Novel synthesis routes for the preparation of low toxic vinyl ester and vinyl carbonate monomers

Article abstract of DOI:10.1080/00397911.2020.1808995

UV curing of photopolymerizable monomers, like (meth)acrylates, has been utilized for coatings for more than half a century and more recently in further developed areas such as tissue engineering. However, these monomers have major disadvantages, e.g., high irritancy and cytotoxicity, which leads to limited use in tissue engineering regarding health issues. Vinyl esters (VE) and vinyl carbonates (VC) can compete with (meth)acrylates in terms of material properties and have significantly lower toxicity, but lack in cost efficient synthesis methods. The purpose of this communication is to establish new pathways to overcome this drawback. It was shown that VEs can be synthesized either by vinyloxy trimethylsilane or by acetaldehyde in excellent yields. Moreover, a new method to synthesize vinyl chloroformate as precursor for VCs in lab scale was evolved by a catalyzed reaction of vinyloxy trimethylsilane with a phosgene solution. Finally, the cytotoxicity tests showed auspicious results.

Full text of DOI:10.1080/00397911.2020.1808995

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Novel synthesis routes for the preparation of low
toxic vinyl ester and vinyl carbonate monomers
Andreas Hofecker , Patrick Knaack , Patrick Steinbauer , Marica Markovic ,
Aleksandr Ovsianikov & Robert Liska
To cite this article: Andreas Hofecker , Patrick Knaack , Patrick Steinbauer , Marica Markovic ,
Aleksandr Ovsianikov & Robert Liska (2020): Novel synthesis routes for the preparation
of low toxic vinyl ester and vinyl carbonate monomers, Synthetic Communications, DOI:
10.1080/00397911.2020.1808995
To link to this article: https://doi.org/10.1080/00397911.2020.1808995
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https://doi.org/10.1080/00397911.2020.1808995
Novel synthesis routes for the preparation of low toxic
vinyl ester and vinyl carbonate monomers
Andreas Hofeckera, Patrick Knaacka, Patrick Steinbauera, Marica Markovicb,
Aleksandr Ovsianikovb, and Robert Liskaa
b
aInstitute of Applied Synthetic Chemistry, TU Wien, Vienna, Austria; Institute of Materials Science and
Technology, TU Wien, Vienna, Austria
ABSTRACT
ARTICLE HISTORY
Received 24 July 2020
UV curing of photopolymerizable monomers, like (meth)acrylates,
has been utilized for coatings for more than half a century and more
recently in further developed areas such as tissue engineering.
However, these monomers have major disadvantages, e.g., high irri-
tancy and cytotoxicity, which leads to limited use in tissue engineer-
ing regarding health issues. Vinyl esters (VE) and vinyl carbonates
(VC) can compete with (meth)acrylates in terms of material proper-
ties and have significantly lower toxicity, but lack in cost efficient
synthesis methods. The purpose of this communication is to estab-
lish new pathways to overcome this drawback. It was shown that
VEs can be synthesized either by vinyloxy trimethylsilane or by acet-
aldehyde in excellent yields. Moreover, a new method to synthesize
vinyl chloroformate as precursor for VCs in lab scale was evolved by
a catalyzed reaction of vinyloxy trimethylsilane with a phosgene
solution. Finally, the cytotoxicity tests showed auspicious results.
KEYWORDS
Low toxic monomers;
photopolymerization; vinyl
carbonates; vinyl ester
GRAPHICAL ABSTRACT
CONTACT Robert Liska
robert.liska@tuwien.ac.at
Institute of Applied Synthetic Chemistry, TU Wien, Vienna
1040, Austria.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2020 The Author(s). Published with license by Taylor & Francis Group, LLC
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License
(http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium,
provided the original work is properly cited, and is not altered, transformed, or built upon in any way.

2
A. HOFECKER ET AL.
Introduction
Since more than a half-century, UV curing of photopolymerizable monomers has been
used for decorative and protective coatings. Especially (meth)acrylates are state-of-the-
art monomers in photopolymerization of such coatings and printing inks.[1–3]
Moreover, they are also widely utilized in further advanced fields, such as 3 D-printing
or tissue engineering, owing to their large variety of commercially available building
blocks, fast curing rates, and good storage stability.[4] Nevertheless, these monomers
have major drawbacks, as for instance cytotoxicity caused by the monomer itself and
also their toxic and irritating degradation products, which lead to a limited applicability
in respect to health and environmental issues.[5] For that reason, vinyl ester (VE) and
vinyl carbonate (VC) monomers were evaluated recently.[5–10] These compounds exhibit
a significant lower toxicity, good storage stability, similar or even better mechanical
properties of the final polymer and sufficient reactivity toward radical polymeriza-
tion.[5–7,9] Lower toxicity can be assigned to the hydrolytic degradation of crosslinked
VEs and VCs to nontoxic and FDA-approved poly(vinyl alcohol).[6]
However, only a few building blocks of these monomers are commercially available due
to toxic, costly or ineffective synthesis methods. Typically, VE monomers are synthesized
by transesterification of carboxylic acids with vinyl acetate in the presence of a catalyst.
The applied catalyst is based on toxic mercury (II) salts, whereas nucleophilic groups can
deactivate the Hgþ-intermediate.[11] Thus, palladium (II) salts are used, as they are less
toxic and stable toward nucleophiles. Still, they are expensive and hard to recycle.[12]
Another synthetic pathway is based on the use of phenyl selenium ethanol as a precur-
sor.[13] However, the poor atom efficiency and multistep reaction disfavors this method.
The preparation of VCs also lacks cheap and efficient synthesis pathways. The most
common method uses vinyl chloroformate (VOCl) reacting with an alcohol in a modi-
fied Einhorn acylation, as here chloroformate replaces acyl chloride.[14] Moreover, pyri-
dine is utilized as catalyst and acid scavenger.[15,16] The vinyl chloroformate pathway is
favorable regarding quantitative yields and an easy work-up procedure. Nonetheless,
over the last years, the number of suppliers has been steadily decreasing. Consequently,
the price has increased tremendously. There are two commercial processes in industrial
scale available.[17] One method is based on the pyrolysis of ethylene glycol bis(chloro-
formate), which is synthesized by acylation of ethylene glycol with phosgene.[18] The
more recent two-step reaction involves phosgene together with mercury bisacetalde-
hyde.[19] In summary, it is required to establish new methods, or to refurb the state-of-
art synthesis of VE and VC monomers, respectively.
The purpose of this communication is to present a more convenient, more economic
and safer pathway to obtain VE in good yields that offer versatile possibilities for these
biocompatible and photopolymerizable monomers. Additionally, the synthesis of VOCl
is improved by excluding mercury educts and facilitate the processability in lab scale.

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Scheme 1. Pathway 1 for the synthesis of VE monomers.
Scheme 2. Pathway 2 for the synthesis of VEs.
Results and discussion
Vinyl esters from vinyloxy trimethylsilane (1)
To overcome the shortages of the available synthetic pathways generating VE mono-
mers, two strategies were evaluated (Schemes 1 and 2).
As shown in Scheme 1, the equilibrium of acetaldehyde can be shifted by the amine
base triethylamine into the temporarily formed vinyl alcohol and can be captured by
trimethylsilyl chloride (TMS-Cl) to obtain vinyloxy trimethylsilane (1). Subsequently,
1 can be reacted with acyl chlorides in the presence of potassium fluoride (KF) and 18-
crown-6 ether to obtain VEs.
In detail, the vinyl donor vinyloxy trimethylsilane (1) was synthesized according to the
procedure of Olofson et al.[20] with some refinements to compile a more convenient process.
Following to the tautomeric base-catalyzed shift of acetaldehyde to vinyl alcohol, the emerg-
ing intermediate was caught with TMS-Cl to obtain 1 and the accruing hydrochloric acid
was neutralized in situ by a tertiary amine. In more detail, an excess of dry acetaldehyde (2.5
equiv.) was slowly dripped into the mixture of dry triethylamine (Et3N) (1.25 equiv.), dry
N,N’-dimethylformamide (DMF) and distilled TMS-Cl (1 equiv.). After the work-up pro-
cedure, 59% of the theoretical yield of a colorless oil could be obtained. Noteworthy, the
usage of 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU) as enolization agent did not lead to for-
mation of the desired product 1. Contrary to this approach, Olofson et al.[20] stated that if
acetaldehyde was directly dripped into the mixture, vinyloxy trimethylsilane (1) could be
obtained only in yields of 15–20%. Therefore, they slowly distilled acetaldehyde into the
mixture with the distillation outlet below the surface of the mixture to obtain 62% theoret-
ical yield. Thereby, it is possible that the reaction solution shoots back into the acetaldehyde
flask due to underinflation causing enormous dangerous reaction heat. However, with our
straightforward strategy no complex reaction apparatus is required to synthesize 1 in good
yields and thus, underinflation can be excluded.
Similar to the work of Olofson et al.,[20] where thiocarbonates were synthesized using
1 as precursor, we used 1 to obtain vinyl esters. Therefore, different acyl chlorides
(2a–c) were reacted with 1 to obtain the aromatic VE vinyl benzoate (3a), the aliphatic
VE vinyl decanoate (3b) and the difunctional VE divinyl adipate (3c) (Table 1). In gen-
eral, 1.5 equiv. of 1 was dropped into a mixture of 1 equiv. freshly distilled acyl chloride

4
A. HOFECKER ET AL.
Table 1. Universality of pathway 1.
Entry
Substrate
R
Product
Yield (%)a
1
2
3
2a
2b
2c
–C6H5
–C9H16
–C4H8COCl
3a
3b
3c
69
64/78b
20/48b
aIsolated yields.
bIsolated yields using acetonitrile as solvent.
Scheme 3. Mechanism of pathway 1.
(2a, b or c), 5 equiv. dry potassium fluoride (KF), 0.1 equiv. dry 18-crown-6 ether in
dry DMF. 18-crown-6-ether was used as phase transfer agent between the organic phase
and the insoluble salt KF. Additionally, the 18-crown-6 ether is designed to catch the
potassium cation. Consequently, the fluoride anion gets more nucleophilic due to the
increased distance to the potassium cation. Thus, the fluoride anion attaches to the sili-
con of 1 and forms a pentavalent intermediate. Based on the increased nucleophilicity
of this intermediate the lone pair of the oxygen of 1 attacks the carbonyl carbon of the
acyl chloride (2) (Scheme 3).[21] The energetically more stable bond between silicon and
fluoride, as compared to the bond between silicon and oxygen, causes the bond of sili-
con and oxygen to break. Simultaneous, the fluoride anion performs partially an ion
exchange with the chloride of the acyl chloride (2) to obtain the corresponding more
reactive fluoroformate.[22] It is important to use at least 3 equiv. of KF in case of traces
of remaining water present to scavenge possibly created fluoric acid to potassium
bifluoride.[23] Noteworthy, the aprotic polar solvent DMF improves the SN2-reaction,
where the desired vinyl ester (3) and the side product trimethylsilyl fluoride
are formed.[24]
The reaction control was carried out by thin layer chromatography (TLC). After an
aqueous work-up procedure, the crude mixture was purified by column chromatography
to afford colorless liquid 3a in 69% yield. To demonstrate the versatility of precursor 1
aliphatic VEs 3b and 3c were synthesized, as well, utilizing the procedure for 3a.
Freshly distilled decanal chloride was used to obtain 78% yield of 3b. The difunctional
VE 3c could be isolated in mediocre yields of 48% with adipoyl chloride as a starting
material (Table 1).

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Table 2. Optimization of the model reaction for pathway 2.
Entry
Solvent
Dielectric constant[27,28]
Molar ratio (4a:5:Et3N)
Yield (%)
1
2
3
4
5
6
7
8
9
Bulk
Acetonitrile
N,N’-dimethylformamide
Dichloromethane
Tetrahydrofuran
Toluene
–
1:1.25:2.50
1:1.25:2.50
1:1.25:2.50
1:1.25:2.50
1:1.25:2.50
1:1.25:2.50
1:1.25:2.50
1:3:4
58a
69a
55a
35a
15a
9a
37.5
36.7
9.1
7.6
2.4
2.4
37.5
37.5
Xylene
Acetonitrile
Acetonitrile
9a
67a
79b
1:2:5
a1H-NMR-yields.
bIsolated yields.
Vinyl esters directly from acetaldehyde (5)
The variety of carboxylic acids applied in the synthesis of VEs is widespread. Thus, the
corresponding acyl chlorides could be interesting for the synthesis of VEs in combin-
ation with vinyloxy trimethylsilane (1). Nonetheless, this reaction lacks in atom effi-
ciency for industrial scale owing to the protecting group. Therefore, pathway 2 was
established (Scheme 2) which overcomes this drawback of route 1.
This pathway is based on the tautomeric vinyl alcohol - acetaldehyde equilibrium,
whereby the vinyl alcohol intermediate should perform an Einhorn acylation[14] with an
acyl chloride. Sladkov et al. described a method for the acylation of the enol form of
acetaldehyde.[25] This is the only one known in literature, in which acetaldehyde reacts
with acyl chloride in an Einhorn acylation[14] to numerous different VEs.
We tried to confirm the work of Sladkov et al. using pyridine as enolization agent
and vinyl benzoate (6a) in a model reaction.[25] After several attempts, no product could
be obtained, as found by others.[26] Before heating the reaction to 45 ꢀC, the proton
nuclear magnetic resonance (1H-NMR) measurements and TLC only showed educts.
After 18 h at 45 ꢀC, the brown reaction mixture consisted of several aldol reaction prod-
ucts. Thus, the base was changed to Et3N. The first attempt using DMF and a molar
ratio of 1 equiv. benzoyl chloride (4a), 1.25 equiv. acetaldehyde (5) and 2.5 equiv. Et3N
led to a crude yield of 55% of 6a. The yield was determined based on the 1H-
NMR spectrum.
To optimize the yields of this system, different solvents were tested. In this test series,
a molar ratio of 1 mol 4a, 1.25 mol acetaldehyde (5) and 2.50 mol Et3N was used. With
acetonitrile (MeCN) an 11% higher conversion of 4a–6a was achieved after one day at
45 ꢀC, compared to the reaction in bulk with 58% yield. Moreover, the reaction in bulk
is difficult to handle and due to overheating during the reaction, polymerization could
occur. The same reaction conditions in N,N’-dimethylformamide (DMF) led to a con-
version of 55%, in dichloromethane to 35%, in tetrahydrofuran to 15%, in toluene and
xylene to 10%. It is necessary to use an aprotic solvent, otherwise the acyl chloride
hydrolyzes, and it is important to keep an eye on the dielectric constant (e) of the

6
A. HOFECKER ET AL.
Table 3. Universality of pathway 2.
Entry
Substrate
R1
Product
R2
Yield (%)b
1
2
3
4
5
6
7
8
4a
4b
4c
4d
4e
4f
4g
4h
4i
–C6H5
–CH3
–C2H5
–C2H3
–C3H7
6a
6b
6c
6d
6e
6f
6g
6h
6i
–C6H5
–CH3
–C2H5
–C2H3
–C3H7
79
–
–
–
–
–COCl
–CH2Cl
–C4H9COCl
–C6H4COClc
–C6H4COCld
–C6H3(COCl)2
–CO2C2H3
–CH2Cl
–C4H9CO2C2H3
–C6H4CO2C2H3c
–C6H4CO2C2H3
–C6H3(CO2C2H3)2
–
–
67a
58
42
72
b
9
10
11
4j
4k
6j
6k
a1H-NMR yield.
bIsolated yields.
cTerephthaloyl chloride.
dIsophthaloyl chloride.
solvent. As shown in Table 2, the order of the yield is in accordance with the order of
e. The utilization of MeCN resulted in the highest yields with 69%. Therefore, MeCN
was used for further experiments.
Another crucial factor is the molar ratio of the educts. Different molar ratios of 4a, 5
and Et3N were examined to elaborate the optimum conditions for this reaction. The
reaction was performed in a sealed penicillin flask using MeCN at 45 ꢀC for 24 h. At
first, the ratio of acetaldehyde 5 was increased compared to the acid chloride 4a and
triethylamine using 1:3:4 for 4a:5:Et3N (Entry 8 in Table 2). However, this did not lead
to an increase in yield. Thus, the ratio was changed to 1:2:5 for 4a:5:Et3N with an
increased content of the tertiary amine using MeCN as solvent. With these conditions,
the highest yield, namely 79%, was achieved after one day. Hence, an increased amount
of acetaldehyde 5 and Et3N increases the conversion of the acid chloride 4a.
Summarized, there is a positive coherence between molar ratio and conversion.
In addition, the versatility of this type of reaction in respect to the used base was
extended by using KF and 18-crown-6 ether under the same conditions as in pathway 1,
but with acetaldehyde instead of 1. Consequently, changing the base caused an at least 20%
lower yield. Finally, 6a was synthesized with optimized conditions in an isolated yield of
79% using Et3N as tertiary amine base, MeCN as solvent and a molar ratio of 1 equiv. acyl
chloride (4a), 2 equiv. acetaldehyde (5), and 5 equiv. triethylamine.
Based on these optimized conditions, a variety of different acyl chlorides (Table 3)
were used to prove the generality of pathway 2 for the synthesis of VEs. Firstly, simple
aliphatic acyl chlorides, such as acetyl chloride (4b), propionyl chloride (4c), acryloyl
chloride (4d) and butyryl chloride (4e), were reacted in the same manner as 4a. After
1
24 h reaction time the mixture turned dark red brown and solidified. A crude H-NMR
sample showed no vinyl peaks in any of these attempts. Furthermore, the work-up pro-
cedure led to a mixture of different aldol reaction products. Two more complex acyl

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7
chlorides, namely oxalyl chloride (4f) and chloroacetyl chloride (4g), were tested in the
1
same way as described before. Similar to the simple aliphatic acyl chlorides, the H-
NMR spectra showed only different aldol products.
It is known from literature,[29] that the a-CH of acyl chlorides has a pKa value of 16,
which is close to the pKa value of acetaldehyde (pKa 17). These similar acidities could
explain the resulting mixture of aldol products. To prove this hypothesis, pivaloyl chlor-
1
ide (4h), lacking an a-CH, was reacted with acetaldehyde. Indeed, the crude H-NMR
spectrum showed formed pivaloyl VE and is in accordance with the literature shifts of
pivaloyl VE.[30]
In addition, this provides evidence that the mechanism of pathway 1 depends on the
pentavalent intermediate. A formed enolate would undergo a fast tautomerization to the
corresponding aldehyde. Based on these findings di- and trifunctional aromatic acyl
chlorides were investigated, as well, because functionality is necessary to build different
polymer networks and structures. Here, divinyl terephthalate (6i) was synthesized using
4 equiv. of 5 and 10 equiv. of Et3N in MeCN. After purification by column chromatog-
raphy, a white solid could be obtained in good yields of 58%.
Furthermore, it was tried to use KF in 18-crown-6-ether, which enolizes acetaldehyde
and nucleophilically attacks the carbonyl C of the acyl chloride.[31] Compared to the
reaction utilizing Et3N, this led only to mediocre yields of 26% of 6i. In addition,
divinyl isophthalate (6j) was synthesized in consonance with the procedure of 6i to
investigate the influence of the steric differences of the distinct conformations of the
phthalic acyl chloride. Similar to 6i the enolization using Et3N led to a significant
higher yield of 42% than the pathway using the enolization effect of the naked F- anion,
which achieved a yield of only 20%. In summary, steric hindrance caused lower yields
independent on the enolization methods applied. Following this, trivinyl trimesate (6k)
was synthesized using 6 equiv. of 5 and 15 equiv. of Et3N in MeCN. After purification
by column chromatography, a white solid could be obtained in good yields of 72%.
In order to verify the expected toxicity of vinyl esters,[6,9,10] 6a was tested exemplarily
on mouse fibroblast cell line L929 and compared with the corresponding (meth)acry-
lates. The cytotoxicity of VE was 4 times lower than of methacrylates and even one
order of magnitude lower than of acrylates, which emphasizes the potential of VEs (see
Supporting Info).
Vinyl carbonates
The synthesis of vinyl carbonates, another low toxic monomer, should be investigated
based on the precursor vinyl chloroformate (7).
For the common synthesis of 7 in lab scale, phosgene is reacted with mercury acetal-
dehyde.[32] However, organic mercury compounds are highly toxic and mercury itself is
accumulated in the body over years and causes mercury poising.[33] As an alternative, a
synthetic route to avoid mercury was established by Bausch & Lomb Inc. for the synthe-
sis of 7 on an industrial level.[34] This reaction was slightly modified to make it access-
ible for lab scale and to enhance safety issues.
In detail, 1.4 equiv. of the protected vinyl alcohol 1 was reacted with 1 equiv. of a
20 wt% phosgene solution in toluene with acetonitrile as solvent in the presence of

8
A. HOFECKER ET AL.
Scheme 4. Synthesis of vinyl chloroformate.
Table 4. Synthesis of different VCs.
Entry
1
Substrate
R
Product
Yield (%)a
95
8a
9a
2
3
8b
8c
9b
9c
>99
91
aIsolated yields.
0.0075 equiv. of palladium acetate to obtain 7 instead of the industrial route[34] using
gaseous phosgene in adiponitrile (Scheme 4). During this catalyzed reaction, the double
bond of 1 coordinates on the surface of the Pd catalyst. Then, TMS reacts with acetate
and the enolate tautomerizes to the keto state. A nucleophilic attack onto the carbonyl
C of phosgene and an additional H-elimination lead to the desired product. The catalyst
is regenerated by reacting TMS-acetate with chloride of phosgene. Here, it is necessary
to avoid traces of water to prevent phosgene from hydrolysis.
It was not possible to obtain pure 7. In the course of the distillation via vigreux col-
umn, the solvent MeCN formed an azeotrope with toluene with a boiling point close to
the one of 7. Nevertheless, the obtained toluene/MeCN solution contained 10% of 7,
which is equivalent to 55% of the theoretical yield. Moreover, the residual solvent does
not disturb the subsequent reaction with an alcohol (8) due to higher volatility of the
solvent, as compared to the resulting product (9).
For testing the applicability of 7 in this pathway, different substrates based on difunc-
tional alcohols were reacted with 7 in the presence of pyridine in an Einhorn acylation.[14]
Firstly, polyethylene glycol (PEG) (8a), widely used in biomedical applications,[35] was
reacted with 2.1 equiv. of 7 to obtain PEG divinyl carbonate (9a) in a nearly quantitative
yield after purification by flash chromatography. The steric more enhanced polypropylene
glycol (PPG) divinyl carbonate (9b) was synthesized in the same manner and reacted with
full conversion of PPG (8b) to the desired product. To show a variety within this

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9
monomer class ethoxylated bisphenol A (8c) was modified with a divinyl carbonate group
to obtain ethoxylated bisphenol A divinyl carbonate (9c) in high yields (Table 4).
Finally, to evaluate the biocompatibility of VCs as shown in other publications,[36,37] 9a
was tested exemplarily on mouse fibroblast cell line L929 and compared with the corre-
sponding (meth)acrylates. It was observed that VC is as cytotoxic as the methacrylate and
one order of magnitude lower than the acrylate, which emphasizes the potential of VCs to
replace acrylates (see Supporting Info).
Conclusion
In this communication, it is demonstrated that mono- and multifunctional aromatic
VEs can be prepared by simply reacting an acyl chloride with acetaldehyde using trie-
thylamine as enolization agent. However, this synthetic route is not versatile enough to
obtain aliphatic VEs. Pathway 1, using vinyloxy trimethylsilane and acyl chlorides in the
presence of KF and 18-crown-6-ether to obtain VEs, could be used as an alternative
synthesis route to receive mono- and difunctional aliphatic VE. Furthermore, this com-
munication also evidenced a successful mercury-free synthesis of vinyl chloroformate in
lab scale and subsequent reaction with an alcohol to obtain VCs. Both, VE and VC
showed significantly lower cytotoxicity compared to the corresponding acrylate, and VE
was even 4 times less cytotoxic than the corresponding methacrylate. This protocol
demonstrates an innovative, cheap and facile synthesis for low toxic monomers applied
in photopolymerization.[5–10] Most recently, this class of polymers has been used in
highly developed fields of medicinal chemistry, and it will enhance the future of 3 D
printing in the field of tissue engineering.[38]
Experimental part
1H-NMR- and 13C-NMR-spectra were measured either on a BRUKER Avance DRX-400
1
FTNMR spectrometer at 400 MHz for H-NMR and at 100 MHz for 13C-NMR or on a
1
BRUKER AC-E-200 FTNMR spectrometer at 200 MHz for H-NMR and 50 MHz for
13C-NMR. Chemical shifts (d) are reported in ppm (s ¼ singulett, d ¼ duplet, t ¼ triplett,
q ¼ quartett, quint ¼ quintet, m ¼ multiplet) and coupling constants (J) in Hz. Deutero-
chloroform (CDCl3) and deuterated dimethyl sulfoxid (d6-DMSO) from the company
Eurisotop were used as solvents and referenced to the solvent peak on literature
data.[39] The grade of deuteration was at least 99.8%. For thin layer chromatography
(TLC) aluminum foils, coated with silicagel 60 F254 from the company Merck were
applied. Column chromatography was performed with a glass column was packed with
silicagel 60 mm from the distributor ROTH. Microanalyses were performed on
PerkinElmer Series II CHNS/O 2400 elemental analyzer.
General procedure for compounds 3a-c
All used glassware was dried and flushed with argon. A 20 mL sealed glass vial was
charged with a solution of distilled acyl chloride (2 mmol) in 5 mL dry DMF, dry KF
(10 mmol), dry 18-crown-6-ether (0.2 mmol) and finally bubbled with argon. The

10
A. HOFECKER ET AL.
mixture was heated to 40–50 ꢀC, vinyloxy-trimethylsilane (3 mmol) was slowly added,
stirred for 20 h, and meanwhile the solution turned red-brownish. The reaction progress
was monitored by TLC, whereas butanol was used to react with the residual acyl chlor-
ide for monitoring the conversion. The solution was diluted in 20 mL ethyl acetate,
washed with water (2 ꢁ 40 mL), brine (2 ꢁ 40 mL), and dried over Na2SO4. The organic
phase was filtered and the solvent was removed under reduced pressure. For further
purification, the red-brownish liquid was cleaned via column chromatography to obtain
a colorless oil.
Vinyl benzoate (3a)[40]
1
Colorless liquid. Yield: 0.2 g (69%). H-NMR (400 MHz, CDCl3): d (ppm) ¼ 8.08 (2 H,
d, J ¼ 8.0 Hz, o-aromatic), 7.60–7.35 (4 H, m, m-, p-aromatic, CH2¼CH), 5.05 (1 H, dd,
J ¼ 13.9, 1.5 Hz, trans-CH2¼), 4.68 (1 H, dd, J ¼ 6.3, 1.5 Hz, cis-CH2¼). 13C-NMR
(50 MHz, DMSO) d (ppm) ¼ 163.52 (C¼O), 141.40 (CH2¼CH), 133.55 (aromatic),
129.94 (aromatic), 128.90 (aromatic), 128.49 (aromatic), 98.13 (CH2¼).
General procedure for compounds 6a-k
All used glassware was dried and flushed with argon. A 20 mL sealed glass vial was
charged with distilled acyl chloride (2 mmol), dried Et3N (10 mmol for 6a–h/20 mmol
for 6i–j/30 mmol for 6k) and stirred in 5 mL dry acetonitrile at room temperature under
argon. Afterwards the reaction mixture was cooled with an ice bath and dried acetalde-
hyde (4 mmol for 6a–h/8 mmol for 6i–j/12 mmol for 6k) was dropped slowly to this
mixture. The solution was heated to 40–50 ꢀC and stirred for 24 h, while it turned
orange brown. The reaction progress was monitored via TLC, whereas butanol was used
to react with the residual acid chloride for monitoring the conversion. Furthermore, the
mixture was diluted in 20 mL ethyl acetate, triethylamine was neutralized with sat.
NH4Cl (2 ꢁ 20 mL), washed with and water (2 ꢁ 40 mL). Before evaporating the solvent,
the organic layer was firstly dried with brine (2 ꢁ 40 mL) and then over Na2SO4. The
organic phase was filtered and concentrated under reduced pressure. For further purifi-
cation, the brownish liquid was cleaned via column chromatography.
Vinyl benzoate (6a)[40]
1
Colorless liquid. Yield 0.23 g (79%). H-NMR (400 MHz, CDCl3): d (ppm) ¼ 8.08 (2 H,
d, J ¼ 8.0 Hz, o-aromatic), 7.60–7.35 (4 H, m, m-, p-aromatic, CH2¼CH), 5.05 (1 H, dd,
J ¼ 13.9, 1.5 Hz, trans-CH2¼), 4.68 (1 H, dd, J ¼ 6.3, 1.5 Hz, cis-CH2¼). 13C-NMR
(50 MHz, DMSO) d (ppm) ¼ 163.52 (C¼O), 141.40 (CH2¼CH), 133.55 (aromatic),
129.94 (aromatic), 128.90 (aromatic), 128.49 (aromatic), 98.13 (CH2¼).
General procedure for compounds 9a-c
A round bottom flask equipped with a stirrer bar was charged with dried alcohol
(7 mmol), dry 50 mL DCM and pyridine (14.7 mmol) and cooled by an ice bath.

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SYNTHETIC COMMUNICATIONSV
11
Afterwards vinyl chloroformate (14.7 mmol) was slowly dropped to the reaction mix-
ture, warranting the reaction temperature does not increase. To ensure, that both func-
tional groups are reacted, an excess of vinyl chloroformate is necessary. Meanwhile, the
1
reaction progress was monitored by H-NMR spectroscopy and via IR. After stirring
overnight, the residual vinyl chloroformate was quenched with water, inhibitor was
added and concentrated in high vacuo. Finally, the product was purified by flash col-
umn chromatography with acetone as solvent to obtain the desired product.
Polyethyleneglycol divinyl carbonate (9a)
1
Slightly yellow viscous oil. Yield: 4.1 g 95%. H-NMR (200 MHz, DMSO): d (ppm) ¼
7.04 (2 H, dd, J ¼ 6.17 Hz, J ¼ 13.9 Hz, 2x CH2¼CH–), 4.92 (2 H, dd, J ¼ 1.78 Hz,
J ¼ 13.9 Hz, 2x trans-CH2¼), 4.67 (2 H, dd, J ¼ 2.01, J ¼ 6.17, 2x cis-CH2¼), 4.27 (4 H, t,
J ¼ 4.6 Hz,
2x–O–CH2–CH2–O–C ¼ O),
3.64
(4 H,
t,
J ¼ 4.6 Hz,
2x
–O–CH2–CH2–O–C¼O), 3.51 (48 H, m, 12x –O–CH2–CH2–O–). 13C-NMR (50 MHz,
DMSO) d (ppm) ¼ 152.07 (C¼O), 142.73 (CH2¼CH), 98.24 (CH2¼CH), 69.73–67.52
(CH2). Anal. Calcd. for C33.6H61.2O18.8 (the sum formula is depending on the results of
the OH-titration): C, 52.68; H, 8.05. Found: C, 52.40; H, 8.09.
Full experimental details, spectroscopic data, biological data, tables, and figures can
be found via the “Supplementary Content” section of this article’s webpage.
Acknowledgements
The authors kindly thank Viktor Savic for his valuable comments.
Funding
The authors kindly acknowledge the financial support by TU Wien in the framework of the
“Top/Anschub Finanzierung.”
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