilic activation of the
epoxide substrate.

Experimental Section
General Information
1

H, 13C1H and the 2D NMR spectra were recorded on a Bruker AV-300,
AV-400 or AV-500 spectrometer using the residual solvent peak for
calibration. Mass spectrometric analyses and X-ray diffraction studies
were performed by the Research Support Group at the ICIQ (Tarragona).
FT-IR measurements were carried out on a Bruker Optics FTIR Alpha
spectrometer. Carbon dioxide was purchased from PRAXAIR and used
without further purification. Solvents used in the synthesis of the

FULL PAPER
complexes were dried using an Innovative Technology PURE SOLV
solvent purification system.

29.79, 26.83, 26.22, 21.34, 21.13, 19.30; FT-IR (neat): 1786 and 1733 cm1
(C=O); HRMS (ESI+, CH3OH): m/z calcd. (C13H22O5) 281.1359 (M+Na)+;
found: 281.1362.

General Procedure for the Bicyclic Terpene Carbonates
All reactions were performed in a 30 mL stainless steel reactor. As a typical
experiment, 560.8 mg (5.0 mmol) of 1-methylcyclohexene oxide (1a) were
introduced in the inner Teflon vessel of a 30 mL autoclave alongside with
34.7 mg (0.05 mmol) of AltBu, 86.1 mg (0.15 mmol) of PPNCl and 1.0 mL
of methyl ethyl ketone (MEK). Three cycles of pressurization and
depressurization of the reactor (pCO2 = 0.5 MPa) were performed, and the
pressure was finally stabilized at 1.0 MPa. The reactor was heated to the
required temperature (T = 85 ºC), and the mixture was then stirred for
another 66 h. Hereafter, the reaction was stopped and the autoclave was
allowed to cool down by immersion in an ice bath for 1 h before venting.
The reaction mixture was diluted in 2.0 mL of CDCl3 and a weighed
quantity of mesitylene (typically around 10 % mol with respect to the
epoxide substrate) was added. A quantitative 1H NMR determination was
carried out on samples consisting of 100 μL of this solution diluted with 0.5
mL of CDCl3. After concentration of the crude reaction mixture in vacuo,
the cyclic carbonate product 1b (3a-methylhexahydrobenzo[d][1,3]dioxol2-one) was isolated upon purification through a short silica path using
CH2Cl2 as eluent.
Data for 3a-methylhexahydrobenzo[d][1,3]dioxol-2-one (1b): 1H NMR (500
MHz, 298 K, CDCl3):  = 4.35 (t, 3J = 4.1 Hz, 1H), 2.09-2.03 (m, 1H), 1.851.80 (m, 2H), 1.76-1.65 (m, 2H), 1.56-1.49 (m, 2H), 1.48 (s, 3H), 1.38-1.27
(m, 1H); 13C1H NMR (126 MHz, 298 K, CDCl3):  = 154.95, 82.92, 81.19,
33.80, 26.01, 23.42, 20.52, 18.80; FT-IR (neat): 1771 cm-1 (C=O); HRMS
(ESI+, CH3OH): m/z calcd. (C8H12O3): 179.0679 (M+Na)+; found: 179.0678.

General Procedure for the Acyclic Terpene Carbonates
All reactions were performed in a 30 mL stainless-steel reactor. In a typical
experiment, 1.07 g (5.0 mmol) of 5-(3,3-dimethyloxiran-2-yl)-3methylpentyl acetate (9a) were introduced in the inner Teflon vessel of a
30 mL autoclave alongside with 34.8 mg (0.05 mmol) of AlCl, 86.1 mg (0.15
mmol) of PPNCl and 1.0 mL of methyl ethyl ketone (MEK). Three cycles
of pressurization and depressurization of the reactor (pCO2 = 0.5 MPa)
were performed, after which the CO2 pressure was finally stabilized at 4.0
MPa. The reactor was heated to the required temperature (T = 85 ºC), and
the mixture was stirred for a further 66 h. Hereafter the reaction was
stopped and the autoclave was allowed to cool down completely by
immersion in an ice bath for 1 h before venting. The reaction mixture was
diluted with 2.0 mL of CDCl3 and a weighed quantity of mesitylene
(typically around 10 % mol with respect to the epoxide substrate) was
added. A quantitative 1H NMR determination was carried out on samples
consisting of 100 μL of this solution diluted with 0.50 mL of CDCl3. The
cyclic carbonate product, 5-(5,5-dimethyl-2-oxo-1,3-dioxolan-4-yl)-3methylpentyl acetate 9b, was isolated in 51% yield by purification using
column chromatography (support: SiO2, eluent: hexane/diethyl ether 1:1
v/v, Rf = 0.16). The by-products 6-hydroxy-3,7-dimethyloct-7-en-1-yl
acetate 9c (Rf = 0.26) and 3,7-dimethyl-6-oxooctyl acetate 9d (Rf = 0.18)
were also isolated and fully characterized; the yields were 1 and 5 %,
respectively.
Data for 5-(5,5-dimethyl-2-oxo-1,3-dioxolan-4-yl)-3-methylpentyl acetate
(9b), mixture of diastereo-isomers with a dr of 51:49: 1H NMR (300 MHz,
298 K, CDCl3):  = 4.28-4.17 (m, 1H), 4.17-4.00 (m, 2H), 2.04 (s, 3H), 1.811.48 (m, 7H), 1.49 (3H), 1.48-1.38 (m, 1H), 1.37 (s, 3H), 1.32-1.06 (m, 1H),
0.94 (d, 3J = 6.3 Hz, 3H); 13C1H NMR (101 MHz, 298 K, CDCl3):  =
171.26, 154.19, 85.95, 85.78, 84.10, 62.67, 35.39, 33.30, 33.18, 29.81,

Data for 6-hydroxy-3,7-dimethyloct-7-en-1-yl acetate (9c), mixture of
diastereo-isomers with a dr of 1:1. 1H NMR (500 MHz, 298 K, CDCl3):  =
4.93-4.87 (m, 1H), 4.81 (s, 1H), 4.13-4.02 (m, 2H), 4.00 (t, 3J = 6.5 Hz, 1H),
2.02 (m, 3H), 1.82 (s, 1H), 1.69 (s, 3H), 1.68-1.18 (m, 6H), 1.13-1.01 (m,
1H), 0.94-0.84 (m, 3H); 13C1H NMR (126 MHz, 298 K, CDCl3):  = 171.33,
171.32, 147.66, 147.56, 111.29, 111.09, 76.28, 76.12, 63.03, 63.01, 35.55,
35.53, 32.69, 32.65, 32.26, 32.21, 29.90, 29.89, 21.11, 19.53, 17.60,
17.44; FT-IR (neat): 1737 cm-1 (C=O); HRMS (ESI+, CH3OH): m/z calcd.
(C12H22O3) 237.1461 (M+Na)+; found: 237.1457.
Data for 3,7-dimethyl-6-oxooctyl acetate (9d): 1H NMR (300 MHz, 298 K,
CDCl3):  = 4.09 (m, 2H), 2.61 (m, 1H), 2.46 (m, 2H), 2.04 (s, 3H), 1.741.33 (m, 5H), 1.09 (d, 3J = 6.9 Hz, 6H), 0.91 (d, 3J = 6.2 Hz, 3H); 13C1H
NMR (101 MHz, 298 K, CDCl3):  = 215.2, 171.6, 63.2, 41.3, 38.2, 35.8,
31.0, 30.0, 21.5, 19.7, 18.8, 18.7; FT-IR (neat): 1737, 1710 cm-1 (C=O);
HRMS (ESI+, CH3OH): m/z calcd. (C12H22O3) 237.1461 (M+Na)+; found:
237.1459.
Crystallographic Studies
The measured crystals were stable under atmospheric conditions;
nevertheless they were treated under inert conditions immersed in
perfluoro-polyether as protecting oil for manipulation. Data Collection:
measurements were made on a Bruker-Nonius diffractometer equipped
with an APPEX II 4K CCD area detector, a FR591 rotating anode with Mo
Kα radiation, Montel mirrors and a Kryoflex low temperature device (T =
−173 °C). Full-sphere data collection was used with ω and φ scans.
Programs used: Data collection Apex2 V2011.3 (Bruker-Nonius 2008),
data reduction Saint+Version 7.60A (Bruker AXS 2008) and absorption
correction SADABS V. 2008−1 (2008). Structure Solution: SHELXTL
Version 6.10 (Sheldrick, 2000) was used.[25] Structure Refinement:
SHELXTL-97-UNIX VERSION.
Crystallographic Data for 1b
C8H12O3, Mr = 156.18, monoclinic, P2(1), a = 7.6622(8) Å, b = 6.4129(6)
Å, c = 7.7635(8) Å,  = 90°,  = 98.300(3)°,  = 90°, V = 377.48(8) Å3, Z =
2, ρ = 1.374 mg·M−3,  = 0.104 mm−1,  = 0.71073 Å, T = 100(2) K, F(000)
= 168, crystal size = 0.40  0.20  0.20 mm3, (min) = 2.651°, (max) =
32.20°, 3344 reflections collected, 2037 reflections unique (Rint = 0.0282),
GoF = 1.063, R1 = 0.0345 and wR2 = 0.0868 [I > 2σ(I)], R1 = 0.0358 and
wR2 = 0.0880 (all indices), min/max residual density = −0.319/0.379 [e·Å−3].
Completeness to θ(32.20°) = 90.4%. CCDC 1451773.
Crystallographic Data for 2b
C11H16O3, Mr = 196.24, monoclinic, P2(1), a = 6.048(4) Å, b = 15.614(9) Å,
c = 6.338(5) Å,  = 90°,  = 117.776(16)°,  = 90°, V = 529.5(6) Å3, Z = 2,
ρ = 1.231 mg·M−3,  = 0.088 mm−1,  = 0.71073 Å, T = 100(2) K, F(000) =
212, crystal size = 0.20  0.20  0.20 mm3, (min) = 2.61°, (max) = 25.89°,
3756 reflections collected, 1719 reflections unique (Rint = 0.1029), GoF =
1.014, R1 = 0.0873 and wR2 = 0.2090 [I > 2σ(I)], R1 = 0.1027 and wR2 =
0.2162 (all indices), min/max residual density = −0.379/0.540 [e·Å−3], flack
parameter x = 0.7(10). Completeness to θ(25.89°) = 98.8%. CCDC
1451771.
Crystallographic Data for 5b

FULL PAPER
C11H14O4, Mr = 210.22, orthorhombic, P2(1)2(1)2(1), a = 6.8787(9) Å, b =
7.5688(9) Å, c = 20.495(3) Å,  = 90°,  = 90°,  = 90°, V = 1067.1(2) Å3,
Z = 4, ρ = 1.309 mg·M−3,  = 0.099 mm−1,  = 0.71073 Å, T = 100(2) K,
F(000) = 448, crystal size = 0.40  0.20  0.20 mm3, (min) = 1.99°, (max)
= 30.60°, 11222 reflections collected, 3225 reflections unique (Rint =
0.0271), GoF = 1.078, R1 = 0.0370 and wR2 = 0.0928 [I > 2σ(I)], R1 =
0.0418 and wR2 = 0.1018 (all indices), min/max residual density =
−0.204/0.314 [e·Å−3], flack parameter x = -0.1(4). Completeness to
θ(30.60°) = 98.7%. CCDC 1451774.

[2]

[3]

Crystallographic Data for 6b
C11H16O4, Mr = 212.24, triclinic, P-1, a = 6.4255(11) Å, b = 9.2997(16) Å, c
= 9.3869(15) Å,  = 103.713(5)°,  = 94.235(5)°,  = 103.972(5)°, V =
523.67(15) Å3, Z = 2, ρ = 1.346 mg·M−3,  = 0.102 mm−1,  = 0.71073 Å,
T = 100(2) K, F(000) = 228, crystal size = 0.06  0.04  0.005 mm3, (min)
= 2.26°, (max) = 25.44°, 11714 reflections collected, 1810 reflections
unique (Rint = 0.0813), GoF = 2.226, R1 = 0.1174 and wR2 = 0.3344 [I >
2σ(I)], R1 = 0.1607 and wR2 = 0.3434 (all indices), min/max residual
density = −0.475/0.421 [e·Å−3]. Completeness to θ(25.44°) = 94.5%.
CCDC 1451772. Note that the very small size of the crystal resulted in poor
quality crystal data; despite this, the atom connectivity patterns as
proposed in Figure 4 could be confirmed.
Crystallographic Data for 7b
C12H16O6, Mr = 256.25, orthorhombic, P2(1)2(1)2(1), a = 8.3285(17) Å, b
= 11.495(2) Å, c = 12.522(3) Å,  = 90°,  = 90°,  = 90°, V = 1198.8(4) Å3,
Z = 4, ρ = 1.420 mg·M−3,  = 0.114 mm−1,  = 0.71073 Å, T = 100(2) K,
F(000) = 544, crystal size = 0.30  0.10  0.10 mm3, (min) = 2.41°, (max)
= 24.70°, 4780 reflections collected, 2006 reflections unique (Rint = 0.0751),
GoF = 1.030, R1 = 0.0625 and wR2 = 0.1430 [I > 2σ(I)], R1 = 0.0922 and
wR2 = 0.1624 (all indices), min/max residual density = −0.245/0.316 [e·Å−3].
Completeness to θ(24.70°) = 99.2%. CCDC 1451775.

Acknowledgements
We thank ICIQ, ICREA, and the Spanish Ministerio de Economía
y Competitividad (MINECO) through project CTQ- 2014-60419-R
and the Severo Ochoa Excellence Accreditation 2014–2018
through project SEV-2013-0319. Dr. Noemí Cabello, Sofía Arnal
and Vanessa Martínez are acknowledged for the mass analyses.
G.F. kindly acknowledges financial support from the European
Community
through
FP7-PEOPLE-2013-IEF
project
RENOVACARB (grant agreement no. 622587), C. M. is grateful
to the Marie Curie COFUND action from the European
Commission for co-financing a postdoctoral fellowship and M.S.
thanks the Erasmus program of the EU for support.
Keywords: aluminium • biocarbonates • carbon dioxide •
homogeneous catalysis • terpenes
[1]

a) M. Aresta, A. Dibenedetto, A. Angelini, Chem. Rev. 2014, 114, 17091742; b) M. Cokoja, C. Bruckmeier, B. Rieger, W. A. Herrmann, F. E.
Kühn, F. E. Angew. Chem. Int. Ed. 2011, 50, 8510-8537; c) Q. Liu, L.
Wu, R. Jackstell, M. Beller, Nat. Commun. 2015, 6, 5933; d) N. Kielland,
C. J. Whiteoak, A. W. Kleij, Adv. Synth. Catal. 2013, 355, 2115-2138; e)
T. Sakakura, K. Kohno, Chem. Commun. 2009, 1312-1330; f) M. Peters,
B. Köhler, W. Kuckshinrichs, W. Leitner, P. Markewitz, T. E. Müller,

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]
[12]

ChemSusChem 2011, 4, 1216-1240; g) D. R. Darensbourg, Chem. Rev.
2007, 107, 2388-2410.
a) D. J. Darensbourg, Inorg. Chem. 2010, 49, 10765-10780; b) S. Klaus,
M. W. Lehenmeier, C. E. Anderson, B. Rieger, Coord. Chem. Rev. 2011,
255, 1460-1479; c) M. R. Kember, A. Buchard, C. K. Williams, Chem.
Commun. 2011, 47, 141-163; d) X.-B. Lu, D. J. Darensbourg, Chem. Soc.
Rev. 2012, 41, 1462-1484; e) G. W. Coates, D. R. Moore, Angew. Chem.
Int. Ed. 2004, 43, 6618-6639.
a) G. A. Olah, A. Goeppert, G. K. S. Prakash, J. Org. Chem. 2008, 74,
487-498; b) A. Bansode, A. Urakawa, J. Catal. 2014, 309, 66-70; c) W.
Wang, S. Wang, X. Ma, J. Gong, Chem. Soc. Rev. 2011, 40, 3703-3727;
d) P. G. Jessop, T. Ikariya, R. Noyori, Chem. Rev. 1995, 95, 259-270.
For a selection: a) A. Tlili, X. Frogneux, E. Blondiaux, T. Cantat, Angew.
Chem. Int. Ed. 2014, 53, 2543-2545; b) T. G. Ostapowicz, M. Schmitz,
M. Krystof, J. Klankermayer, W. Leitner, Angew. Chem. Int. Ed. 2013, 52,
12119-12123; c) T. Mita, J. Chen, Y. Sato, Org. Lett. 2014, 16, 22002203; d) B. Yu, L.-N. He, ChemSusChem 2015, 8, 52-62; e) Y. Li, T. Yan,
K. Junge, M. Beller, Angew. Chem. Int. Ed. 2014, 53, 10476-10480; f) D.
Yu, S. P. Teong, Y. Zhang, Coord. Chem. Rev. 2015, 293–294, 279–291.
For recent reviews: a) J. W. Comerford, I. D. V. Ingram, M. North, X. Wu,
Green Chem. 2015, 17, 1966-1987; b) C. Martín, G. Fiorani, A. W. Kleij,
ACS Catal. 2015, 5, 1353-1370; c) G. Fiorani, W. Guo, A. W. Kleij, Green
Chem. 2015, 17, 1375-1389; d) P. P. Pescarmona, M. Taherimehr, Catal.
Sci. Technol. 2012, 2, 2169-2187.
High reactivity systems: a) Y. Qin, H. Guo, X. Sheng, X. Wang, F. Wang,
Green Chem. 2015, 17, 2853-2858; b) T. Ema, Y. Miyazaki, S. Koyama,
Y. Yano, T. Sakai, Chem. Commun. 2012, 48, 4489-4491; c) C. J.
Whiteoak, N. Kielland, V. Laserna, E. C. Escudero-Adán, E. Martin, A.
W. Kleij, J. Am. Chem. Soc. 2013, 135, 1228-1231; d) C. J. Whiteoak, N.
Kielland, V. Laserna, F. Castro-Gómez, E. Martin, E. C. Escudero-Adán,
C. Bo, A. W. Kleij, Chem. Eur. J. 2014, 20, 2264-2275.; e) J. Qin, P.
Wang, Q. Li, Y. Zhang, D. Yuan, Y. Yao, Chem. Commun. 2014, 50,
10952-10955.
a) M. Cokoja, M. E. Wilhelm, M. H. Anthofer, W. A. Herrmann, F. E. Kühn,
ChemSusChem 2015, 8, 2436-2454; b) Q. He, J. W. O’Brien, K. A.
Kitselman, L. E. Tompkins, G. C. T. Curtis, F. M. Kerton, Catal. Sci.
Technol. 2014, 4, 1513-1528; c) A. Tlili, E. Blondiaux, X. Frogneux, T.
Cantat, Green Chem. 2015, 17, 157-168.
Efficient recycling under mild reaction conditions: a) C. J. Whiteoak, A.
H. Henseler, C. Ayats, A. W. Kleij, M. A. Pericàs, Green Chem. 2014, 16,
1552-1559; b) W. Desens, C. Kohrt, M. Frank, T. Werner,
ChemSusChem 2015, 8, 3815-3822; c) M. North, B. Wang, C. Young,
Energy Environ. Sci. 2011, 4, 4163-4170; d) S. Liang, H. Liu, T. Jiang, J.
Song, G. Yang, B. Han, Chem. Commun. 2011, 47, 2131-2133.
Successful systems have been communicated reporting ample substrate
scope: a) V. Laserna, G. Fiorani, C. J. Whiteoak, E. Martin, E. EscuderoAdán, A. W. Kleij, Angew. Chem. Int. Ed. 2014, 53, 10416-10419; b) C.J.
Whiteoak, E. Martin, E. Escudero-Adán, A. W. Kleij, Adv. Synth. Catal.
2013, 355, 2233-2239; c) C. Beattie, M. North, P. Villuendas, C. Young,
J. Org. Chem. 2013, 78, 419-426; d) C. J. Whiteoak, E. Martin, M.
Martínez Belmonte, J. Benet-Buchholz, A. W. Kleij, Adv. Synth. Catal.
2012, 354, 469-476; For a seminal contribution: e) W. J. Kruper, D. V.
Dellar, J. Org. Chem. 1995, 60, 725-727.
As far as we know the only examples report the formation of limonene
based carbonates, see: a) C. M. Byrne, S. D. Allen, E. B. Lobkovsky, G.
W. Coates, J. Am. Chem. Soc. 2004, 126, 11404-11405; b) O.
Hauenstein, M. Reiter, S. Agarwal, B. Rieger, A. Greiner, Green. Chem.
2016, 18, 760-770; c) M. Bähr, A. Bitto, R. Mülhaupt, Green Chem. 2012,
14, 1447-1454.
H. Zhang, H. B. Liu, J. M. Yue, Chem. Rev. 2014, 114, 883-898.
For examples including either terpene or fatty acid based
(poly)carbonates: a) L. Peña Carrodeguas, J. González-Fabra, F.
Castro-Gómez, C. Bo, A. W. Kleij, Chem. Eur. J. 2015, 21, 6115-6122;
For examples using renewable “fatty acid” based epoxides, see: b) M.
Alves, B. Grignard, S. Gennen, C. Detrembleur, C. Jerome, T. Tassaing,

FULL PAPER

[13]

[14]

[15]

[16]

[17]

[18]

RSC Adv. 2015, 5, 53629-53636; c) J. Langanke, L. Greiner, W. Leitner,
Green Chem. 2013, 15, 1173-1182; d) P. G. Parzuchowski, M. JurczykKowalska, J. Ryszkowska, G. Rokicki, J. Appl. Polym. Sci. 2006, 102,
2904-2914; e) M. Bähr, R. Mülhaupt, Green Chem. 2012, 14, 483-489; f)
Y.-Y. Zhang, X.-H. Zhang, R.-J. Wei, B.-Y. Du, Z.-Q. Fan, G.-R. Qi, RSC
Adv. 2014, 4, 36183–36188.
a) R. Ciriminna, M. Lomeli-Rodriguez, P. Demma Carà, J. A. LopezSanchez, M. Pagliaro, Chem. Commun. 2014, 50, 15288-15296; b) N. J.
van Zee, G. W. Coates, Angew. Chem. Int. Ed. 2015, 54, 2665 -2668.
Recently, Schäffner et al. reported on the synthesis of bio-sourced cyclic
carbonates and their use as alternative plasticizers, see: B. Schäffner, M.
Blug, D. Kruse, M. Polyakov, A. Köckritz, A. Martin, P. Rajagopalan, U.
Bentrup, A. Brückner, S. Jung, D. Agar, B. Rüngeler, A. Pfennig, K.
Müller, W. Arlt, B. Woldt, M. Graß, S. Buchholz, ChemSusChem 2014, 7,
1133-1139.
Higher reaction temperatures tended to create different phases in the
reactor where an ideal mixing of the substrate, CO2 and catalyst
components was not possible leading to lower conversion levels.
A larger scale reaction using 10 g (65.8 mmol) of cis/trans limonene oxide
and CO2 (1.0 MPa) in a 45 mL stainless steel autoclave at 85ºC for 66 h
was also probed. Somewhat lower conversion (35%) and isolated yield
(3.7 g, 29%) was obtained compared to formation of 4b in Figure 3 (43%
isolated yield). We ascribe this to a lower CO2-to-substrate ratio inside
the reactor; however, the result suggests that larger-scale synthesis of
4b is potentially feasible. See Supporting Information for more details.
For the acyclic terpene oxide substrates we found that the use of the AlCl
complex provided the best combination of conversion and selectivity and
therefore proceeded with this complex. Note that again MEK was used
as solvent since the acyclic terpene oxides are viscous oils and a
relatively high loading of AlCl and the nucleophilic additive are required.
The neat reaction between methyl cyclohexene oxide and CO2 (Table 1,
entry 11; only 1% conversion) is further reason for considering the use
of a solvent in these reactions.
In some of the reactions we noted an imperfect mass balance by
combining the molar amounts of cyclic carbonate, starting epoxide and
by-products as reported in Table 2. We observed that upon cooling the
reaction mixture that under certain conditions up to 10-15% of epoxide
remained in other sections of the reactor, i.e. not in the Teflon insert

[19]

[20]

[21]

[22]

[23]

[24]
[25]

containing the reaction mixture. In a separate experiment we determined
this amount by washing these sections following 1H NMR analysis: this
showed unambiguously the presence of the epoxide substrate.
The formation of oligo/polyether side products is rationalized by the
sluggish nature of these conversions while increasing the viscosity of the
reaction mixture. As such the transport of CO2 towards the reactive
center is hampered and becomes a limiting factor, and side reactions
such as oligo/polyether formation become more significant.
For allylic alcohol formation from epoxides using strong bases: a) R. P.
Thummel, B. Rickborn, J. Org. Chem. 1971, 36, 1365-1368; b) M. J.
Södergren, S. K. Bertilsson, P. G. Andersson, J. Am. Chem. Soc. 2000,
122, 6610-6618. The triphenolate ligand of the Al complex may act as a
basic residue promoting relatively slow allylic alcohol formation.
For Lewis acid catalyzed Meinwald rearrangement of epoxides see: a) J.
R. Lamb, Y. Jung, G. W. Coates, Org. Chem. Front. 2015, 2, 346-349; A
recent contribution showed the use of Al-catalysis as a means to
rearrange internal epoxides to ketones, see: b) J. R. Lamb, M. Mulzer, A.
M. LaPointe, G. W. Coates, J. Am. Chem. Soc. 2015, 137, 15049-15054.
a) M. L. Senyek, Isoprene Polymers in Encyclopedia of Polymer Science
and Technology, John Wiley & Sons, 2002. Please note that Lewis acid
catalyzed Diels-Alder chemistry of myrcene has also been reported, refer
to: b) D. Yin, C. Li, B. Li, L. Tao, D. Yin, Adv. Synth. Catal. 2005, 347,
137-142.
For detailed mechanistic description of the key steps (epoxide ringopening, CO2 insertion and ring-closure) involved in organic carbonate
formation using binary catalysts comprising a Lewis acid and a
nucleophilic additive: a) F. Castro-Gomez, G. Salassa, A. W. Kleij, C. Bo,
Chem. Eur. J. 2013, 19, 6289-6298; b) M. North, R. Pasquale, Angew.
Chem. Int. Ed. 2009, 48, 2946-2948; Very recently, the formation of in
situ prepared organic carbonates was mechanistically linked towards
diastereo-selective conversions with a key role for the Lewis acid catalyst,
see: c) W. Guo, V. Laserna, E. Martin, E. C. Escudero-Adán, A. W. Kleij,
Chem. Eur. J. 2016, 22, 17221727.
J. Rintjema, W. Guo, E. Martin, E. C. Escudero-Adán, A. W. Kleij, Chem.
Eur. J. 2015, 21, 10754-10762.
G. M. Sheldrick, SHELXTL Crystallographic System, version 6.10;
Bruker AXS, Inc.: Madison, WI, 2000.

FULL PAPER
Entry for the Table of Contents:

FULL PAPER
Bioconversions: A general catalytic
method for the challenging coupling
between terpene oxides and CO 2 has
been developed furnishing bicyclic
and acyclic bio-carbonates in
appreciable yields. The chemoselectivity features of both types of
carbonate syntheses was studied in
detail, and the first crystallographic
analyses of such terpene carbonate
scaffolds are presented. The results
pave the way for the use of terpenes
as synthons towards new materials
and fine chemicals.

Giulia Fiorani,* Moritz Stuck, Carmen
Martín, Marta Martínez Belmonte, Eddy
Martin, Eduardo C. Escudero-Adán and
Arjan W. Kleij*

Page No. – Page No.

Catalytic Coupling of Carbon Dioxide
with Terpene Scaffolds: Access to
Challenging Bio-based Organic
Carbonates