1. One-pot Dehydration and Oxidative Co-dimerization of Benzylic Alcohols with Silver Trilflate
Authors: Desiree Chace, Mrinali Sharma, Dorey Thomas, Amanda Murrell, Brandon Quillian
Abstract
New carbon−carbon bond technologies are an important area of study due to the
usefulness of converting small molecules into value-added materials such as plastics, fuels, and
medicines. We have discovered a new and simple one-pot procedure to convert benzylic alcohols
in new carbon−carbon coupling products. Specifically, reaction of benzylic alcohols with
silvertrifluoromethane sulfonate (AgOTf) at 90˚ C in dioxane leads to the oxidative co-
dimerization of vinylarene intermediates to yield en-dibenzenes, which is also known as
hydrovinylation. Herein, we discuss our efforts to understand this unique reaction including
mechanistic and substrate scope studies.
Introduction
Throughout all of organic chemistry carbon-carbon bond building is essential to many of
today’s plastics, pharmaceuticals, dyes, and clothing1. The growth of carbon-carbon bonds using
mild reaction conditions such as moderate heating, using less toxic organic solvents, having
fewer additives for a reaction to occur, or having a catalytic process is extremely desirable in
chemistry today as the price of chemicals increase along with the environmental concerns of
chemicals. One way to make new carbon-carbon bonds is by hydrovinylation. Hydrovinylation is
a chemical process that occurs when a hydrogen and vinyl group is added to an alkyl group.
Hydrovinylation is a type of carbon-carbon addition, but it is not as common as some of the

2. carbon-carbon addition pathways such as radical polymerization or cyclization reactions.
Hydrovinylation is important due to the chemistry occurring within this report that suggests new
environmentally friendly pathways to developing pharmaceuticals, polymers, and biofuels.
In general, alkyl alcohols can be dehydrated to an alkene with the use of a strong acid. It
was discovered recently that silver triflate is a BrØnsted acid that promotes oxidative
dimerization.2,3 In this report, alcohol dehydration is observed but in addition to hydrovinylation.
This suggests that the reaction is experiencing the dehydration by the triflic acid, but some sort
carbon-carbon coupling or radical chemistry is occurring as well.
In the beginning of this project a newly developed Ruthenium catalyst
((BPA)RuBr(PPh3)2) was being tested to see if it promoted new carbon-carbon bond addition
(Figure 1 and Figure 2). The reaction seemed to work, and provided hydrovinylation products
(Figure 3). However, through analysis of the control reactions by NMR and GC-MS, it was
discovered that the Ruthenium catalyst only oxidized the alcohol but otherwise didn’t have any
reaction and decomposed. The Ruthenium catalyst was then excluded and further analysis on the
other reactants was focused on and is discussed in more detail.
Results and Discussion
Once it was discovered that the Ruthenium catalyst essentially had no carbon-carbon
addition properties the AgOTF, dodecene, and KOH were examined. It was observed that the
AgOTF with the dodecene caused the dehydration product along with carbon-carbon coupling of
the styrene (dehydration product) and dodecene, which proved to be interesting and led to us to
investigate the full potential of AgOTF. After all of the control reactions were run, it was
discovered that the AgOTF was the sole reactant that was causing the dehydration and the

3. hydrovinylation products. The 1-phenylethanol was then monitored with three equivalents of
AgOTF for 1, 24, and 48 hours at 90°C. After one hour the alcohol was converted completely to
the dehydrated product and suggests this part of the reaction occurs very quickly. After 24 hours
there was styrene and a small amount of hydrovinylation product was observed, and after 48
hours the styrene was completely converted to the hydrovinylation product which suggests that
this overall reaction occurs relatively quickly. When the same reactions were performed at room
temperature there was no reaction observed.
Figure 1: Ruthenium catalyst
Figure 2: Ruthenium catalyst alkylation prediction

4. Figure 3: Reaction of the Ruthenium catalyst with other reactants
AgOTF in inorganic and organometallic chemistry was previously believed to only strip
halides off of the transition metal for other reactivity at that particular coordination site. And
upon much digging it was reported in several articles using multiple transition metals along with
the use of silver triflate produced carbon cyclization and thought that it was the transition metal
complex, but after our findings we believe that it was the AgOTF doing the chemistry rather than
the transition metal complex.4-8 A recent article discovered that AgOTF is actually a hidden
BrØnsted Acid, and leads to the dehydration of the alcohol in our reaction.2
As the reaction of the AgOTF with 1-phenylethanol proceeded, some interesting
observations were documented. At about the 48 hour mark there was pure silver that precipitated
from the reaction (Figure 4). There is more than dehydration occurring in this reaction, and it is

5. perhaps a radical reaction occurring after the dehydration. This is speculated because the silver in
AgOTF is Ag1 and after 48 hours of heating it becomes Ag0 or pure silver metal. This strongly
suggests that there is some reduction-oxidation chemistry occurring in the reaction. It is
commonly known that if a molecule is reduced, another molecule is oxidized. We believe that
the silver is being reduced and causes oxidation to occur and leads to the hydrovinylation
product. Styrene was ran under the same conditions as the 1-phenylethanol to see if the same
hydrovinylation products occurred along with the precipitated silver, and it did, which supports
our theory of the reduction-oxidation chemistry.
Figure 4: Pure silver precipitate from the reactions
Several controls were run to observe if there is any possible radical process occurring in
the reaction. The 1-phenylethanol was heated for 48 hours with AgOTF, no O2, and in the dark;
styrene was observed along with an ether product. When light was added to the reaction both the

6. dehydration and hydrovinylation products were observed. When the 1-phenylethanol was ran
with AgOTF, light, and excess O2 was added there was no reaction observed, and it is believed
that this occurs because O2 quenches radicals and thus is possibly stopping the reaction from
occurring. Since there were no hydrovinylation products in the dark and no products under
excess O2, the data supports the idea of a radical process at the dehydration step.
The AgOTF was also investigated to see if this reaction could also be catalytic. The 1-
phenylethanol was heated at 90°C for 48 hours with 0.2, 0.5, and 1 equivalents of AgOTF. With
0.2 equivalents AgOTF there was no reaction, with 0.5 equivalents of AgOTF the only product
observed was styrene, and with 1 equivalent of the AgOTF the major product was styrene and
the minor product was the hydrovinylation compound. This suggests that the reaction is not
catalytic, which was almost known to be the case since reduction-oxidation chemistry is involved
in this reaction. With the reduction-oxidation chemistry occurring in this reaction we already
believed that this was not a catalytic process because Ag0 is very stable and is difficult to push
back to the Ag1 oxidation state.
The last area to be investigated is the scope of the alcohols that can have a reaction to
produce the dehydration products and hydrovinylation products. 1-phenylbutanol was heated at
90°C with the AgOTF for 48 hours and only the dehydration product was observed, which was
confirmed by GC-MS and NMR (d= 3JHH = 16.7 Hz, dq = 3JHH = 11.7 Hz). In this reaction there
was no silver produced and no hydrovinylation products and suggests that the methyl group is
blocking the radical from occurring. When the 1-phenylbutanol was reacted in O2 deficient
conditions there was no reaction and when reacted in excess O2 conditions only oxidation of the
alcohol occurred. These reactions are not fully understood and more alcohol substrates are
currently being tested to see the extent of the reactivity with the AgOTF. So far, this reaction

7. seems to be very sensitive, but as stated, the extent of the reactivity of the AgOTF is being
investigated.
Experimental
In this experiment 1-phenylethanol was used at 1 molar equivalents with 3 equivalents
AgOTF and 3 mL of dioxane and put into a pressure tube (or test tube with a rubber septa) and
heated at approximately 90°C in an oil bath for 48 hours with occasional aliquots being taken out
at 1, 24, and 48 hours for monitoring by GC-MS or NMR. The aliquots were washed with a
small amount of hexanes (1-5 mL) and then filtered through a celite pipet column. Enough of the
sample was used to cover the bottom of a GC-MS vile (a few drops) and then the vile was filled
to the 0.5 mL mark and was ran on the GC-MS instrument using the 50-250 method and analysis
was later performed on the spectra. For the control reactions, 10 molar equivalents of styrene
was used with 3 equivalents of AgOTF in 3 mL of dioxane and was heated, extracted, and
analyzed the same as the 1-phenylethanol. Any silver that precipitated in the form of flakes,
balls, or stars were filtered through a funnel covered with 1 in. filter paper and rinsed with
acetone.
Conclusion
The reaction of 1-phenylethanol has shown to be a one-pot reaction to convert the benzyl
alcohol into E)-but-1-ene-1,3-diyldibenzene (hydrovinylation product) through dehydration from
the hidden BrØnsted acid, AgOTF, which is followed by a radical dimerization of styrene to
form the hydrovinylation products. The 1-phenylethanol reacts with the AgOTF to form the
dehydration product, styrene, and then the silver is reduced and oxidizes the alkene formed by
the dehydration of the alcohol to then form a radical cation. The radical cation is then believed to

8. couple to a styrene and thus forms the hydrovinylation product. This reaction has proven to be
very sensitive, but various benzylic, allylic, primary, secondary, and tertiary alcohols are being
investigated for the extent of the reactivity of AgOTF.
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