Unexpected cleavage of ether bonds of 1,3-dimethoxypropane in Grignard-Wurtz synthesis of a MgCl2-donor adduct

Article abstract of DOI:10.1016/j.molcata.2015.12.003

Diethers are an important group of electron donors in Ziegler-Natta catalysts. A simple diether, 1,3-dimethoxypropane was studied as an electron donor in Grignard-Wurtz synthesis of a MgCl₂-donor adduct. 1,3-Dimethoxypropane was unexpectedly found to undergo a cleavage reaction during the synthesis producing methoxy groups (OCH₃). Each mole of 1,3-dimethoxypropane produced approximately 2 moles of methoxy groups, which are probably bound to magnesium chloride as methoxymagnesium chloride. A Grignard reagent, BuMgCl formed in the Grignard-Wurtz reaction most likely causes the cleavage of the ether bonds in 1,3-dimethoxypropane and there seem to be at least two parallel reaction paths taking place and producing at least two different by-products. The first step in the cleavage of 1,3-dimethoxypropane is a Grignard reagent (BuMgCl) induced elimination of OCH₃, which gives 3-methoxy-1-propene. This intermediate product reacts further in a substitution reaction caused by the Grignard reagent producing 1-heptene as the by-product. The cleavage of the ether bond in 3-methoxy-1-propene and formation of OCH₃ can also occur through another reaction path, which produces propene as the by-product.

Full text of DOI:10.1016/j.molcata.2015.12.003

Journal of Molecular Catalysis A: Chemical 413 (2016) 94–99
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Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Unexpected cleavage of ether bonds of 1,3-dimethoxypropane in
Grignard–Wurtz synthesis of a MgCl –donor adduct
2
∗
Ville Nissinen, Sami Pirinen, Tuula T. Pakkanen
Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu, Finland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 October 2015
Received in revised form 8 December 2015
Accepted 9 December 2015
Available online 11 December 2015
Diethers are an important group of electron donors in Ziegler–Natta catalysts. A simple diether, 1,3-
dimethoxypropane was studied as an electron donor in Grignard–Wurtz synthesis of a MgCl2–donor
adduct. 1,3-Dimethoxypropane was unexpectedly found to undergo a cleavage reaction during the syn-
thesis producing methoxy groups (OCH3). Each mole of 1,3-dimethoxypropane produced approximately
2
moles of methoxy groups, which are probably bound to magnesium chloride as methoxymagnesium
chloride. A Grignard reagent, BuMgCl formed in the Grignard–Wurtz reaction most likely causes the
cleavage of the ether bonds in 1,3-dimethoxypropane and there seem to be at least two parallel reac-
tion paths taking place and producing at least two different by-products. The first step in the cleavage
of 1,3-dimethoxypropane is a Grignard reagent (BuMgCl) induced elimination of OCH3, which gives 3-
methoxy-1-propene. This intermediate product reacts further in a substitution reaction caused by the
Grignard reagent producing 1-heptene as the by-product. The cleavage of the ether bond in 3-methoxy-
Keywords:
MgCl2
Ether cleavage
Diether
1
,3-Dimethoxypropane
Ziegler–Natta catalysis
1
-propene and formation of OCH3 can also occur through another reaction path, which produces propene
as the by-product.
©
2015 Elsevier B.V. All rights reserved.
1
. Introduction
MgCl2 has become a widely studied and commercially impor-
ı-MgCl . The reaction can be described using four reaction equa-
tions:
2
Mg + RCl → RMgCl
RMgCl ꢀ MgCl + MgR2
(1)
(2)
(3)
(4)
tant compound after it was discovered to be a suitable support
material for Ziegler–Natta catalysts [1]. In order to have useful
properties in the catalysis, MgCl has to be highly disordered. This
activated MgCl2 (or ı-MgCl ) can be prepared in several ways.
Methods include mechanical and chemical activation or their com-
2
2
2
Mg + 2 RCl ꢀ MgCl + R2
2
2
RMgCl + RCl ꢀ MgCl + R2
2
bination [2,3]. In mechanical activation, ordered ˛-MgCl is grinded
2
in a ball mill [4]. Chemical activation methods enable better con-
trol over the morphology, the size and size distribution of particles
and have thus widely replaced traditional mechanical activation
methods [2]. In the most common chemical method, adducts of
The first step of the reaction is formation of Grignard reagent
(Eq. (1)) [9,10]. In solutions of Grignard reagents, an equilibrium
(Schlenk equilibrium) between alkyl magnesium chloride and the
products, magnesium dialkyl and magnesium chloride, is reached
(Eq. (2)) [9,11]. Alkyl chloride can also react with Mg or RMgCl form-
ing magnesium chloride in Wurtz coupling reactions (Eq. (3) and
(4)) [12].
Lewis bases acting as electron donors can coordinatively bind
to unsaturated magnesium atoms of MgCl2. Two types of electron
donors (internal and external) are used in Ziegler–Natta cata-
lysts. Internal electron donors are added during the preparation
of precatalyst, whereas external electron donors are added to the
precatalyst with the co-catalyst in the polymerization [2]. Inter-
MgCl and Lewis bases are first formed. Afterwards, the Lewis base
2
is removed and ı-MgCl2 is obtained [5,6]. Activated MgCl2 can
also be prepared with so called Grignard–Wurtz reaction, which
is an easy one-step chemical method [3,7,8]. In Grignard–Wurtz
reaction, magnesium metal reacts with n-alkyl chloride producing
nal electron donors have a significant role in formation of ı-MgCl2
∗ Corresponding author.
E-mail addresses: vnissine@uef.fi (V. Nissinen), tuula.pakkanen@uef.fi
[
13,14]. It has been shown that these donors affect relative sta-
(
T.T. Pakkanen).
bilities of different catalytically relevant surfaces (namely (104)
http://dx.doi.org/10.1016/j.molcata.2015.12.003
381-1169/© 2015 Elsevier B.V. All rights reserved.
1

V. Nissinen et al. / Journal of Molecular Catalysis A: Chemical 413 (2016) 94–99
95
and (110)) and thus the structure of MgCl2 [15]. Both internal
and external electron donors also have a great influence on the
properties of Ziegler–Natta catalysts and polymers produced. The
productivity and hydrogen response of the catalyst as well as the
stereoregularity, molar mass and molar mass distribution of the
polymers formed are affected by the electron donors [2,15]. Elec-
tron donors regulate the content and distribution of active species
by competing from the same surface sites and also affect the stere-
ospesificity of active sites due to steric effects [13,16,17]. Typical
electron donors in Ziegler–Natta catalysts are e.g. aromatic esters,
phthalates, diethers and succinates [18]. Diethers are perhaps the
most interesting group of electron donors due to their ability to pro-
duce highly isotactic polypropylene with a very high productivity
without the presence of an external electron donor [19].
products formed were isolated and washed in the glove box and
then dried as mentioned before.
2.3. Characterization of the solid products
Magnesium content of solid products was determined by
an EDTA (ethylenediaminetetraacetic acid) titration. Amounts of
organic molecules bound to the solid products were determined
1
by H NMR spectroscopy (Bruker AMX-400 spectrometer). For this
analysis, solids were dissolved in a 10% (V/V) D2SO4/D2O solu-
tion and sodium acetate was used as an internal standard. The
chlorine content of the products was obtained on the basis of the
determined mole fractions of magnesium, organic moieties and
unreacted donor compounds.
Solid state 13C NMR spectra of the products were recorded. Mea-
surements were conducted with a Bruker AMX-400 spectrometer
using a cross polarization and a magic angle spinning with the fol-
lowing parameters: a spin rate 4500 Hz, a relaxation delay 4 s, a
contact time 3.0 ms and a number of scans 10000. Glycine was
used as an external standard. IR spectra of solid products were
measured using a Nicolet Impact 400D spectrometer. Spectra were
recorded using a DRIFT (diffuse reflectance infrared Fourier trans-
formation) unit mounted inside a glove box. Number of scans was
In our studies, MgCl2 supports have been synthesized with
Grignard–Wurtz reaction in the presence of different ethers as elec-
tron donors [20–22]. In the case of diethers, we have observed a
cleavage of the C O bond during the Grignard–Wurtz synthesis.
The cleavage reaction is undesired if the aim is the synthesis of
MgCl supports containing diethers as electron donors. The cleav-
2
age reaction can also be adverse if it takes place during the other
steps of catalyst preparation (e.g. addition of TiCl ) or even during
4
polymerization. The aim of this study is to gain insight into the
cleavage reaction of diethers, especially 1,3-dimethoxypropane,
which is the simplest of 1,3-diethers. The cleavage reactions of
simple ethers have been studied [23–25] in the past decades, but
according to our knowledge no reports on the cleavage of diethers
in the Grignard–Wurtz synthesis have been published.
−
1
32 and resolution 2 cm
.
2.4. Characterization of the liquid and gas phases
Also liquid and gas phases of some reaction mixtures were ana-
lyzed. Liquid phases were analyzed with 1H NMR spectroscopy.
Samples were taken directly from the liquid phases and measured
2
. Experimental
in CDCl . TMS was used as an internal standard. Gas phases of
3
the reaction mixtures were analyzed using IR spectroscopy and
gas chromatography. An IR spectrum was recorded with a Bruker
Vertex 70 spectrometer. Number of scans was 16 and resolution
2
.1. Materials
Octane (reagent grade, 98%), 1-chlorobutane (ReagentPlus, 99%),
-methoxy-1-propene (97%) and butylmagnesium chloride (2.0 M
−
1
2
cm . A gas cuvette was approximately 16 cm long and equipped
3
with ZnSe windows. A gas chromatogram was recorded using a
Hewlett-Packard 6890 Series GC system which was equipped with
a Chromosorb column and a hot wire detector. Helium was used
as a carrier gas. For analysis of the gas phase of the reaction mix-
ture, the autoclave was thoroughly cooled with an ice bath after
the heating. Samples were taken from the autoclave through a long
copper tube which was also cooled with an ice bath.
solution in diethyl ether) were purchased from Sigma–Aldrich
and 1,3-dimethoxypropane (98%) from CHEMOS GmbH. Ethers, 1-
chlorobutane and octane were dried and stored over activated 3 Å
molecular sieves. Magnesium turnings (99.9+%) were purchased
◦
from Acros Organics and dried in an oven at 110 C for two days
prior to the synthesis. All reactions and handling of products were
strictly done under an argon or nitrogen atmosphere using a glove
box and Schlenk techniques.
3. Results and discussion
2.2. Grignard–Wurtz synthesis
3.1. Grignard–Wurtz synthesis with 1,3-dimethoxypropane as an
electron donor
Syntheses were mostly carried out in an autoclave. Follow-
ing amounts of reagents were used: 0.5 g (0.021 mol) magnesium;
some small crystals of iodine; 6.45 ml (0.062 mol) 1-chlorobutane;
Grignard–Wurtz synthesis was performed in the presence of
1,3-dimethoxypropane as an electron donor in an autoclave using
magnesium and 1-chlorobutane as starting materials and octane
as a solvent. The molar ratio of 1,3-dimethoxypropane to mag-
nesium was 1:2. The powder X-ray diffraction analysis indicated
that the solid product formed was highly disordered. The diffrac-
togram of the product differed notably from that of ı-MgCl2 (the
diffractograms are presented in Fig. SA1 in Supplementary informa-
tion). According to solid state CP/MAS 13C NMR spectrum (Fig. 1),
the product contained 1,3-dimethoxypropane and another com-
pound, which was preliminarily identified as methanol or methoxy
groups. The relative content of 1,3-dimethoxypropane was signif-
icantly lower than that of methanol or methoxy groups. In the IR
spectrum of the solid product (Fig. SA2), the typical O H stretch-
1
.27 ml (0.010 mol) 1,3-dimethoxypropane and 20 ml octane.
Reagents were packed into the autoclave in the glove box. After
◦
packing, the autoclave was heated at 130 C for 2 h with a constant
mixing. The solid product formed was separated by a filtration in
the glove box where the product was also washed with octane (3
times 10 ml). The product was then dried in vacuum at room tem-
perature at least for two days. After washing and drying the product
was fine white powder.
Some syntheses were also carried out in glassware at an atmo-
spheric pressure in order to take samples from the reaction mixture
during the reaction. The reagents were packed in the glove box
into a two-necked flask equipped with a reflux condenser. The
◦
−1
flask was then heated at 130 C for 2 h with an oil bath and mixed
ing vibration at 3350 cm for a possible methanol had a very low
−
1
with a magnetic stirrer. A constant argon flow through the system
ensured an oxygen and moisture free atmosphere. Samples were
taken from the reaction mixture using two-headed needles. Solid
intensity compared to the C O stretching vibration at 1000 cm
.
Thus, it was highly probable that the solid product formed con-
tained methoxy groups instead of methanol. 1H NMR spectrum

9
6
V. Nissinen et al. / Journal of Molecular Catalysis A: Chemical 413 (2016) 94–99
adding 1,3-dimethoxypropane to ı-MgCl according to Eq. (6). Syn-
2
thesis of ı-MgCl was conducted according to reaction Eqs. (1)–(4)
2
as in previous case. An ethyl ether solution of butylmagnesium
chloride was added to the MgCl –1,3-dimethoxypropane complex
2
◦
and the mixture was heated at 130 C for 2 h in an autoclave using
octane as a solvent. 1,3-Dimethoxypropane was partially cleaved
producing methoxy groups (Eq. (7)). Characterization results of
complexes formed in both reactions (denoted by Complex 6 and
Complex 7) are presented in Supplementary information section
SB. The experiment indicated that butylmagnesium chloride is very
likely responsible for cleavage reaction of 1,3-dimethoxypropane
in Grignard–Wurtz reaction.
◦
2
5 C / 2h
ı-MgCl2 + 1, 3-dimethoxypropane
→
MgCl /1, 3-dimethoxypropane
(6)
2
octane
Fig. 1. CP/MAS 13C NMR spectrum of the product from the Grignard–Wurtz
synthesis with 1,3-dimethoxypropane as an electron donor. 13dmp = 1,3-
dimethoxypropane; Oct = octane; MeO = methoxy group; ss = spinning sideband.
◦
1
30 C / 2h
MgCl /1, 3-dimethoxypropane+BuMgCl
→
CH3OMgCl +1, 3-dimethoxypropane(7)
2
octane
3.3. Analysis of the solid and liquid phases of the reaction mixture
of the solid product dissolved in a D SO /D O solution (Fig. SA3)
during the reaction
2
4
2
supported these findings. As the product was dissolved in the
D SO /D O solution, complexes were decomposed and methoxy
2
4
2
In order to determine the cleavage rate of 1,3-
dimethoxypropane during the Grignard–Wurtz reaction, the
synthesis was performed in the presence of 1,3-dimethoxypropane
in a glassware at an atmospheric pressure using the same amounts
of reagents and the same reaction temperature as in the autoclave
synthesis. Samples were taken from the reaction mixture as
the reaction proceeded. Solid products were isolated, washed
groups were found to react with the acid producing methanol,
1
1
detected by H NMR. Based on the H NMR analysis and EDTA titra-
tion, molar ratios of 1,3-dimethoxypropane and methoxy groups
to magnesium in the solid product were 0.047 and 0.82, respec-
tively. The molar ratio of chlorine to magnesium was 1.26. It can be
concluded that most of 1,3-dimethoxypropane was cleaved during
the reaction and every mole of 1,3-dimethoxypropane produced
approximately 2 moles of methoxy groups. The product consists
most probably of methoxymagnesium chloride and a small amount
of unreacted 1,3-dimethoxypropane. Formation of other alkoxy-
magnesium chlorides has been reported under similar reaction
conditions from different sources of alkoxy groups [26–29].
1
and then dissolved in D SO /D O for H NMR analysis. The
2
4
2
results are summarized in Fig. 2, where the molar amounts of
1,3-dimethoxypropane and methoxy groups per gram of the solid
product are presented as a function of the reaction time.
In the beginning, the solid magnesium product formed con-
tained more 1,3-dimethoxypropane than methoxy groups. As the
reaction proceeded, the amount of 1,3-dimethoxypropane in the
solid product decreased rapidly and simultaneously the amount of
methoxy groups increased. 1,3-Dimethoxypropane is possibly first
bound to magnesium chloride formed in Grignard–Wurtz reaction
and later undergoes a cleavage reaction in which methoxy groups
are produced.
Two other diethers (1,1-dimethoxyethane and 2,2-
dimethoxypropane) were also studied as electron donors in
Grignard–Wurtz synthesis. Reaction conditions and amounts
of reagents were kept the same as in the case of 1,3-
1
13
dimethoxypropane. Based on XRD, H NMR, CP/MAS C NMR and
IR analyses, the solid products formed were highly disordered
and consisted mostly of methoxymagnesium chloride as in the
case of 1,3-dimethoxypropane (Table SA1 and Figs. SA4–6 in
Supplementary information).
The liquid phase of the reaction mixture samples was also ana-
lyzed with 1H NMR spectroscopy (Fig. 3). In the early stages of
reaction (t = 20 min and t = 30 min) there were two new unsatu-
rated compounds present in the liquid phase. The compounds were
identified as 3-methoxy-1-propene and 1-heptene on the basis of
3.2. The cause of the cleavage reaction
1
H NMR spectra. Pure compounds were used as the references.
The cause of the cleavage of 1,3-dimethoxypropane was
examined under various reaction conditions. First, 1,3-
dimethoxypropane was heated in an autoclave in the presence
◦
of 1-chlorobutane and octane at 130 C for 2 h to find out if
1
,3-dimethoxypropane was stable in the reaction conditions. No
cleavage of ether bond was observed.
Next, 1,3-dimethoxypropane was heated in the presence ı-
MgCl , synthesized according to reaction Eqs. (1)–(4). Aim of this
2
experiment was to find out if heat and presence of ı-MgCl2 are
sufficient to cleave 1,3-dimethoxypropane (Eq. (5)). Cleavage of
1
,3-dimethoxypropane was nor observed in this case. Instead, a
crystalline MgCl –1,3-dimethoxypropane complex was obtained.
2
Characterization results of this crystalline complex (denoted by
Complex 5) are presented in Supplementary information Section
SB.
◦
1
30 C / 2h
ı-MgCl2 + 1, 3-dimethoxypropane
→
MgCl /1, 3-dimethoxypropane
(5)
2
octane
Butylmagnesium chloride formed in Grignard–Wurtz reaction
according to Eq. (1) was considered as one possible cause of the
cleavage reaction of 1,3-dimethoxypropane. In order to examine
Fig. 2. The molar amounts of 1,3-dimethoxypropane and methoxy groups per gram
of the solid product as a function of the reaction time. t = 0 corresponds to the
moment heating was started.
this, MgCl –1,3-dimethoxypropane complex was synthesized by
2

V. Nissinen et al. / Journal of Molecular Catalysis A: Chemical 413 (2016) 94–99
97
Fig. 3. 1H NMR spectrum (regions 3.8–6.0 ppm and 3.2–3.6 ppm, presented on different intensity scales) of the liquid phase of the reaction mixture from the Grignard–Wurtz
synthesis in the presence of 1,3-dimethoxypropane as an electron donor at different intervals from the beginning of the reaction. MeOPr = 3-methoxy-1-propene, BuCl = 1-
chlorobutane, 13dmp = 1,3-dimethoxypropane.
As the reaction proceeded, the amount of 3-methoxy-1-propene
decreased and in the end of the reaction (t = 120 min) there was
virtually none. 1-Heptene was still present in the end of the reac-
tion.
methoxy/magnesium ratio of 1:2 (the diffractogram presented in
Fig SD1). The gas and liquid phases of the reaction mixture were
also analyzed for possible by-products. 1-Heptene was present in
1
the liquid phase ( H NMR spectrum presented in Fig. SD2) and
These results can be rationalized so that in the first step
the cleavage of 1,3-dimethoxypropane produces 3-methoxy-1-
propene. This probable intermediate product seems to react further
producing 1-heptene. In both steps, one methoxy group is cleaved.
propene was detected in the gas phase on the basis of IR analysis (IR
spectrum presented in Fig. SD3). This provided further evidence of
3-methoxy-1-propene being an intermediate product in the cleav-
age reaction producing the both observed by-products (propene
and 1-heptene).
3.4. Analysis of the gas phase of the reaction mixture
Analyses of the gas phase of the reaction mixture revealed
3.6. Reaction paths for the cleavage of 1,3-dimethoxypropane
another possible by-product. An IR study of the gas phase indicated
a presence of a terminal alkene, which on the basis of IR spectrum
The two final by-products (1-heptene and propene) formed in
the cleavage of 1,3-dimethoxypropane in Grignard–Wurtz synthe-
sis indicated that there were at least two different parallel reaction
paths for the cleavage of diether. A possible reaction path, which
results in formation of 1-heptene as a by-product, is presented in
Scheme 1.
1,3-Dimethoxypropane is probably first bound to magnesium
chloride formed in the Grignard–Wurtz reaction. Under the reac-
tion conditions used, butylmagnesium chloride is also formed
from magnesium and 1-chlorobutane according to Eq. (1). Butyl-
magnesium chloride is a strong nucleophile and it reacts as its
corresponding carbanion. The first step in the reaction path is an
(
Fig. SC1) is likely propene. The IR spectrum also indicated that the
gas sample contains another compound, probably an alkane. The
gas chromatography of the sample supported these findings. Gas
chromatograms of the gas phase of the reaction mixture and pure
propene, which was used as a reference, are shown in Fig. SC2 in
Supplementary information.
3.5. Grignard–Wurtz synthesis with 3-methoxy-1-propene as an
electron donor
The intermediate product 3-methoxy-1-propene was also stud-
ied as an electron donor in the Grignard–Wurtz synthesis. The
synthesis in the autoclave was conducted under the same reac-
tion conditions as in the case of 1,3-dimethoxypropane. The
molar ratio of 3-methoxy-1-propene to magnesium was 1:2.
The solid magnesium product formed contained methoxy groups
and the morphology of the product was similar to that of
the 1,3-dimethoxypropane case. Based on powder X-ray diffrac-
tion analysis, the product was highly disordered containing
both MgCl2 and methoxymagnesium chloride due to the low
elimination of OCH by BuMgCl [23]. One of the methoxy groups is
3
detached and 3-methoxy-1-propene is formed. In this step, butane
is also formed via ␤-hydrogen abstraction and it could be the other
gaseous compound observed in the gas phase of the reaction mix-
ture.
Second step in the cleavage reaction is a substitution caused
by BuMgCl. The last methoxy group is detached and 1-heptene is
formed. There are two possibilities how the carbanion of BuMgCl
can attack, namely 1,2-addition and 1,4-addition [24,25]. The

9
8
V. Nissinen et al. / Journal of Molecular Catalysis A: Chemical 413 (2016) 94–99
Scheme 1. Proposed reaction path for the cleavage of 1,3-dimethoxypropane, which results in formation of 1-heptene as the by-product.
resulting products are the same in both cases. The solid product
formed in the reaction is methoxymagnesium chloride.
Propene was found to be the other possible by-product in
the second cleavage reaction. Propene can be formed in thermal
decomposition of 3-methoxy-1-propene intermediate (Scheme 2).
The reaction is a pericyclic retro ene reaction in which 3-methoxy-
gas phase of the reaction mixture was analyzed by gas chromatog-
raphy, which indicated that propene can be present in the gas phase
(the gas chromatogram in Fig. SE2). IR spectrum of the gas phase
of the reaction mixture (Fig. SE3) did not provide any clear evi-
dence of propene being present in the gas phase because of strong
overlapping absorptions of unreacted 3-methoxy-1-propene.
1
-propene decomposes to propene and formaldehyde [30]. This
retro ene reaction happens only at much higher temperatures (typ-
ically >400 C) than that used in the present synthesis. This makes
4. Conclusions
◦
the described mechanism unlikely.
Almost a complete cleavage of the ether bonds in 1,3-
Formation of propene has been reported to take place in the
cleavage reaction of diallyl ether [25]. Propene formation, which
results from transfer of ꢀ-electrons and a Grignard reagent acting
as a reducing agent, was considered to be an abnormal reaction.
The mechanism of the reaction has not been explained. Kharasch
et al. [31] have studied the cleavage of ethers by Grignard reagents
dimethoxypropane during a Grignard–Wurtz synthesis of a
MgCl –diether adduct was observed. The cleavage reaction results
2
in formation of methoxy groups which exist as methoxymagne-
sium chloride. Butylmagnesium chloride is most likely responsible
for this cleavage reaction. There are at least two parallel reac-
tion paths, which produce different by-products (1-heptene and
propene). Probable reaction paths to 1-heptene and propene by-
products were presented. The cleavage reaction of diethers can
be highly undesired and adverse if it occurs in the preparation
of Ziegler–Natta catalysts or even during the polymerization. The
possible cleavage reactions have to be considered when preparing
in the presence of various metal halides (MgCl not included). They
2
have reported formation of propene in the cleavage of phenyl allyl
ether by Grignard reagent and cobaltous chloride. Ohkubo et al. [32]
have reported selective cleavage reactions of allylic ethers in the
presence of low valent titanium species, MgCl2 and magnesium.
Reaction mechanism was proposed to proceed through titanacy-
clopropane and/or an anion radical intermediate. Products of the
reaction were methoxy ion and allyl anion or allyl radical, which
can react further producing propene.
MgCl support in the presence diether electron donors.
2
Acknowledgements
On the basis of these literature results, we examined heating
of 3-methoxy-1-propene in the presence of magnesium and ı-
MgCl2 (synthesized with Grignard–Wurtz reaction) using octane
We gratefully acknowledge a financial support from the Finnish
Funding Agency for Technology and Innovation and European
Union/European Regional Development Fund (grant 70054/09).
◦
1
as a solvent (reaction conditions 130 C/2 h). A solution-state
H
NMR analysis (in D SO /D O solution) of the solid product revealed
2
4
2
partial cleavage of 3-methoxy-1-propene to methoxy groups. This
Appendix A. Supplementary data
indicated that magnesium and ı-MgCl could cause partial decom-
2
position of 3-methoxy-1-propene in reaction conditions even in
the absence of titanium species. 1-Heptene was not found to be
present in the liquid phase of the reaction mixture (Fig. SE1). The
Supplementary information contains characterization results
(PXRD, IR spectrum and solution state H NMR spectrum)
of the solid product from the Grignard–Wurtz synthesis with
1
1
,3-dimethoxypropane as an electron donor. Powder X-ray diffrac-
13
tograms, CP/MAS
C NMR spectra and IR spectra of the
solid products from the Grignard–Wurtz syntheses with 1,1-
dimethoxyethane and 2,2-dimethoxypropane as electron donors
are presented. The Analyses of the gas phase of the reaction
mixture from the synthesis with 1,3-dimethoxypropane as an
electron donor are also included. The characterization (PXRD, IR
spectra and solid state 13C NMR spectra) of Complexes 5-7 is
presented. The analyses of the solid product and liquid and gas
Scheme 2. Thermal decomposition of 3-methoxy-1-propene via pericyclic retro ene
reaction.

V. Nissinen et al. / Journal of Molecular Catalysis A: Chemical 413 (2016) 94–99
[15] T. Taniike, M. Terano, J. Catal. 293 (2012) 39–50.
99
phases of the reaction mixture from Grignard–Wurtz synthesis
[
16] D. Fregonese, V. Di Noto, A. Peloso, S. Bresadola, Macromol. Chem. Phys. 200
1996) 2122–2126.
17] J.C. Chadwick, Macromol. Symp. 173 (2001) 21–35.
with 3-methoxy-1-propene as an electron donor are shown. Sup-
plementary information presents also the analyses of the liquid and
gas phases of the reaction mixture from heating of 3-methoxy-1-
propene in the presence of Mg and ı-MgCl2. Supplementary data
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.molcata.2015.12.003.
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