Diphenyl Carbonate: A Highly Reactive and Green Carbonyl Source for the Synthesis of Cyclic Carbonates

Article abstract of DOI:10.1021/acs.joc.8b01695

A practical, safe, and highly efficient carbonylation system involving a diphenyl carbonate, an organocatalyst, and various diols is presented herein and produces highly valuable cyclic carbonates. In reactions with a wide range of diols, diphenyl carbonate was activated by bicyclic guanidine 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst, which successfully replaced highly toxic and unstable phosgene or its derivatives while maintaining the desired high reactivity. Moreover, this new system can be used to synthesize sterically demanding cyclic carbonates such as tetrasubstituted pinacol carbonates, which are not accessible via other conventional methods.

Full text of DOI:10.1021/acs.joc.8b01695

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Article
Diphenyl Carbonate: A Highly Reactive and Green
Carbonyl Source for the Synthesis of Cyclic Carbonates
Ek Raj Baral, Jun Hee Lee, and Jeung Gon Kim
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b01695 • Publication Date (Web): 06 Sep 2018
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Diphenyl Carbonate: A Highly Reactive and Green Carbonyl
Source for the Synthesis of Cyclic Carbonates
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Ek Raj Barala, Jun Hee Leeb,*, and Jeung Gon Kima,*
a. Department of Chemistry and Research Institute of Physics and Chemistry, Chonbuk National
University, Jeonju 54896, Republic of Korea
b. Department of Advanced Materials Chemistry, Dongguk University, Gyeongju 38066,
Republic of Korea
Email: jeunggonkim@jbnu.ac.kr (JGK), leejunhee@dongguk.ac.kr (JHL)
Table of Contents
Abstract
A practical, safe and highly efficient carbonylation system involving a diphenyl carbonate, an
organocatalyst, and various diols is presented herein and produces highly valuable cyclic
carbonates. In reactions with a wide range of diols, diphenyl carbonate was activated by bicyclic
guanidine 1,5,7ꢀtriazabicyclo[4.4.0]decꢀ5ꢀene (TBD) as a catalyst, which successfully replaced
highly toxic and unstable phosgene or its derivatives while maintaining the desired high
reactivity. Moreover, this new system can be used to synthesize sterically demanding cyclic
carbonates such as tetrasubstituted pinacol carbonates, which are not accessible via other
conventional methods.
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Introduction
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Over 8 million tons of phosgene, a versatile and highly reactive C1 building block, is
produced annually for the manufacture of pharmaceuticals, herbicides, insecticides, dyes,
polymers, and many other organic compounds.1−3 Due to its high toxicity and the risk of
accidents, phosgene is generally prepared and consumed at its site of production in the
manufacture of isocyanates, polycarbonates, polyurethanes, etc. Only limited quantities of
phosgene can be shipped to other locations.4 Moreover, extensive safety procedures are
necessary to prevent exposure to phosgene gas.5 Hence, substantial efforts have been made to
develop phosgene substitutes that allow safe and easy handling in industrial processes as well as
in research laboratories.6 For example, liquid diphosgene7,8 and solid triphosgene9 are widely
used in many laboratories, but these compounds are still toxic. As safer replacements for
phosgene, both alkyl chloroformates10 and 1,1’ꢀcarbonyldiimidazole (CDI)11,12 have become the
preferred reagents for carbonylation reactions. However, these reagents are still derived from
phosgene, and their high reactivities necessitate dry and inert conditions for handling and storage.
The direct use of carbon monoxide has also been extensively investigated for carbonylation
reactions.13,14 However, the use of this highly toxic gas requires expensive highꢀpressure
equipment and specific safety systems that limit its use.
Organic carbonates are another class of carbonylation reagents.15–17 The use of organic
carbonates in carbonylation reactions is highly desirable from a green chemistry perspective,
since these reagents can be obtained from nonꢀphosgene sources and they are less toxic.
Dimethyl carbonate (DMC), a representative carbonylation reagent, is a stable liquid and much
easier to handle than gaseous phosgene.18,19 Even though various carbonylation reactions have
been developed via the use of DMC, it is far less reactive than phosgene. Hence, some of these
reactions required harsh reaction conditions or suffer from low efficiencies.20−22 To overcome
these limitations caused by the poor reactivity of DMC, diphenyl carbonate (DPC, 1) has
attracted considerable attention as an alternative reagent. As an inexpensive benchꢀstable solid, 1
is broadly available and can be conveniently used in laboratories without any special
precautions.23 The high reactivity and synthetic utility of 1 are exemplified by the syntheses of
bisphenolꢀAꢀpolycarbonate(commercialized by AsahiꢀKasei)24, aliphatic polycarbonates,25
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polyureas,26 and carbamates.27 Nevertheless, relatively harsh conditions are still necessary for
these carbonylation reactions relative to the conditions required when using phosgene.
Based on the knowledge accumulated during our studies toward the development of
guanidineꢀ and amidineꢀmediated synthetic transformations,28,29 we envisioned that 1 could
interact with an appropriately chosen organosuperbase to give a more reactive catalytic species
or intermediate in the given reaction.30 Accordingly, we turned our attention to finding a suitable
organosuperbase catalysts to use with 1, enabling the development of a highly efficient and
convenient carbonylation of 1,2ꢀdiols, which would provide valuable cyclic carbonates that are
otherwise difficult to access (Scheme 1). Presented herein is the successful development of an
organocatalyst (TBD)ꢀmediated carbonylation with DPC and a diol to produce a wide range of
cyclic carbonates including sterically congested compounds that are hard to access via other
methods.
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Scheme 1. Highly efficient and convenient carbonylation system using diphenyl carbonate.
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Results and Discussion
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As summarized in Table 1, we initiated our investigation by testing a number of amine
catalysts in the formation of cyclic carbonate 3a via the carbonylation of 1ꢀphenylethaneꢀ1,2ꢀdiol
(2a) with DPC (1). Based on its high catalytic activity in transesterification and transamidation
reactions, we first examined the bicyclic guanidine 1,5,7ꢀtriazabicyclo[4.4.0]decꢀ5ꢀene (TBD) as
the catalyst.31,32 To our delight, the reaction of 1 in the presence of TBD (2 mol%) and diol 2a
(1.1 equiv) in 2ꢀmethyltetrahydrofuran (2ꢀMeꢀTHF) at 30 °C for 2 hours gave anticipated cyclic
carbonate 3a in an excellent conversion (>99%) and isolated yield (99%, Table 1, entry 1). Using
the conditions shown in entry 1, a variety of other amine catalysts were examined.33 Highly
nucleophilic amines such as 1,4ꢀdiazabicylo[2.2.2]octane (DABCO)34 and 4ꢀ
(dimethylamino)pyridine (DMAP)35 afforded poor conversions of 3% and 7%, respectively
(entries 4 and 5), while other guanidine organosuperbases such as 7ꢀmethylꢀ1,5,7ꢀ
triazabicyclo[4.4.0]decꢀ5ꢀene (MTBD)36 and 1,8ꢀdiazabicyclo[5.4.0]undecꢀ7ꢀene (DBU)32
furnished cyclic carbonate 3a in decent yields (entries 2 and 3). No desired product 3a was
obtained using amines with low basicities, such as pyridine, imidazole and triethylamine, as
catalysts (entries 6–8). These results suggested that the basicity of the amine rather than their
nucleophilicity correlates well with the catalytic reactivity in this carbonylation reaction. A
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variety of Lewis acid catalysts, such as FeBr2,37 ZnCl2,38 AlCl3,38 I2,39 and BF3 Et2O,40 were also
•
evaluated but failed to produce 3a under otherwise identical conditions (entries 9−13).
Having the highly efficient carbonylation system consisting of DPC (1) and TBD in hand,
we next examined other reaction parameters. First, we scrutinized solvent effects. High
efficiencies were observed for the formation of 3a when a range of polar aprotic solvents,
including 2ꢀMeꢀTHF, THF, 1,4ꢀdioxane, and DMF, were used (entries 1 and 14−16). Among
these solvents, industrially preferred 2ꢀMeꢀTHF showed the best efficiency (99%, entry 1).41,42 In
contrast, a moderate yield of 53% was obtained when using CH3CN as the solvent (entry 17).
Polar protic solvents were also tested. Water was found to be inefficient for this carbonylation,
presumably to the insolubility of DPC in it (entry 18). The sterically demanding tBuOH afforded
good conversion (entry 19), whereas iPrOH exhibited a moderate conversion of 62% (entry 20)
presumably due to the competitive hydrogen bonding interactions between diol 2a and the
sterically less demanding solvent (i.e., iPrOH) with the TBD catalyst. Interestingly, nonpolar
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solvents such as dichloromethane and toluene significantly retarded the carbonylation reaction
and gave carbonate 3a in only 23% and 25% yields, respectively (entries 21 and 22). Notably,
this trend in solvent effects is the opposite of that found in the ringꢀopening polymerization of
lactide, in which TBD showed better catalytic activity in nonpolar solvents than in polar ones.30
Lastly, when we reduced the catalyst loading to 1 mol% and 0.5 mol%, the yield of 3a decreased
proportionally to 69% and 59%, respectively (entries 23 and 24). A moderate yield was obtained
when the carbonylation reagent was replaced with DMC, suggesting that DPC (1) is much more
reactive under these conditions (entry 25). When the reaction was performed in the absence of a
solvent, a poor conversion was obtained (entry 26).
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It is worth mentioning that the carbonylation can be conveniently performed using basic
laboratory techniques and does not require any special equipment such as a drybox, Schlenk
lines, or a highꢀpressure reactor. This organocatalytic reaction can also be conveniently
performed without rigorously drying the solvent.
To further demonstrate the practicality and scalability of the protocol, we performed a
gramꢀscale synthesis of 3a under the optimized reaction conditions. In practice, the multigramꢀ
scale reaction of 1 (3.00 g, 14.0 mmol) and 2a (2.13 g, 14.5 mmol) was conveniently carried out
in the presence of TBD (2 mol%) and 2ꢀMeꢀTHF at 30 for 3 hours. Gratifyingly, we isolated
cyclic carbonate 3a in a comparable high yield of 91%.
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Table 1. Optimization of Cyclic Carbonate Synthesis Using Diphenyl Carbonatea
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Entry
Catalyst
TBD
Solvent
Yieldb
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2
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5
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8
9
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
>99 (99)c
MTBD
DBU
83
70
3
DABCO
DMAP
Pyridine
Imidazole
TEA
7
0
0
0
FeBr2
0
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23
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25d
26e
ZnCl2
AlCl3
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
THF
0
0
I2
0
BF3ꢁOEt2
TBD
0
84
80
90
53
0
TBD
1,4ꢀDioxane
DMF
TBD
TBD
CH3CN
H2O
TBD
TBD
tBuOH
80
62
25
23
69
59
32
TBD
iPrOH
TBD
1,2ꢀDCE
Toluene
2ꢀMeꢀTHF
2ꢀMeꢀTHF
2ꢀMeꢀTHF
–
TBD
TBD (1 mol%)
TBD (0.5 mol%)
TBD
TBD
aReaction conditions: 1 (0.50 mmol, 1.0 equiv), 2a (0.55 mmol, 1.1 equiv), catalyst (2 mol%),
b
1
and solvent (0.8 mL) at 30
for 2 h. Yields were determined by H NMR using
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c
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hexamethylbenzene as an internal standard. Isolated yield is given in parentheses. Dimethyl
carbonate (0.50 mmol, 1.0 equiv) was used in place of DPC (1). eIn the absence of a solvent.
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Scheme 2. Substrate Scope: Terminal Diolsa,b
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aReaction conditions: 1 (0.50 mmol, 1.0 equiv), 2 (0.55 mmol, 1.1 equiv), TBD (2 mol%), and 2ꢀ
methyltetrahydrofuran (0.8 mL) at 30 for 2 h. bYield of isolated 3. cReaction time: 4 h.
With the optimal conditions in hand, we next investigated the scope of diol substrates. As
shown in Scheme 2, a wide range of terminal 1,2ꢀdiols reacted smoothly with 1 to afford
corresponding cyclic carbonates 3 under the optimized conditions. A series of styrene carbonates
(3a–d) were obtained in good to excellent yields. Hence, the reactions of 1,2ꢀdiols equipped with
phenyl, 4ꢀtolyl and 4ꢀfluorophenyl substituents delivered the corresponding cyclic carbonates 3a,
3b, and 3c in 99%, 88%, and 69% yields, respectively. Notably, we were delighted to find that
steric congestion at the internal hydroxyl group of the diol moiety did not hamper the reactivity,
and 1,1ꢀdisubstituted vicinal diol 2d also underwent carbonylation without a difficulty, affording
3d bearing a quaternary center in 81% yield. Similarly, the unsubstituted 1,2ꢀdiol, ethylene
glycol (2e), participated in the reaction to afford ethylene carbonate (3e) in an excellent yield of
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91%. Additionally, various alkylꢀsubstituted terminal 1,2ꢀdiols were smoothly converted to the
corresponding carbonates 3f–j in good to excellent yields, suggesting that neither steric nor
electronic variations of the alkyl substituents altered the efficiency of the reaction. Only
chloromethylꢀsubstituted diol (2i) required a prolonged reaction time (4 h).
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Scheme 3. Substrate Scope: Internal Diolsa,b
aReaction conditions: 1 (0.50 mmol, 1.0 equiv), 2 (0.55 mmol, 1.1 equiv), TBD (2 mol%), and 2ꢀ
b
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methyltetrahydrofuran (0.8 mL) at 30 for 2–12 h. Yield of isolated 3. Yield in parentheses
1
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e
was determined by H NMR using hexamethylbenzene as an internal standard. At 100 . At
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60 . Reaction conditions: 1 (0.75 mmol, 1.5 equiv) and 2 (0.50 mmol, 1.0 equiv), TBD (2
mol%), and 2ꢀmethyltetrahydrofuran (0.8 mL) at 30 for 3 h.
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We next examined internal vicinal diols possessing various substitution patterns around
the hydroxyl groups (Scheme 3). Indeed, a large number of catalysts have been reported to
convert epoxides to cyclic carbonates using CO2 as the C1 source.43,44 In general, these catalytic
methods suffer from severe limitations regarding the number and size of the substituents around
the threeꢀmembered heterocycle.45−50 In stark contrast, the size and number of substituents at
either position of the diol showed little influence on the developed carbonylation, making this a
highly practical and useful method for the preparation of various cyclic carbonates. Hence, a
wide range of internal 1,2ꢀdiols (2k–2u) including cyclic ones, regardless of the number of
substituents and stereochemistry, all smoothly delivered the corresponding cyclic carbonates
(3k–3u) with isolated yields ranging from 99% to 52%; however, slightly elevated temperatures
and longer reaction times were necessary in some cases. A range of 1,2ꢀdisubstituted vicinal
diols smoothly underwent the expected carbonylation under ambient reaction conditions,
providing corresponding cyclic carbonates 3k–3p. Diol 2n, equipped with ester functionalities,
produced cyclic carbonate 3n in a relatively low conversion (52%). It seems likely that the ester
functional groups may interact with the TBD catalyst to afford a series of side products. cisꢀ1,2ꢀ
Cyclooctanediol (2q) exhibited good efficiency at 60 and afforded bicyclic carbonate 3q in 96%
yield. Additionally, the TBDꢀcatalyzed reaction successfully provided access to tricyclic
carbonate 3r in an excellent yield of 91% from enantioenriched trisubstituted diol 2r. More
importantly, we were pleased to find that sterically more congested vicinal diol 2s was also well
tolerated and afforded corresponding tetrasubstituted cyclic carbonate 3s in 92% yield, which
cannot be prepared via the coupling of CO2 with 2,3ꢀdimethylꢀ2,3ꢀepoxybutane.51 Gratifyingly,
we also found that the developed reaction conditions are applicable to aromatic 1,2ꢀdiols. Both
catechol (2s) and 4ꢀmethylcatechol (2t) participated in the carbonylation reaction to afford
catechol carbonates 3t and 3u.52
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We conducted a series of experiments to elucidate the reaction mechanism. First, we
investigated which of the sequential alcoholꢀ and phenolꢀsubstitution steps of the hydroxyl
groups in vicinal diol 2 is the rateꢀdetermining step (Scheme 4). To this end, the two sterically
differentiated vicinal diols were each subjected to the standard reaction conditions, and the
1
progress of each reaction was carefully monitored by H NMR (Scheme 4a). Interestingly,
regardless of the steric environment around the secondary hydroxyl groups of 2f and 2h, we did
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not observe any significant differences in the carbonylation rates of these two diols. However,
when a mixture of equal amounts of 2f and 2h was allowed to react under similar reaction
conditions, DPC (1) showed a moderate preference for sterically less demanding 2f over 2h
(Scheme 4b).
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Scheme 4. Rate Comparison Study of Sterically Different Vicinal Diols 3f and 3h. a) Parallel
Comparison b) Competitive Comparison.
As depicted in Scheme 5, these observations indicate that the TBDꢀcatalyzed
transcarbonation of 1 occurs predominantly at the terminal alcohol in 2 via an intermolecular
reaction as the slow, rateꢀdetermining step to liberate the more acidic phenol as the leaving group.
The second intramolecular substitution of the remaining secondary alcohol is a fast step. The
identical kinetic patterns from the rates of DPC consumption and cyclic carbonate formation also
support that the first transcarbonylation step regulates the overall kinetics (Figure 1).
The different product distributions in the competitive experiment led us to hypothesize
that the intermediates and products might be in equilibrium with each other for the competitive
carbonate formation. A crossover experiment performed using a 1:1 mixture of diol 2f and cyclic
carbonate 3h gave the exchange products 3f (22%) and 2h (24%), supporting the results of the
competitive reaction (eq 1).
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Additionally, a commercially available enantioenriched sample of 2a (85.5% ee) was
subjected to identical conditions, and it afforded desired cyclic carbonate 3a in 99% yield with
both nearly complete chirality transfer (>98% enantiospecificity) and retention of the
configuration at the oxygenꢀbearing carbon (eq 2).53 Given the easy availability of a diverse
range of alkylꢀ, arylꢀ, and heteroarylꢀsubstituted 1,2ꢀdiols in enantiopure form, this catalytic
protocol could be a general, convenient route to access chiral cyclic carbonates.54 Moreover, it is
worth mentioning that some transitionꢀmetalꢀcatalyzed cycloaddition reactions of enantiopure
terminal epoxides and carbon dioxide suffer from unexpected partial racemization of the
resulting cyclic carbonates.55,56
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O
O
1st alcohol-phenol
exchange
2nd alcohol-phenol
exchange
O
OH
2
O
PhO
O
O
+
OH
HO
- PhOH
- PhOH
PhO
OPh
R
R
Rate-Determining Step
R
1
3
Scheme 5. Sequential Carbonation between Vicinal Diol and DPC
Figure 1. Rates Comparison of DPC Reacted and Cyclic Carbonate Produced
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O
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OH
OH
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O
OH
+
(1)
+
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OH
30 °C, 1 d
O
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3h
3f
2h
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(22%)
(24%)
O
O
OH
O
O
TBD (2 mol%)
OH
+
(2)
2-Me-THF
30 °C, 2 h
PhO
OPh
1a
(R)-2a
(R)-3a
99% yield
>98% es
Figure 2. Comparison of Catalyst Performance
Lastly, to explore the origin of the high catalytic activity of TBD, we conducted a
comparative study between the TBD catalyst and other strong amidine bases such as DBU and
MTBD in the formation of cyclic carbonate 3a from 2a. For each reaction, the conversion of 2a
1
to 3a was measured by H NMR after 5, 10, and 30 min (Figure 2). Beginning early in the
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reaction, TBD (pKa = 26.0) exhibited a vastly superior catalytic performance over both MTBD
(pKa = 25.5) and DBU (pKa = 24.3). Interestingly, DBU and MTBD promoted the carbonylation
of the diol with almost identical reaction rates. These results suggest that there is no correlation
between the catalytic activity and the basicity of these organosuperbases. Based on previous
experimental and computational studies on TBDꢀmediated transesterification reactions, we
assume that the bifunctional nature of the TBD catalyst might play a central role in the developed
carbonylation reaction.32,57,58 The hydrogenꢀbonding ability of N−H would provide Lewis acidic
character to TBD, which is believed to enhance the reactivity over DBU and MTBD. However,
at present, it is still unclear whether each alcoholꢀphenol exchange reaction occurs via a
nucleophilic addition mechanism or a hydrogen bonding mechanism. Further investigations to
elucidate the precise mechanism of the reaction are currently underway in our laboratory.
In conclusion, we have developed a transitionꢀmetalꢀfree, organocatalytic carbonylation
reaction of vicinal diols using bicyclic guanidine TBD as the catalyst and diphenyl carbonate as
the carbonyl source. This operationally simple protocol is a phosgeneꢀfree, highly efficient
method for the preparation of various highly valuable cyclic carbonates under mild reaction
conditions. The reaction proceeded smoothly with a wide range of vicinal diols including cyclic
and aromatic diols as well as sterically demanding triꢀ and tetrasubstituted diols.59 The reaction
was also amenable to multigram syntheses. The preliminary mechanistic studies suggested that
diphenyl carbonate can be efficiently activated by the TBD catalyst for two consecutive phenolꢀ
and alcoholꢀsubstitution reactions. Future investigations will focus on elucidating the mechanism
of the activation of diphenyl carbonate by this catalyst. The results will be reported in due course.
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EXPERIMENTAL SECTION
General Experimental Methods. Unless otherwise stated, all reagents were purchased from
commercial suppliers and used as received without further purification. Analytical thinꢀlayer
chromatography (TLC) was performed on silica gel 60 F254 glass plates, and spots were
visualized by UV fluorescence (254 nm) quenching and KMnO4 staining. Flash column
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chromatography was performed on silica gel 60 (230–400 mesh). H, C, and F NMR spectra
were recorded on a Bruker Avance III HD 400 MHz Fourier transform NMR spectrometer at
ambient temperature. Chemical shifts are reported in parts per million relative to residual solvent
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CDCl3 (7.26 ppm for 1H and 77.0 ppm for 13C), and coupling (J) constants are expressed in hertz
(Hz). The 1H NMR multiplicities are abbreviated as follows: s = singlet, d = doublet, t = triplet, q
= quartet, dd = doublet of doublets, ddd = doublet of doublet of doublets, ddt = doublet of
doublet of triplets, ddq = doublet of doublet of quartets, dtd = doublet of triplet of doublets, and
m = multiplet. Enantiomeric excess (ee) values were determined using an Agilent 1200 series
HPLC system equipped with a UV detector with Daicel Chiralcel ODꢀH column (5 ꢀm particle
size, 4.5 × 250 mm) at 40 °C. Optical rotation was recorded on a Perkin Elmer polarimeter 241 at
the sodium D line (1.0 dm path length) at 20 °C. Infrared (IR) spectra were recorded on a
Thermo Fisher Nicolet iS5 FTꢀIR Spectrometer using thin film samples on KBr plates, and are
reported in terms of frequency of absorption (cm–1). High resolution mass spectra were obtained
from the Korea Basic Science Institute (Daegu, Korea) on a JEOL JMS 7000 high resolution
spectrometer using the technique of electron impact ionization (EI).
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General Procedure for the Synthesis of Cyclic Carbonates. To a solution of diphenyl
carbonate (1, 0.10 g, 0.50 mmol, 1.0 equiv) and a vicinal diol (0.55 mmol, 1.1 equiv) in 2ꢀMeꢀ
THF (0.8 mL) was added TBD (1.4 mg, 0.010 mmol, 2.0 mol%). The resultant mixture was
stirred in an oil bath at the indicated temperature. After completion of the reaction as determined
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by TLC or H NMR spectroscopy, 1 drop of acetic acid was added to the reaction mixture. The
obtained mixture was directly purified by flash column chromatography on silica gel to afford
the desired cyclic carbonate (hexanes/ethyl acetate was gradually changed from 9:1 to 4:1).
When TLC showed that a cyclic carbonate is essentially copolar with phenol (i.e., 3l and 3m),
the following procedure was applied just prior to flash column chromatography to remove
phenol. Upon completion of the reaction, the reaction mixture was diluted with ethyl acetate. The
mixture was washed successively with 35% NaOH solution (10 mL × 2), water (10 mL × 2) and
brine (10 mL), dried over anhydrous MgSO4, filtered and concentrated using a rotary evaporator
to afford the crude mixture.
Procedure for the Gram Scale Reaction. A 100ꢀmL flask containing a magnetic stir bar was
charged with 1 (3.00 g, 14.0 mmol, 1.00 equiv), 2a (2.13 g, 15.5 mmol, 1.10 equiv), 2ꢀMeꢀTHF
(22 mL), and TBD (38.9 mg, 0.280 mmol, 2.00 mol%). The flask was sealed with a rubber
septum, and the reaction mixture was stirred at 30 °C for 3 h. After completion of the reaction as
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determined by TLC, the reaction was quenched with several drops of acetic acid. After
evaporation of the solvent using a rotary evaporator, the obtained residue was directly purified
by flash column chromatography on silica gel to afford cyclic carbonate 3a as a white solid (2.10
g, 91%).
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4-Phenyl-1,3-dioxolan-2-one (3a):37 Following the general procedure at 30 °C for 2 h, 3a was
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obtained as a white solid (81 mg, 99%). H NMR (400 MHz, CDCl3) δ 7.46−7.40 (m, 3H),
7.37−7.34 (m, 2H), 5.67 (t, J = 8.0 Hz, 1H), 4.79 (t, J = 8.7 Hz, 1H), 4.33 (dd, J = 8.7, 8.0 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ 154.8, 135.7, 129.6, 129.1 (2C), 125.8 (2C), 77.9, 71.1.
4-(p-Tolyl)-1,3-dioxolan-2-one (3b):60 Following the general procedure at 30 °C for 2 h, 3b was
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obtained as a white solid (78 mg, 88%). H NMR (400 MHz, CDCl3) δ 7.16 (s, 4H), 5.55 (t, J =
8.0 Hz, 1H), 4.68 (t, J = 8.4 Hz, 1H), 4.24 (t, J = 8.4 Hz, 1H), 2.29 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 154.9, 139.8, 132.6, 129.8 (2C), 125.9 (2C), 78.0, 71.1, 21.1.
4-(4-Fluorophenyl)-1,3-dioxolan-2-one (3c):61 Following the general procedure at 30 °C for 2 h,
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3c was obtained as a colorless oil (63 mg, 69%). H NMR (400 MHz, CDCl3) δ 7.37−7.34 (m,
2H), 7.14−7.10 (m, 2H), 5.67 (t, J = 8.0 Hz, 1H), 4.80 (t, J = 8.4 Hz, 1H), 4.32 (t, J = 8.4 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ 163.3 (d, J = 248.0 Hz), 154.6, 131.5 (d, J = 3.3 Hz), 127.9
(d, J = 8.6 Hz, 2C), 116.3 (d, J = 22.0 Hz, 2C), 77.4, 71.0; 19F NMR (376 MHz, CDCl3) δ ꢀ111.0.
4-Methyl-4-phenyl-1,3-dioxolan-2-one (3d):62 Following the general procedure at 30 °C for 2 h,
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3d was obtained as a colorless oil (72 mg, 81%). H NMR (400 MHz, CDCl3) δ 7.43−7.39 (m,
2H), 7.37−7.33 (m, 3H), 4.48 (s, 2H), 1.83 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 154.3, 141.0,
128.9 (2C), 128.5, 123.8 (2C), 84.1, 76.2, 27.2.
1,3-Dioxolan-2-one (3e):63 Following the general procedure at 30 °C for 2 h, 3e was obtained as
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a colorless oil (40 mg, 91%). H NMR (400 MHz, CDCl3) δ 4.47 (s, 4H); C NMR (100 MHz,
CDCl3) δ = 155.5, 64.6 (2C).
4-Methyl-1,3-dioxolan-2-one (3f):50 Following the general procedure at 30 °C for 2 h, 3f was
obtained as a colorless oil (46 mg, 90%). 1H NMR (400 MHz, CDCl3) δ 4.83−4.75 (m, 1H), 4.48
(dd, J = 8.4, 8.0 Hz, 1H), 3.95 (dd, J = 8.4, 8.0 Hz, 1H), 1.39 (d, J = 6.4 Hz, 3H); 13C NMR (100
MHz, CDCl3) δ 154.9, 73.4, 70.5, 19.0.
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4-Tetradecyl-1,3-dioxolan-2-one (3g): Following the general procedure at 30 °C for 2 h, 3g was
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obtained as a white solid (0.12 g, 84%). H NMR (400 MHz, CDCl3) δ 4.73−4.66 (m, 1H), 4.51
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(t, J = 8.1 Hz, 1H), 4.05 (dd, J = 8.3, 7.3 Hz, 1H), 1.84−1.75 (m, 1H), 1.72−1.62 (m, 1H),
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1.50−1.15 (m, 24H), 0.87 (t, J = 6.8 Hz, 3H); C NMR (100 MHz, CDCl3) δ 155.0, 77.0, 69.3,
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33.8, 31.9, 29.62, 29.61, 29.60, 29.58, 29.52, 29.4 (2C), 29.2, 29.1, 24.3, 22.6, 14.1.; IR (KBr)
2919, 2847, 1779 (C=O), 1382, 1181, 1073 cm–1; High Resolution MS (EI) Calcd. For C17H32O3
[M]+: 284.2351, Found: 284.2349.
4-(tert-Butyl)-1,3-dioxolan-2-one (3h):64 Following the general procedure at 30 °C for 2 h, 3h
was obtained as a colorless oil (71 mg, 98%). 1H NMR (400 MHz, CDCl3) δ 4.42−4.36 (m, 2H),
13
4.24−4.18 (m, 1H), 0.95 (s, 9H); C NMR (100 MHz, CDCl3) δ 155.1, 83.6, 65.6, 33.3, 24.0
(3C).
4-(Chloromethyl)-1,3-dioxolan-2-one (3i):50 Following the general procedure at 30 °C for 4 h,
3i was obtained as a white solid (53 mg, 78%). 1H NMR (400 MHz, CDCl3) δ 4.97 (dtd, J = 9.0,
5.6, 4.0 Hz, 1H), 4.66−4.56 (m, 1H), 4.39 (dd, J = 9.0, 5.6 Hz, 1H), 3.75 (ddd, J = 16.0, 12.0, 4.0
Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 154.2, 74.3, 66.9, 43.7.
4-((Allyloxy)methyl)-1,3-dioxolan-2-one (3j):37 Following the general procedure at 30 °C for 2
h, 3j was obtained as a colorless oil (74 mg, 94%). 1H NMR (400 MHz, CDCl3) δ 5.89−5.79 (m,
1H), 5.28−5.17 (m, 2H), 4.84−4.78 (m, 1H), 4.48 (t, J = 8.4 Hz, 1H), 4.37 (dd, J = 8.4, 6.0 Hz,
1H), 4.04−4.01 (m, 2H), 3.69−3.56 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 154.9, 133.6, 117.7,
75.0, 72.4, 68.7, 66.1.
4,5-Dimethyl-1,3-dioxolan-2-one (3k):37 Following the general procedure at 30 °C for 12 h, 3k
was isolated as a mixture of two inseparable diastereomers (48 mg, 83%, 88:12 dr). Major
diastereoisomer: 1H NMR (400 MHz, CDCl3) δ 4.86−4.78 (m, 2H), 1.35 (d, J = 6.3 Hz, 6H); 13C
1
NMR (100 MHz, CDCl3) δ 154.6, 76.0 (2C), 14.3 (2C). Minor diastereoisomer: H NMR (400
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MHz, CDCl3) δ 4.36−4.28 (m, 2 H), 1.44 (d, J = 6.0 Hz, 6H); C NMR (100 MHz, CDCl3) δ
154.5, 79.8 9 (2C), 18.3 (2C).
(4S,5R)-4,5-diphenyl-1,3-dioxolan-2-one (3l):65 The general procedure was applied at 40 °C for
12 h. The reaction was quenched with a portion of acetic acid and diluted with ethyl acetate. The
mixture was washed with 35% NaOH (10 mL × 2). The organic layer was washed with water (10
mL × 2) and brine (10 mL) and dried over anhydrous MgSO4. After filtration, the solvents were
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removed under reduced pressure. The crude mixture was purified by flash column
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chromatography on silica gel to afford 3l as a white solid. (106 mg, 88%). H NMR (400 MHz,
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CDCl3) δ 7.19–7.11 (m, 6H), 6.97–6.93 (m, 4H), 5.99 (s, 2H); C NMR (100 MHz, CDCl3) δ
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154.8, 132.8 (2C), 128.8 (2C), 128.2 (4C), 126.1 (4C), 82.1 (2C).
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(4R,5R)-4,5-diphenyl-1,3-dioxolan-2-one (3m):37 The general procedure was applied at 30 °C
for 3 h. The reaction was quenched with a portion of acetic acid and diluted with ethyl acetate.
The mixture was washed with 35% NaOH (10 mL × 2). The organic layer was washed with
water (10 mL × 2) and brine (10 mL) and dried over anhydrous MgSO4. After filtration, the
solvents were removed under reduced pressure. The crude mixture was purified by flash column
chromatography on silica gel to afford 3m as a white solid. (107 mg, 89%). 1H NMR (400 MHz,
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CDCl3) δ 7.46−7.42 (m, 6H), 7.34−7.30 (m, 4H), 5.44 (s, 2H); C NMR (100 MHz, CDCl3) δ
154.0, 134.7 (2C), 129.7 (2C), 129.2 (4C), 126.0 (4C), 85.3 (2C).
Diethyl (4S,5S)-2-oxo-1,3-dioxolane-4,5-dicarboxylate (3n):37 Following the general
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procedure at 100 °C for 12 h, 3n was obtained as a colorless oil (60 mg, 52%). H NMR (400
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MHz, CDCl3) δ 5.09 (s, 2H), 4.34 (q, J = 7.2 Hz, 4H), 1.35 (t, J = 7.2 Hz, 6H); C NMR (100
MHz, CDCl3) δ 166.0 (2C), 152.1, 74.8 (2C), 63.3 (2C), 13.9 (2C).
(3aR,6aS)-Tetrahydro-4H-cyclopenta[d][1,3]dioxol-2-one (3o):37 Following the general
procedure at 30 °C for 3 h, 3o was obtained as a white solid (64 mg, 99%). 1H NMR (400 MHz,
13
CDCl3) δ 5.11−5.07 (m, 2H), 2.15−2.08 (m, 2H), 1.82−1.59 (m, 4H); C NMR (100 MHz,
CDCl3) δ 155.4, 81.9 (2C), 33.0 (2C), 21.4.
(3aR,7aS)-Hexahydrobenzo[d][1,3]dioxol-2-one (3p):37 Following the general procedure at
1
30 °C for 12 h, 3p was obtained as a white solid (62 mg, 87%). H NMR (400 MHz, CDCl3) δ
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4.69−4.64 (m, 2H), 1.89−1.85 (m, 4H), 1.64−1.54 (m, 2H), 1.44−1.35 (m, 2H); C NMR (100
MHz, CDCl3) δ = 155.3, 75.7 (2C), 26.6 (2C), 19.0 (2C).
(3aR,9aS)-Octahydrocycloocta[d][1,3]dioxol-2-one (3q):66 Following the general procedure at
1
60 °C for 6 h, 3q was obtained as a white solid (82 mg, 96%). H NMR (400 MHz, CDCl3) δ
4.71−4.65 (m, 2H), 2.06−1.91 (m, 4H), 1.74−1.65 (m, 2H), 1.55−1.35 (m, 4H), 1.29−1.19 (m,
2H); 13C NMR (100 MHz, CDCl3) δ 154.1, 81.1 (2C), 27.0 (2C), 25.9 (2C), 25.1 (2C).
(3aR,4R,6R,7aS)-3a,5,5-Trimethylhexahydro-4,6-methanobenzo[d][1,3]dioxol-2-one (3r):37
Following the general procedure at 30 °C for 12 h, 3r was obtained as a white solid (89 mg 91%).
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1H NMR (400 MHz, CDCl3) δ 4.58 (dd, J = 8.4, 1.8 Hz, 1H), 2.39−2.33 (m, 2H), 2.20 (t, J = 5.4
Hz, 1H), 2.09−1.99 (m, 2H), 1.55 (s, 3H), 1.33 (s, 3H), 1.28 (d, J = 11.6 Hz, 1H), 0.85 (s, 3H);
13C NMR (100 MHz, CDCl3) δ 154.4, 87.0, 77.2, 50.1, 38.63, 38.62, 33.2, 26.8, 26.7, 25.9, 23.8.
4,4,5,5-Tetramethyl-1,3-dioxolan-2-one (3s):37 Following the general procedure at 100 °C for
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12 h, 3s was obtained as a white solid (66 mg, 92%). H NMR (400 MHz, CDCl3) δ = 1.39 (s,
12H). 13C NMR (100 MHz, CDCl3) δ = 153.8, 85.9 (2C), 22.2 (2C).
Benzo[d][1,3]dioxol-2-one (3t):67 Following the general procedure with 1 (0.75 mmol) and 2t
(0.50 mmol) at 30 °C for 3 h, 3t was obtained as a white solid (44 mg, 64%). 1H NMR (400 MHz,
13
CDCl3) δ 7.28−7.22 (m, 4H); C NMR (100 MHz, CDCl3) δ 151.2, 143.2 (2C), 124.8 (2C),
110.4 (2C).
5-Methylbenzo[d][1,3]dioxol-2-one (3u): Following the general procedure with 1 (0.75 mmol)
1
and 2u (0.50 mmol) at 30 °C for 3 h, 3u was obtained as a white solid (62 mg, 83%). H NMR
(400 MHz, CDCl3) δ 7.11 (d, J = 8.2 Hz, 1H), 7.05 (s, 1H), 7.02−6.99 (m, 1H), 2.40 (s, 3H); 13C
NMR (100 MHz, CDCl3) δ = 151.5, 143.2, 141.1, 135.2, 125.1, 110.8, 109.8, 21.4; IR (KBr)
1832 (C=O), 1640, 1495, 1328, 1263, 1242, 1149, 1035, 955, 923, 870 cm0ꢀ1; High Resolution
MS (EI) Calcd. For C8H6O3[M]+:150.0317, Found: 150.0315.
Procedure for the Reaction Rate Comparison Test of the Carbonylation of Terminal 1,2-
Diols (2f and 2h) with DPC (Scheme 4 and Figure 1). (a) In two separate 4ꢀmL glass vials,
diphenyl carbonate (1) (0.50 mmol, 1.0 equiv) and the respective diols (2f and 2h) (0.55 mmol,
1.1 equiv) were dissolved in 0.8 mL of 2ꢀMeꢀTHF. Then, TBD (1.4 mg, 2.0 mol%) was added to
each vial. The resulting mixtures were stirred at 30 °C. After time intervals of 2 min, 5 min, 10
min, 20 min, 30 min, and 60 min, an aliquot of each reaction mixture was transferred to CDCl3
with a drop of acetic acid. A drop of D2O was added to remove the broad alcohol and residual
water peaks to improve accuracy. The yields of the respective carbonates and the amount of
1
unreacted DPC were calculated from the H NMR spectra by using hexamethylbenzene as an
internal standard.
(b) In a 4 mLꢀglass vial, DPC (1) (0.50 mmol, 1.0 equiv), 2f (0.50 mmol, 1.0 equiv), and 2f (0.50
mmol, 1.0 equiv) were dissolved in 0.8 mL of 2ꢀMeꢀTHF. Then, TBD (1.4 mg, 2.0 mol%) was
added. The resulting mixture was stirred at 30 °C. After time intervals of 2 min, 5 min, 10 min,
20 min, 30 min, and 60 min, an aliquot of the reaction mixture was transferred to CDCl3 with a
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drop of acetic acid. A drop of D2O was added to remove the broad alcohol and residual water
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peaks to improve accuracy. The yields of the formed carbonates were calculated from the H
NMR spectra by using hexamethylbenzene as an internal standard.
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Procedure for the Crossover Experiment between Terminal Diol 2f and Cyclic Carbonate
3h. In a 4 mLꢀglass vial, the cyclic carbonate (3h) (0.50 mmol, 1.0 equiv) and propane 1,2ꢀdiol
(2f) (0.50 mmol, 1.0 equiv) were dissolved in 0.8 mL of 2ꢀMeꢀTHF. TBD (1.4 mg, 2.0 mol%)
was added, and then the resulting mixture was stirred at 30 °C. After one day, an aliquot of the
reaction mixture was transferred to CDCl3 with a drop of acetic acid. A drop of D2O was added
to remove the broad alcohol and residual water peaks to improve accuracy. The yields of the
carbonate (3f) and diol (2h) were calculated from the 1H NMR spectra by using
hexamethylbenzene as an internal standard.
Procedure for the Chirality Transfer Experiment. In a 4 mLꢀglass vial, DPC (1) (0.50 mmol,
1.0 equiv) and (R)ꢀ1ꢀphenylꢀ1,2ꢀethanediol (2a) (0.55 mmol, 1.1 equiv) were dissolved in 0.8
mL of 2ꢀMeꢀTHF. TBD (1.4 mg, 2.0 mol%) was added, and then the resulting mixture was
stirred at 30 °C for 2 h. After evaporation of the solvent using a rotary evaporator, the obtained
residue was directly purified by flash column chromatography on silica gel to afford (R)ꢀ3a as a
white solid (81 mg, 99%). 1H NMR (400 MHz, CDCl3) δ 7.46−7.40 (m, 3H), 7.37−7.34 (m, 2H),
13
5.67 (t, J = 8.0 Hz, 1H), 4.79 (t, J = 8.7 Hz, 1H), 4.33 (dd, J = 8.7, 8.0 Hz, 1H); C NMR (100
MHz, CDCl3) δ 154.8, 135.7, 129.6, 129.1 (2C), 125.8 (2C), 77.9, 71.1. HPLC: Chiralcel ODꢀH
column, 1.0 mL/min, hexane/2ꢀpropanol = 90.0:10.0, 220 nm, tmajor 15.7 min (R), tminor 18.8 min
25
(S). [α]D –37.0 (c 0.68, CHCl3) for 84.0% ee. The ee of a commercial sample of (R)ꢀ2a was
determined to be 85.5%. HPLC: Chiralcel OJꢀH column, 1.0 mL/min, hexane/2ꢀpropanol =
95.0:5.0, 220 nm, tmajor 16.5 min (R), tminor 17.6 min (S).68
Procedure for the Comparison of Catalyst Performance. In three separate 4 mLꢀglass vials,
DPC (1) (0.50 mmol, 1.0 equiv) and 1ꢀphenylꢀ1,2ꢀethanediol (2a) (0.55 mmol, 1.1 equiv) were
dissolved in 0.8 mL of 2ꢀMeꢀTHF. Then, 2.0 mol% of the three different catalysts, 1,5,7ꢀ
triazabicyclo[4.4.0]decꢀ5ꢀene (TBD, 1.4 mg), 1,8ꢀdiazabicyclo[5.4.0]undecꢀ7ꢀene (DBU, 1.5
mg), and 7ꢀmethylꢀ1,5,7ꢀtriazabicyclo[4.4.0]decꢀ5ꢀene (MTBD, 1.5 mg) were added, one
catalyst to each vial. The resulting mixtures were stirred at 30 °C. After time intervals of 5 min,
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10 min, and 30 min, an aliquot of each reaction mixture was transferred to CDCl3 with a drop of
acetic acid. A drop of D2O was added to remove the broad alcohol and residual water peaks to
1
improve accuracy. The yields of the formed cyclic carbonate (3a) were calculated from the H
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NMR spectra by using hexamethylbenzene as an internal standard.
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ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website. Copies
of NMR spectra, HPLC traces and DSC data (PDF)
Corresponding Authors
*J.G.K.: eꢀmail, jeunggonkim@jbnu.ac.kr
*J.H.L.: eꢀmail, leejunhee@dongguk.ac.kr
ORCID
Jeung Gon Kim: 0000ꢀ0003ꢀ1685ꢀ2833
Jun Hee Lee: 0000ꢀ0003ꢀ4108ꢀ5074
Ek Raj Baral: 0000ꢀ0002ꢀ8834ꢀ630X
Notes
The authors declare no competing financial interest.
ACKNOWLEDGEMENTS
This research was supported by the National Research Foundation of Korea (NRFꢀ
2018R1D1A1B07048318 to J.G.K. and 2017R1D1A1B03029926 to J.H.L.) and the Dongguk
University Research Fund of 2018 (J.H.L.). We sincerely thank prof. Seung Hwan Cho and Mr.
Yeosan Lee (POSTECH) for acquiring the HPLC data.
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