New selectivities from old catalysts. Occlusion of Grubbs' catalysts in PDMS to change their reactions

Article abstract of DOI:10.1016/j.jorganchem.2006.09.022

This article describes new selectivities for Grubbs' first and second generation catalysts when occluded in a hydrophobic matrix of polydimethylsiloxane (PDMS). Occlusion of catalysts in mm-sized slabs of PDMS is accomplished by swelling with methylene chloride then removing the solvent under vacuum. The catalysts are homogenously dissolved in PDMS yet remain catalytically active. Many substrates that react by olefin metathesis with Grubbs' catalysts freely dissolved in methylene chloride also react by olefin isomerization with occluded catalysts. Eleven examples of substrates that exhibit dual reactivity by undergoing olefin isomerization with occluded catalysts and olefin metathesis with catalysts dissolved in methylene chloride are reported. Most of these substrates have olefins with allylic phosphine oxides, carbonyls, or ethers. Control experiments demonstrate that isomerization is occurring in the solvent by decomposition of the catalyst from a ruthenium carbene to a proposed ruthenium hydride. This work was extended by heating occluded Grubbs' first generation catalyst to 100 °C in 90% MeOH in H₂O in the presence of various alkenes to transform the Grubbs' catalyst into an isomerization catalyst for unfunctionalized olefins. This work demonstrates that occlusion of organometallic catalysts in PDMS has important implications for their reactions and can be used as a method to control which reactions they catalyze.

Full text of DOI:10.1016/j.jorganchem.2006.09.022

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Journal of Organometallic Chemistry 691 (2006) 5278–5288
www.elsevier.com/locate/jorganchem
New selectivities from old catalysts. Occlusion of Grubbs’ catalysts in
PDMS to change their reactions
*
M. Brett Runge, Martin T. Mwangi, Ned B. Bowden
University of Iowa, Department of Chemistry, 423K Chemistry Building, Iowa City, IA 52242, United States
Received 28 June 2006; received in revised form 10 September 2006; accepted 12 September 2006
Available online 20 September 2006
Abstract
This article describes new selectivities for Grubbs’ first and second generation catalysts when occluded in a hydrophobic matrix of
polydimethylsiloxane (PDMS). Occlusion of catalysts in mm-sized slabs of PDMS is accomplished by swelling with methylene chloride
then removing the solvent under vacuum. The catalysts are homogenously dissolved in PDMS yet remain catalytically active. Many sub-
strates that react by olefin metathesis with Grubbs’ catalysts freely dissolved in methylene chloride also react by olefin isomerization with
occluded catalysts. Eleven examples of substrates that exhibit dual reactivity by undergoing olefin isomerization with occluded catalysts
and olefin metathesis with catalysts dissolved in methylene chloride are reported. Most of these substrates have olefins with allylic phos-
phine oxides, carbonyls, or ethers. Control experiments demonstrate that isomerization is occurring in the solvent by decomposition of
the catalyst from a ruthenium carbene to a proposed ruthenium hydride. This work was extended by heating occluded Grubbs’ first gen-
eration catalyst to 100 °C in 90% MeOH in H2O in the presence of various alkenes to transform the Grubbs’ catalyst into an isomer-
ization catalyst for unfunctionalized olefins. This work demonstrates that occlusion of organometallic catalysts in PDMS has
important implications for their reactions and can be used as a method to control which reactions they catalyze.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Grubbs’ catalysts; Polydimethylsiloxane; Metathesis; Olefin isomerization; Ruthenium
1. Introduction
16]. One prominent example of a new reaction catalyzed
by the Grubbs’ catalysts is its transformation into an olefin
isomerization catalyst. Many examples of these isomeriza-
tion reactions are for only a select range of substrates with
an olefin allylic to an amide, ether, or alcohol
[6,8,12,14,15,17]. In other work, transformation of the
Grubbs’ catalyst into an olefin isomerization catalyst is
more general but requires heat or the addition of H2 or alk-
oxides [3,12,18]. In many of these prior examples, olefin
isomerization was in competition with olefin metathesis
and a complex mixture of products was observed. In one
report, isomerization was favored when a silyl enol ether
was added to the reaction mixture, and in other reports
the ratio of isomerization to metathesis product was
affected by the choice of solvent or other additives
[6,8,12,14,15,17]. The exact mechanism for isomerization
is unknown, but it is believed to proceed through a ruthe-
nium hydride that forms during the course of the reaction.
The Grubbs’ olefin metathesis catalysts have proven to
be invaluable in small molecule synthesis for their ability
to catalyze ring closing metathesis reactions and to bond
two molecules together through cross metathesis [1]. These
catalysts are notable as they are stable to many different
functional groups and solvents while the second generation
catalyst is as active as the Schrock metathesis catalyst [2].
Recently, new reactions beyond metathesis have been dis-
covered that are catalyzed by the Grubbs’ catalysts that
open up new synthetic transformations. Examples of these
new reactions include olefin isomerization, deprotection of
tertiary amines, isomerization of allylic alcohols to ketones,
Kharasch reaction, and hydrosilylation of carbonyls [3–
*
Corresponding author. Tel.: +1 319 335 1198; fax: +1 319 335 1270.
E-mail address: ned-bowden@uiowa.edu (N.B. Bowden).
0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.09.022

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5279
In this article, we report two important advances with
Grubbs’ metathesis catalysts. First, we describe a method
that allows one to decide whether to react substrates by
olefin metathesis or isomerization with the Grubbs’ cata-
lysts. Second, we report a method to make the Grubbs’ first
generation catalyst an isomerization catalyst for a wide
range of substrates. These methods increase the number
and types of products that can be synthesized with the
Grubbs’ catalysts and add another level of control to
how they react.
This work is built on our prior efforts to occlude the
Grubbs’ catalysts in a cross-linked, hydrophobic mem-
brane of polydimethylsiloxane (PDMS) [19]. Catalysts
are swelled into mm-sized PDMS slabs with methylene
chloride that is removed under vacuum to yield occluded
catalysts. PDMS is a new ‘‘solvent’’ for the catalysts that
is both apolar and very viscous [20]. To react, reagents
diffuse from an aqueous solvent into PDMS, react with
the catalyst, and then the product diffuses from PDMS
back to the solvent. Occluding catalysts in PDMS mem-
branes has an important impact on how they react and
introduced new selectivities and reactivities to mature cat-
alysts. During our work, we discovered that although
many substrates react by metathesis with occluded
Grubbs’ catalysts, some substrates reacted by olefin isom-
erization with occluded catalysts (Fig. 1). Interestingly,
substrates that reacted by isomerization with occluded
catalysts also reacted by metathesis with freely dissolved
Grubbs’ catalyst in methylene chloride. This difference
in products was very interesting as it made it possible
to choose whether to react a substrate by metathesis or
isomerization.
2. Methods and characterization
2.1. Materials
Allyldiphenylphosphine oxide, dimethyl allylphospho-
nate, diethyl allylphosphonate, allyl phenyl ether, eugenol,
diethyl allylmalonate, 10-undecene-1-ol, allyl bromide, 1-
hepten-4-ol, pyridinium chlorochromate, 1-hexanol, vinyl
acetic acid, benzylidene-bis(tricyclohexylphosphine)dichlo-
roruthenium, and benzylidene[1,3-bis(2,4,6-trimethylphenyl)-
2-imidazolidinylidene]dichloro(tricyclohexylphosphine)-
ruthenium were purchased from Acros or Aldrich at their
highest purity and used as received. 2-Propenylhexanoate,
hept-1-en-4-one, and phenyl-2-propenylether were synthe-
sized using literature procedures [21,22]. All solvents were
reagent grade, purchased from Acros, freeze-pump-thawed
three times, and stored under N2. Geduran silica gel 60 was
purchased from Fisher and used for all purifications. Syl-
gard 184 elastomer (PDMS) was purchased from Essex
Brownell.
2.2. Characterization
1H and 13C NMR spectra were recorded with a Bruker
DPX 300 using CDCl3 with 1% TMS as the solvent and
1
internal standard. H NMR and 13C NMR were recorded
at 300 and 75 MHz, respectively. A few complex mixtures
of isomers were formed that were unable to be separated.
As a result, partial hydrogen assignments are given where
appropriate. Isomers present include E and Z olefins and
single or multiple isomerization products. NMR spectra
were compared with the same molecules published in the
literature or very similar molecules and literature references
are provided for these molecules.
We extended this work to develop a general olefin isom-
erization catalyst from the Grubbs’ first generation catalyst
that reacts with a wide range of substrates. In this article,
we will report which reagents react by olefin isomerization
with occluded catalysts but still react by metathesis with
freely dissolved catalysts in methylene chloride. In addi-
tion, we will describe how heating the Grubbs’ first gener-
ation catalyst caused it to become a general isomerization
catalyst.
2.3. Preparation of occluded Grubbs’ catalyst in
polydimethylsiloxane (PDMS)
Sylgard 184 elastomer base and curing agent were mixed
in a 10:1 ratio respectively, degassed for 30 min, poured
into petri dishes to approximately a 1 mm thickness, and
degassed for 1 h before placing in a 65 °C oven overnight.
The PDMS slabs were swelled with CH2Cl2 and pentane
three times to remove residual platinum catalyst and oligo-
mers. The PDMS slabs were cut into mm-sized slabs, dried,
and degassed before taking into a glove box. Grubbs first
generation catalyst (1.045 g, 1.27 mmol) was dissolved in
14.7 mL of CH2Cl2 and added to a Schlenk flask with
21.98 g of PDMS. The PDMS was allowed to swell with
the catalyst solution for 3 h with frequent shaking upon
which the solution was completely absorbed into the
PDMS. The CH2Cl2 was then removed under vacuum
overnight. The PDMS slabs were washed with CH2Cl2
three times to remove residual catalyst from the outer sur-
face, dried under vacuum, weighed (22.64 g) and then
stored in a glove box. The concentration of catalyst in
PDMS was determined from the difference in weight of
Fig. 1. (a) Many terminal olefins react with Grubbs’ catalysts dissolved in
methylene chloride and with occluded catalysts in methanol/water by
cross metathesis. (b) We discovered that some olefins react by metathesis
with Grubbs’ catalysts in methylene chloride will also react by isomeri-
zation with occluded catalysts in methanol/water. This discovery allows
one to choose whether to use these catalysts to promote metathesis or
isomerization.

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M. Brett Runge et al. / Journal of Organometallic Chemistry 691 (2006) 5278–5288
the PDMS before and after the occlusion of the catalyst to
give 29.93 mg of catalyst per g of PDMS.
2.4.4. Hexyl-2-butenoate (4b)
The general procedure above was followed with 5 mol%
of Grubbs’ second generation catalyst in 3 mL solvent at
1
2.4. General olefin isomerization procedure for Undec-9-en-
1-ol (8b)
50 °C for 20 h. H NMR (CDCl3): d 0.89 (t, 3H), 1.29–
1.37 (m, 6H), 1.64 (m, 2H), 1.87 (m, 3H), 4.11 (t,
J = 6.6 Hz, 2H), 5.84 (m, 1.8 Hz, 1H), 6.96 (dq, J = 15.6,
6.6 Hz, 1H). 13C NMR (CDCl3): d 13.98, 17.92, 22.53,
25.60, 28.63, 31.44, 64.32, 122.79, 144.34, 166.66.
In a glove box, 1.69 g of PDMS occluded with Grubbs
first generation catalyst (50.6 mg, 61.5 lmol) was placed
in a Schlenk flask, removed from the glove box, and
attached to a Schlenk line. Seven milliliter of 10% H2O/
90% MeOH were added under N2 and freeze-pump-thawed
twice. 10-Undecene-1-ol (1.036 g, 6.1 mmol) was added
under N2 and the flask was placed in a 100 °C oil bath
for 15 h. The solvent was decanted off and diluted with
50 mL H2O and the product was extracted with CH2Cl2.
The product was purified by vacuum distillation to yield
a colorless oil: (0.788 g, 76%). The NMR spectra matched
literature precedents [23]. Multiple isomers were present.
1H NMR (CDCl3): d 0.86–0.99 (m, 1H), 1.29 (m, 10H),
1.53–1.64 (m, 5.4H) 1.94–2.02 (m, 2.6H), 3.62 (t,
J = 6.9 Hz, 2H), 5.38–5.42 (m, 2H). 13C NMR 12.70,
13.96, 17.88, 22.71, 25.57, 25.68, 25.71, 26.78, 27.02,
28.87, 29.08, 29.19, 29.27, 29.29, 29.37, 29.42, 29.45,
29.47, 29.51, 29.53, 29.56, 29.66, 32.48, 32.50, 32.56,
32.75, 62.99, 123.60, 124.54, 129.18, 129.23, 130.23,
130.79, 131.58, 131.91.
2.4.5. Isoeugenol (5b)
The general procedure was followed with 1 mol% of
Grubbs’ second generation catalyst in 7 mL solvent at
1
100 °C for 20 h. H NMR (CDCl3): d 1.85 (dd, J = 6.6,
1.8 Hz, 3H, CH3CH@CH), 3.87 (s, 3H), 5.61 (s, 1H,
OH), 6.07 (dq, J = 15.6, 6.6 Hz, 1H, CH3CH@CH), 6.31
(dq, J = 15.6, 1.8 Hz, 1H, CH3CH@CH), 6.82–6.87 (m,
3H). 13C NMR (CDCl3): d 18.30, 55.77, 107.83, 114.30,
119.24, 123.36, 130.67, 130.59, 144.69, 146.50.
2.4.6. Phenyl-1-propenylether (7b)
The general procedure above was followed with 4 mol%
of Grubbs’ second generation catalyst in 3 mL solvent at
50 °C for 18 h. NMR spectra matched those in the litera-
ture [21]. 1H NMR (CDCl3): d 1.67 (dd, E isomer,
J = 6.9, 1.8 Hz, 0.75H), 1.72 (dd, Z isomer, J = 6.9,
1.8 Hz, 2.25H), 4.88, (dq, Z isomer J = 6, 6.9 Hz, 0.75H),
5.36 (dq, E isomer, J = 12.2, 6.9 Hz, 0.25H), 6.36–6.45
(m, 1H). 13C NMR (CDCl3): d 9.36, 12.24, 107.45,
108.27, 116.14, 116.27, 122.31, 129.52, 140.84, 141.94,
157.52.
2.4.1. Diethyl-1-propenylphosphonate (1b)
The procedure above was followed with 5 mol% of
Grubbs’ second generation catalyst in 3 mL solvent at
50 °C for 20 h. The product was purified by distillation
and its NMR spectra matched those from the literature
2.4.7. Hexan-1-ol (9b)
1
[24]. H NMR (CDCl3): d 1.32 (t, 6H), 1.92 (m, 3H), 4.10
The above procedure was followed with 5 mol% of
Grubbs’ second generation catalyst in 3 mL solvent at
50 °C for 24 h. NMR spectra matched that of hexanol.
1H NMR (CDCl3): d 0.86 (t, J = 6.6 Hz, 3H), 1.24–1.32
(m, 6H), 1.50–1.55 (m, 2H), 3.58 (t, J = 6.6 Hz, 2H). 13C
NMR (CDCl3): d 13.91, 22.55, 25.37, 31.58, 32.65, 62.83.
(m, 4H), 5.68 (m, 1 H), 6.69–6.89 (m, 1H). 13C NMR
(CDCl3): d 16.31 (d, J = 5.9 Hz), 20.08 (d, J = 24.0 Hz),
61.65 (d, J = 5.4 Hz), 118.37 (d, J = 187.5 Hz), 149.09 (d,
J = 5 Hz).
2.4.2. Dimethyl-1-propenylphosphonate (2b)
The general procedure was followed with 5 mol% of
Grubbs’ second generation catalyst in 5 mL solvent at
65 °C for 20 h. NMR spectra matched those from the liter-
ature [24]. 1H NMR (CDCl3): d 1.87 (m, 3H), 3.64 (d,
J = 11.1 Hz, 6H), 5.58 (m, 1H) 6.75 (m, 1H). 13C NMR
(CDCl3): d 19.98 (d, J = 23.3 Hz), 52.05 (d, J = 5.9 Hz),
116.87 (d, J = 187.4 Hz), 149.92 (d, J = 4.7 Hz).
2.4.8. Hept-2-en-4-one (10b)
The above procedure was followed with 1 mol% of
Grubbs second generation catalyst at 100 °C for 2 h. The
1
product was purified by distillation. H NMR (CDCl3): d
0.92 (t, J = 7.5 Hz, 3H), 1.60–1.70 (m, 2H) 1.90 (dd,
J = 6.9, 1.5 Hz, 3H), 2.51 (t, J = 7.5 Hz, 2H), 6.12 (dq,
J = 15.6, 1.8 Hz, 1H), 6.85 (dq, J = 15.6, 6.6 Hz, 1H).
13C NMR (CDCl3): d 13.74, 17.64, 18.13, 41.83, 131.94,
142.22, 200.52.
2.4.3. 1-Propenyldiphenylphosphine oxide (3b)
The general procedure was followed with 1 mol% of
Grubbs’ second generation catalyst in 7 mL solvent at
50 °C for 13 h. NMR spectra matched those found in the
2.4.9. N,N-Dibutyl-2-buteneamide (11b)
The general procedure above was followed with 2 mol%
of Grubbs second generation catalyst at 100 °C for 4 h. The
NMR spectra agreed with the literature [26]. 1H NMR
(CDCl3): d 0.88–0.95 (m, 6H), 1.24–1.37 (m, 4H), 1.48–
1.58 (m, 4H), 1.88 (dd, J = 6.6, 1.8 Hz, 3H), 3.27 (t,
J = 7.5 Hz, 2H), 3.35 (t, J = 7.5 Hz, 1H), 6.21 (dq,
J = 14.1, 1.8 Hz, 1H), 6.91 (dq, J = 14.1, 6.9 Hz, 1H).
1
literature [25]. H NMR (CDCl3): 1.99 (m, 3H), 6.26 (m,
1H), 6.69 (m, 1H), 7.42–7.55 (m, 6H), 7.65–7.72 (m, 4H).
13C NMR (CDCl3): d 19.41 (d, J = 18.4 Hz), 122.62 (d,
J = 103.2 Hz), 127.48 (d, J = 11 Hz), 130.15 (d, J = 9.4),
130.66 (d, J = 2.9 Hz), 132.26 (d, J = 104.3 Hz), 146.70
(d, J = 2.9 Hz) [25].

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13C NMR (CDCl3): d 13.81, 13.90, 18.17, 20.06, 20.29,
30.04, 31.76, 46.34, 47.77, 121.97, 141.01, 166.11.
2.5.4. 1,4-Bis(3-methoxy-4-hydroxyphenyl)-but-2-ene (5c)
The general procedure above was followed with 1 mol%
of Grubbs second generation catalyst at 25 °C for 5 h. The
product was purified by chromatography on silica gel elut-
ing with 20% ethyl acetate/80% hexane and increasing to
50% ethyl acetate/50% hexane. Mixture of E and Z iso-
mers. NMR spectra matched those in the literature [28].
1H NMR (CDCl3): d 3.29 (E isomer, d, J = 4.8 Hz,
2.4H), 3.44 (Z isomer, d, J = 6.9 Hz, 1.6H), 3.83–3.85
(overlapping singlets, 6H), 5.55–5.67 (m, 2H), 6.67–6.72
(m, 3H), 6.82–6.88 (m, 3H).
2.5. Cross metathesis with freely dissolved Grubbs’ first
generation catalyst in methylene chloride for 1,4-dihexoxy-1-
butene (9c)
Using Schlenk techniques, Grubbs’ second generation
catalyst (53 mg, 63 lmol) was dissolved in 3 mL of degassed
CH2Cl2. Hexyl-2-propenylether (0.179 g, 1.3 mmol) was
added and the reaction was heated to reflux for 12 h. The
solvent was evaporated and the product was purified by
chromatography on silica gel eluting with 5% ethyl ace-
tate/95% hexane to give product as colorless liquid. NMR
spectra matched those in the literature [21]. 1H NMR
(CDCl3): 0.86–0.91 (m, 6H), 1.26–1.38 (m, 12H), 1.53–
1.64 (m, 4H), 2.14–2.22 (m, 1H), 2.32–2.39 (m, 1H), 3.35–
3.43 (m, 4H), 3.63 (t, E isomer, J = 6.6 Hz, 1H), 3.71 (t, Z
isomer, J = 6.6 Hz, 1H), 4.36 (q, Z isomer, J = 7.2 Hz,
0.5H), 4.74 (dt, E isomer, J = 12.6, 7.2 Hz, 0.5H), 5.98
(dt, Z isomer, J = 6.3, 1.2 Hz, 0.5H), 6.29 (d, E isomer
J = 12.6 Hz, 0.5 Hz). 13C NMR (CDCl3): d 13.95, 13.98,
22.55, 22.60, 24.71, 25.46, 25.65, 25.84, 28.43, 29.23,
29.69, 29.72, 31.54, 31.56, 31.68, 31.71, 69.10, 70.47,
70.77, 70.96, 71.57, 72.17, 99.79, 102.40, 146.12, 147.54.
2.5.5. 2,7-Bis-ethoxycabonyl-oct-4-enedioic acid diethylester
(6c)
The general procedure was followed with the exception
2 mol% of Grubbs second generation catalyst was used
and the reaction was performed at 25 °C for 5 h. The prod-
uct was purified by column chromatography on silica gel
eluting with 10% ethyl acetate/90% hexane. NMR spectra
1
matched those in the literature [19,29]. H NMR (CDCl3):
d 1.24–1.29 (m, 12H), 2.55–2.59 (m, 3.2 H), 2.65–2.70 (m,
0.8H), 3.38 (t, J = 7.5 Hz, 2H), 4.15–4.24 (m, 8H), 5.42–
5.45 (m, 0.4H), 5.49–5.52 (m, 1.6H) 13C NMR (CDCl3):
d 14.05, 26.57, 31.61, 51.75, 51.95, 61.36, 127.86, 128.85,
168.80.
2.5.1. Tetraethyl-2-butene-1,4-diphosphonate (1c)
The general procedure was followed and the product
was purified by distillation. E and Z isomers were isolated
and the NMR spectra matched those in the literature [27].
1H NMR (CDCl3): 1.32 (t, J = 6.9 Hz, 12H), 2.59–2.65 (m,
4H), 4.11 (m, 8H), 5.61–5.69 (m, 2H). 13C NMR (CDCl3):
d 16.38 (d, J = 3.2 Hz), 16.42 (d, J = 2.8 Hz), 30.52 (d,
J = 146 Hz), 30.52 (d, J = 137 Hz), 61.87 (d, J = 3.8 Hz),
61.91 (d, J = 3.1 Hz), 122.76 (t, J = 1.8 Hz), 124. 28 (t,
J = 1.8 Hz).
2.5.6. 1,4-Diphenoxy-2-butene (7c)
The general procedure was followed except the reaction
was performed at 25 °C. The product was purified by chro-
matography on silica gel eluting with 5% ethyl acetate/95%
hexane. NMR spectra matched those in the literature [30].
1H NMR (CDCl3): d 4.57–4.59 (m, 4H), 6.09–6.11 (m, 2H),
6.90–6.98 (m, 6H), 7.24–7.31 (m, 4H). 13C NMR (CDCl3):
d 67.61, 114.70, 120.92, 128.41, 129.47, 158.47.
2.5.7. Icos-10-ene-1,20-diol (8c)
The general procedure above was followed with the
exception 2 mol% catalyst was used. The product was puri-
fied by chromatography on silica gel eluting with 30% ethyl
acetate/70% hexane. NMR spectra matched those in the lit-
2.5.2. Tetramethyl-2-butene-1,4-diphosphonate (2c)
The general procedure above was followed with the
exception 2 mol% of catalyst was used. NMR spectra
1
1
agreed with those in the literature [27]. H NMR (CDCl3):
erature [19,29]. H NMR (CDCl3): d 1.28 (s, 26H), 1.52–
E and Z isomers d 2.64–2.77 (m, 4H), 3.80 (d, J = 10.8 Hz,
12H), 5.64–2.77 (m, 2H). 13C NMR (CDCl3): d 29.48, (d,
J = 141.8 Hz), 29.54 (d, J = 142.1 Hz) 52.63 (d,
J = 6.7 Hz), 52.68 (d, J = 7.4 Hz), 122.61 (t, J = 1.7 Hz),
124.16 (t, J = 2.1 Hz).
1.58 (m, 4H), 1.95–2.02 (m, 4H), 3.64 (t, J = 6.6 Hz, 4H),
5.35–5.40 (m, 2H). 13C NMR (CDCl3): d 25.74, 27.18,
28.71, 29.10, 29.26, 29.41, 29.43, 29.46, 29.57, 29.61,
29.73, 32.57, 32.80, 63.09, 129.88, 130.35.
2.6. Control experiment
2.5.3. 1,6-Dihexyl-3-hexenedioate (4c)
The general procedure above was followed with the
exception 2 mol% of catalyst was used. The product was
purified by chromatography on silica gel eluting with 5%
ethyl acetate/95% hexane. Mixture of E and Z isomers.
1H NMR (CDCl3): d 0.89 (t, J = 6.9 Hz, 6H), 1.27–1.37
(m, 12H), 1.57–1.67 (m, 4H), 3.07–3.11 (m, 4H), 4.05–
4.10 (m, 4H), 5.68–5.80 (m, 2H), 13C NMR (CDCl3): d
13.99, 22.51, 25.54, 28.53, 31.40, 33.19, 37.93, 64.91,
124.52, 125.95, 171.66.
In a glove box, 1.06 g of PDMS occluded with Grubbs’
second generation catalyst (30.5 mg, 36 lmol) was placed
in a Schlenk flask. Using standard Schlenk techniques,
4 mL solvent (degassed 10% H2O/90% MeOH) was
added, followed by the addition of dimethyl allylphosph-
onate (108 mg, 0.72 mmol). The reaction was heated to
65 °C for 2 h. The reaction was cooled to 25 °C and
dimethyl allylphosphonate (50.4 mg, 0.36 mmol) was
added. The reaction was stirred vigorously for 1 min to