Exploring the reactivity of a ruthenium complex in the metathesis of biorenewable feedstocks to generate value-added chemicals in memory of Professor the Lord Lewis of Newnham: Mentor, encourager, and Ph.D. advisor.

Article abstract of DOI:10.1016/j.jorganchem.2015.09.018

Tricyclohexylphosphine[4,5-dimethyl-1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene][2-thienylmethylene]ruthenium(II) dichloride proves active for the ring-closing metathesis of linalool and citronellene, the self-metathesis of eugenol, and to some extent the ethenolysis of methyl oleate. Microwave heating and continuous-flow processing have been used as tools for performing the reactions. For the ring-closing metathesis reactions, transition from batch to flow processing for scale-up of the reaction is possible but it proves problematic in the case of cross-metathesis.

Full text of DOI:10.1016/j.jorganchem.2015.09.018

Accepted Manuscript
Exploring the reactivity of a Ruthenium complex in the metathesis of biorenewable
feedstocks to generate value-added chemicals
Kathryn A. Alexander, Emily A. Paulhus, Gillian M.L. Lazarus, Nicholas E. Leadbeater
PII:
S0022-328X(15)30147-9
10.1016/j.jorganchem.2015.09.018
JOM 19233
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 11 August 2015
Revised Date: 13 September 2015
Accepted Date: 18 September 2015
Please cite this article as: K.A. Alexander, E.A. Paulhus, G.M.L. Lazarus, N.E. Leadbeater, Exploring
the reactivity of a Ruthenium complex in the metathesis of biorenewable feedstocks to generate value-
added chemicals, Journal of Organometallic Chemistry (2015), doi: 10.1016/j.jorganchem.2015.09.018.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
EXPLORING THE REACTIVITY OF A RUTHENIUM COMPLEX IN
THE METATHESIS OF BIORENEWABLE FEEDSTOCKS TO
GENERATE VALUE-ADDED CHEMICALS
Kathryn A. Alexander, Emily A. Paulhus, Gillian M. L. Lazarus and Nicholas E. Leadbeater*
Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs,
CT 06269, United States.
E-mail: nicholas.leadbeater@uconn.edu
In memory of Professor the Lord Lewis of Newnham: Ph.D. advisor, mentor, and
encourager
A ruthenium complex proves active for the ring-closing metathesis of linalool and citronellene, the self-
metathesis of eugenol, and to some extent the ethenolysis of methyl oleate. Microwave heating and continuous-
flow processing have been used as tools for performing the reaction.
KEYWORDS: Metathesis; Ruthenium; Biorenewable; N-Heterocyclic Carbene; Valorization
ABSTRACT
Tricyclohexylphosphine[4,5-dimethyl-1,3-bis(2,4,6-trimethylphenyl)imidazol-2-
ylidene][2-thienylmethylene]ruthenium(II) dichloride proves active for the ring-closing
metathesis of linalool and citronellene, the self-metathesis of eugenol, and to some extent
the ethenolysis of methyl oleate. Microwave heating and continuous-flow processing have
been used as tools for performing the reaction. For the ring-closing metathesis reactions,
transition from batch to flow processing for scale-up of the reaction is possible, but it
proves problematic in the case of cross-metathesis.
1

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1. INTRODUCTION
The conversion of biomass into biofuels has been a topic of increasing research interest in
the chemistry community. This has been driven by environmental concerns, political
drivers, and commercial success [1]. Although they account for only around 2% of the
biomass produced annually, fats and oils constitute approximately 35% of the renewable
feedstocks currently used by the chemical industry [2,3]. They are most frequently
converted into fatty acid monoesters (biodiesels) by means of transesterification reactions
with low molecular-weight alcohols such as methanol and ethanol [4]. Alongside efforts
focused around biofuels production, the valorization of biomass is also gaining momentum;
that is the transformation of biorenewable feedstocks into value-added commodity
chemicals [5,6]. Again, oleochemicals are attractive starting materials due to their
availability on large scale at commodity prices and the fact that they contain multiple
functional groups with which chemistry can be performed [7]. The presence of double
bonds in fats and oils means that they are amenable to derivatization by means of alkene
metathesis [8]. Transition-metal catalyzed alkene metathesis has proven to be a powerful
tool in organic synthesis [9,10] but one of the issues with using biomass in these reactions
can be the sensitivity of the catalyst to either the range of functional groups present or the
purity of the feedstock. However, with the development of more rugged catalysts, these
problems are being overcome. The ruthenium-based catalyst systems pioneered by Grubbs
and coworkers have found particular application due to their tolerance to air, water, and
polar organic functional groups [11,12].
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It is possible to perform cross metathesis, ring-opening metathesis, ring-closing
metathesis and ethenolysis (reaction with ethene) on biomass substrates depending on
their structure. Most attention has focused on either self-metathesis [13] or ethenolysis
[13,14] of methyl oleate or analogous monoglycerides, where the products are either long-
chain internal alkenes or shorter-chain terminal alkenes, respectively. The ethenolysis of
oils (triglycerides) has been less widely explored [15], as have metathesis reactions of
terpenes such as citronellene [16,17] and linalool [18,19,20,21], and phenylpropenoids
such as eugenol [19,22,23].
In our group, we have an interest in developing cleaner, greener synthetic methods
and, as part of this endeavor, we use microwave heating and continuous-flow processing as
enabling technologies. Microwave heating offers safe, easy, and highly reproducible access
to elevated temperatures [24]. It is also possible to perform reactions under an atmosphere
of reactive gases [25]. Conventionally heated continuous-flow processing is proving to be a
viable alternative to the traditional batch methods for preparative chemistry [26,27].
Inherent advantages include enhanced safety, ease of scale-up, and efficient mixing of
reagents. It is possible to control reaction parameters precisely and to affect chemistry
across a wide temperature range successfully. As with microwave heating, reactive gases
can be used as reagents in flow processing [28]. The small volumes of flow reactors
ameliorate the hazards of high-pressure gas reactions and enable improved mixing with
the liquid phase. We have recently turned our attention to the use of these tools for
performing alkene metathesis reactions on bio-renewable feedstocks and present our
results here.
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2. RESULTS AND DISCUSSION
2.1. CATALYST SELECTION
The selection of appropriate catalyst candidates was considered of key importance. Given
the scale on which alkene metathesis reactions would need to be performed when using
bio-renewable feedstocks as sources of value-added commodity chemicals, cost,
availability, and licensing are important factors to take into account. Our attention turned
to a series of three royalty-free catalysts that have become available in the last few years
[29,30,31]. They are based on a second-generation Grubbs type motif, bearing N-
heterocyclic carbene (NHC) and tricyclohexylphosphine ligands (Figure 1). The difference
between the three complexes comes either in the nature of the alkylidene unit (A vs B) or
the NHC group (B vs C). Of the three, C has seen particular application in metathesis so our
attention focused on this complex.
Figure 1: Ruthenium complexes discussed in this study
4

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2.2. RING-CLOSING METATHESIS OF LINALOOL
Our starting point was to study the ring-closing metathesis (RCM) of linalool to yield 1-
methylcyclopent-2-enol (1) and isobutene, both of which are valuable precursors to high-
energy fuels (Scheme 1) [32]. Although the RCM of linalool involves passing through a
sterically-hindered intermediate, hydroxyl groups in an allylic position are known to
accelerate the rate of carbene-exchange between the adjacent vinyl group and external
ruthenium alkylidenes [19]. This enhancement is sufficient to overcome the significant
steric deactivation. While generally, catalyst loadings of 1-5 mol% are used to achieve high
product conversion efficiencies [18], one of the most effective catalysts to date is the
pseudohalide-functionalized ruthenium complex D where 100% conversion can be
obtained after 15 min heating in refluxing chloroform when using a loading of 0.5 mol%
loading, or after 1 h at a loading of 0.05 mol% [21].
5

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Scheme 1: Ring-closing metathesis of linalool
Using C as our catalyst, we decided to screen the reaction in two solvents: toluene
and dimethylcarbonate (DMC). The latter was selected since it is classified as a green
solvent [33]. Working at a catalyst loading of 0.1 mol% and after heating at 80 °C for 1 h,
we obtained 40% and 43% conversions in DMC and toluene respectively (Table 1, entries
1
&2). We also performed the reaction solvent-free under the same reaction conditions
(entry 3). Although we were able to obtain a conversion of 70%, we also observed
significant oligomer formation, presumably due to competing cross-metathesis reactions.
Returning to toluene as the solvent, we probed the effects of temperature on the reaction,
finding that 80 °C was optimal (entries 4-6). Complete conversion was obtained after
heating at 80 °C for 20 min by increasing the catalyst loading from 0.1 mol% to 0.5 mol%
(entry 7). We were able to reduce the reaction time to just 10 minutes and obtain
quantitative conversion (entry 8). However, halving the catalyst loading to 0.25 mol%
resulted in a concommitant drop in product conversion (entry 9). Thus, our optimized
conditions were 0.5 mol% C, heating at 80 °C for 10 minutes.
Table 1: The ring-closing metathesis of linalool using C.
6

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Entry Solvent
Catalyst Loading (mol%) Time (min)
Temperature (°C)
80
Conversion (%)
1
2
3
4
5
6
7
8
9
toluene
DMC
0.1
0.1
0.1
0.1
0.1
0.1
0.5
0.5
0.25
60
60
60
60
60
60
20
10
20
43
40
70
3
80
80
25
40
100
80
80
80
-
toluene
toluene
toluene
toluene
toluene
toluene
24
28
100
100
65
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2.3. RING-CLOSING METATHESIS OF CITRONELLENE
There have only been relatively few reports of the RCM of citronellene to date (Scheme 2).
A tungsten oxo-complex was used as the catalyst, with a 68% yield of 3-
methylcyclopentene (2) being obtained after heating in 1,2,4-trichlorobenzene at 90 °C for
1
h using a loading of 2 mol% [16]. Moving to ruthenium, Grubbs Type 1 (E) has been
employed in a relative reactivity study [19]. Citronellene was found to be significantly less
reactive than linalool, thus confirming the “allylic alcohol effect”. With conditions in hand
for the RCM of linalool, we wanted to see if we could extend our protocol to citronellene as
a substrate.
Scheme 2: Ring-closing metathesis of citronellene
Employing C as the catalyst and performing the reaction in toluene at 80 °C for 1 h
with a loading of 0.5 mol%, complete conversion of citronellene to 2 was obtained (Table 2,
entry 1). We performed the reaction using microwave heating in a sealed tube to avoid
product loss since 2 has a boiling point of 64 °C. After the reaction was complete, 2 was
isolated from the catalyst, solvent, and any unreacted starting material by trap-to-trap
distillation. We probed the effects of catalyst loading, finding that quantitative conversion
was obtained when using 0.2 mol% C but this dropped to 33% when further reducing the
loading to 0.1 mol% (entries 2&3). The decreased reactivity of citronellal over linalool is
8

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seen in this result when comparing identical reactions (Table 1, entry 1 vs Table 2, entry 3).
We again probed the effects of reaction temperature and time, finding that complete
conversion can be obtained in 20 mins at 80 °C when using a catalyst loading of 0.5 mol%
(entries 4&5).
Table 2: The ring-closing metathesis of citronellal using C.
Entry Solvent
Catalyst Loading (mol%) Time (min)
Temperature (°C)
Conversion (%)
1
2
3
4
5
toluene
toluene
toluene
toluene
toluene
0.5
0.2
0.1
0.5
0.5
60
60
60
60
20
80
80
80
25
80
100
100
33
40
100
2.4. SELF-METATHESIS OF EUGENOL
Eugenol, a phenolic member of the phenylpropene family, is extracted from plants such as
cloves. It has been used in a limited number of cross-metathesis reactions [19,22]. There is
one report of self-metathesis in which 0.3 mol% E is used as the catalyst and the reaction is
performed at room temperature for 24 h [23]. A 71% yield of stilbene 3 is obtained. We
therefore decided to probe the activity of C in this reaction (Scheme 3).
9

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Scheme 3: Ring-closing metathesis of eugenol
We started by performing the reaction at room temperature, using a catalyst loading of 0.5
mol% C and obtained a 48% conversion to 3 after 1 h (Table 3, entry 1). Performing the
reaction at 80 °C increased the conversion to 60% (entry 2). Believing that the catalyst was
being deactivated over time, we performed the reaction using a catalyst loading of 0.5
mol% and, after 60 mins, we added a second dose of 0.5 mol% C. By doing this, we were
able to obtain a 93% conversion to 3 (entry 3). Changing from toluene to DMC as solvent
had a deleterious effect on the reaction (entry 4).
Table 3: The self-metathesis of eugenol using C.
Entry Solvent
Catalyst Loading (mol%) Time (min)
Temperature (°C)
Conversion (%)
1
2
3
4
toluene
toluene
toluene
DMC
0.5
60
r.t.
80
80
80
48
60
93
0
0.5
60
0.5 + 0.5
0.5
60 + 60
60
2.5. CROSS-METATHESIS OF METHYL OLEATE
Our final class of reaction for study was the cross-metathesis of methyl oleate and ethene to
yield methyl 9-decenoate (4) and 1-decene (5) (Scheme 4). The formation of terminal
alkenes from biorenewable feedstocks is particularly attractive. It would allow for the
subsequent preparation of commodity chemicals from natural seed oils and their
derivatives instead of petroleum products. Indeed, the products from the ethenolysis of
methyl oleate find application in a range of industrial sectors including cosmetics,
detergents, and soaps, [34] as well as being a potential renewable biofuel source [35].
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Ethenolysis reactions involve the formation of metal methylidene species as key
intermediates in the catalytic cycle. Most metathesis catalysts are unstable as methylidene
complexes and also as the corresponding unsubstituted metallocyclobutane, and so
undergo rapid decomposition [36]. Therefore, the ethenolysis of methyl oleate is a good
gauge for the relative activity of C compared to other alkene metathesis catalysts. A range
of ruthenium complexes have been used for the reaction [37], with those bearing NHC
ligands being amongst the most active [38]. Perhaps the best currently known catalysts in
this class are a series of N-aryl, N-alkyl NHC ruthenium complexes [39]. They exhibit high
selectivity and catalyst loadings as low as 500 ppm can be used. Cyclic alkyl amino carbene
complexes (F) also prove to be highly active catalysts, operating at loadings as low as 3
ppm [40].
Scheme 4: Cross-metathesis of methyl oleate and ethene
We started our investigations using a catalyst loading of 0.1 mol% C and performing
the reaction in a microwave unit interfaced with a gas-loading accessory [41,42]. We have
used this tool previously for performing reactions involving gaseous reagents [43]. It is
possible both to flush reaction vessels with inert gas as well as load up to 17 bar of gas.
Operating at an ethene pressure of 7 bar and performing the reaction solvent-free, we
obtained a 25% conversion to 4 and 5 after 20 min at 60 °C. (Table 5, entry 1). Performing
the reaction in toluene or DMC as a solvent increased the conversion to 27% and 32%
1
1

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respectively (entries 2&3). Using DMC as the solvent and increasing the catalyst loading to
0
.5 mol% resulted in a 45% conversion to 4 and 5 (entry 4). This was not improved upon
by increasing the reaction time from 20 min to 60 min (entry 5) suggesting that the
catalyst, while initially highly active, is quickly deactivated.
Table 4: The cross-metathesis of methyl oleate and ethene using C.a
Entry Solvent
Catalyst Loading (mol%) Time (min)
Temperature (°C)
Conversion (%)
1
2
3
4
5
none
0.5
0.5
0.5
0.5
0.5
20
20
20
20
60
60
60
60
60
60
25
27
32
45
46
toluene
toluene
DMC
DMC
a) Reactions performed under 7 bar ethene pressure
2.6. REACTION SCALE-UP
Having performed reaction scouting and optimization studies, we wanted to turn our
attention to the scale-up of the ring closing metathesis of linalool and citronellene, and the
self-metathesis of eugenol. We decided to employ continuous-flow processing as a tool in
this endeavor. Flow processing has been used before for metathesis reactions [44]. Most
attention has been focused on cross-metathesis and self-metathesis [45,46,47,48], along
with examples of ethenolysis [45,49]. In our case, we wanted to probe the effectiveness of
flow processing as a tool primarily for ring-closing metathesis, a process that has been less
studied in flow mode [46,47].
1
2

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Since the reaction takes place in a narrow gauge tube and is under a positive
pressure (back-pressure regulator at the exit of the flow stream), a concern was that since
they could not escape from the reactor as they were generated, the gaseous byproducts
formed in the ring-closing metathesis could react with the product or with each other to
compromise the efficiency of the process. However, we found this not to be the case when
performing the ring-closing metathesis of linalool and citronellene (Scheme 5). Passing the
reaction mixture of substrate, 0.5 mol% C in toluene through a 10 mL volume coil heated to
-
1
8
0 °C at a flow rate of 1 mL min (corresponding to a residence time of 10 min) we
observed complete conversion of linalool to 1. The buildup of the isobutene byproduct was
clearly observable as the course of the reaction proceeded, bubbles of gas forming between
slugs of liquid. In the case of citronellene, 2 was formed quantitatively when performing
the reaction under the same conditions, the only change being that the flow rate was
halved, giving a residence time of 20 min. The transition from batch to flow was not as
smooth when performing the self-metathesis of eugenol. Operating at 80 °C, using a
catalyst loading of 0.5 mol% C, and with a residence time of 30 min, a conversion of only
4
0% was obtained (Scheme 5). In this case, we do believe that the back-reaction could pose
a problem. Not only would it reduce the effectiveness of the process but also the
ethenolysis reaction has already been shown to deactivate the catalyst over time.
1
3

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0
.5 mol% C
1
100%
OH
toluene
o
Flow: 80 C, 10 min residence time
0
.5 mol% C
2
3
100%
40%
toluene
o
Flow: 80 C, 20 min residence time
MeO
HO
0
.5 mol% C
toluene
o
Flow: 80 C, 30 min residence time
Scheme 5: Metathesis reactions performed using flow processing
3. CONCLUSION
In summary, we have probed the activity of a ruthenium NHC complex, C, in a number of
metathesis reactions using biorenewable feedstocks as substrates. It proves active for the
ring-closing metathesis of linalool and citronellene, the self-metathesis of eugenol, and to
some extent the ethenolysis of methyl oleate. For the ring-closing metathesis reactions,
transition from batch to flow processing for scale-up of the reaction is possible, but it
proves problematic in the case of cross-metathesis.
1
4

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4
. EXPERIMENTAL SECTION
.1. General experimental
Chemicals were used as purchased, unless stated otherwise. Ruthenium complex C
4
(Tricyclohexylphosphine[4,5-dimethyl-1,3-bis(2,4,6-trimethylphenyl)imidazol-2-
®
ylidene][2-thienylmethylene]ruthenium(II) dichloride; catMETium RF 3) was purchased
1
13
from Strem Chemicals. NMR Spectra ( H, C) were performed at 298 K on either a Brüker
Avance Ultra Shield 300 MHz NMR, Brüker DRX-400 400 MHz NMR, or Brüker Avance 500
1
MHz NMR. H-NMR Spectra obtained in CDCl
3
were referenced to residual non-deuterated
13
chloroform (7.26 ppm) in the deuterated solvent. C- NMR Spectra obtained in CDCl
3
were
referenced to chloroform (77.3 ppm).
Reactions employing microwave heating were performed using a CEM Discover microwave
unit and, where appropriate, equipped with a gas-loading accessory. Reactions using
continuous-flow processing were performed using either a Uniqsis FlowSyn or a Vapourtec
R-Series unit.
4
.2. Ring-closing metathesis of linalool
To a 10 mL glass tube equipped with a Teflon-coated stirbar was added linalool (69 mg,
.45 mmol), C (2 mg, 0.5 mol%), and toluene (1 mL, 0.45 M). The tube was then placed in
0
an oil bath that had been heated to 80 °C. The solution was allowed to stir uncapped for 10
min. The reaction mixture was then cooled to room temperature and transferred to a
round-bottom flask. The reaction tube was then rinsed twice with diethyl ether (2 mL),
1
5

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adding the washings to the round bottom flask. The solvents were removed in vacuo by
rotary evaporation. The residue was dissolved in CDCl and filtered in to a clean round-
3
bottom flask through a pipet filled with a small volume of Celite. The product mixture was
analyzed by NMR spectroscopy and GC-MS.
4.3. Ring-closing metathesis of citronellene
To a 10-mL capacity glass microwave tube equipped with a Teflon-coated stir bar was
added citronellene (69 mg, 0.45 mmol), C (2 mg, 0.5 mol%), and toluene (1 mL, 0.45 M).
The tube was sealed with a septum and placed into the microwave cavity. The reaction
mixture was heated to 80 °C using an initial microwave power of 100 W and setting a
pressure cut-off of 250 psi for safety purposes. Once at temperature, the contents of the
tube were maintained at 80 °C for 20 min. After completion of the heating time, the
reaction vessel was cooled to room temperature before removing from the microwave unit.
1
Due to the volatility of the product (2), conversion was assayed by H NMR spectroscopy of
an aliquot of the crude reaction mixture.
4
.4. Self-metathesis of eugenol
The reaction was performed in an analogous manner to that for linalool, but using eugenol
74 mg, 0.45 mmol) as the substrate, and heating the reaction mixture at 80 °C for 30 min.
The product mixture was analyzed by NMR spectroscopy and GC-MS.
(
1
6

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4.5. Cross-metathesis of methyl oleate
To a 10-mL capacity glass microwave tube equipped with a Teflon-coated magnetic stir bar
was placed methyl oleate (139 mg, 0.47 mmol), C (2 mg, 0.5 mol%), and toluene (1 mL, 0.47
M). The reaction vessel was placed into the microwave cavity, the gas-loading accessory
connected. The tube was loaded with a pressure of 7 bar of ethene. The reaction mixture
was heated to 60 °C using an initial microwave power of 100 W and setting a pressure cut-
off of 250 psi for safety purposes. Once at temperature, the contents of the tube were
maintained at 80 °C for 20 min. After completion of the heating time, the reaction vessel
was cooled to room temperature before releasing the pressure, removing the tube from the
microwave unit, and transferring the contents to a round-bottom flask. The reaction tube
was then rinsed twice with diethyl ether (2 mL), adding the washings to the round bottom
flask. The solvents were removed in vacuo by rotary evaporation. The residue was
dissolved in CDCl
3
and filtered in to a clean round-bottom flask through a pipet filled with a
small volume of Celite. The product mixture was analyzed by GC-MS.
4.6. Scale-up of the ring-closing metathesis of linalool
A 50 mL glass bottle was charged with linalool (1.84 g, 12 mmol), C (50 mg, 0.5 mol%), and
toluene (25 mL, 0.48 M). The solution was thoroughly mixed until it became a completely
homogenous clear dark green solution. The flow reactor was readied using the equipment
manufacturer’s suggested start-up sequence, followed by heating the reactor coil to 80 °C.
The reaction mixture was then loaded into the reactor. Product collection commenced
immediately after this switch. After the reaction mixture had been completely loaded into
1
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the reactor, the reactor pump was set back to pumping solvent. After the product had been
fully discharged from the reactor coils, the resulting green solution could then be purified.
Toluene was carefully removed using rotary evaporation at room temperature leaving the
crude product. The crude product was dissolved in a small amount of 90:10 by volume
mixture of hexanes to ethyl acetate and loaded onto a plug of silica. The plug was then
rinsed thoroughly with 90:10 by volume mixture of hexanes to ethyl acetate and the
solvent was stripped in vacuo in a room temperature water bath. The product was assayed
1
by NMR spectroscopy, relative to an internal standard. H NMR (CDCl
3
, 300 MHz) δ ppm
1
.30 (s, 3 H), 1.83 (m, 2 H), 2.22 (m, 1 H), 2.38 (m, 1 H), 2.59 (br, 1 H), 5.66 ppm (m, 2 H).
4
.7. Scale-up of the ring-closing metathesis of citronellene
A 50 mL glass bottle was charged with (69 mg, 0.45 mmol), C (2 mg, 0.5 mol%), and toluene
1 mL, 0.45 M). The solution was thoroughly mixed until it became a completely
(
homogenous clear dark green solution. The flow reactor was readied using the equipment
manufacturer’s suggested start-up sequence followed by heating the reactor coil to 80 °C.
The reaction mixture was then loaded into the reactor. Product collection was commenced
immediately after this switch. After the reaction mixture had been completely loaded into
the reactor, the reactor pump was set back to pumping solvent. After the product had been
1
fully discharged from the reactor coils, the product conversion was first assayed by H NMR
spectroscopy of an aliquot of the crude reaction mixture. The product was then isolated by
1
a trap-to-trap distillation of 2 from the crude reaction mixture. H NMR (CDCl
3
, 300 MHz) δ
ppm 1.02 (d, 3H), 1.30 (m, 1H), 2.05 (m, 1H), 2.30 (m, 2H), 2.73 (m. 1H), 5.66 (m, 2H).
1
8

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4.8. Scale-up of the self-metathesis of eugenol
A 50 mL glass bottle was charged with eugenol (1.864 g, 12 mmol), C (50 mg, 0.5 mol%),
and toluene (25 mL, 0.48 M). The reaction was performed using the same protocol as that
1
for linalool. H NMR (CDCl
3
, 300 MHz) δ ppm 6.82 (d, 2H), 6.71 (2H, m), 6.69 (2H, s). 5.66
(2H, m), 5.52 (2H, s), 3.86 (6H, s), 3.31 (4H, d).
5. ACKNOWLEDGEMENTS
Funding from the National Science Foundation [CAREER award CHE-0847262 (NEL,
GMLL); REU award CHE-1062946 (KAA, EAP)] and the University of Connecticut (NEL,
GMLL) is acknowledged. CEM Corp., Uniqsis Ltd, and Vapourtec Ltd are thanked for
equipment support.
6. REFERENCES
1
.
For background, see: (a) A. Pandey, C. Larroche, S. Ricke, C.-G. Dussap, E.
Gnansounou (Eds.), Biofuels: Alternative Feedstocks and Conversion Processes,
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