Synthesis of Cyclic Carbonates from Epoxides and Carbon Dioxide by Using Bifunctional One-Component Phosphorus-Based Organocatalysts

Article abstract of DOI:10.1002/cssc.201500612

Numerous bifunctional organocatalysts were synthesized and tested for the atom-efficient addition of carbon dioxide and epoxides to produce cyclic carbonates. These catalysts are based on phosphonium salts containing an alcohol moiety in the side chain for substrate activation through hydrogen bonding. In the model reaction, converting 1,2-butylene oxide with CO₂, 19 catalysts were tested to determine structure-activity relationships. In total, 28 epoxides were converted with CO₂ to give the respective cyclic carbonates in yields of up to 99%. Even at 45C, the most active catalyst was able to produce cyclic carbonates selectively in high yields. The carbonates were generally obtained as analytically pure products after simple filtration over silica gel. This single-component catalyst system works under neat and mild reaction conditions and tolerates several useful moieties. Two heads are better than one! Bifunctional organocatalysts are synthesized and tested in the catalytic reaction of epoxides and carbon dioxide to give the respective cyclic carbonates. Product formation is significantly increased by hydrogen-bond donation from the bifunctional phosphonium catalyst.

Full text of DOI:10.1002/cssc.201500612

DOI: 10.1002/cssc.201500612
Full Papers
Synthesis of Cyclic Carbonates from Epoxides and Carbon
Dioxide by Using Bifunctional One-Component
Phosphorus-Based Organocatalysts
Hendrik Büttner, Johannes Steinbauer, and Thomas Werner*[a]
Dedicated to Professor Uwe Rosenthal on the occasion of his 65th birthday.
Numerous bifunctional organocatalysts were synthesized and
tested for the atom-efficient addition of carbon dioxide and
epoxides to produce cyclic carbonates. These catalysts are
based on phosphonium salts containing an alcohol moiety in
the side chain for substrate activation through hydrogen bond-
ing. In the model reaction, converting 1,2-butylene oxide with
CO2, 19 catalysts were tested to determine structure–activity
relationships. In total, 28 epoxides were converted with CO2 to
give the respective cyclic carbonates in yields of up to 99%.
Even at 458C, the most active catalyst was able to produce
cyclic carbonates selectively in high yields. The carbonates
were generally obtained as analytically pure products after
simple filtration over silica gel. This single-component catalyst
system works under neat and mild reaction conditions and tol-
erates several useful moieties.
Introduction
The primary feedstock of organic chemicals is based on fossil
carbon sources, which undoubtedly are finite resources. With
regards to sustainable chemical processes, the development of
alternative and renewable sources of raw materials is of great
interest. In the past two decades, CO2 utilization has become
a major field in catalysis, producing value-added organic chem-
icals from this C1 building block.[1] As a consequence, CO2 is
less treated as a waste product and focus has changed to its
application as a useful C1 synthon. In general, there are two
strategies to produce valuable organic compounds from
carbon dioxide. The reductive transformation of CO2 usually in-
volves high-energy reducing agents, such as hydrogen or bor-
anes, to produce useful chemicals, such as methanol[2] or
formic acid.[3] The respective nonreductive products can be ob-
tained when strained ring systems, such as epoxides or oxe-
tanes, are introduced.[4] Although the reaction of CO2 and ep-
oxides is known and established, the development of active
catalysts for the selective formation of either cyclic carbonates
or polycarbonates is still of great interest in academia and in
industry. For instance, polycarbonates derived from CO2 and
epoxides are useful building blocks for the production of poly-
urethanes, allowing a significant reduction of the environmen-
tal impact in comparison with conventional polyether polyol
building blocks in respect to greenhouse gas emissions and
abiotic depletion.[5] Cyclic carbonates are versatile organic
compounds applied as polar aprotic solvents,[6] as electrolytes
in lithium batteries,[7] or as raw materials for polymers[8] and
fine chemicals.[9] Moreover, the structural motif of five-mem-
bered organic carbonates also occurs in natural products.[10]
Recent reviews from Kleij et al.,[11] North et al.,[12] and Kerton
et al.[13] elucidated the special place in catalysis research re-
served for the production of cyclic carbonates. In particular,
alkali-metal halides, especially potassium iodide, alongside
phase-transfer catalysts or suitable solvents have been utilized
as catalysts.[14] Moreover, Lewis acidic metal complexes based
on salen,[15] salphen,[16] [N2O2],[17] aminotrisphenolate,[18] or por-
phyrin ligand systems,[19] as well as polyoxometalates (POMs)[20]
and iron(III) complexes,[21] proved to be excellent catalysts for
the formation of cyclic carbonates from epoxides and CO2.
These binary systems reach outstanding initial turnover fre-
quencies (TOFs) of up to 36000 hÀ1.[18a] However, a nucleophilic
species for the ring opening of the epoxide is essential. The
nucleophile or cocatalyst is almost always provided by an or-
ganic salt or an amine, respectively (Scheme 1). Furthermore,
Lewis acidic homogeneous metal complexes significantly accel-
erate the addition of CO2 to epoxides, but there is only very
low or even no catalytic activity if there is no nucleophile or
cocatalyst, respectively, nor an appropriate solvent.
Recently, Kleij et al. emphasized the advantages of organoca-
talysis in the field of CO2 utilization.[22] In general, organocata-
lysts are cheap, robust, nontoxic, and bench-stable organic
molecules that do not necessarily require inert reaction condi-
tions.[23] Nevertheless, metal-containing catalysts are the domi-
nating systems for the addition of CO2 to epoxides, although
their usage involves metal waste production and possibly con-
tamination of the product. In terms of sustainable and low-
cost processes, metal-free catalysis is attractive, since another
significant benefit of organocatalysts is undoubtedly the
[a] H. Büttner, J. Steinbauer, Dr. T. Werner
Leibniz-Institut für Katalyse e. V. (LIKAT Rostock)
Albert-Einstein-Str. 29 a, 18059 Rostock (Germany)
E-mail: thomas.werner@catalysis.de
Supporting Information for this article is available on the WWW under
http://dx.doi.org/10.1002/cssc.201500612.
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the choice of 1 and 2. In addition, the halide species
is provided by the alkylation reagent, and therefore,
it is also easy to adjust (Table 1).
The catalysts 3a–3 f were obtained by simple alky-
lation of 1a or 1b in yields of up to 99% (Table 1, en-
tries 1–6). Because trimethylphosphine (1a) was com-
mercially available as a 1.0m solution in toluene, the
Scheme 1. Dual mode of activation of epoxides by an electrophile (E, for example, Lewis
or Brønsted acids) and nucleophile (Nu, for example, halides or amines) for the formation
of cyclic carbonates.
Table 1. Synthesis of bifunctional organocatalysts 3.
carbon-based scaffold associated with the high po-
tential of structural modification, especially in terms
of catalyst immobilization.[24] Hence, there have been
numerous reports on organocatalysts that efficiently
produce cyclic carbonates from CO2 and epoxides,
that is, ammonium,[25] phosphonium,[26] pyridinium,[27]
and imidazolium salts;[14b,28] amines/superbases;[29]
zwitterionic organic frameworks;[30] N-heterocyclic
carbenes;[31] and azaphosphatranes.[32] In addition,
not only Lewis acidic homogeneous metal complexes
are able to activate epoxides, but Brønsted acids can
also significantly catalyze the formation of cyclic car-
bonates due to intermolecular hydrogen-bond inter-
actions. Particularly, in the presence of alcohols,[14b,33]
phenol derivatives,[14h,29c,34] carboxylic acids,[35] sila-
nols,[36] chitosan,[37] cellulose,[14f,38] lignin,[14d] b-cyclo-
dextrin,[39] amino acids,[40] and alcohols[14a,41] the reac-
tion of epoxides and CO2 was accelerated.
Entry
Phosphine 1
2
X
T
t
[h]
Product
Yield
[%][a]
[8C]
1
2
3
4
5
6
7
8
1a, R=Me
1a, R=Me
1a, R=Me
1b, R=nBu
1b, R=nBu
1b, R=nBu
1c, R=Ph
1c, R=Ph
1c, R=Ph
1b, R=nBu
1d, R=nOct
1e, R=Cy
2a
2b
2c
2a
2b
2c
2a
2b
2c
2d
2c
2c
Cl
Br
I
Cl
Br
I
Cl
Br
I
100
70
60
100
100
60
–
24
24
1
24
24
24
–
3a
3b
3c
3d
3e
3 f
3g
3h
3i
62[b]
88[b]
84[b]
81
99
99
–
–
26[b]
99
>99
96[b]
–
–
9
100
60
60
60
48
18
5
10
11
12
I
I
I
3j
3k
3l
24
[a] Yield of product isolated. [b] Absolute toluene was used as the solvent.
reactions of 1a with alcohols 2a–2c to form the correspond-
ing salts 3a–3c were performed in toluene. In general, a sol-
vent was not necessary for the synthesis of 3; an additional
solvent was only employed if solid phosphines (1c and 1e)
were present (Table 1, entries 9 and 12). The temperature cru-
cially influenced the yield of the nucleophilic substitution reac-
tion. Since the CÀX bond length increases and CÀX bond dis-
sociation energy decreases from CÀCl to CÀBr to CÀI,[42] the
synthesis of 3 with chloride and bromide counterions (3a, 3b,
3d, and 3e) were performed at 70–1008C to obtain reasonable
yields (Table 1, entries 1, 2, 4, and 5). In contrast, for the syn-
thesis of iodide-containing organocatalysts 3c, 3 f, 3j, 3k, and
3l, a temperature of 608C was usually sufficient to obtain
yields of up to >99% (Table 1, entries 3, 6, and 10–12). Where-
as (2-hydroxy)ethyltriphenylphosphonium chloride (3g) and
bromide (3h) were commercially available, the analogous
iodide salt 3i was isolated in a poor yield of 26%; however, it
completed the series of phenyl-substituted catalysts 3g–3i.
From our initial studies, iodide salts were the most active cata-
lysts; therefore, tri-n-octylphosphine (1d) and tricyclohexyl-
phosphine (1e) were alkylated with 2c to form the corre-
sponding organic salts 3k and 3l in excellent yields (Table 1,
entries 11 and 12). Apart from the flexible alkyl-linked bifunc-
tional phosphonium salts 3a–3l, we were also interested in
catalysts with a more rigid linkage between the functional
group (Scheme 3).
Herein, we give a full account on our previously reported bi-
functional phosphorus-based organocatalyst.[25a] The structural
influences of the one-component catalyst, regarding distance
of functional groups, substituents, and halide, were examined
in the model reaction of 1,2-epoxybutane (8a) and CO2. Under
optimized reaction conditions, several terminal and internal ep-
oxides were converted into the corresponding cyclic carbon-
ate.
Results and Discussion
Catalyst synthesis
The privileged structure of the bifunctional phosphorus-based
organocatalysts was obtained by a nucleophilic substitution re-
action of a phosphine 1 with a haloalcohol 2 (Scheme 2).
Scheme 2. Synthesis of bifunctional organocatalysts 3 through the straight-
forward alkylation of phosphines 1 with haloalcohols 2.
Depending on the employed phosphine 1 and the alkylation
reagent 2, the structure of the organocatalyst can be easily
modified. The steric demands of the phosphonium center in 3
are determined by the substituents of phosphine 1. Moreover,
the distance between functional groups can be set through
Hence, 2-hydroxyphenyldiphenylphosphine (4a) was alkylat-
ed with iodomethane (5) to examine the resultant catalyst 6a
in the coupling reaction of CO2 and epoxides. Under compara-
tively mild reaction conditions at room temperature 4a was
methylated with 5 and the corresponding phosphonium salt
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Table 2. Conversion of epoxide 8a and CO2 into the corresponding cyclic
carbonate 9a with phosphonium-based organocatalysts 3, 6, or 7.[a]
Entry
Catalyst
Yield 9a [%]
1208C[b]
908C[c]
1[d]
2[d]
3[d]
4[d]
5[d]
6[d]
7a
7b
7c
7d
7e
7 f
93
83
56
0
36
25
19
-
Scheme 3. Synthesis of catalyst 6a with an aromatic linkage of alcohol and
phosphonium moieties.
6a was isolated in 96% yield. It is worth mentioning that all
synthesized catalysts 3a–3l and 6a could be handled under
ambient conditions.
0
-
0
-
7
3a
3b
3c
3d
3e
3 f
3g
3h
3i
0
95
99
96
99
93
65
66
56
97
98
51
0
2
8
Catalyst screening
9
21
57
86
92
0
The conversion of 8a with CO2 to produce 1,2-butylene car-
bonate (9a) was chosen as a model reaction to examine the
catalytic activity of the bifunctional organocatalysts 3 under
solvent-free conditions (Scheme 4).
10
11
12
13[d]
14[d]
15
16
17
18
1
78
78
92
92
3j
Scheme 4. Model reaction of 8a and CO2 to produce 9a to evaluate the
most active bifunctional organocatalyst 3.
3k
3l
The first screening experiments were performed at 1208C,
with an initial pressure of CO2 of 1.0 MPa, for 4 h with 2 mol%
of the organocatalyst (Table 2). To set a catalytic benchmark,
bifunctional organocatalysts 3 and 6a, along with tetra-n-bu-
tylphosphonium salts 7, were tested in the coupling reaction
of CO2 and 8a (Table 2, entries 1–6). Of these tetra-n-butyl-
phosphonium salts 7, only tetra-n-butylphosphonium chloride
(7a) and bromide (7b) showed satisfying yields of 93 and 83%
at 1208C, respectively (Table 2, entries 1 and 2). Furthermore,
[Bu4P]-based catalysts with non-nucleophilic counterions TsOÀ,
19
6a
94
88
[a] Yields were determined by GC flame ionization detector (FID) with n-
hexadecane as a standard. [b] Reaction conditions: 2 mol% 3, 6, or 7;
1208C; p(CO2)=1.0 MPa; 4 h. [c] Reaction conditions: 2 mol% 3, 6, or 7;
908C; p(CO2)=1.0 MPa; 2 h. [d] Catalysts were commercially available and
used as purchased.
assume that this could be explained by the low solubility of
3a in 8a. However, when catalysts 3b and 3c were employed,
excellent yields of 9a were obtained at 1208C, but only poor
yields at 908C (Table 2, entries 8 and 9).
Compared with Me3P-based catalysts 3a–3c, the increased
chain length for tri-n-butyl-substituted phosphonium salts 3d–
3 f led, on one hand, to completely soluble catalysts in the
substrate 8a and, on the other hand, to excellent yields at
1208C (Table 2, entries 10–12).
The triphenyl-substituted organocatalysts 3g–3i showed
only moderate yields in the model reaction (Table 2, en-
tries 13–15). Among these catalysts, the bromide salt 3h con-
verted at least 66% of the starting material into the cyclic car-
bonate. Also, excellent yields of 97 and 98% of 9a were ob-
tained with propyl-bridged bifunctional catalyst 3j or (2-hy-
droxyethyl)tri-n-octylphosphonium iodide (3k), respectively,
were present as catalysts (Table 2, entry 16 and 17). Under
model reaction conditions at 1208C, catalyst 3l proved to be
less active, yielding only 51% of 9a (Table 2, entry 18). The aro-
matic-linked bifunctional organocatalyst 6a was also very
active, converting 94% of 8a into 9a (Table 2, entry 19). In
À
PF6À, and BF4 were employed (Table 2, entries 4–6). These ex-
periments elucidated the importance of a nucleophile for cata-
lytic activity because 7d–7 f did not catalyze the reaction at
all. Under less drastic reaction conditions of 908C, 1.0 MPa, 2 h,
and 2 mol% catalyst, the yield of 9a dropped significantly. The
best result for 7 again was detected in the presence of 7a
(Table 2, entry 1). However, only a poor yield of 36% was ob-
tained. In general, for both reaction conditions at either 120 or
908C, a distinct trend was observed for the halide counterion
of [Bu4P]-based systems 7a–7c. Whereas non-nucleophilic
counterions in 7d–7 f prevented any catalytic reaction, the car-
bonate yield increased with increasing nucleophilicity of the
halide; thus the best yield was observed in the presence of
chloride, which represented a hard counterion (7a). In contrast,
soft counterions, such as iodide (7c), led to only moderate
yields of 9a. These trends follow the order of nucleophilicity in
aprotic polar solvents.
When 2-hydroxyethyltrimethylphosphonium chloride (3a)
was employed as a catalyst at 120 or 908C, no formation of
cyclic carbonate 9a was observed (Table 2, entry 7). We
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contrast to catalysts 7a–7 f at 1208C, several bifunctional orga-
nocatalysts permitted excellent yields of at least 93% (Table 2,
entries 8–12, 16, 17, and 19) and a catalyst screening under
less drastic conditions was performed to deduce the most
active bifunctional organocatalyst. The reaction conditions
were adjusted to 908C, p(CO2)=1.0 MPa, 2 h, and 2 mol% 3.
Under these reaction conditions, only iodide-based catalysts
3 f, 3k, and 3l permitted excellent yields of up to 92% of
cyclic carbonate 9a (Table 2, entries 12, 17, and 18). In contrast,
catalysts containing chloride (3d and 3g) and bromide (3b,
3e, and 3h) counterions showed a dramatic decrease in the
yield of carbonate 9a (Table 2, entries 8, 10, 11, 13, and 14).
Moreover, in the presence of catalysts 3a, 3b, 3g, and 3h no
or very low catalytic activity was observed in the model reac-
tion. These experiments revealed more clearly the dependence
of the halide, substituents at the phosphorus center, and dis-
tance of the alcohol moiety to the phosphorus atom on the
catalytic activity of 3. For bifunctional phosphorus-based orga-
nocatalysts 3, the yield of 9a increased with the order of the
atomic number of the halide from ClÀ <BrÀ <IÀ. This trend
was observed for Me3P- (3a–3c), Bu3P- (3d–3 f), and Ph3P-
based (3g-3i) catalysts at 908C (Table 2, entries 7–16). A com-
parison of 7a–7c and 3d–3 f reveals the special role of the al-
cohol moiety within the bifunctional organocatalysts (Table 2,
entries 1–3 and 10–12). The order of reactivity of the halide
species of 3d–3 f is inverse to that of [Bu4P]-based systems
7a–7c. This manner of reaction, regarding the nucleophilicity
of the bifunctional organocatalyst, is characteristic for a substi-
tution reaction in polar protic solvents. Intramolecular hydro-
gen bonding between the halide and alcohol moiety presuma-
bly results in this reversal of nucleophilicity for bifunctional cat-
alysts 3 compared with monofunctional catalysts 7. Surprising-
ly, under these conditions, catalysts 3i and 3l resulted in even
higher yields than at elevated reaction temperatures of 1208C
(Table 2, entries 15 and 18). As mentioned above, the substitu-
ents at the phosphorus center in 3 also had a distinct impact
on the reaction yield. By taking the results of iodide-based cat-
alysts 3c, 3 f, 3i, 3k, and 3l into account, the yield increases
for the general catalyst structure HO(CH2)2PR3 with substituent
R from Me<Ph !CyꢀnBuꢀnOct. This trend may be attribut-
ed to increased nucleophilicity of the iodide, since the bulki-
ness of the cation results in a weaker ion pair.[43] Furthermore,
the linker between the alcohol moiety and phosphorus atom
significantly influenced the yield of 9a. When 3j, a C3-linked
system, was employed as catalyst, a yield of only 78% was ob-
served. The C2-bridged catalysts 3 f and 6a gave excellent
yields of 92 and 88%, respectively.
Figure 1. Effect of the reaction temperature on the yield of 9a in the pres-
ence of catalyst 3 f. Reaction conditions: 2 mol% 3 f, 30–1208C,
p(CO2)=1.0 MPa, 2 h. Yields were determined by GC-FID and n-hexadecane
was used as a standard.
mation of cyclic carbonate 9a was observed within only 2 h.
Moreover, at 608C, almost half of epoxide 8a was converted
into the desired product 9a. At temperatures of ꢂ908C, excel-
lent yields were obtained. Thus, experiments to determine the
dependence of yield on reaction time, amount of catalyst (3 f),
and carbon dioxide pressure were performed at 908C.
The effect of reaction time was examined between 0.25 and
3 h at 908C and p(CO2)=1.0 MPa (Figure 2). The conversion of
Figure 2. Effect of the reaction time on the yield of 9a in the presence of
catalyst 3 f. Reaction conditions: 2 mol% 3 f, 908C, p(CO2)=1.0 MPa, 0.25–
3.0 h. Yields were determined by GC-FID and n-hexadecane was used as
a standard.
epoxide 8a proceeded quickly within the first 1 h. Remarkably,
after only 0.25 h more than the half of substrate 8a was con-
verted and a yield of 67% of 9a was detected. A reaction time
of 2 h yielded 95% of cyclic carbonate 9a; however, for full
conversion and a quantitative yield of 9a, a reaction time of
3 h was necessary. The influence of the catalyst concentration
was investigated after 3 h to distinguish the effects on the re-
action outcome (Figure 3). The amount of catalyst 3 f in the
model reaction was varied between 0 and 2 mol%. The best
yields of 9a were observed in the presence of 1.5 and
2.0 mol% of 3 f to give yields of 97 and 98%, respectively.
A low catalyst loading of 1 mol% of 3 f also resulted in a good
conversion, yielding 81% of 9a; however, a further decrease in
the amount of catalyst caused a significant decrease in the
yield of 9a. Notably, in the absence of catalyst 3 f no product
was formed. Furthermore, the carbon dioxide pressure was in-
vestigated between 0.3 and 3.0 MPa (Figure 4). In the model
However, the monofunctional phosphorus-based catalysts 7
showed less catalytic activity than the best bifunctional orga-
nocatalysts 3. Hence, the most active catalyst, 3 f, was chosen
to optimize the reaction conditions.
Effect of reaction parameters
With regard to the investigated reaction parameters, tempera-
ture had the most decisive effect on the model reaction
(Figure 1). However, even at temperatures of ꢁ408C, the for-
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Table 3. Effect of solvent in the model reaction employing catalyst 3 f.[a]
Entry Solvent
Conversion of 8a
Yield of 9a
[%]
[%]
1
2
3
4
5
6
7
–
84
21
43
62
55
34
9
84
15
43
61
55
29
4
MeOH
EtOH
n-butanol
n-hexanol
tert-amyl alcohol
CH2Cl2
8
9
10
11
12
13
THF
MTBE
1,4-dioxane
CH3CN
37
17
28
12
–
37
16
22
5
45
9
Figure 3. Effect of the amount of catalyst 3 f on the yield of 9a. Reaction
conditions: 0–2 mol% 3 f, p(CO2)=1.0 MPa, 908C, 3 h. Yields were deter-
mined by GC-FID and n-hexadecane was used as a standard.
MEK
1,2-propylene carbonate
12
(9b)
14
9a
16
0
[a] The conversion of 8a and yield of 9a were determined by GC-FID
with n-hexadecane as an internal standard. Reaction conditions: 1.0m so-
lution of 8a (5 mL), 2 mol% 3 f, 908C, 1.0 MPa, 1.0 h. MTBE=methyl tert-
butyl ether.
prevented any catalytic reaction at all (Table 3, entries 13 and
14). Hence, we assume that the reaction of 8a and CO2 is in-
hibited by product 9a. The assumption of product inhibition
was also supported by results of experiments concerning the
time dependence of the reaction (Figure 2). The reaction quick-
ly proceeded within the first 30 min and a yield of 72% of 9a
was observed. However, for full conversion, an additional
150 min were required, which indicated product inhibition.
Although solvents decelerate the catalytic activity of 3 f, n-
butanol is the most promising candidate if solid substrates
should be converted into the respective cyclic carbonates.
Nevertheless, in terms of green chemistry and efficiency of re-
sources, the solvent-free reaction process is favorable.[44]
Figure 4. Effect of CO2 pressure on the yield of 9a in the presence of cata-
lyst 3 f. Conditions: 2 mol% 3 f, 908C, 2 h, p(CO2, 908C)=constant. Yields
were determined by GC-FID and n-hexadecane was used as a standard.
reaction, carbonate 9a was obtained in excellent yields for CO2
pressures of ꢂ0.5 MPa. At a very low pressure of 0.3 MPa, the
yield decreased slightly. By considering the conversion of 8a
and the yield of cyclic carbonate 9a, a CO2 pressure of 1.0 MPa
was chosen for further investigations.
Effect of the solvent
Substrate scope
Although organocatalyst 3 f was completely soluble in epoxide
8a, several solvents were tested in the model reaction. There
are reports that demonstrate significant enhancement of the
catalytic activity if solvents are employed.[25b,26b,c] A solvent is
also necessary for more complex and solid substrates. There-
fore, compound 8a was allowed to react with CO2 in the pres-
ence of 13 different solvents and 2 mol% of organocatalyst 3 f
(Table 3).
To investigate the applicability of bifunctional phosphorus-
based organocatalyst 3 f, the substrate scope was examined
(Table 4). Based on the results of the reaction parameter
screening, the standard reaction conditions were defined at 90
and 458C. Alkyl- and aryl-substituted substrates 8a–8g were
converted in excellent yields of ꢂ97% at 908C (Table 4, en-
tries 1–7). Lowering the reaction temperature, while increasing
the reaction time and amount of catalyst, for these substrates
also led to excellent levels of the formation of 9. In general,
the synthesis of 9e could be performed at 238C and atmos-
pheric CO2 pressure in the presence of 10 mol% of 3 f (Table 4,
entry 5). However, only 23% of 9e was isolated and tempera-
tures of at least 458C are reasonable. Epichlorohydrin 8h was
converted into 9h in excellent yield under both conditions
(Table 4, entry 8). Glycidol (8i) is prone to polymerization[45]
and 1H NMR spectroscopy of the crude reaction revealed
a polymeric byproduct. However, glycerol carbonate 9i was
isolated in 54% yield at 908C and 56% yield at 458C (Table 4,
entry 9). Glycidol-derived ether and ester derivatives 8j–8o
To clarify significant effects, the reaction time was set to
1.0 h. A benchmark was set under neat reaction conditions
with a conversion of 84% of 8a and a yield of 9a of 84%
(Table 3, entry 1). Among the employed alcohols, n-butanol
gave the highest yield of 61% of 9a, but alcohols decreased
the reaction rate for catalyst 3 f (Table 3, entries 2–6). Dichloro-
methane proved to be completely inappropriate as a solvent
for the coupling reaction of 8a and CO2 (Table 3, entry 7). Nei-
ther common ethers, such as THF, MTBE, and 1,4-dioxane, nor
acetonitrile or 2-butanone (MEK) had any positive effect on the
yield of 9a (Table 3, entries 8–12). Interestingly, 1,2-propylene
carbonate (9b) gave only 9% yield and the product 9a itself
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and, although 9m was a solid under these conditions, a yield
of 90% was recorded. In addition to 8n–8o, various unsaturat-
ed epoxides 8p–8r were employed as substrates (Table 4, en-
tries 16–18). The corresponding carbonates 9n–9r are poten-
tial building blocks for homo- and copolymerization products
with a cyclic carbonate unit in the backbone.[25b] We were very
pleased to isolate these products in yields of up to 99% under
both reaction conditions. When isoprene monoxide 8r was
employed, moderate yields of 25 and 18% were obtained
(Table 4, entry 18). Because no byproduct formation was ob-
served, it was assumed that a higher degree of substitution in
8r resulted in steric hindrance for the nucleophilic activation
of 3 f, and therefore, in a decrease of the reaction rate. Methyl
10-undecenoate is accessible from castor oil and represents
a substrate based on renewable raw materials.[46] The respec-
tive epoxide 8s was smoothly converted into the cyclic car-
bonate 9s at 90 and 458C in excellent yields of 97 and 87%,
respectively. Pure organic cyclic carbonates 9 could be easily
isolated by simple filtration over silica from the crude reaction
mixture and subsequent removal of volatile compounds under
vacuum, except for product 9s and its synthesis at 458C. Due
to incomplete conversion and the high boiling point of sub-
strate 8s, flash chromatography was carried out for purifica-
tion. Nonetheless, the catalyst proved to be very active under
both reaction conditions and tolerated a number of useful
moieties.
Table 4. Substrate scope for the formation of terminal cyclic carbonates
9.
Entry
Product 9
Yield [%]
908C[a]
458C[b]
1
2
3
4
5
6
9a
9b
9c
9d
9e
9 f
97
92
99
99
99
82
82
81
76
98
97
(23)[c]
97
95
7
9g
91
8
9h
9i
99
54
97
97
97
98
99
96
56
92
92
87
90
82
The preparation of internal carbonates 11 is often neglected
in the examination of substrate scope. The steric hindrance of
nucleophilic ring opening of the epoxide 10 usually causes
lower yields and, as a consequence, more drastic reaction con-
ditions are required. Hence, the reaction conditions were ad-
justed for the conversion of internal epoxides 10 to the respec-
tive carbonates 11, and the reactions were carried out at 908C,
18 h, p(CO2)=1.0 MPa, and at 1208C, 6 h, p(CO2)=4.0 MPa
(Table 5). When cis-2,3-butylene oxide (10a) was employed,
reasonable yields of 58% were obtained at 908C with a cis/
trans ratio of 55:45 for 11 a (Table 5, entry 1). At 1208C, a similar
selectivity for the isomers was obtained; however, the yield
was only moderate at 33% for 2,3-butylene carbonate (11 a).
While stilbene oxide (10b) is solid, n-butanol was employed as
the solvent; this proved to be the most suitable one according
to the results of the experiments in Table 3, entries 2 and 3.
Moreover, the reaction time was prolonged to 66 h at 908C
and p(CO2)=1.0 MPa to obtain 61% yield when cis-10b and
62% when trans-10b was used. The corresponding carbonates
11 b were formed almost exclusively as trans isomers and only
slight amounts of cis-carbonate 11 b were formed when cis-
10b was introduced. The bulkiness of the phenyl substituents
led to a comparatively low reaction rate for catalyst 3 f, and
therefore, the coupling reaction was performed for 66 h. More-
over, the reaction at 1208C led to isomerization of epoxide
10b, producing the corresponding ketone from Meinwald rear-
rangement as a possible side reaction (Scheme 5). Hence, the
coupling reaction was only performed at 908C. In addition,
several bi- and tricyclic oxiranes 10c–10j were tested as sub-
strates in the coupling reaction with CO2 (Table 5, entries 4–
12). Cyclohexene oxide (10c) tends to polymerize to give the
9
10
11
12
13
14
9j
9k
9l
9m
9n
15
9o
98
99
16
17
18
19
9p
9q
9r
89
99
25
97
82
98
18
87
9s
[a] Reaction conditions: 2 mol% 3 f, 908C, p(CO2)=1.0 MPa, 3 h. [b] Reac-
tion conditions: 5 mol% 3 f, 458C, p(CO2)=1.0 MPa, 18 h. [c] Reaction
conditions: 10 mol% 3 f, 238C, p(CO2)=0.1 MPa, 18 h.
were selectively converted into their respective cyclic carbo-
nates 9j–9o in yields of ꢂ97% at 908C (Table 4, entries 10–
15). At 458C, again very good yields of 82–99% were obtained
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Table 5. Conversion of epoxide 10a and CO2 into the corresponding
cyclic carbonate 11 a in the presence of bifunctional organocatalyst 3 f.
Entry
Product 11
Yield [%]
1208C[b]
908C[a]
58
33
1
11 a
11 b
(55:45)[c]
(53:47)[c]
2
3
61[d]
62[d]
–
4
5
33
69
11 c
11 d
11 e
11 f
11 g
6[e]
42[e]
6
7
8
9
–
36
23
(50:50)[f]
23
(50:50)[f]
77
48
42
40
10
11
11 h
11 i
0
0
0[g]
0[g]
12
13
11 j
79
89
Scheme 5. Possible reaction mechanism for the insertion of CO2 into internal
epoxides 10 (as well as for terminal epoxides 8) in the presence of organo-
catalyst 3 f.
11 k
65[h] (40:60)[c]
[a] Reaction conditions: 2 mol% 3 f, 908C, p(CO2)=1.0 MPa, 18 h. [b] Re-
action conditions: 2 mol% 3 f, 1208C, p(CO2)=4.0 MPa, 6 h. [c] The cis/
trans ratio was determined by 1H and/or 13C NMR spectroscopy. [d] n-Bu-
tanol was employed as the solvent and the reaction time was set to 66 h.
[e] Performed with 2 mol% 7c. [f] Diastereomeric ratios were determined
by 1H and/or 13C NMR spectroscopy. [g] Reaction time of 66 h. [h] Reac-
tion conditions: 5 mol% 3 f, 1008C, p(CO2)=5.0 MPa, 24 h.
ed in the synthesis of cyclic carbonates derived from renew-
able sources. Oleochemical carbonates are suggested as indus-
trial lubricants, fuel additives, and polymer plasticizers; starting
materials for polyesters and polycarbonate materials; and as
raw materials for the synthesis of non-isocyanate polyuretha-
nes.[8c,14c,48] As a prototypical substrate, epoxidized methyl
oleate (10k) was converted with CO2 into the respective cyclic
carbonate 11 k in 65% yield with a cis/trans ratio of 40:60
(Table 5, entry 13). As a byproduct, the ketone derived from
Meinwald rearrangement was observed in less than <1%
yield.[49]
corresponding homo- and copolymers in the reaction with
CO2.[47] Notably, only cyclic carbonate cis-11 c was formed
under both reaction conditions with a yield of up 69% at
1208C (Table 5, entry 4). If tetra-n-butylphosphonium iodide
(7c) is used instead of 3 f, significantly lower yields were ob-
tained (Table 5, entry 5). Thus, for the remaining substrates,
compound 3 f was used as the catalyst. The naturally occurring
unsaturated bicyclic carbonate[10] 11 d was less reactive, and
therefore, it was isolated in only 36% yield (Table 5, entry 6).
The moderate yield was attributed to the less flexible back-
bone caused by the double bond in the cyclohexene ring.
Cyclic carbonate 10e was isolated in 23% yield under both re-
action conditions of 90 and 1208C (Table 5, entry 7). Cyclopen-
tene oxide (10 f) was isolated in up to 77% yield (Table 5,
entry 8) in the cis configuration only. Similar cis selectivity was
observed for the dihydrofuran-derived epoxide 10g; however,
the presence of the oxygen atom within the strained ring
system led to a decrease in yield to 48% at 908C (Table 5,
entry 9). Unfortunately, no reaction was observed when cyclo-
octene oxide (10h) or norbornene oxide (10i) were employed
as substrates (Table 5, entries 10 and 11).
In accordance with previous reports and based on our ex-
periments, a plausible mechanism proceeds in three steps
(Scheme 5).[50] An epoxide 10 could be activated due to hydro-
gen-bond interactions and/or due to electrostatic interactions
of the phosphonium species of catalyst 3 f. A nucleophilic sub-
stitution reaction at the less hindered carbon atom of the
iodide forms an alcoholate, followed by another nucleophilic
attack from the alcoholate towards CO2. An acyclic carbonate
can be formed, which then undergoes an intramolecular sub-
stitution reaction, producing cyclic carbonate 11 with libera-
tion of the catalyst 3 f. As a possible byproduct, the ketone
can be formed by Meinwald rearrangement of the halohydrin
derivative.
Conclusions
In contrast, indene oxide (11 j) was isolated in up to 89%
yield at 1208C, 6 h p(CO2)=4.0 MPa, in the presence of
2 mol% of 3 f (Table 5, entry 12). Additionally, we were interest-
Bifunctional phosphorus-based organocatalysts 3 were synthe-
sized by a simple nucleophilic substitution reaction of phos-
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pressure was kept constant at 1.0 MPa. Subsequently, the reactor
was cooled to ꢁ208C on an ice bath and CO2 was released slowly.
Product 9 was purified by filtration through a short plug of silica
gel with CH2Cl2 and subsequent removal of volatile compounds
under reduced pressure.
phine 1 and haloalcohol 2 or iodomethane (5). Catalyst screen-
ing under two different screening reaction conditions revealed
that the most active catalyst was 3 f. Simple tetra-n-butylphos-
phonium salts 7 showed significantly lower yields in the model
reaction than those with 3 f, so it can be assumed that the al-
cohol function increased the catalytic activity for the synthesis
of 9a from 8a and CO2. The addition of 13 different solvents
showed no enhancement of catalytic activity compared with
neat reaction conditions. Moreover, no reaction was observed
when product 9a itself was employed as a solvent, which indi-
cated product inhibition for this reaction. The effects of tem-
perature, time, amount of catalyst, and CO2 pressure on the
yield were investigated. Finally, the substrate scope was evalu-
ated for terminal and internal epoxides 8 and 10. Terminal ep-
oxides 8 were converted in excellent yields at 908C, p(CO2)=
1.0 MPa, within 3 h in the presence of 2 mol% of 3 f. Even
under very mild reaction conditions of 458C, excellent yields of
cyclic carbonate 9 were obtained. The catalyst proved to be
very active and selective under both reaction conditions and
tolerated a number of useful moieties. Although the nucleo-
philic activation of internal epoxides 10 by halide of 3 f was
hindered due to steric demand of the substrate molecule 10,
reasonable yields of up to 89% were obtained at 90 and
1208C. Oleochemical cyclic carbonates based on renewable
sources were obtained in 65% yield under relatively harsh re-
action conditions. Studies towards the selective conversion of
epoxidized fatty acid esters and CO2 into the respective cyclic
carbonates under appropriate conditions are currently ongo-
ing.
Coupling reaction of CO2 and terminal epoxides at 458C
(GP4)
In a typical reaction, a 45 cm3 stainless-steel autoclave was charged
with 3 f (0.05 equiv) and epoxide 8 (1.00 equiv). The reactor was
purged once with CO2 and an initial pressure of 0.5–0.7 MPa was
set. The reaction mixture was stirred for 18 h at 458C while the
CO2 pressure was kept constant at 1.0 MPa. Subsequently, the reac-
tor was cooled to ꢁ208C on an ice bath and CO2 was released
slowly. Product 9 was purified by filtration through a short plug of
silica gel with CH2Cl2 and subsequent removal of volatile com-
pounds under reduced pressure.
Coupling reaction of CO2 and internal epoxides at 908C
(GP5)
In a typical reaction, a 45 cm3 stainless-steel autoclave was charged
with 3 f (0.05 equiv) and epoxide 10 (1.00 equiv). The reactor was
purged once with CO2 and an initial pressure of 0.5–0.7 MPa was
set. The reaction mixture was stirred for 18 h at 908C while the
CO2 pressure was kept constant at 1.0 MPa. Subsequently, the reac-
tor was cooled to ꢁ208C on an ice bath and CO2 was released
slowly. Product 11 was purified by filtration through a short plug
of silica gel with CH2Cl2 or flash chromatography and subsequent
removal of volatile compounds under reduced pressure.
Experimental Section
Coupling reaction of CO2 and internal epoxides at 1208C
(GP6)
Preparation of bifunctional catalysts (GP1)
In a typical reaction, a 45 cm3 stainless-steel autoclave was charged
with 3 f (0.02 equiv) and epoxide 10 (1.00 equiv). The reactor was
purged once with CO2 and an initial pressure of 4.0 MPa was set.
The reaction mixture was stirred for 6 h at 1208C. Subsequently,
the reactor was cooled to ꢁ208C on an ice bath and CO2 was re-
leased slowly. Product 11 was purified by filtration through a short
plug of silica gel with CH2Cl2 or flash chromatography and subse-
quent removal of volatile compounds under reduced pressure.
A
mixture of phosphine 1 (1.00 equiv) and halohydrin 2
(1.00 equiv) were stirred for 1–24 h at 60–1008C under an argon at-
mosphere. The crude product was washed with diethyl ether and
dried in vacuo.
Catalyst and parameter screening (GP2)
A
45 cm3 stainless-steel autoclave was charged with catalyst
(0.001–0.02 equiv) 3, 6a, or 7 and 8a (2.00 g, 27.7 mmol). The reac-
tor was sealed and charged with 0.3–3.0 MPa CO2 at 238C until
equilibrium was reached. The reaction mixture was stirred for 0.25–
3.00 h at 30–1208C. Afterwards, the reactor was cooled to ꢁ208C
on an ice bath and CO2 was released slowly. The reaction mixture
was analyzed by GC by using a 7890A Series GC instrument from
Agilent Technologies. The conversion of epoxide 8a and yield of
9a were determined by using n-hexadecane as an internal stan-
dard.
(2-Hydroxyethyl)trimethylphosphonium chloride (3a)
In accordance with GP1, a solution of 1a in toluene (1.0m, 10 mL,
10 mmol) and 2a (824 mg, 10.2 mmol) were stirred for 24 h at
1008C. Product 3a (976 mg, 6.23 mmol, 62%) was obtained as
a colorless solid. 1H NMR (300 MHz, D2O): d=1.90 (d, 2J(H,P)=
14.5 Hz, 9H), 2.49 (dt, 3J(H,P)=13.1 Hz, 3J(H,H)=6.2 Hz, 2H),
3.99 ppm (dt, 2J(H,P)=19.9 Hz, 3J(H,H)=6.2 Hz, 2H); 13C NMR
(75 MHz, [D4]MeOH): d=9.1 (d, 1J(C,P)=55.0 Hz, 3”CH3), 27.7 (d,
1J(C,P)=54.9 Hz, CH2), 56.2 ppm (d, 2J(C,P)=7.5 Hz, CH2);
31P{1H} NMR (121 MHz, D2O): d=25.70 ppm; IR (ATR): n˜ =3205 (br
vs), 2987 (s), 2931 (m), 2888 (m), 2815 (w), 1474 (w), 1426 (w), 1385
(s), 1319 (m), 1286 (vs), 1236 (m), 1180 (m), 1055 (vs), 1014 (vs), 985
(vs), 972 (vs), 893 (s), 855 (vs), 778 (s), 770 (s) 731 cmÀ1 (s); elemen-
tal analysis calcd (%) for C5H14ClOP (156.59): C 38.35, H 9.01,
P 19.78, Cl 22.64; found: C 38.43, H 8.85, P 19.78, Cl 22.39.
Coupling reaction of CO2 and terminal epoxides at 908C
(GP3)
In a typical reaction, a 45 cm3 stainless-steel autoclave was charged
with 3 f (0.02 equiv) and epoxide 8 (1.00 equiv). The reactor was
purged once with CO2 and an initial pressure of 0.5–0.7 MPa was
set. The reaction mixture was stirred for 3 h at 908C while the CO2
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(2-Hydroxyethyl)trimethylphosphonium bromide (3b)[51]
33.87 ppm; IR (ATR): n˜ =3252 (br m), 2958 (s), 2930 (s), 2871 (s),
2360 (m), 1621 (m), 1461 (s), 1382 (m), 1312 (m), 1228 (m), 1150
(m), 1051 (s), 1003 (m), 967 (m), 912 (m), 809 (m), 721 cmÀ1 (m);
HRMS (ESI): m/z calcd for C14H32OP [M+ÀBr]: 247.2185; found:
247.2187.
In accordance with GP1, a solution of 1a in toluene (1.0m, 8.0 mL,
8.0 mmol) and 2b (944 mg, 7.56 mmol) were stirred for 24 h at
708C. Product 3b (1.34 g, 6.65 mmol, 88%) was obtained as a color-
less solid. 1H NMR (300 MHz, D2O): d=1.90 (d, 2J(H,P)=14.5 Hz,
9H), 2.49 (dt, 3J(H,P)=13.1, 3J(H,H)=6.2 Hz, 2H), 4.00 ppm (dt,
2J(H,P)=19.9 Hz,
3J(H,H)=6.2 Hz,
2H);
13C NMR
(75 MHz,
[D4]MeOH): d=9.2 (d, 1J(C,P)=55.6 Hz, 3”CH3), 27.7 (d, 1J(C,P)=
55.2 Hz, CH2), 56.3 ppm (d, 2J(C,P)=7.2 Hz, CH2); 31P{1H} NMR
(121.5 MHz, D2O): d=25.69 ppm; IR (ATR): n˜ =3271 (br vs), 2984 (s),
2926 (m), 2886 (m), 1473 (w), 1429 (w), 1383 (m), 1318 (m), 1287
(vs), 1234 (w), 1179 (m), 1117 (w), 1050 (vs), 1011 (vs), 967 (vs), 891
(s), 853 (vs), 776 (s), 727 cmÀ1 (s); elemental analysis calcd (%) for
C5H14OPBr (201.04): C 29.87, H 7.02, P 15.41, Br 39.74; found:
C 30.04, H 7.14, P 15.56, Br 39.80.
Tri-n-butyl-(2-hydroxyethyl)phosphonium iodide (3 f)
In accordance with GP1, compounds 1b (1.62 g, 8.00 mmol) and
2c (1.43 g, 8.31 mmol) were stirred for 24 h at 608C. Product 3 f
(2.96 g, 7.91 mmol, 99%) was obtained as a colorless solid. H NMR
(300 MHz, CDCl3): d=0.99 (t, 3J(H,H)=7.0 Hz, 9H), 1.48–1.66 (m,
1
3
3
12H), 2.32–2.42 (m, 6H), 2.73 (dt, J(H,P)=11.7 Hz, J(H,H)=5.9 Hz,
2
3
2H), 4.12 (dt, J(H,P)=20.6 Hz, J(H,H)=5.5 Hz, 2H), 4.30 ppm (brs,
1H; OH); 13C NMR (75 MHz, CDCl3): d=13.4 (s, 3”CH3), 19.8 (d,
1J(C,P)=47.3 Hz, 3”CH2), 22.9 (d, 1J(C,P)=49.2 Hz, CH2), 23.7 (d,
2J(C,P)=4.8 Hz, 3”CH2), 23.8 (d, J(C,P)=15.6 Hz, 3”CH2), 54.7 ppm
3
(2-Hydroxyethyl)trimethylphosphonium iodide (3c)
(d, 2J(C,P)=7.1 Hz, CH2), 31P{1H} NMR (121.5 MHz, CDCl3): d=
33.80 ppm; IR (ATR): n˜ =3672 (w), 3314 (br m), 2959 (s), 2928 (m),
2874 (m), 1461 (m), 1383 (m), 1311 (w), 1230 (w), 1073 (s), 1010
(m), 968 (w), 915 (w), 796 (m), 739 cmÀ1 (m); HRMS (ESI): m/z calcd
for C14H32OP [M+ÀI]: 247.2185; found: 247.2185.
In accordance with GP1, a solution of 1a in toluene (1.0m, 9.0 mL,
9.0 mmol) and 2-iodoethanol (2c, 1.55 g, 9.00 mmol) were stirred
for 1 h at 608C. Product 3c (1.87 g, 7.54 mmol, 84%) was obtained
as a colorless solid. 1H NMR (300 MHz, D2O): d=1.91 (d, 2J(H,P)=
14.5 Hz, 9H), 2.50 (dt, 3J(H,P)=13.1 Hz, 3J(H,H)=6.2 Hz, 2H),
4.00 ppm (dt, 2J(H,P)=19.9 Hz, 3J(H,H)=6.1 Hz, 2H); 13C NMR
(75 MHz, [D4]MeOH): d=9.4 (d, 1J(C,P)=54.1 Hz, 3”CH3), 27.7 (d,
1J(C,P)=54.2 Hz, CH2), 56.3 ppm (d, 2J(C,P)=7.4 Hz, CH2);
31P{1H} NMR (121.5 MHz, D2O): d=25.69 ppm; IR (ATR): n˜ =3328 (br
vs), 2971 (s), 2928 (s), 2893 (s), 2171 (m), 1479 (m), 1405 (s), 1330
(s), 1311 (m), 1289 (vs), 1230 (s), 1168 (m), 1054 (vs), 1015 (vs), 971
(vs), 952 (vs), 885 (s), 862 (vs), 770 (vs), 736 cmÀ1 (s); elemental
analysis calcd (%) for C5H14OPI (248.04): C 24.21, H 5.69, P 12.49, I
51.16; found: C 24.64, H 5.67, P 12.79, I 51.35.
(2-Hydroxyethyl)triphenylphosphonium iodide (3i)
In accordance with GP1, a solution of 1c (10.00 g, 38.14 mmol) and
2c (4.57 mL, 58.6 mmol) in toluene (20 mL) was stirred for 48 h at
1008C. Product 3i (4.28 g, 9.85 mmol, 26%) was obtained as a pale
yellow solid. 1H NMR (300 MHz, CDCl3): d=3.73 (dt, 2J(H,P)=
11.9 Hz, 3J(H,H)=6.0 Hz, 2H), 3.96–4.09 (m, 2H), 4.28 (t, 3J(H,H)=
6.6 Hz, 1H), 7.60–7.67 (m, 6H), 7.69–7.71 (m, 2H), 7.72–7.78 ppm
(m, 7H); 13C NMR (75 MHz, CDCl3): d=26.7 (d, 1J(C,P)=50.9 Hz,
CH2), 55.0 (d, 2J(C,P)=5.2 Hz, CH2), 117.6 (d, 1J(C,P)=86.7 Hz, C),
130.1 (d, 2J(C,P)=12,7 Hz, CH), 133.6 (d, 3J(C,P)=10.3 Hz, CH),
Tri-n-butyl-(2-hydroxyethyl)phosphonium chloride (3d)
In accordance with GP1, compounds 1b (404 mg, 2.00 mmol) and
2a (157 mg, 1.95 mmol) were stirred for 24 h at 1008C. Product 3d
4
134.8 ppm (d, J(C,P)=3.0 Hz, CH), 31P{1H} NMR (121.5 MHz, CDCl3):
1
d=24.46 ppm; IR (ATR): n˜ =3304 (br w), 2869 (w), 1586 (w), 1481
(w), 1436 (m), 1419 (w), 1338 (w), 1307 (w), 1109 (s), 1067 (m), 1015
(w), 995 (m), 826 (w), 752 (m), 733 (m), 686 (vs), 541 (s), 506 (s), 493
(vs), 436 cmÀ1 (m); elemental analysis calcd (%) for C20H20IOP
(434.25): C 55.32, H 4.64, P 7.13, I 29.22; found: C 55.50, H 4.30,
P 6.97, I 29.39.
(445 mg, 1.57 mmol, 81%) was obtained as a colorless oil. H NMR
(300 MHz, CDCl3): d=0.98 (t, 3J(H,H)=7.1 Hz, 9H), 1.49–1.62 (m,
3
3
12H), 2.31–2.42 (m, 6H), 2.60 (dt, J(H,P)=11.7 Hz, J(H,H)=5.8 Hz,
2
3
2H), 4.09 (dt, J(H,P)=21.0 Hz, J(H,H)=5.8 Hz, 2H), 6.27 ppm (brs,
1H; OH); 13C NMR (75 MHz, CDCl3): d=13.4 (s, 3”CH3), 19.5 (d,
1J(C,P)=47.2 Hz, 3”CH2), 23.0 (d, 1J(C,P)=49.7 Hz, CH2), 23.7 (d,
2J(C,P)=4.8 Hz, 3”CH2), 23.9 (d, J(C,P)=15.5 Hz, 3”CH2), 54.8 ppm
3
(d, 2J(C,P)=7.5 Hz, CH2); 31P{1H} NMR (121.5 MHz, CDCl3): d=
34.00 ppm; IR (ATR): n˜ =3224 (br m), 2959 (s), 2932 (s), 2872 (s),
1630 (m), 1463 (m), 1407 (m), 1382 (m), 1313 (m), 1229 (m), 1055
(m), 996 (m), 967 (m), 911 (m), 808 (m), 718 cmÀ1 (m); HRMS (ESI):
m/z calcd for C14H32OP [M+ÀCl]: 247.2185; found: 247.2184.
Tri-n-butyl-(3-hydroxypropyl)phosphonium iodide (3j)
In accordance with GP1, compounds 1b (1.62 g, 8.00 mmol) and
2d (1.43 g, 8.30 mmol) were stirred for 18 h at 608C. Product 3j
(2.96 g, 7.91 mmol, 99%) was obtained as a colorless oil. 1H NMR
(300 MHz, CDCl3): d=0.97 (t, 3J(H,H)=7.0 Hz, 9H), 1.46–1.63 (m,
12H), 1.86–1.99 (m, 2H), 2.31–2.39 (m, 6H), 2.50–2.60 (m, 2H), 3.06
(brs, 1H; OH), 3.73–3.77 ppm (m, 2H); 13C NMR (75 MHz, CDCl3):
Tri-n-butyl-(2-hydroxyethyl)phosphonium bromide (3e)
In accordance with GP1, compounds 1b (535 mg, 2.64 mmol) and
2b (330 mg, 2.64 mmol) were stirred for 24 h at 1008C. Product 3e
1
1
d=13.4 (s, 3”CH3), 16.7 (d, J(C,P)=49.3 Hz, CH2), 19.2 (d, J(C,P)=
1
2
3
(855 mg, 2.61 mmol, 99%) was obtained as a colorless oil. H NMR
47.2 Hz, 3”CH2), 23.6 (d, J(C,P)=4.7 Hz, 3”CH2), 23.8 (d, J(C,P)=
15.2 Hz, 3”CH2), 24.7 (d, 2J(C,P)=4.5 Hz, CH2), 60.7 ppm (d,
3J(C,P)=13.6 Hz, CH2); 31P{1H} NMR (121.5 MHz, CDCl3): d=
34.71 ppm; IR (ATR): n˜ =3346 (br w), 2957 (m), 2930 (m), 2870 (m),
1616 (w), 1461 (m), 1403 (m), 1381 (m), 1313 (w), 1228 (w), 1146
(w), 1070 (m), 1058 (s), 1012 (m), 968 (w), 970 (w), 808 (m),
717 cmÀ1 (m); HRMS (ESI): m/z calcd for C15H34OP [M+ÀI]:
261.2342; found: 261.2338.
(300 MHz, CDCl3): d=0.97 (t, 3J(H,H)=7.1 Hz, 9H), 1.45–1.62 (m,
3
3
12H), 2.32–2.42 (m, 6H), 2.67 (dt, J(H,P)=11.8 Hz, J(H,H)=5.8 Hz,
2
3
2H), 4.07 (dt, J(H,P)=20.8 Hz, J(H,H)=5.8 Hz, 2H), 4.93 ppm (brs,
1H; OH); 13C NMR (75 MHz, CDCl3): d=13.4 (s, 3”CH3), 19.6 (d,
1J(C,P)=47.1 Hz, 3”CH2), 22.9 (d, 1J(C,P)=49.6 Hz, CH2), 23.7 (d,
2J(C,P)=4.8 Hz, 3”CH2), 23.9 (d, J(C,P)=15.5 Hz, 3”CH2), 54.8 ppm
3
(d, 2J(C,P)=7.0 Hz, CH2); 31P{1H} NMR (121.5 MHz, CDCl3): d=
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14.0 mmol), 3 f (261 mg, 0.697 mmol), and CO2 were converted
into the desired carbonate. Product 9a (1.50 g, 12.9 mmol, 92%)
was obtained as a colorless oil. H NMR (300 MHz, CDCl3): d=1.03
(t, J=7.4 Hz, 3H), 1.69–1.87 (m, 2H), 4.09, (dd, J=8.4 Hz, 7.0 Hz,
1H), 4.53 (dd, J=8.3 Hz, 7.9 Hz, 1H), 4.62–4.71 ppm (m, 1H);
13C{1H} NMR (75 MHz, CDCl3): d=8.4 (CH3), 26.9 (CH2), 69.0 (CH2),
78.0 (CH), 155.1 ppm (C=O); elemental analysis calcd (%) for
C5H8O3 (116.12): C 51.72, H 6.94; found: C 51.63, H 6.72.
(2-Hydroxyethyl)tri-n-octylphosphonium iodide (3k)
In accordance with GP1, compounds 1d (1.89 g, 5.09 mmol) and
2c (942 mg, 5.48 mmol) were stirred at for 5 h 608C. Product 3k
(2.76 g, 5.09 mmol, >99%) was obtained as a colorless oil. H NMR
1
1
(300 MHz, CDCl3): d=0.89 (t, 3J(H,H)=6.7 Hz, 9H), 1.26–1.36 (m,
24H), 1.43–1.64 (m, 12H), 2.29–2.39 (m, 6H), 2.72 (dt, 3J(H,P)=
11.6 Hz, 3J(H,H)=5.8 Hz, 2H), 4.10 (dt, 2J(H,P)=20.7 Hz, 3J(H,H)=
5.8 Hz, 2H), 4.33 ppm (brs, 1H; OH); 13C NMR (75 MHz, CDCl3): d=
1
3
14.0 (s, CH3), 19.8 (d, J(C,P)=46.8 Hz, CH2), 21.7 (d, J(C,P)=5.0 Hz,
1
4-Methyl-1,3-dioxolan-2-one (9b)[34a]
CH2), 22.5 (s, CH2), 22.6 (d, J(C,P)=49.1 Hz, CH2), 28.8 (s, CH2), 28.9
(s, CH2), 30.6 (d, J(C,P)=14.8 Hz, CH2), 31.6 (s, CH2), 54.7 ppm (d,
3
2J(C,P)=7.4 Hz, CH2); 31P{1H} NMR (121.5 MHz, CDCl3): d=
33.62 ppm; IR (ATR): n˜ =3672 (w), 3314 (br m), 2955 (m), 2922 (s),
2854 (m), 1459 (w), 1378 (w), 1227 (w), 1056 (m), 954 (w), 720 cmÀ1
(w); elemental analysis calcd (%) for C26H56IOP (542.60): C 57.55,
H 10.40, P 5.71, I 23.29; found: C 57.47, H 10.36, P 5.96, I 23.50.
In accordance with GP3, compounds 8b (1.49 g, 25.7 mmol), 3 f
(192 mg, 0.513 mmol), and CO2 were converted into the desired
carbonate. Product 9b (2.59 g, 25.3 mmol, 99%) was obtained as
a colorless oil. In accordance with GP4, compounds 8b (1.04 g,
17.9 mmol), 3 f (322 mg, 0.860 mmol), and CO2 were converted
into the desired carbonate. Product 9b (1.50 g, 14.7 mmol, 82%)
1
was obtained as a colorless oil. H NMR (300 MHz, CDCl3): d=1.50
Tricyclohexyl(2-hydroxyethyl)phosphonium iodide (3l)
(d, J=6.2 Hz, 3H), 4.04 (dd, J=8.4 Hz, 7.2 Hz, 1H), 4.58 (dd, J=
8.4 Hz, 7.7 Hz, 1H), 4.80–4.92 ppm (m, 1H); 13C{1H} NMR (75 MHz,
CDCl3): d=19.3 (CH3), 70.6 (CH2), 73.5 (CH), 155.0 ppm (C=O); ele-
mental analysis calcd (%) for C4H6O3 (102.09): C 47.06, H 5.92;
found: C 46.71, H 5.55.
In accordance with GP1, compounds 1e (368 mg, 1.31 mmol) and
2c (255 mg, 1.49 mmol) were dissolved in toluene (1 mL) and
stirred for 24 h at 608C. Product 3l (570 mg, 1.26 mmol, 96%) was
obtained as a colorless solid. 1H NMR (300 MHz, CDCl3): d=1.25–
1.63 (m, 15H), 1.79–2.06 (m, 15H), 2.47–2.61 (m, 3H), 2.70 (dt,
2J(H,P)=11.6 Hz, 3J(H,H)=6.1 Hz, 2H), 4.11 (dt, 2J(H,P)=16.9 Hz,
3J(H,H)=6.1 Hz, 2H), 4.30 ppm (brs, 1H; OH); 13C NMR (75 MHz,
CDCl3): d=19.6 (d, 1J(C,P)=42.4 Hz, CH2), 25.4 (s, CH2), 26.4 (d,
3J(C,P)=12.0 Hz, CH2), 27.2 (d, 2J(C,P)=3.9 Hz, CH2), 30.5 (d,
4-Butyl-1,3-dioxolan-2-one (9c)[34a]
In accordance with GP3, compounds 8c (2.81 g, 28.1 mmol), 3 f
(208 mg, 0.556 mmol), and CO2 were converted into the desired
carbonate. Product 9c (4.02 g, 27.9 mmol, 99%) was obtained as
a colorless oil. In accordance with GP4, compounds 8c (939 mg,
9.38 mmol), 3 f (187 mg, 0.500 mmol), and CO2 were converted
into the desired carbonate. Product 9c (1.11 g, 7.70 mmol, 82%)
2
1J(C,P)=40 Hz, CH), 55.0 ppm (d, J(C,P)=5.9 Hz, CH2), 31P{1H} NMR
(121.5 MHz, CDCl3): d=33.06 ppm; elemental analysis calcd (%) for
C20H38OPI (452.40): C 53.10, H 8.47, P 6.85, I 28.05; found: C 53.04,
H 8.22, P 7.05, I 27.69.
1
was obtained as a colorless oil. H NMR (300 MHz, CDCl3): d=0.92
(t, J=7.0 Hz, 3H), 1.31–1.48 (m, 4H), 1.62–1.83 (m, 2H), 4.06 (dd,
J=8.4 Hz, 7.2 Hz, 1H), 4.52 (dd, J=8.2 Hz, 7.9 Hz, 1H), 4.65–
4.75 ppm (m, 1H).; 13C{1H} NMR (75 MHz, CDCl3): d=13.7 (CH3),
22.2 (CH2), 26.4 (CH2), 33.5 (CH2), 69.3 (CH2), 70.0 (CH), 155.0 ppm
(C=O); elemental analysis calcd (%) for C7H12O3 (144.17): C 58.32,
H 8.39; found: C 58.25, H 8.33.
(2-Hydroxyphenyl)(methyl)diphenylphosphonium iodide
(6a)[52]
In accordance with GP1, a suspension of 4a (278 mg, 1.00 mmol)
and 5 (147 mg, 1.04 mmol) in diethyl ether (10 mL) was stirred
16 h at 238C. The product was filtered and washed with diethyl
ether (2”5 mL) to give 6a (402 mg, 0.957 mmol, 96%) as a color-
less solid. 1H NMR (300 MHz, CDCl3): d=2.75 (d, 1J(H,P)=13.9 Hz,
3H), 6.75 (ddd, J=1.5, 7.9, 14.7 Hz, 1H), 6.91–6.97 (m, 1H), 7.65–
7.49 (m, 9H), 7.70–7.77 (m, 2H), 8.03 (dd, J=6.0, 8.3 Hz, 1H),
4-Hexyl-1,3-dioxolan-2-one (9d)[34b]
In accordance with GP3, compounds 8d (3.48 g, 27.1 mmol), 3 f
(203 mg, 0.542 mmol), and CO2 were converted into the desired
carbonate. Product 9d (4.67 g, 27.1 mmol, >99%) was obtained as
a colorless oil. In accordance with GP4, compounds 8d (991 mg,
7.73 mmol), 3 f (146 mg, 0.390 mmol), and CO2 were converted
into the desired carbonate. Product 9d (1.08 g, 6.27 mmol, 81%)
1
9.68 ppm (s, 1H, OH); 13C NMR (75 MHz, CDCl3): d=9.8 (d, J(C,P)=
1
3
59.4 Hz, CH3), 102.3 (d, J(C,P)=92.4 Hz, C), 118.6 (d, J(C,P)=6.7 Hz,
CH2), 119.0 (d, 1J(C,P)=90.2 Hz, C), 120.4 (d, 2J(C,P)=13.0 Hz, CH),
2
3
130.1 (d, J(C,P)=12.9 Hz, CH), 132.7 (d, J(C,P)=10.8 Hz, CH), 133.8
(d, 3J(C,P)=9.5 Hz, CH), 134.6 (d, 8j(C,P)=2.8 Hz, CH), 137.5 (d,
8j(C,P)=2.2 Hz, CH), 162.0 ppm (d, 2J(C,P)=2.5 Hz, C); 31P{1H} NMR
(121.5 MHz, CDCl3): d=20.85 ppm; IR (ATR): n˜ =3046 (br s), 2951
(s), 1580 (s), 1488 (m), 1438 (vs), 1338 (s), 1295 (s), 1244 (s), 1210
(s), 1190 (m), 1162 (m), 1133 (s), 1113 (vs), 1081 (s), 994 (m), 909
(vs), 835 (s), 782 (s), 764 (s), 752 (vs), 741 (vs), 727 (m), 717 (s), 705
(s), 685 (vs), 641 (s), 534 (m), 524 (vs), 496 (vs), 475 (vs), 464 (vs),
434 (s), 409 (vs), 379 cmÀ1 (s).
1
was obtained as a colorless oil. H NMR (300 MHz, CDCl3): d=0.90
(t, J=6.9 Hz, 3H), 1.27–1.51 (m, 8H), 1.63–185 (m, 2H), 4.08 (dd,
J=8.4 Hz, 7.2 Hz, 1H), 4.53 (dd, J(H,H)=8.3 Hz, 7.9 Hz, 1H), 4.66–
4.74 ppm (m, 1H); 13C{1H} NMR (75 MHz, CDCl3): d=13.8 (CH3), 22.3
(CH2), 24.2 (CH2), 28.6 (CH2), 31.4 (CH2), 33.7 (CH2), 69.3 (CH2), 77.0
(CH), 155.0 ppm (C=O); elemental analysis calcd (%) for C9H16O3
(172.22): C 62.77, H 9.36; found: C 63.07, H 8.97.
4-Ethyl-1,3-dioxolan-2-one (9a)[53]
4-Phenyl-1,3-dioxolan-2-one (9e)[34a]
In accordance with GP3, compounds 8a (2.02 g, 28.0 mmol), 3 f
(208 mg, 0.556 mmol), and CO2 were converted into the desired
carbonate. Product 9a (3.15 g, 27.2 mmol, 97%) was obtained as
a colorless oil. In accordance with GP4, compounds 8a (1.01 g,
In accordance with GP3, compounds 8e (3.34 g, 27.8 mmol), 3 f
(208 mg, 0.556 mmol), and CO2 were converted into the desired
carbonate. Product 9e (4.42 g, 26.9 mmol, 97%) was obtained as
a colorless solid. In accordance with GP4, compounds 8e (997 mg,
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4-(Hydroxymethyl)-1,3-dioxolan-2-one (9i)[53]
8.30 mmol), 3 f (156 mg, 8.30 mmol), and CO2 were converted into
the desired carbonate. Product 9e (1.03 g, 6.27 mmol, 76%) was
obtained as a colorless solid.
In accordance with GP3, compounds 8i (1.85 g, 25.00 mmol), 3 f
(187 mg, 0.500 mmol), and CO2 were converted into the desired
carbonate. Product 9i (1.61 g, 13.6 mmol, 54%) was obtained as
a colorless oil. In accordance with GP4, compounds 8i (969 mg,
13.1 mmol), 3 f (253 mg, 0.676 mmol), and CO2 were converted
into the desired carbonate. Product 9i (868 mg, 7.35 mmol, 56%)
A 10 mL Schlenk tube was charged with 8e (1.192 g, 9.921 mmol)
and 3 f (326 mg, 0.871 mmol). Atmospheric CO2 pressure was ap-
plied by using the balloon technique and the reaction mixture was
allowed to stir for 18 h at 238C. Desired cyclic carbonate 9e
(381 mg, 2.32 mmol) was obtained after flash chromatography
(SiO2, cyclohexane (Cy)/EtOAc=10:1) as a colorless solid. 1H NMR
(400 MHz, CDCl3): d=4.35 (dd, J=8.6 Hz, 7.9 Hz, 1H), 4.79–4.83 (m,
1H), 5.69 (dd, J=8.6 Hz, 8.0 Hz, 1H), 7.36–7.48 ppm (m, 5H);
13C{1H} NMR (75 MHz, CDCl3): d=71.1 (CH2), 77.9 (CH), 125.8 (CH),
129.2 (2”CH), 129.7 (2”CH), 135.7 (C), 154.8 ppm (C=O); elemental
analysis calcd (%) for C9H8O3 (164.16): C 65.85, H 4.91; found:
C 65.77, H 4.90.
1
was obtained as a colorless oil. H NMR (300 MHz, [D6]DMSO): d=
3.51 (dd, J=12.6 Hz, 3.3 Hz, 1H), 3.67 (dd, J=12.6 Hz, 3.3 Hz, 1H),
4.28 (dd, J=8.2 Hz, 5.8 Hz, 1H), 4.49 (dd, J=8.4 Hz, 8.2 Hz, 1H),
4.76–4.83 (m, 1H), 5.26 ppm (t, J=5.6 Hz, 1H); 13C{1H} NMR
(75 MHz, [D6]acetone): d=61.8, 66.2, 77.4, 155.6 ppm (C=O).
4-(Isopropyloxymethyl)-1,3-dioxolan-2-one (9j)[54]
In accordance with GP3, compounds 8j (2.09 g, 18.0 mmol), 3 f
(129 mg, 0.345 mmol), and CO2 were converted into the desired
carbonate. Product 9j (2.80 g, 17.4 mmol, 97%) was obtained as
a colorless oil. In accordance with GP4, compounds 8j (1.03 g,
8.85 mmol), 3 f (161 mg, 0.430 mmol), and CO2 were converted
into the desired carbonate. Product 9j (1.36 g, 8.49 mmol, 96%)
4-Benzyl-1,3-dioxolan-2-one (9 f)[34b]
In accordance with GP3, compounds 8 f (1.98 g, 14.8 mmol), 3 f
(111 mg, 0.297 mmol), and CO2 were converted into the desired
carbonate. Product 9 f (2.56 g, 14.4 mmol, 97%) was obtained as
a pale yellow oil. In accordance with GP4, compounds 8 f, 980 mg,
7.30 mmol), 3 f (140 mg, 0.374 mmol), and CO2 were converted
into the desired carbonate. Product 9 f (1.27 g, 7.13 mmol, 98%)
was obtained as a pale yellow oil. 1H NMR (300 MHz, CDCl3): d=
3.00 (dd, J=14.2 Hz, 6.5 Hz, 1H), 3.16 (dd, J=14.2 Hz, 6.3 Hz, 1H),
4.18 (dd, J=8.6 Hz, 6.9 Hz, 1H), 4.44 (dd, J=8.5 Hz, 7.9 Hz, 1H),
4.89–4.98 (m, 1H), 7.21–7.39 ppm (m, 5H); 13C{1H} NMR (75 MHz,
CDCl3): d=39.7 (CH2), 68.6 (CH2), 77.6 (CH), 127.7 (CH), 129.1 (2”
CH), 129.5 (2”CH), 134.1 (C), 151.0 ppm (C=O); elemental analysis
calcd (%) for C10H10O3 (178.19): C 67.41, H 5.66; found: C 67.60,
H 5.59.
1
was obtained as a colorless oil. H NMR (300 MHz, CDCl3): d=1.15
(d, J=6.2 Hz, 6H), 3.56–3.67 (m, 3H), 4.37 (dd, J=8.3 Hz, 6.1 Hz,
1H), 4.45–4.50 (m, 1H), 4.75–4.82 ppm (m, 1H); 13C{1H} NMR
(75 MHz, CDCl3): d=21.7 (CH3), 21.8 (CH3), 66.3 (CH2), 67.0 (CH2),
72.8 (CH), 75.1 (CH), 155.0 ppm (C=O); elemental analysis calcd (%)
for C7H12O4 (160.17): C 52.49, H 7.55; found: C 52.23, H 7.44.
4-(Isobutyloxymethyl)-1,3-dioxolan-2-one (9k)[55]
In accordance with GP3, compounds 8k (1.95 g, 15.0 mmol), 3 f
(118 mg, 0.345 mmol), and CO2 were converted into the desired
carbonate. Product 9k (2.52 g, 14.5 mmol, 97%) was obtained as
a colorless oil. In accordance with GP4, compounds 8k (964 mg,
7.40 mmol), 3 f (144 mg, 0.385 mmol), and CO2 were converted
into the desired carbonate. Product 9k (1.19 g, 6.83 mmol, 92%)
4-(4-Chlorophenyl)-1,3-dioxolan-2-one (9g)[53]
In accordance with GP3, compounds 8g (1.99 g, 12.8 mmol), 3 f
(96 mg, 0.26 mmol), and CO2 were converted into the desired car-
bonate. Product 9g (2.43 g, 12.2 mmol, 95%) was obtained as a col-
orless solid. In accordance with GP4, compounds 8g (996 mg,
6.44 mmol), 3 f (122 mg, 0.326 mmol), and CO2 were converted
into the desired carbonate. Product 9g (1.16 g, 5.84 mmol, 91%)
1
was obtained as a colorless oil. H NMR (300 MHz, CDCl3): d=0.89
(d, J=6.7 Hz, 6H), 1.87 (sept, J=6.7 Hz, 1H,), 3.27 (d, J=5.5 Hz,
2H) 3.60 (dd, J=3.6 Hz, J=11.0 Hz, 1H), 3.68 (dd, J=3.9 Hz, J=
11.0 Hz, 1H), 4.42 (dd, J=8.3 Hz, 6.0 Hz, 1H), 4.50 (m, 1H), 4.77–
4.85 ppm (m, 1H); 13C{1H} NMR (75 MHz, CDCl3): d=19.1 (2”CH3),
28.4 (CH), 66.3 (CH2), 69.3 (CH2), 75.1 (CH), 78.8 (CH2), 155.0 ppm
(C=O).
1
was obtained as a white solid. H NMR (300 MHz, CDCl3): d=4.31
(dd, J=8.6 Hz, 7.8 Hz, 1H), 4.81 (dd, J=8.6 Hz, 8.3 Hz, 1H), 5.67
(dd, J=8.0 Hz, 7.9 Hz, 1H), 7.29–7.34 (m, 2H), 7.41–7.45 ppm (m,
2H); 13C{1H} NMR (75 MHz, CDCl3): d=71.0 (CH), 77.2 (CH), 127.2
(2”CH), 129.5 (2”CH), 134.2 (C), 135.7 (C), 154.5 ppm (C=O).
4-(tert-Butyloxymethyl)-1,3-dioxolan-2-one (9l)[56]
4-(Chloromethyl)-1,3-dioxolan-2-one (9h)[34a]
In accordance with GP3, compounds 8l (1.97 g, 15.1 mmol), 3 f
(115 mg, 0.307 mmol), and CO2 were converted into the desired
carbonate. Product 9l (2.54 g, 14.6 mmol, 97%) was obtained as
a colorless oil. In accordance with GP4, compounds 8l (989 mg,
7.60 mmol), 3 f (144 mg, 0.385 mmol), and CO2 were converted
into the desired carbonate. Product 9l (1.15 g, 6.60 mmol, 87%)
In accordance with GP3, compounds 8h (2.02 g, 21 mmol), 3 f
(163 mg, 0.434 mmol), and CO2 were converted into the desired
carbonate. Product 9h (2.94 g, 21.5 mmol, 99%) was obtained as
a colorless oil. In accordance with GP4, compounds 8h (1.03 g,
11.2 mmol), 3 f (203 mg, 0.542 mmol), and CO2 were converted into
the desired carbonate. Product 9h (1.46 g, 10.7 mmol, 96%) was
1
was obtained as a colorless oil. H NMR (300 MHz, CDCl3): d=1.19
1
obtained as a colorless oil. H NMR (300 MHz, CDCl3): d=3.69–3.83
(s, 9H), 3.53 (dd, J=10.3 Hz, 3.6 Hz, 1H), 3.62 (dd, J=10.3 Hz,
4.5 Hz, 1H), 4.38 (dd, J=8.3 Hz, 5.8 Hz, 1H), 4.45–4.50 (m, 1H),
4.73–4.81 ppm (m, 1H); 13C{1H} NMR (75 MHz, CDCl3): d=27.2 (3”
CH3), 61.2 (CH2), 65.5 (CH2), 73.8 (C), 75.1 (CH), 155.1 ppm (C=O); el-
emental analysis calcd (%) for C8H14O4 (174.20): C 55.16, H 8.10;
found: C 55.07, H 7.96.
(m, 2H), 4.42 (dd, J=8.9 Hz, 5.7 Hz, 1H), 4.60 (dd, J=8.9 Hz, 8.3 Hz,
1H), 4.94–5.02 ppm (m, 1H); 13C{1H} NMR (75 MHz, CDCl3): d=43.6
(CH2), 66.9 (CH2), 74.2 (CH), 154.1 ppm (C=O); elemental analysis
calcd (%) for C4H5ClO3 (136.53): C 35.19, H 3.69; found: C 35.02,
H 3.81.
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4-(Phenoxymethyl)-1,3-dioxolan-2-one (9m)[34a]
4-(But-3-enyl)-1,3-dioxolan-2-one (9q)[34a]
In accordance with GP3, compounds 8m (3.64 g, 24.2 mmol), 3 f
(180 mg, 0.481 mmol), and CO2 were converted into the desired
carbonate. Product 9m (4.58 g, 23.6 mmol, 98%) was obtained as
a white solid. In accordance with GP4, compounds 8m (991 mg,
6.60 mmol), 3 f (125 mg, 0.334 mmol), and CO2 were converted
into the desired carbonate. Product 9m (1.15 g, 5.92 mmol, 90%)
In accordance with GP3, compounds 8q (1.58 g, 15.6 mmol), 3 f
(118 mg, 0.315 mmol), and CO2 were converted into the desired
carbonate. Product 9q (2.19 g, 15.4 mmol, 99%) was obtained as
a yellow oil. In accordance with GP4, compounds 8q (999 mg,
10.2 mmol), 3 f (190 mg, 0.508 mmol), and CO2 were converted
into the desired carbonate. Product 9q (1.41 g, 9.92 mmol, 98%)
1
1
was obtained as a white solid. H NMR (300 MHz, CDCl3): d=4.15
was obtained as a yellow oil. H NMR (400 MHz, CDCl3): d=1.74–
(dd, J=10.7 Hz, 3.6 Hz, 1H), 4.25 (dd, J=10.6 Hz, 4.2 Hz, 1H), 4.52–
4.65 (m, 2H), 5.00–5.07 (m, 1H), 6.90–6.94 (m, 2H), 7.00–7.05 (m,
1H), 7.29–7.35 ppm (m, 2H); 13C{1H} NMR (75 MHz, CDCl3): d=66.2
(CH2), 66.8 (CH2), 74.1 (CH), 114.6 (CH), 122.0 (2”CH), 129.7 (2”CH),
154.6 (C=O), 157.5 ppm (C); elemental analysis calcd (%) for
C10H10O4 (194.19): C 61.85, H 5.19; found: C 61.72, H 4.84.
1.82 (m, 1H), 1.89–1.98 (m, 1H), 2.14–2.30 (m, 2H), 4.09 (dd, J=
8.4 Hz, 7.2 Hz, 1H), 4.54 (m, 1H), 4.70–4.77 (m, 1H), 5.04–5.12 (m,
2H), 5.74–5.84 ppm (m, 1H); 13C{1H} NMR (100 MHz, CDCl3): d=
28.6 (CH2), 33.0 (CH2), 69.3 (CH2), 76.3 (CH), 116.4 (CH2), 136.0 (CH),
154.9 ppm (C=O).
4-Methyl-4-vinyl-1,3-dioxolan-2-one (9r)[57]
4-[(Allyloxy)methyl]-1,3-dioxolan-2-one (9n)[34b]
In accordance with GP3, compounds 8r (1.94 g, 23.0 mmol), 3 f
(170 mg, 0.454 mmol), and CO2 were converted into the desired
carbonate. Product 9r (732 mg, 5.71 mmol, 25%) was obtained as
a yellow oil. In accordance with GP4, compounds 8r (1.00 g,
11.9 mmol), 3 f (224 mg, 0.598 mmol), and CO2 were converted into
the desired carbonate. Product 9r (268 mg, 2.09 mmol, 18%) was
In accordance with GP3, compounds 8n (2.00 g, 17.5 mmol), 3 f
(137 mg, 0.366 mmol), and CO2 were converted into the desired
carbonate. Product 9n (2.75 g, 17.5 mmol, 99%) was obtained as
a colorless oil. In accordance with GP4, compounds 8n (2.00 g,
17.5 mmol), 3 f (328 mg, 0.876 mmol), and CO2 were converted
into the desired carbonate. Product 9n (2.26 g, 14.3 mmol, 82%)
1
obtained as a yellow oil. H NMR (300 MHz, CDCl3): d=1.60 (s, 3H),
1
4.19 (d, J=8.4 Hz, 1H), 4.28 (d, J=8.3 Hz, 1H), 5.33 (d, J=10.8 Hz,
1H), 5.44 (d, J=17.3 Hz, 1H), 5.95 ppm (dd, J=17.3, 10.9 Hz, 1H);
13C{1H} NMR (75 MHz, CDCl3): d=24.0 (CH3), 74.3 (CH2), 82.5 (C),
116.5 (CH2), 136.8 (CH), 154.4 ppm (C=O).
was obtained as a colorless oil. H NMR (300 MHz, CDCl3): d=3.62
(dd, J=11.1 Hz, 3.8 Hz, 1H), 3.70 (dd, J=11.0 Hz, 3.9 Hz, 1H), 4.05
(m, 2H), 4.40 (dd, J=8.4 Hz, 6.2 Hz, 1H), 4.51 (dd, J=8.4 Hz, 8.3 Hz,
1H), 4.79–4.86 (m, 1H), 5.20–5.32 (m, 1H), 5.23–5.26 (m, 1H), 5.80–
5.93 ppm (m, 1H); 13C{1H} NMR (75 MHz, CDCl3): d=66.2 (CH2), 68.8
(CH2), 72.5 (CH2), 75.0 (CH), 117.9 (CH2), 133.6 (CH), 154.9 ppm
(C=O).
Methyl-9-(2-oxo-1,3-dioxolan-4-yl)nonanoate (9s)
In accordance with GP3, compounds 8s (1.00 g, 4.67 mmol), 3 f
(37 mg, 0.10 mmol), and CO2 were converted into the desired car-
bonate. Product 9s (1.17 g, 4.54 mmol, 97%) was obtained as a col-
orless oil. In accordance with GP4, compounds 8s (995 mg,
4.64 mmol), 3 f (89 mg, 0.24 mmol), and CO2 were converted into
the desired carbonate. Product 9s (1.04 g, 4.03 mmol, 87%) was
obtained after flash chromatography on silica gel (Cy/EtOAc=1:1)
(2-Oxo-1,3-dioxolan-4-yl)methyl methacrylate (9o)[25b]
In accordance with GP3, compounds 8o (4.00 g, 24.2 mmol), 3 f
(208 mg, 0.556 mmol), and CO2 were converted into the desired
carbonate. Product 9o (4.58 g, 23.6 mmol, 98%) was obtained as
a yellow oil. In accordance with GP4, compounds 8o (1.00 g,
7.04 mmol), 3 f (132 mg, 0.353 mmol), and CO2 were converted
into the desired carbonate. Product 9o (1.30 g, 6.98 mmol, 99%)
1
as a colorless oil. H NMR (300 MHz, CDCl3): d=1.30–1.40 (m, 9H),
1.44–1.49 (m, 1H), 1.58–1.71 (m, 3H), 1.76–1.86 (m, 1H), 2.30 (t, J=
7.5 Hz, 2H), 3.66 (s, 3H), 4.04–4.08 (m,1H), 4.52 (dd, J=8.5 Hz,
7.8 Hz, 1H), 4.66–4.73 ppm (m, 1H); 13C{1H} NMR (75 MHz, CDCl3):
d=24.3 (CH2), 24.8 (CH2), 30.0 (CH2), 29.0 (2”CH2), 29.1 (CH2), 33.8
(CH2), 34.0 (CH2), 51.4 (CH3), 69.3 (CH2), 77.0 (CH), 155.0 (C=O),
174.2 ppm (CO2CH3); HRMS (ESI-TOF-MS): m/z calcd for C13H22O5
[M++Na]: 281.1359; found: 281.1359.
1
was obtained as a yellow oil. H NMR (300 MHz, CDCl3): d=1.95–
1.96 (m, 3H), 4.30–4.37 (m, 2H), 4.41–4.46 (m, 1H), 4.56–4.61 (m,
1H), 4.95–5.02 (m, 1H), 5.65–5.67 (m, 1H), 6.15–6.16 ppm (m, 1H);
13C{1H} NMR (75 MHz, CDCl3): d=18.1 (CH3), 63.4 (CH2), 66.0 (CH2),
73.8 (CH), 127.3 (CH2), 135.1 (C), 154.4 (C=O), 166.6 ppm (C=O); ele-
mental analysis calcd (%) for C8H10O5 (186.16): C 51.61, H 5.41;
found: C 51.74, H 5.49.
4,5-Dimethyl-1,3-dioxolan-2-one (11a)[34a]
In accordance with GP5, compounds 10a (994 mg, 13.8 mmol), 3 f
(262 mg, 0.700 mmol), and CO2 were converted into the desired
carbonate. Product 11 a (927 mg, 7.98 mmol, 58%) was obtained
as a colorless oil with a cis/trans ratio of 55:45. In accordance with
GP6, compounds 10a (540 mg, 7.49 mmol), 3 f (54 mg, 0.14 mmol),
and CO2 were converted into the desired carbonate. Product 11 a
(285 mg, 2.45 mmol, 33%) was obtained as a colorless oil with
4-Vinyl-1,3-dioxolan-2-one (9p)[34b]
In accordance with GP3, compounds 8p (954 mg, 13.6 mmol), 3 f
(110 mg, 0.294 mmol), and CO2 were converted into the desired
carbonate. Product 9p (1.38 g, 12.1 mmol, 89%) was obtained as
a pale yellow oil. In accordance with GP4, compounds 8p (1.00 g,
14.3 mmol), 3 f (269 mg, 0.719 mmol), and CO2 were converted
into the desired carbonate. Product 9p (1.35 g, 11.8 mmol, 82%)
was obtained as a pale yellow oil. 1H NMR (300 MHz, CDCl3): d=
4.19 (dd, J=8.6 Hz, 7.6 Hz, 1H), 4.60 (m, 1H), 5.13 (m, 1H), 5.45 (m,
1H), 5.52 (m, 1H), 5.90 ppm (m, 1H); 13C{1H} NMR (75 MHz, CDCl3):
d=69.0 (CH2), 77.3 (CH), 121.1 (CH2), 132.1 (CH), 154.7 ppm (C=O).
1
a cis/trans ratio of 53:47. H NMR (300 MHz, CDCl3, 238C): cis-11 a:
d=1.33–1.39 (m, 6H), 4.79–4.88 (m, 2H); trans-11 a: d=1.42–1.48
(m, 6H), 4.29–4.38 ppm (m, 2H); 13C{1H} NMR (75 MHz, CDCl3): cis-
11 a: d=14.3 (2”CH3), 76.0 (2”CH), 154.6 ppm (C=O); trans-11 a:
d=18.3 (2”CH3), 79.9 (2”CH), 154.5 ppm (C=O).
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4,5-Diphenyl-1,3-dioxolan-2-one (11b)[58]
CDCl3): mixture of diastereomers dr=50:50: d=7.4 (CH2), 7.5 (CH2),
18.3 (CH3), 25.0 (CH2), 25.6 (CH2), 26.0 (CH2), 26.9 (CH2), 28.9 (CH2),
29.2 (CH2), 32.1 (CH), 32.3 (CH2), 34.0 (CH), 35.3 (CH2), 58.4 (CH2),
75.5 (CH), 76.0 (CH), 76.4 (CH), 155.2 (C=O), 155.2 ppm (C=O); ele-
mental analysis calcd (%) for C15H28O6Si (332.47): C 54.19, H 8.49,
Si 8.45; found: C 54.17, H, 8.73, Si 8.57.
In accordance with GP5, compounds cis-10b (751 mg, 3.83 mmol)
and 3 f (73 mg, 0.20 mmol) were dissolved in n-butanol (0.8 mL).
The reactor was sealed and charged with CO2. After a reaction
time of 66 h at 908C, the crude product was purified by flash chro-
matography on silica gel (Cy/EtOAc=20:1). Product 11 b (559 mg,
2.33 mmol, 61%, cis/trans=4:96) was obtained as a colorless solid.
In accordance with GP5, compounds trans-10b (1.00 g, 5.10 mmol)
and 3 f (95 mg, 0.25 mmol) were dissolved in n-butanol (1.0 mL).
The reactor was sealed and charged with CO2. After a reaction
time of 66 h at 908C, the crude product was purified by flash chro-
matography on silica gel (Cy/EtOAc=20:1). Product 11 b (756 mg,
3.15 mmol, 62%, cis/trans=0:100) was obtained as a colorless
cis-Tetrahydro-8H-cyclopenta-1,3-dioxol-2-one (11 f)[34a]
In accordance with GP5, compounds 10 f (845 mg, 10.0 mmol), 3 f
(191 mg, 0.510 mmol), and CO2 were converted into the desired
carbonate. Product 11 f (986 mg, 7.70 mmol, 77%) was obtained as
colorless needles. In accordance with GP6, compounds 10 f
(377 mg, 4.48 mmol), 3 f (36 mg, 0.10 mmol), and CO2 were con-
verted into the desired carbonate. Product 11 f (256 mg,
2.02 mmol, 42%) was obtained as colorless needles. 1H NMR
(300 MHz, CDCl3): d=1.60–1.85 (m, 4H), 2.12–2.18 (m, 2H), 5.08–
5.13 ppm (m, 2H); 13C{1H} NMR (75 MHz, CDCl3): d=21.5 (CH2), 33.1
(2”CH2), 81.8 (2”CH), 154.4 ppm (C=O).
1
solid. H NMR (300 MHz, CDCl3): cis-11 b: d=6.00 (s, 2H), 6.94–6.97
(m, 4H), 7.14–7.20 (m, 6H); trans-11 b: d=5.45 (s, 2H), 7.31–7.36
(m, 4H), 7.43–7.48 ppm (m, 6H); 13C{1H} NMR (75 MHz, CDCl3): d=
85.4 (2”CH), 126.1 (4”CH), 129.2 (4”CH), 129.8 (2”CH), 134.8 (2”
C), 154.1 ppm (C=O).
cis-Cyclohexene carbonate (11c)[34a]
(3aR,7aS)-Tetrahydrofuro[3,4-d][1,3]dioxol-2-one (11g)[61]
In accordance with GP5, compounds 10c (1.00 g, 10.2 mmol), 3 f
(190 mg, 0.508 mmol), and CO2 were converted into the desired
carbonate. Product 11 c (482 mg, 3.39 mmol, 33%) was obtained as
a colorless solid. In accordance with GP6, compounds 10c (1.64 g,
16.7 mmol), 3 f (123 mg, 0.329 mmol), and CO2 were converted
into the desired carbonate. Product 11 c (1.86 g, 13.1 mmol, 69%)
was obtained as a colorless solid. 1H NMR (300 MHz, CDCl3): d=
1.36–1.48 (m, 2H), 1.57–1.69 (m, 2H), 1.85–1.93 (m, 4H), 4.65–
4.72 ppm (m, 2H); 13C{1H} NMR (75 MHz, CDCl3): d=19.1 (2”CH2),
26.8 (2”CH2), 75.7 (2”CH), 155.3 ppm (C=O); elemental analysis
calcd (%) for C7H10O3 (142.15): C 59.14, H 7.09; found: C 58.81,
H 6.74.
In accordance with GP5, compounds 10g (860 mg, 10.0 mmol), 3 f
(188 mg, 0.502 mmol), and CO2 were converted into the desired
carbonate. Product 11 g (623 mg, 4.79 mmol, 48%) was obtained
as colorless needles. In accordance with GP6, compounds 10g
(1.01 g, 11.73 mmol), 3 f (88 mg, 0.24 mmol), and CO2 were con-
verted into the desired carbonate. Product 11 g (607 mg,
4.67 mmol, 40%) was obtained as colorless needles. 1H NMR
(300 MHz, CDCl3): d=3.58 (ddd, J=11.1 Hz, 2.2 Hz, 1.2 Hz, 2H), 4.24
(dd, J=11.0 Hz, 1.3 Hz, 2H), 5.21 ppm (dd, J=2.1 Hz, 1.2 Hz, 2H);
13C{1H} NMR (75 MHz, CDCl3): d=73.0 (2”CH2), 80.0 (2”CH),
154.3 ppm (C=O).
cis-Indene carbonate (11j)[34a]
(3aR,10aS)-3a,4,7,10a-Tetrahydrobenzo[d][1,3]dioxol-2-one
(11d)[59]
In accordance with GP5, compounds 10j[62] (994 mg, 7.52 mmol),
3 f (140 mg, 0.374 mmol), and CO2 were converted into the desired
carbonate. Product 11 j (1.052 g, 5.972 mmol, 79%) was obtained
as a colorless solid. In accordance with GP6, compounds 10j[62]
(504 mg, 3.81 mmol), 3 f (27 mg, 0.072 mmol), and CO2 were con-
verted into the desired carbonate. Product 11 j (590 mg,
In accordance with GP6, compounds 10d[60] (1.01 g, 10.5 mmol), 3 f
(78 mg, 0.21 mmol), and CO2 were converted into the desired car-
bonate. After recrystallization (Et2O), product 11 d (523 mg,
3.73 mmol, 36%) was obtained as colorless needles. 1H NMR
(300 MHz, CDCl3): d=2.19–2.28 (m, 2H), 2.55–2.65 (m, 2H), 4.97–
5.03 (m, 2H), 5.90–5.98 ppm (m, 2H); 13C{1H} NMR (75 MHz, CDCl3):
d=27.0 (2”CH2), 74.6 (2”CH), 125.6 (2”CH), 154.9 ppm (C=O).
3.35 mmol, 89%) was obtained as
a
colorless solid.1H NMR
(300 MHz, CDCl3): d=3.40–3.41 (m, 2H); 5.43–5.48 (m, 1H), 6.01 (d,
J=6.7 Hz, 1H) 7.32–7.46 (m, 3H), 7.50–7.53 ppm (m, 1H);
13C{1H} NMR (75 MHz, CDCl3): d=38.0 (CH), 79.7 (CH), 83.5 (CH),
125.6 (CH), 126.5 (CH), 128.2 (CH), 131.0 (CH), 136.4 (CH), 140.0
(CH), 154.7 ppm (C=O); elemental analysis calcd (%) for C10H8O3
(176.17): C 68.18, H 4.58; found: C 68.16, H: 4.54.
5-[2-(Triethoxysilyl)ethyl]hexahydrobenzo[d][1,3]dioxol-2-
one (10e)
In accordance with GP5, compounds 10e (2.00 g, 6.93 mmol), 3 f
(130 mg, 0.347 mmol), and CO2 were converted to the desired car-
bonate. Product 11 e (510 mg, 1.58 mmol, 23%) was obtained as
a colorless oil after flash chromatography on silica gel (Cy/EtOAc=
20:1) with a diastereomeric ratio (dr) of 50:50. In accordance with
GP6, compounds 10e (2.00 g, 6.93 mmol), 3 f (52 mg, 0.14 mmol),
and CO2 were converted into the desired carbonate. Product 11 e
(525 mg, 1.63 mmol, 23%) was obtained as a colorless oil after
flash chromatography on silica gel (Cy/EtOAc=20:1) with a dr of
50:50. 1H NMR (300 MHz, CDCl3) mixture of diastereomers dr=
50:50; double set of signals: d=0.59–0.65 (m, 4H), 0.92–1.01 (m,
1H), 1.20–1.26 (m, 20H), 1.30–1.45 (m, 6H), 1.53–1.68 (m, 4H),
1.78–1.84 (m, 1H), 2.07–2.35 (m, 4H), 3.82 (q, J=7.0 Hz, 12H),
4.60–4.72 (m, 3H), 4.75–4.79 ppm (m, 1H); 13C{1H} NMR (75 MHz,
Methyl 8-(5-octyl-2-oxo-1,3-dioxolan-4-yl)octanoate (11 k)[48a]
Compounds 10k[63] (1.10 g, 3.53 mmol) and 3 f (66.0 mg,
0.176 mmol) were charged into in a 45 cm3 stainless-steel reactor
equipped with a magnetic stirrer. The reactor was sealed and
charged with 3.5 MPa CO2 until equilibrium was reached. The reac-
tor was heated to 1008C for 24 h and the CO2 pressure was kept
constant at 5.0 MPa. The reactor was cooled to an ambient tem-
perature and CO2 was released slowly. The crude product was puri-
fied by flash chromatography on silica gel (Cy/EtOAc=20:1). Prod-
uct 11 k (817 mg, 2.29 mmol, cis/trans=40:60; 65%) was obtained
1
as a colorless oil. H NMR (300 MHz, CDCl3): cis isomer: d=0.87 (t,
ChemSusChem 2015, 8, 2655 – 2669
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J=13.7 Hz, 3H), 1.20–1.80 (m, 26H), 2.30 (t, J=7.5 Hz, 2H), 3.66 (s,
3H), 4.56–4.65 ppm (m, 2H); trans isomer: d=0.87 (t, J=13.7 Hz,
3H), 1.20–1.80 (m, 26H), 2.30 (t, J=7.5 Hz, 2H), 3.66 (s, 3H), 4.16–
4.27 ppm (m, 2H); 13C{1H} NMR (75 MHz, CDCl3): cis isomer: d=14.2
(CH3), 22.7 (CH2), 24.9 (CH2), 25.7 (CH2), 25.8 (CH2), 28.9–29.5 (8”
CH2), 31.9 (CH2), 34.1 (CH2), 51.6 (OCH3), 80.0 (CH), 80.1 (CH), 154.9
(-CO3-), 174.3 ppm (-CO-); trans isomer: d=14.2 (CH3), 22.7 (CH2),
24.7 (CH2), 24.9 (CH2), 25.7 (CH2), 28.9–29.5 (7”CH2), 31.9 (CH2),
33.9 (2”CH2), 51.6 (OCH3), 82.1 (CH), 82.1 (CH), 154.8 (-CO3-),
174.3 ppm (-CO-); IR (ATR): n˜ =2925 (m), 2855 (m), 1796 (vs), 1735
(s), 1458 (w), 1436 (w), 1369 (w), 1248 (w), 1168 (s), 1087 (m), 1039
(s), 775 cmÀ1 (m); elemental analysis calcd (%) for C20H36O5 (356.50):
C 67.38, H 5.18; found: C 67.56, H: 5.18.
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Acknowledgements
We wish to thank the Federal Ministry of Research and Education
(BMBF) for financial support (Chemische Prozesse und stoffliche
Nutzung von CO2: Technologien für Nachhaltigkeit und Klima-
schutz, grant 01 RC 1004a).
Keywords: carbon dioxide · organocatalysis · phosphorus ·
structure–activity relationships · catalyst design
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Published online on July 17, 2015
ChemSusChem 2015, 8, 2655 – 2669
www.chemsuschem.org
2669
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim