Intramolecular etherification of five-membered cyclic carbonates bearing hydroxyalkyl groups

Article abstract of DOI:10.1039/c2gc35265f

We report a new one-pot synthetic route to tetrahydrofuran derivatives, which were unexpectedly produced under basic conditions by intramolecular etherification of substituted five-membered cyclic carbonates. For alcohols with vicinal hydroxyl groups, and additional OH groups at the β-position, intramolecular etherification leading to 3-hydroxytetrahydrofuran derivatives was observed. These reactions were studied for compounds having from 2 to 6 hydroxyl groups per molecule, and the mechanism was proposed. The developed method provides a new environmentally friendly approach to the synthesis of five-membered cyclic ether derivatives under non-acidic conditions. The Royal Society of Chemistry.

Full text of DOI:10.1039/c2gc35265f

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PAPER
Intramolecular etherification of five-membered cyclic carbonates bearing
hydroxyalkyl groups†
Karolina M. Tomczyk, Piotr A. Guńka, Paweł G. Parzuchowski, Janusz Zachara and Gabriel Rokicki*
Received 21st February 2012, Accepted 28th March 2012
DOI: 10.1039/c2gc35265f
We report a new one-pot synthetic route to tetrahydrofuran derivatives, which were unexpectedly
produced under basic conditions by intramolecular etherification of substituted five-membered cyclic
carbonates. For alcohols with vicinal hydroxyl groups, and additional OH groups at the β-position,
intramolecular etherification leading to 3-hydroxytetrahydrofuran derivatives was observed. These
reactions were studied for compounds having from 2 to 6 hydroxyl groups per molecule, and the
mechanism was proposed. The developed method provides a new environmentally friendly approach to
the synthesis of five-membered cyclic ether derivatives under non-acidic conditions.
reactions are equipment corrosion and high separation costs.8
Recently, some solid acid catalysts based on zeolite or ion
Introduction
Cyclic carbonates are synthesized with the use of carbon dioxide
– a cheap, easily available but environmentally burdensome
exchange resin have been developed and used in etherification
processes.9 Anhydro sugar alcohols find application as thera-
peutics, food additives, surfactants and in polymers synthesis.10
starting material. They can be obtained almost directly from oxi-
ranes and carbon dioxide, or indirectly in the reaction of vicinal
diols with a “green monomer” – dimethyl carbonate. In combi-
nation with diamines biscyclic carbonates give way to the for-
mation on non-isocyanate polyurethanes. However, cyclic
carbonates bearing substituents containing free hydroxyl groups
alone can be a source of many valuable compounds.
Cyclic ethers such as tetrahydrofuran are easily available from
1,4-diols by a cyclodehydration reaction carried out under acidic
conditions.1 However, when secondary and tertiary alcohols are
used elimination and isomerization takes place besides the intra-
molecular etherification.
In the case of 1,4-diols containing an additional hydroxyl
group at the 2-position or two OH groups at the 2-positions, 3,3-
hydroxytetrahydrofuran or 3,4-dihydroxytetrafuran are produced,
respectively. The synthesis of 3-hydroxytetrahydrofuran from
( )-1,2,4-butanetriol in the presence of p-toluenesulfonic acid
monohydrate was described by Belleau and Au-Young.2 Obtain-
ing 3,4-dihydroxytetrahydrofuran from meso-erythritol carried
out in the presence of trifluoromethanesulfonic acid3 or p-tolue-
nesulfonic acid was reported by Arceo et al.4
Isosorbide, a diol containing two fused THF rings, is indust-
rially produced by dehydration of sorbitol using a strong acid
catalyst.5 Typical catalysts are sulfuric acid,6 hydrochloric acid
and phosphoric acid.7 The disadvantages of the acid catalyzed
It is also known that four-membered cyclic ethers, oxetanes,
can be easily obtained from the respective triols through six-
membered cyclic carbonates via intramolecular etherification. 3-
Methyl-3-hydroxymethyloxetane can be obtained in high yield
(81%) in the reaction of 1,1,1-tris(hydroxymethyl)ethane with
diethyl carbonate in the presence of basic catalyst (KOH).11 The
synthesis proceeds by intramolecular etherification of the six-
membered cyclic carbonate with the methylol group (Scheme 1).
According to the same reaction pathway, 3-ethyl-3-hydroxy-
methyloxetane was obtained from trimethylolpropane.12
As far as five-membered cyclic carbonate is concerned,
depending on the catalyst and chemical structures of reagents,
the reaction of alcohols with 1,3-dioxolan-2-ones can proceed
according to two different mechanisms, in which after deproto-
nation alkoxy group attacks carbonyl carbon atom (reaction a) or
alkyl carbon atom (reaction b) of the cyclic carbonate
(Scheme 2).
The reaction (a) in which linear carbonate linkages are formed
is reversible, whereas reaction (b), in which ether linkages are
formed, is irreversible. As a consequence, even for a very low
etherification reaction rate, after long reaction times the for-
mation of ether derivatives is observed in relatively high yields.
Faculty of Chemistry, Warsaw University of Technology, Noakowskiego
3, 00-664 Warsaw, Poland. E-mail: gabro@ch.pw.edu.pl; Fax: + 48 22
628 2741; Tel: + 48 22 234 7562
†Electronic supplementary information (ESI) available: additional spec-
troscopic, and crystallographic data. CCDC numbers 868593–868594.
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c2gc35265f
Scheme 1 Synthesis of 3-methyl-3-hydroxymethyloxetane from 1,1,1-
tris(hydroxymethyl)ethane and diethyl carbonate.11
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Scheme 2 Two reaction pathways of five-membered cyclic carbonates
with alcohols.
In our earlier work13 it was reported that the presence of alkaline
catalysts favors etherification. In the reaction of ethylene carbon-
ate with 1,6-hexanediol at 140 °C in the presence of K2CO3
mainly oligo(oxyethylene)s were formed. On the other hand, the
reaction carried out in the presence of a neutral catalyst such as
NaCl led to oligo(hexamethylene carbonate)s with high selectiv-
ity. However, when the reaction temperature was increased
(170 °C), a higher extent of etherification was observed again. It
should be mentioned that the length of the diol hydrocarbon
chain strongly influences etherification. For a shorter diol, such
as 1,4-butanediol, even in the presence of NaCl at 145 °C the
product containing 60% of oligo(oxyethylene) fragments was
obtained. A similar effect was observed for diols containing het-
eroatoms such as oxygen and sulfur at the β-position in relation
to the OH group and polyethers are formed almost selectively.
When propylene carbonate was used instead of ethylene carbon-
ate in the reaction with alcohols, etherification was dramatically
suppressed. The steric effect and the presence of electron donat-
ing methyl groups in the 1,3-dioxolan-2-one ring directs the
alkoxy group attacks selectively on the carbonyl carbon atom
and only a small amount of ether units was present in the
product. Thus, the reaction of 1,4-butanediol with propylene car-
bonate at 155 °C even in the presence of an alkaline catalyst
such as K2CO3 proceeds with formation of mainly oligo(tetra-
methylene carbonate)s.13
In the case of alkyl substituted five-membered cyclic carbon-
ates containing an OH group at the α-position in relation to the
1,3-dioxolan-2-one ring, no intramolecular etherification leading
to 3-hydroxyoxetane was observed.14 In the reaction of glycerol
with dimethyl carbonate in the presence of K2CO3 carried out
under mild conditions 5-hydroxymethyl-1,3-dioxolan-2-one is
formed almost quantitatively (Scheme 3). At higher temperatures
(>170 °C) intermolecular etherification takes place and hyper-
branched polyglycerol is produced.14 When the reaction was
carried out at 180 °C under vacuum in the presence of zeolite A
or γ-alumina catalyst, glycidol could be distilled off in a rela-
tively high yield (86%).15
Scheme 3 Synthesis of 5-hydroxymethyl-1,3-dioxolan-2-one and its
derivatives in the reaction of glycerol with dimethyl carbonate in the
presence of potassium carbonate.14,15
stoichiometric amount of triethylamine hydrochloride as a bur-
densome waste. Recently, instead of chlorine containing
reagents, for the synthesis of five- and six-membered cyclic
carbonates dimethyl carbonate (DMC) has been applied. DMC is
a cheap and easily available “green” monomer produced on
industrial scale, that makes the method based on DMC very
convenient.20
Results and discussion
In the present study we have investigated the possibility of
obtaining tetrahydrofuran derivatives containing additionally
cyclic carbonate rings from substituted five-membered cyclic
carbonates with hydroxyl groups at β-position in relation to the
carbonate ring. The reaction mechanisms have been proposed
and discussed, especially those for processes in which carbo-
hydrates were used as starting materials.
It was found that substituted five-membered cyclic carbonate
containing hydroxyl groups at β-position in relation to carbonate
ring undergoes after longer time (21 h) intramolecular etherifica-
tion in the presence of basic catalyst such as K2CO3 heated at
80 °C, and as a result 3-hydroxytetrahydrofuran (3) is formed as
a main product. However, after short time (5 h) in the reaction of
( )-1,2,4-butanetriol with dimethyl carbonate the main product,
depending on molar ratio of reagents, was 4-(2-hydroxyethyl)-
1,3-dioxolan-2-one (1) or 4-(3,5-dioxa-4-oxyhexyl)-1,3-
dioxolan-2-one (5) (Scheme 4). To obtain cyclic carbonate 1 in a
high yield, the reaction should be carried out at the first stage
under reflux without removing methanol from the reaction
mixture.
Five- and six-membered cyclic carbonates can be obtained
according to two main synthetic routes. The first one is the
addition reaction of carbon dioxide to cyclic ethers such as oxi-
ranes16 or oxetanes.17 In the second method, 1,2- or 1,3-diols are
used as starting materials in the reaction with phosgene or its
derivatives (diphosgene or triphosgene).18 Ariga et al.19 devel-
oped a method for the synthesis of six-membered cyclic
carbonates using ethyl chloroformate and triethylamine. The dis-
advantage of the latter two methods is the formation of a
When ( )-1,2,4-butanetriol was reacted with dimethyl carbon-
ate used in stoichiometric ratio at 80 °C in the presence of pot-
assium carbonate, 4-(2-hydroxyethyl)-1,3-dioxolan-2-one (1)
was obtained in high yield (93%) after 5 h. For higher excesses
of DMC, butanetriol dicarbonate (5) was obtained. Under the
same reaction conditions, but for longer reaction time (21 h)
mainly 3-hydroxytetrahydrofuran (3) was obtained (Scheme 4).
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Scheme 6 Reaction of ( )-1,2,6-hexanetriol with dimethyl carbonate
in the presence of potassium carbonate.
Scheme 4 Reaction of ( )-1,2,4-butanetriol with dimethyl carbonate in
the presence of potassium carbonate.
Scheme 5 Reaction of 1,4-butanediol with dimethyl carbonate in the
presence of sodium methoxide.
Scheme 7 Reaction of meso-erythritol with dimethyl carbonate in the
presence of potassium carbonate.
It is worth mentioning that Ren and Liu21 obtained 1 starting
from ( )-1,2,4-butanetriol in a five step process, including the
protection and deprotection strategy.
The five-membered cyclic ether 2 is produced according to
the mechanism, in which the primary alkoxy group attacks the
alkyl carbon atom in the 1,3-dioxolan-2-one ring (reaction a,
Scheme 4) and as a result an unstable hydrocarbonate group is
formed, which after decarboxylation is transformed into a
hydroxyl group. This reaction is irreversible. The primary alkoxy
group of 1 can also attack the carbonyl carbon atom of the cyclic
carbonate (reaction b) leading to a less stable six-membered
cyclic carbonate (6). Thus, taking into account that the latter
reaction is reversible, more product of the irreversible reaction
should be present in the reaction mixture after longer times.
Moreover, the intramolecular etherification of 4-(hydroxy-
methyl)-1,3-dioxan-2-one (6) also leads to 3. It was observed
that a higher excess of DMC in the first step suppresses the for-
mation of cyclic ether 3 (Scheme 4).
(8) (79%), and 4-(5,7-dioxa-6-oxyhexyl)-1,3-dioxolan-2-one (9)
(67%), depending on the molar ratio of the reactants used. The
seven-membered cyclic ether oxepan-2-ol (10) was not identified
in the postreaction mixture (Scheme 6). Intramolecular etherifica-
tion of 8 does not proceed due to the relatively small kinetic
effect of the formation of unstable seven-membered cyclic ether
– oxepan-2-ol (10). After long heating times, intermolecular
etherification takes place and the branched polyether 11 is
obtained.
It was observed by us that the presence of additional hydroxyl
groups at the α-position in relation to the five-membered carbon-
ate ring in 4-(hydroxymethyl)-1,3-dioxolan-2-one enhances
intramolecular etherification and a tetrahydrofuran ring is pro-
duced even in the presence of a neutral catalyst and at relatively
low reaction temperatures.
It should be mentioned that when 1,4-butanediol was used in
the reaction with dimethyl carbonate (Scheme 5) a very small
extent of intramolecular etherification was observed for the reac-
tion carried out at 90 °C in the presence of basic catalyst such as
K2CO3. The use of a much stronger base like sodium methoxide
led to the formation of tetrahydrofuran (7) in much higher yield
(48%, after 4 h at 90 °C) (Scheme 5).
In the case of alkyl substituted five-membered cyclic carbon-
ate containing hydroxyl groups at the γ-position in relation to the
carbonate ring, no intramolecular etherification under these con-
ditions was observed. In the reaction of ( )-1,2,6-hexanetriol
with DMC carried out at 80 °C in the presence of K2CO3, two
products were obtained: 4-(4-hydroxybutyl)-1,3-dioxolan-2-one
When meso-erythritol [(2R,3S)-butane-1,2,3,4-tetraol] con-
taining four vicinal hydroxyl groups was reacted with dimethyl
carbonate in stoichiometric ratio at 90 °C in the presence of
K2CO3, (3R,4S)-3,4-dihydroxytetrahydrofuran (14) was obtained
in high yield (86%) (Scheme 7).
It was found that at the reaction beginning, 4-(1,2-dihydroxy-
ethyl)-1,3-dioxolan-2-one (12) is formed as an intermediate.
In the FTIR spectrum of the intermediate an absorption band at
1789 cm−1, which is characteristic for a carbonyl group of a five-
membered cyclic carbonate can be observed. This absorption
band disappeared after 12 h of heating at 90 °C (Fig. 1).
This reaction proceeds according to the same mechanism
discussed for ( )-1,2,4-butanetriol. Moreover, the presence of
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Fig. 1 FTIR (KBr) spectra of the intermediates of the reaction of
meso-erythritol with stoichiometric molar ratio of dimethyl carbonate
carried out at 90 °C in the presence of K2CO3 after: (a) 7 h, (b) 8 h, (c)
12 h.
Fig. 3 ORTEP plot of the molecular structure of 15. Thermal ellip-
soids are drawn at 50% probability level.
Scheme 8 Synthesis of (4R,4′S)-4,4′-bi(1,3-dioxolane-2-one) (16) in
the reaction of meso-erythritol with an excess of dimethyl carbonate in
the presence of potassium carbonate at 70 °C.
1.3379(16)–1.3417(16) Å for the bridging oxygen atoms. These
values are typical for five-membered carbonate rings retrieved
from the Cambridge Structural Database (CSD)22 – 1.191(8) Å
and 1.342(11) Å for terminal and bridging oxygen atoms,
respectively.23 Individual molecules are connected in a 3D
network via C–H⋯O hydrogen bonds. Double columns of mol-
ecules connected via hydrogen bridges involving tetrahydrofuran
oxygen atoms and carbon atoms adjacent to them may be distin-
guished in the supramolecular organisation in the structure
(C4–H4B⋯O4i hydrogen bond, where i = −1/2 + x, 3/2 − y,
1 − z). Such columns, exhibiting the symmetry of p21 rod group,
are in turn connected into a spatial structure via hydrogen
bonds involving terminal oxygen atoms of the carbonate group
(C4–H4A⋯O1ii hydrogen bond, where ii = 1 − x, 1/2 + y,
1/2 − z).
Fig. 2 1H NMR (400 MHz, CDCl3) spectrum of 15.
an additional OH group enhances the attack on the alkyl
carbon atom of the cyclic carbonate due to the formation of
intramolecular hydrogen bonds with the carbonyl groups and the
tetrahydrofuran derivative 14 if formed in a relatively short time.
It was found that when the reaction of meso-erythritol was
carried out with molar excess of dimethyl carbonate under the
same reaction conditions, (1R,5S)-2,4,7-trioxa-3-oxy-bicyclo
[3.3.0]octane (15) a bicyclic derivative of tetrahydrofuran and
1,3-dioxolan-2-one was formed in high yield (Scheme 7). The
1
product structure was confirmed by H and 13C NMR, HRMS,
FTIR as well as X-ray crystallography. The methylene group
protons appear as dd and ddd at 4.27 and 3.56 ppm, respectively.
The methine group protons appear as a dd at 5.20 ppm (Fig. 2).
In the 13C NMR spectrum of 15 the signals corresponding to the
methine and methylene carbon atoms are present at 79.99 and
72.94 ppm, respectively (Fig. S1†). The signal at 154.36 ppm
can be assigned to a carbonyl carbon atom of cyclic carbonate.
In the FTIR spectrum an absorption band corresponding to the
carbonyl group of the five-membered cyclic carbonate
(1793 cm−1) was present and no absorption band of the hydroxyl
group was observed.
The structure of compound 15 is depicted in Fig. 3 and
selected bond lengths and angles are collected in Table S1.† It
consists of two edge-sharing rings one of which adopts an envel-
ope conformation – the tetrahydrofuran ring, and the other is flat
– the carbonate ring. The angle between the mean ring planes
equals 103.51(7)°. The carbonate ring is strained with C–O dis-
tances equal to 1.1969(16) Å for the terminal oxygen atom and
As it was earlier found, lowering the reaction temperature
reduces the extent of etherification. In the reaction of meso-
erythritol with an excess of DMC carried out at 70 °C in the
presence of K2CO3 biscyclic carbonate 16 can be obtained and
isolated (Scheme 8). However, the yield of (4R,4′S)-4,4′-bi(1,3-
dioxolane-2-one) (16) was rather low (5%). The structure of 16
1
1
was confirmed by H and 13C NMR, HRMS, and FTIR. The H
NMR spectrum of the biscyclic carbonate 16 is similar to that of
(1R,5S)-2,4,7-trioxa-3-oxy-bicyclo[3.3.0]octane 15. The methine
group protons appear in the range of 5.16–5.10 ppm as a multi-
plet, but the methylene group protons appear at 4.60 and
4.39 ppm as two doublets of doublets (Fig. 4). In the 13C NMR
spectrum the signals corresponding to the methine and methyl-
ene carbon atom are present at 74.91 and 64.68 ppm, respect-
ively. There is also one signal at 154.16 ppm, which is assigned
to the carbonyl carbon atom of biscyclic carbonate (Fig. S2†). In
the FTIR spectrum two absorption bands corresponding to the
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carbonyl group of cyclic carbonate (1807 and 1783 cm−1) were
observed and no absorption band characteristic for the hydroxyl
groups was found.
The application of ethylene carbonate instead of dimethyl car-
bonate and a neutral catalyst such as NaCl in the reaction with
meso-erythritol led almost exclusively to (1R,5S)-2,4,7-trioxa-3-
oxy-bicyclo[3.3.0]octane (15) (yield 96%), despite the lower
reaction temperature (70 °C). The process was carried out with
the use of toluene as an azeotrope-forming solvent removing
ethylene glycol from the reaction system.
It was found that intramolecular etherification of cyclic car-
bonate can proceed also with secondary OH groups. However, in
contrast to primary OH groups (meso-erythritol), this etherifica-
tion needs longer reaction times or higher temperatures. Thus,
D-sorbitol [(2S,3R,4R,5R)-hexane-1,2,3,4,5,6-hexol] containing
six vicinal hydroxyl groups in a molecule in the reaction with
dimethyl carbonate carried out at 90 °C in the presence of
K2CO3, produces (1R,4S,5R,6R)-6-(1,3-dioxolan-2-one-4-yl)-
2,4,7-trioxa-3-oxy-bicyclo[3.3.0]octane (20) in 43% yield
(Scheme 9). Increasing the reaction temperature (above 110 °C)
in the presence of the same catalyst causes additional intramole-
cular etherification and isosorbide (22) as a final product is
obtained (Scheme 9).
The reaction of D-sorbitol with dimethyl carbonate in the pres-
ence of a basic catalyst can proceed according to two reaction
pathways (Scheme 9). When the reaction started from primary
hydroxyl group at position 6, 4-(1,2,3,4-tetrahydroxybutyl)-1,3-
dioxolan-2-one (17) is formed (pathway a) as an intermediate.
Then, as a result of the attack of the secondary alkoxy group on
the methylene group of cyclic carbonate, followed by decarboxy-
lation, 3,6-sorbitan [(3S)-2-(1,2-dihydroxyethyl)-3,4-dihydroxy-
tetrahydrofuran] (18) is produced (Scheme 9). It should be added
that similarly to the reaction of DMC with meso-erythritol, six-
membered cyclic carbonate 23 can be formed as an intermediate.
Moreover, in this case six-membered cyclic carbonate containing
alkyl substituents at positions 4 and 6 are more stable as was
observed by Rokicki et al.24 and Hatano et al.1
At the next step, under an excess of DMC, the intermediate
with a five-membered cyclic carbonate (19) is formed. The inter-
mediate 19 is transformed into (1R,4S,5R,6R)-6-(1,3-dioxolan-
2-one-4-yl)-2,4,7-trioxa-3-oxy-bicyclo[3.3.0]octane (20) in the
reaction with an excess of DMC or by intramolecular etherifica-
tion into isosorbide (22). Higher temperatures (>110 °C)
enhance the etherification. (1R,4S,5R,6R)-6-(1,3-Dioxolan-2-
one-4-yl)-2,4,7-trioxa-3-oxy-bicyclo[3.3.0]octane, due to high
melting point (215–216 °C) can be easily purified by recrystalli-
zation from acetonitrile. The structure of 20 was confirmed by
1H and 13C NMR (Fig. 5 and S3†), HRMS, FTIR, as well as
X-ray crystallography. In the FTIR spectrum two absorption
bands corresponding to the carbonyl group of different cyclic
carbonates (1806 and 1777 cm−1) were observed and no absorp-
tion band of the hydroxyl group was found.
Fig. 4 1H NMR (400 MHz, DMSO-d6) spectrum of 16.
Scheme 9 Reaction of D-sorbitol with dimethyl carbonate carried out in the presence of potassium carbonate.
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organisation of molecules in the crystal structure of 20 is analo-
gous to that present in compound 15 even though a bulky substi-
tuent was introduced into compound 20. Neighbouring
molecules related by a 21 screw axis are connected via C–H⋯O
hydrogen bonds into columns, which are in turn linked with one
another in a 3D network.
Experimental
Materials
( )-1,2,4-Butanetriol (BDH Laboratory Reagent), ( )-1,2,6-hexa-
netriol (Koch–Light Laboratories LTD), (2R,3S)-butane-1,2,3,4-
tetraol (Sigma), sodium methoxide, dimethyl carbonate (Sigma-
Aldrich), ethylene carbonate (Aldrich), D-sorbitol, potassium
carbonate, sodium chloride, anhydrous magnesium sulfate,
hydrochloric acid, 1,4-dioxane, dichloromethane, toluene, tetra-
hydrofuran, acetone, acetonitrile, ethyl acetate, hexane (Polish
Chemical Reagents, Gliwice) were used as received.
Fig. 5 1H NMR (400 MHz, DMSO-d6) spectrum of 20.
Measurements
IR spectra were recorded on a Biorad FTIR spectrometer (KBr
pellets). 1H NMR and 13C NMR spectra were recorded on a
Varian VXR 400 MHz spectrometer. The two-dimensional NMR
spectra were recorded on Varian VNMRS 600 MHz spec-
trometer. Chemical shifts are reported in δ units and coupling
constants are reported in Hz. Deuterated solvents were used and
tetramethylsilane served as internal standard. High-resolution
(HR) electrospray ionisation (ESI) mass spectra were recorded
on a LCMS IT-TOF instrument. Optical rotation was measured
at the sodium line at ambient temperature in acetonitrile solution.
Single crystals of 15 and 20 were grown from dichloromethane–
hexane mixture and acetonitrile, respectively. Suitable monocrys-
tals were selected under a polarizing microscope, mounted in
inert oil (Immersion Oil type A, Cargill) and transferred to the
cold gas stream of the diffractometer. Diffraction data were
measured on the Agilent κ-CCD Gemini A Ultra diffractometer
at 100(2) K with mirror-focused Cu-Kα radiation for 15 and
with graphite-monochromated Mo-Kα radiation for 20. Cell
refinement and data collection as well as data reduction
and analysis were performed with the CrysAlisPRO software.25
The structures were solved by direct methods and subsequent
Fourier-difference synthesis with SHELXS-97 and refined
by full-matrix least-squares against F2 with SHELXL-9726
within the OLEX2 program suite.27 All non-hydrogen atoms
were refined anisotropically. Hydrogen atoms except for H2, H5
in compound 15, H2 and H3 in compound 20 were introduced at
calculated positions and refined as riding atoms with isotropic
displacement parameters equal to 1.2 times that of the parent
atoms. In case of compound 20 the absolute structure was not
determined basing on diffraction experiment and the absolute
configuration was assigned to agree with that of the molecule’s
precursor. Data were analysed using OLEX2 and PLATON.28
Fig. 3 and 6 were created using ORTEP-3 for Windows.29
Crystal data and structure refinement parameters are given in
Table S3.†
Fig. 6 ORTEP plot of the molecular structure of 20. Thermal ellip-
soids are drawn at 50% probability level.
When the reaction of D-sorbitol with DMC starts from the OH
group at position 1 (reaction pathway b, Scheme 9) 1,4-sorbitan
[(3S)-2-(1,2-dihydroxyethyl)-3,4-dihydroxytetrahydrofuran] (25)
as the intermediate is produced. As it can be noticed in this tetra-
hydrofuran derivative, two hydroxyl groups are in trans
configuration and biscyclic carbonate like 20 can not be formed
due to the high stress of the potential five-membered carbonate
ring. The final product, isosorbide (22), is produced according to
both reaction pathways.
Selected geometrical parameters of 20 determined from X-ray
crystal study are given in Table S3.† The molecule of compound
20, presented in Fig. 6, can be derived from the molecule of
compound 15 by substituting the H3B hydrogen with a flat ring
of ethylene glycol carbonate. The C–O bond lengths in the car-
bonate groups are typical for systems containing five-membered
carbonate rings. They are equal to 1.1972(19) Å and 1.202(2) Å
for terminal oxygen atoms and range from 1.333(2) to 1.3411
(19) Å for the bridging ones. The angle between mean ring
planes of the fused carbonate and tetrahydrofuran rings is
slightly larger than in compound 15 and equals 107.29(9)°,
whereas the C3C5C6O5 dihedral angle, describing the mutual
orientation of the other carbonate ring and the tetrahydrofuran
ring amounts to 68.74(18)°. The tetrahydrofuran ring adopts
an envelope conformation. Interestingly, the supramolecular
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1
Synthesis of 4-(2-hydroxyethyl)-1,3-dioxolan-2-one (1)
yellow liquid (yield 67%) was obtained. H NMR (400 MHz,
CDCl3): 4.91–4.82 (m, 1H, CHcyc.), 4.59 (dd, 1H, CH2cyc., J1 =
8.0 Hz, J2 = 8.5 Hz), 4.38–4.23 (m, 2H, CH2OC(O)O), 4.14 (dd,
1H, CH2cyc., J1 = 7.3 Hz, J2 = 8.6 Hz), 3.79 (s, 3H, CH3),
2.21–2.07 (m, 2H, CH2CH2O). 13C NMR (400 MHz, CDCl3):
155.43 (CvOcyc.), 154.74 (CvOlin.), 74.16 (CHcyc.), 69.45
(CH2cyc.), 63.75 (CH2OC(O)O), 55.29 (CH3), 33.31 (CHCH2).
FTIR (KBr): 2962–2873 (C–H), 1803 (CvOcyc.), 1749
(CvOlin.), 1284–1264 (C–O), 1174–1063 (C–O), 792 (linear
carbonate), 774 (carbonate ring).
In a 25 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 1.36 g (0.0128 mol) of ( )-1,2,4-
butanetriol, 1.15 g (0.0128 mol) of dimethyl carbonate, and
0.02 g (0.14 mmol) of potassium carbonate were placed. The
reaction was carried out at 80 °C, and the reaction progress was
monitored by TLC. After the disappearance of the starting
material, methanol was distilled off under reduced pressure.
Then, the residue was washed with 3% HCl, water and extracted
with ethyl acetate (3 × 30 cm3). The combined organic phases
were dried by anhydrous magnesium sulfate, and evaporated to
dryness. The product was purified by column chromatography
(silica gel, ethyl acetate). 1.34 g of 1 as colorless liquid (yield
79%) was obtained. 1H NMR (400 MHz, CDCl3): 4.97–4.88
(m, 1H, CHcyc.), 4.59 (dd, 1H, CH2cyc., J1 = 7.9Hz, J2 = 8.5 Hz),
4.19 (dd, 1H, CH2cyc., J1 = 7.5 Hz, J2 = 8.6 Hz), 3.87–3.74
(m, 2H, CH2OH), 2.24 (bs, 1H, OH), 2.09–1.91 (m, 1H,
CH2CH2OH). 13C NMR (400 MHz, CDCl3): 155.03 (CvO),
75.03 (CHcyc.), 69.68 (CH2cyc.), 57.85 (CH2OH), 35.85
(CH2CH2OH). FTIR (KBr): 3400 (OH), 2959–2892 (C–H),
1790 (CvO), 1182–1064 (C–O), 777 (carbonate ring).
Synthesis of 4-(4-hydroxybutyl)-1,3-dioxolan-2-one (8)30
In a 25 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 2.55 g (0.0190 mol) of ( )-1,2,6-
hexanetriol, 1.71 g (0.0189 mol) of dimethyl carbonate, and
0.03 g (2.17 mmol) of potassium carbonate were placed. The
reaction was carried out at 80 °C, and the reaction progress was
monitored by TLC. After the disappearance of the starting
material, methanol was distilled off under reduced pressure.
Then, the residue was washed with 3% HCl, water and extracted
with dichloromethane (3 × 30 cm3). The combined organic
phases were dried with anhydrous magnesium sulfate, and evap-
orated to dryness. The product was purified by column chrom-
atography (silica gel, tetrahydrofuran). 1.86 g of 8 as a colorless
Synthesis of 3-hydroxytetrahydrofuran (3)2
In a 25 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 5.01 g (0.0472 mol) of ( )-1,2,4-
butanetriol, 4.25 g (0.0472 mol) of dimethyl carbonate, and
0.06 g (4.35 mmol) of potassium carbonate were placed. Reac-
tion was carried out at 80 °C, and the reaction progress was mon-
itored by FTIR spectroscopy until complete decay of the
absorption band corresponding to carbonyl groups. Then, metha-
nol was distilled off under reduced pressure. The product was
purified by vacuum distillation (111–112 °C, 4 mmHg) to afford
3 as a colorless liquid (yield 93%). 1H NMR (400 MHz,
CDCl3): 4.39 (ddt, 1H, CHOH, J1 = 1.9 Hz, J2 = 3.8 Hz, J3 =
5.7 Hz), 3.88 (dt, 1H, CH2CH2O, J1 = 7.0 Hz, J2 = 8.5 Hz),
3.74 (dt, 1H, CH2CH2O, J1 = 4.1 Hz, J2 = 8.5 Hz), 3.69 (dd,
1H, CHCH2O, J1 = 3.9 Hz, J2 = 9.7 Hz), 3.65 (ddd, 1H,
CHCH2O, J1 = 1.9 Hz, J2 = 9.7 Hz, J3 = 1.0 Hz), 1.99 (ddt, 1H,
CH2CH2O, J1 = 5.7 Hz, J2 = 8.7 Hz, J3 = 13.3 Hz), 1.82 (m,
1H, CH2CH2O). 13C NMR (400 MHz, CDCl3): 75.24
(CHCH2O), 71.38 (CHOH), 66.57 (CH2CH2O), 35.14
(CH2CH2O). FTIR (KBr): ν = 3401 (O–H), 2951–2876 (C–H),
1122–1048 (C–O). Analysis of the isolated product was consist-
ent with that reported in the reference.
1
liquid (yield 61%) was obtained. H NMR (400 MHz, CDCl3):
4.76–4.66 (m, 1H, CHcyc.), 4.53 (t, 1H, CH2cyc., J = 8.2 Hz),
4.14 (t, 1H, OH, J = 6.3 Hz), 4.07 (dd, 1H, CH2cyc., J1 = 7.2 Hz,
J2 = 8.5 Hz), 3.65 (t, 2H, CH2OH, J = 6.1 Hz), 1.88–1.78
(m, 1H, CH2CH), 1.78–1.67 (m, 3H, CH2CH + CH2CH2OH),
1.65–1.54 (m, 1H, CH2CH2CH), 1.54–1.41 (m, 1H,
CH2CH2CH). 13C NMR (400 MHz, CDCl3): 155.69 (CvOcyc.),
69.29 (CHcyc.), 67.25 (CH2cyc.), 62.14 (CH2OH), 33.57
(CH2CH), 28.10 (CH2CH2OH), 20.80 (CH2CH2CH). FTIR
(KBr): 3528 (O–H), 2945–2870 (C–H), 1791 (CvOcyc.), 1268
(C–O), 1173–1063 (C–O), 776 (carbonate ring).
Synthesis of 4-(5,7-dioxa-6-oxyoctyl)-1,3-dioxolan-2-one (9)1
In a 150 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 13.09 g (0.0976 mol) of ( )-1,2,6-
hexanetriol, 87.90 g (0.9758 mol) of dimethyl carbonate, and
0.13 g (9.42 mmol) of potassium carbonate were placed. The
reaction was carried out at 80 °C, and the reaction progress was
monitored by TLC, and by FTIR spectroscopy until complete
decay of the absorption band corresponding to hydroxyl groups.
Then, methanol and the excess of dimethyl carbonate were dis-
tilled off under reduced pressure. Then, the residue was washed
with 3% HCl, water and extracted with dichloromethane (3 ×
50 cm3). The combined organic phases were dried with anhy-
drous magnesium sulfate, and evaporated to dryness. 17.44 g of
Synthesis of 4-(3,5-dioxa-4-oxyhexyl)-1,3-dioxolan-2-one (5)
In a 50 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 2.73 g (0.0257 mol) of ( )-1,2,4-
butanetriol, 23.17 g (0.2572 mol) of dimethyl carbonate, and
0.03 g (2.17 mmol) of potassium carbonate were placed. The
reaction was carried out at 80 °C, and the reaction progress was
monitored by TLC, and by FTIR spectroscopy until complete
decay of the absorption band corresponding to hydroxyl groups.
Then, methanol and the excess of dimethyl carbonate were dis-
tilled off under reduced pressure. The product was purified by
vacuum distillation (59–60 °C, 1 mbar). 3.38 g of 2 as a light
1
9 as a light yellow liquid (yield 82%) were obtained. H NMR
(400 MHz, CDCl3): 4.67–4.59 (m, 1H, CHcyc.), 4.45 (t, 1H,
CH2cyc., J = 8.2 Hz), 4.04 (t, 2H, CH2OC(O)O), J = 6.4 Hz),
3.98 (dd, 1H, CH2cyc., J1 = 7.2 Hz, J2 = 8.5 Hz), 3.66 (s, CH3,
1H), 1.78–1.67 (m, 1H, CH2CH), 1.67–1.57 (m, 3H, CH2CH +
CH2CH2O), 1.54–1.42 (m, 1H, CH2CH2CH), 1.42–1.31 (m, 1H,
CH2CH2CH). 13C NMR (400 MHz, CDCl3): 155.68 (CvOcyc.),
This journal is © The Royal Society of Chemistry 2012
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Synthesis of (1R,5S)-2,4,7-trioxa-3-oxy-bicyclo[3.3.0]octane (15)
– variant B
154.85 (CvOlin.), 69.20 (CHcyc.), 67.30 (CH2cyc.), 67.30
(CH2OC(O)O), 54.72 (CH3), 33.31 (CH2CH), 28.11
(CH2CH2OC(O)O), 20.93 (CH2CH2CH). FTIR (KBr):
2960–2872 (C–H), 1800 (CvOcyc.), 1749 (CvOlin.), 1265
(C–O), 1171–1065 (C–O), 794 (linear carbonate), 776 (carbon-
ate ring). Analysis of the isolated product was consistent with
that reported in the reference.
In a 250 cm3 three-neck flask equipped with a magnetic stirrer,
thermometer, Dean–Stark receiver, condenser, and a gas inlet,
10.32 g (0.0845 mol) of (2R,3S)-butane-1,2,3,4-tetraol, 22.32 g
(0.2536 mol) of ethylene carbonate, 0.15 g (2.57 mmol) of
sodium chloride, and 80 cm3 of toluene were placed. The reac-
tion was carried out at 70 °C under reduced pressure (180 Tr),
collecting ethylene glycol in a Dean–Stark receiver. When the
glycol was collected, the azeotropic solvent evaporated under
vacuum. The product was purified by column chromatography
(silica gel, ethyl acetate). 10.55 g of 15 (yield 96%) were
Synthesis of (3R,4S)-3,4-dihydroxytetrahydrofuran (14)3
In a 100 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 8.80 g (0.0721 mol) of (2R,3S)-
butane-1,2,3,4-tetraol, 6.49 g (0.0720 mol) of dimethyl carbon-
ate, 0.10 g (7.25 mmol) of potassium carbonate, and 40 cm3 of
1,4-dioxane were placed. The reaction was carried out at 90 °C,
and the reaction progress was monitored by FTIR spectroscopy
until complete decay of the absorption band corresponding to
carboxyl group. Then, methanol and 1,4-dioxane were distilled
off under reduced pressure. The product was purified by vacuum
distillation (102–103 °C, 2 mmHg) to afford 14 as a colorless
1
obtained. Mp. 76–77.5 °C. H NMR (400 MHz, CDCl3): 5.20
(dd, 2H, CH, J1 = 1.2 Hz, J2 = 2.1 Hz), 4.26 (dd, 2H, CH2, J1 =
1.4 Hz, J2 = 11.0 Hz), 3.56 (ddd, 2H, CH2, J1 = 1.2 Hz, J2 = 2.3
Hz, J3 = 12.4 Hz). 13C NMR (400 MHz, CDCl3): 154.36
(CvO), 79.99 (CHOC(O)O), 72.30 (CH2O). FTIR (KBr):
2964–2871 (C–H), 1793 (CvO), 1167–1110 (C–O), 1093–1049
(C–O), 771 (carbonate ring).
Synthesis of (4R,4′S)-4,4′-bi(1,3-dioxolane-2-one) (16)
1
viscous oil (86%). H NMR (400 MHz, CDCl3): 4.24 (m, 2H,
In a 250 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 11.87 (0.0972 mol) of (2R,3S)-
butane-1,2,3,4-tetraol, 87.56 g (0.9720 mol) of dimethyl carbon-
ate, 0.13 g (9.42 mmol) of potassium carbonate, and 40 cm3 of
tetrahydrofuran were placed. The reaction was carried out at
70 °C, and the reaction progress was monitored by TLC, and by
FTIR spectroscopy observing the changes of the signals derived
from the cyclic carbonate carbonyl group and hydroxyl groups.
Then, methanol, tetrahydrofuran, and the excess of dimethyl car-
bonate were distilled off under reduced pressure. The residue
was taken up in dichloromethane, and the precipitated product
was filtered off. Recrystallization from acetone yielded 5% of 16.
Mp. 170–172 °C. HRMS for C6H6O6: calculated [M + Na]+ =
CHOH), 3.89 (dd, 2H, CH2O, J1 = 5.2 Hz, J2 = 9.6 Hz), 3.72
(dd, 2H, CH2O, J1 = 3.4 Hz, J2 = 9.6 Hz), 3.68 (bs, 2H, OH).
13C NMR (400 MHz, CDCl3): 72.82 (CH2O), 71.30 (CHOH).
FTIR (KBr): ν = 3400 (O–H), 2950–2880 (C–H), 1129–1057
(C–O). Analysis of the isolated product was consistent with that
reported in the reference.
Synthesis of (1R,5S)-2,4,7-trioxa-3-oxybicyclo[3.3.0]octane (15) –
variant A
In a 150 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 9.89 g (0.0810 mol) of (2R,3S)-
butane-1,2,3,4-tetraol, 73.02 g (0.8106 mol) of dimethyl carbon-
ate, 0.12 g (8.69 mmol) of potassium carbonate, and 30 cm3 of
1,4-dioxane were placed. The reaction was carried out at 90 °C,
and the reaction progress was monitored by FTIR spectroscopy
until complete decay of the absorption band corresponding to
hydroxyl groups. Then, methanol, 1,4-dioxane, and the excess of
dimethyl carbonate were distilled off under reduced pressure.
The residue was washed with 3% HCl, and water. Dichloro-
methane was added in five 50 cm3 portions in order to collect
the product. Combined organic phases were dried with an-
hydrous magnesium sulfate, and left for crystallization. The crys-
talline product was purified by recrystallization from
dichloromethane. 7.9 g of 15 (yield 74%) were obtained. Mp
1
197.0057 g mol−1, found [M + Na]+ = 197.0049 g mol−1. H
NMR (400 MHz, DMSO-d6): 5.16–5.10 (m, 2H, CH), 4.60 (dd,
2H, CH2, J1 = 8.6 Hz, J2 = = 9.1 Hz), 4.39 (dd, 2H, CH2, J1 =
5.8 Hz, J2 = 9.1 Hz). 13C NMR (400 MHz, DMSO-d6): 154.16
(CvO), 74.91 (CH), 64.68 (CH2). FTIR (KBr): 2968–2862
(C–H), 1810 (CvO), 1785 (CvO), 1145–1083 (C–O), 771
(carbonate ring).
Synthesis of (1R,4S,5R,6R)-6-(1,3-dioxolan-2-one-4-yl)-2,4,7-
trioxa-3-oxy-bicyclo[3.3.0]octane (20)
In a 50 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 2.89 g (0.0159 mol) of D-sorbitol,
14.29 g (0.1586 mol) of dimethyl carbonate, 20 cm3 of 1,4-
dioxane, and 0.02 g (0.145 mmol) of potassium carbonate were
placed. The reaction was carried out at 80 °C, and the reaction
progress was monitored by TLC, and by FTIR spectroscopy
until complete decay of the absorption band corresponding to
hydroxyl groups. Then, it was cooled down and the obtained
precipitate was filtrated off. The product was purified by recrys-
tallization from acetonitrile. 1.48 g of 20 (yield 43%) was
obtained. Mp. 215–216 °C, [α]D −3 (c, 0.4, acetonitrile). HRMS
for C8H8O7: calculated [M + Na]+ = 239.0162 g mol−1, found
76.0–77.5 °C. HRMS for C5H6O4: calculated [M + Na]+
=
153.0158 g mol−1, found [M + Na]+ = 153.0152 g mol−1. H
NMR (400 MHz, CDCl3): 5.19 (dd, 2H, CH, J1 = 1.2 Hz, J2 =
2.1 Hz), 4.24 (dd, 2H, CH2, J1 = 1.2 Hz, J2 = 11.2 Hz),
3.55 (ddd, 2H, CH2, J1 = 1.2 Hz, J2 = 2.2 Hz, J3 = 12.4 Hz).
13C NMR (400 MHz, CDCl3): 154.36 (CvO), 79.99 (CHOC
(O)O), 72.30 (CH2O). FTIR (KBr): 2949–2874 (C–H), 1793
(CvO), 1168–1111 (C–O), 1092–1050 (C–O), 772 (carbonate
ring).
1
1756 | Green Chem., 2012, 14, 1749–1758
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1
[M + Na]+ = 239.0172 g mol−1. H NMR (400 MHz, DMSO-
derivatives. In case of compounds with four vicinal hydroxyl
groups it is difficult to obtain biscyclic carbonates in the reaction
with DMC, even for the reaction carried out at a lower tempera-
ture and in the presence of neutral catalyst. The presented syn-
thetic pathway represents an environmentally friendly approach
to the synthesis of five-membered cyclic ether derivatives under
non-acidic conditions. The biscyclic carbonates containing the
tetrahydrofuran ring can be used in the synthesis of biodegrad-
able non-isocyanate polyurethanes.
d6): 5.38–5.36 (m, 2H, CHOC(O)Obiscyc.), 4.99 (ddd, 1H,
CHcyc., J1 = 5.5 Hz, J2 = 6.4 Hz, J3 = 8.7 Hz), 4.62 (dd, 1H,
CH2cyc., J1 = 8.6 Hz, J2 = 8.6 Hz), 4.44 (dd, 1H, CH2cyc., J1 =
8.5 Hz, J2 = 6.5 Hz), 4.18 (d, 1H, CH2biscyc., J = 12.0 Hz), 3.98
(dd, 1H, CHObiscyc., J1 = 2.2 Hz, J2 = 5.4/Hz), 3.69 (m, 1H,
CH2biscyc.). 13C NMR (400 MHz, DMSO-d6): 144.95
(CvOcyc.), 144.22 (CvOcyc.), 71.41 (CHObiscyc.), 71.10
(CHcyc.), 69.92 (OCH2CHOC(O)Obiscyc.), 64.35 (OCHCHOC
(O)Obiscyc.), 62.11 (CH2biscyc.), 56.63 (CH2cyc.). FTIR (KBr):
2985–2882 (C–H), 1806 (CvOcyc.), 1777 (CvOcyc.),
1193–1178 (C–O), 774 (carbonate ring).
Acknowledgements
This research has been supported by the National Science Centre
of Poland, grant no. N N209 028240.
Synthesis of isosorbide (22)31
In a 100 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 3.15 g (0.0173 mol) of D-sorbitol,
15.58 g (0.1729 mol) of dimethyl carbonate, 20 cm3 of 1,4-
dioxane, and 0.02 g (0.145 mmol) of potassium carbonate were
placed. The reaction was carried out at 90 °C, and the reaction
progress was monitored by TLC. Then, methanol, 1,4-dioxane
and excess of dimethyl carbonate were distilled off and the reac-
tion temperature was increased to 120 °C. At this temperature
intense carbon dioxide liberation was observed. The product was
purified by vacuum distillation (126–127 °C, 1 mmHg). 1.07 g
of 22 (yield 42%) was obtained. Mp. 61–63 °C. 1H NMR
(400 MHz, CDCl3): 4.64 (t, 1H, CHO, J = 4.9 Hz), 4.40–4.33
(m, 2H, CHO + CHOH), 4.29 (dd, 1H, CHOH, J1 = 5.7 Hz, J2 =
11.4 Hz), 3.97 (d, 1H, CH2, J = 10.0 Hz), 3.92–3.82 (m, 2H,
CH2,), 3.54 (dd, 1H, CH2, J1 = 5.8 Hz, J2 = 9.4 Hz), 3.05–2.55
(bs, 2H, OH). 13C NMR (400 MHz, CDCl3): 88.25 (CHO),
81.80 (CHO), 76.65 (CHOH), 75.90 (CH2), 73.64 (CHOH),
72.43 (CH2). FTIR (KBr): 3383 (O–H), 2948–2877 (C–H),
1123–1046 (C–O). Analysis of the isolated product was consist-
ent with that reported in the reference.
Notes and references
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Synthesis of tetrahydrofuran
In a 25 cm3 three-neck flask equipped with a magnetic stirrer,
condenser and thermometer, 0.99 g (0.011 mol) of 1,4-butane-
diol, 3.02 g (0.0335 mol) of dimethyl carbonate, and 1.85 g
(0.0342 mol) of sodium alkoxide, and 6 cm3 of 1,4-dioxane
were placed. The reaction was carried out at 90 °C, and the reac-
tion progress was monitored by gas chromatography. Then,
methanol, 1,4-dioxane, excess of dimethyl carbonate, and tetra-
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Conclusions
Diols with vicinal hydroxyl groups easily form five-membered
cyclic carbonates in high yields in the reaction with dimethyl
carbonate in the presence of an alkaline catalyst such as K2CO3.
However, compounds with an additional OH group at the
β-position in relation to the vicinal OH groups after longer reac-
tion times while undergoing the same reaction conditions causes
intramolecularetherification resulting in 3-hydroxytetrahydrofuran
This journal is © The Royal Society of Chemistry 2012
Green Chem., 2012, 14, 1749–1758 | 1757

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