Silver catalyzed proto- and sila-Nakamura-type α-vinylation of silyl enol ethers with dichloroacetylene. Divergent formation of stereochemically pure tri- and tetrasubstituted olefins

Article abstract of DOI:10.1016/j.tetlet.2019.151370

The silver-catalyzed reaction of silyl enol ethers with dichloroacetylene (DCA) is described. When DCA was used as a solution in diethyl ether, we found that the silyl group was transferred to the vinyl group, resulting in stereochemically pure tetrasubstituted olefins. However, when DCA was used as a solution in the more polar acetonitrile, protonation was the major pathway, and trisubstituted olefins were the dominant products.

Full text of DOI:10.1016/j.tetlet.2019.151370

Journal Pre-proofs
Silver catalyzed proto- and sila-Nakamura-type α-vinylation of silyl enol ethers
with dichloroacetylene. Divergent formation of stereochemically pure tri- and
tetrasubstituted olefins
Lun Li, Kimberly A. Wasik, Brian J. Frost, Laina M. Geary
PII:
S0040-4039(19)31161-X
https://doi.org/10.1016/j.tetlet.2019.151370
TETL 151370
DOI:
Reference:
Tetrahedron Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
23 September 2019
30 October 2019
5 November 2019
Please cite this article as: Li, L., Wasik, K.A., Frost, B.J., Geary, L.M., Silver catalyzed proto- and sila-Nakamura-
type α-vinylation of silyl enol ethers with dichloroacetylene. Divergent formation of stereochemically pure tri- and
tetrasubstituted olefins, Tetrahedron Letters (2019), doi: https://doi.org/10.1016/j.tetlet.2019.151370
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover
page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will
undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing
this version to give early visibility of the article. Please note that, during the production process, errors may be
discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier Ltd.

Silver catalyzed proto- and sila-Nakamura-type α-vinylation of silyl enol
ethers with dichloroacetylene. Divergent formation of stereochemically
pure tri- and tetrasubstituted olefins.
Lun Li,† Kimberly A. Wasik, Brian J. Frost, and Laina M. Geary*
University of Nevada, Reno, Department of Chemistry, Reno, Nevada, 89557, USA.
Supporting Information Placeholder
Cl
H
Cl
TMS
Cl
O
O
OTMS
10 mol% AgOTf
10 mol% AgOTf
R
Cl
R
R
Cl
Cl
Cl
Cl
1 M in Et2O
1 M in MeCN
10 examples
28-75% yield
7 examples
45-76% yield
ABSTRACT: The silver-catalyzed reaction of silyl enol ethers with dichloroacetylene (DCA) is
described. When DCA was used as a solution in diethyl ether, we found that the silyl group was
transferred to the vinyl group, resulting in stereochemically pure tetrasubstituted olefins.
However, when DCA was used as a solution in the more polar acetonitrile, protonation was the
major pathway, and trisubstituted olefins were the dominant products.
Tri- and tetrasubstituted alkenes are ubiquitous structures in organic chemistry, thus a
significant amount of research has gone into developing synthetic routes towards alkenes.
However, the stereocontrolled synthesis of multi-substituted alkenes remains a significant
challenge in organic synthesis.1 Traditional methods of olefin syntheses, including Wittig,2
Julia,3 and Peterson olefinations,4 require prefunctionalized reagents, produce significant
amounts of byproducts, and often lead to mixtures of isomers. More recent approaches minimize
preactivation by “building out” from suitable C2 building blocks, either via the hydro- and

carbometalation of alkynes5 or via the synthesis of stereodefined vinyl halides and vinyl silanes
that can be sequentially functionalized via transition metal cross-coupling reactions.6
Organ7 and others8 have developed modular syntheses of polysubstituted olefins from
commercially available or easily accessible 1,1- and 1,2-dihaloalkenes. Trichloroethylene has
also been identified as an inexpensive and useful C2 building block for constructing
polysubstituted olefins. Trichloroethylene can be converted into dichloroacetylene (DCA) in situ,
and reacted with alcohols and amines to generate dichlorovinyl ethers and amides that could be
further elaborated via palladium-catalyzed cross coupling reactions.9
A. Hilt's CoI catalyzed reactions of dienes with alkynes (refs 11,12)
R1
OR
CoBr2(dppe)/
ZnI2/Bu4NBH4
(10 mol%)
OR
or
or
R1
R1
R2
RO
40 °C, 16 hr
R2
R2
target: concerted [4+2] cycloaddition
OTMS OTMS
B. Target arene & discovery:
MeO
Cl
Cl
Cl
OTMS
-MeOH
(trace by GC-MS)
Cl
(not observed)
Cl
Cu(MeCN)4PF6
(10 mol%)
observed: stepwise addition across  bond
50 °C, 24 hr
Cl
MeO
1a
(1 equiv)
O
Cl
O
Cl
2a
H
TMS
2.0 M, Et2O
(2 equiv)
Cl
O
Cl
MeO
MeO
4a
25% yield
3a
18% yield
C. Halides and nucleophilic alkynes and C-nucleophiles with alkyne electrophiles:
Dihalosilylalkenes (refs 15,16)
TMS
Nakamura reaction (ref 14)
O
O
O
Ar
R3CCH
1. X1-TMS
2. NX2S
R1
OEt
R1
OEt
TMS
X1
R2
R3
cat. In(OTf)3
R2
-78 C
rt, 1 h
Ar
X2
elaborate halogen sources
cryogenic conditions
requires highly activated alkynes
requires monosubstituted alkynes
Scheme 1. A. Hilt’s cobalt catalyzed reaction of O-functionalized dienes with alkynes. B.
Observed reactivity of Danishefsky’s diene 1a and dichloroacetylene 2 C. Other reactions of
electrophiles and nucleophiles with alkynes.

We imagined that if DCA could be engaged in cycloaddition chemistry, we could access
a wide variety of dichlorinated (hetero)cycles. The electron-rich Danishefsky’s diene has been
frequently used in the synthesis of oxygen-substituted six-membered rings via Diels-Alder
cycloadditions with olefins.10 Hilt and co-workers have described a series of cobalt-catalyzed
reactions of simple 1,3-butadienes11 and mono-O-functionalized 1,3-butadienes12 with alkynes
that yielded six-membered Diels-Alder adducts as either the 1,4-hexadiene or benzene,
depending on the location of the oxygen substituent (Scheme 1, A). We therefore sought to
develop an analogous benzannulation reaction of dichloroacetylene (DCA) via a Diels-Alder
cycloaddition with Danishefsky’s and related dienes to synthesize substituted o-
dichlorobenzenes (Scheme 1, B). However, while we were only able to detect a trace amount of
the targeted dichlorobenzene derivative by GC-MS, we were pleased to observe the addition of
the enol ether across DCA to yield tri- and tetrasubstituted olefins 3a and 3b.
DCA has been previously shown to react with lithium enolates only under strongly basic
conditions.13 An alternate approach to the reaction of enolates with alkynes is the Nakamura
reaction (Scheme 1, C, right). This process however, is also very limited as it requires a highly
activated carbonyl compounds and monosubstituted alkynes.14 Other methods of synthesizing α–
vinyl carbonyl compounds include palladium15 or base16 catalyzed cross-coupling with vinyl
electrophiles. Dihalosilylolefins are highly useful synthetic intermediates, generally prepared by
the addition of dihalides17 to or dihalide equivalents18 to silylacetylenes (Scheme 1, C, left).
Our serendipitous discovery that silyl enol ethers added across DCA in the presence of a
catalyst to generate β,γ-unsaturated ketones both with and without silyl transfer inspired us to
develop conditions that could selectively generate either protonated or silylated dichloroalkenes.

We began our optimization process by evaluating the performance of several Lewis acids in the
reaction between the silyl enol ether of acetophenone, 1b, and DCA 2 (Table 1). For the
convenience and safety of using DCA,19 we prepared DCA as an ether solution (~1 M), which
can be stored in a freezer for one week.20 To our surprise, the copper complex that we discovered
the reaction with failed to catalyze the reaction between 1b and 2 (Entry 1). Extensive screening
of more than 40 catalysts (see Electronic Supporting Information (ESI) for additional details)
revealed that copper triflate (Entry 2) and silver triflate (Entry 3) both led to moderate isolated
yields for the product 3a (30% and 28% yield, respectively) after 24 hours; most of the screened
catalysts were ineffective, and only unreacted 1b and/or acetophenone 5 could be detected.
When copper triflate was employed as the catalyst, increasing the reaction time from 24 to 48
hours was ineffective (Entry 4); this is attributed to the rapid copper catalyzed decomposition of
silyl enol ether 1b. However, when silver triflate was employed as the catalyst, decomposition of
1b was slower, and thus increasing the reaction time from 24 to 48 hours improved the isolated
1
yield of 3b from 28% to 40% (Entry 3 versus 5) as determined by H NMR analysis. We also
detected a third byproduct, 3b´, by 1H NMR spectroscopy.21
Continuing with silver triflate as our optimum catalyst, we turned to screening other
reaction variables. Changing the solvent to a mixture of diethyl ether with other solvents did not
improve the yield (see ESI for additional solvent screening details). The application of nonpolar
solvents, such as toluene (Entry 6) and hexane (Entry 7), gave only 17% and 10% conversion to
3b, and increased production of 3b´. A slightly more polar solvent, CH2Cl2, gave a better result
(30% yield of 3b and comparable production of 3b´, entry 8). More polar solvents, such as
MeCN (Entry 9) and DMF (Entry 10), were much less effective. In most of the screening

conditions, acetophenone 5 was the major component in the crude reaction mixture, which was
presumably produced via the decomposition of silyl enol ether 1b.
Table 1. Selected optimization experiments between silyl enol ether 1a and dichloroacetylene 2.
Cl
O
Cl
OTMS
O
Cl
H
TMS
[M] (10 mol%)
Cl
Cl
Solvent
Additive
T °C, 48 h
Cl
3b
O
4b
2
1b
1M in Et2O
(~5 equiv)
CH3
(1 equiv)
5
Solventb
Additive
3b:4b:5
Entry [M] (10 mol%)
T (°C)
yield (%)c
3b:3b'
1d
Cu(MeCN)4PF6
Cu(OTf)2
-
-
-
-
-
-
-
-
-
-
-
-
0
(30)
(28)
25
40
17
10
30
15
0
50
50
50
50
50
50
50
50
50
50
50
80
80
80
80
80
2d
3d
4
5
6
7
AgOTf
Cu(OTf)2
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
AgOTf
1:0:2.4
1:0:1.3
1:0:3.6
1:0.1
1:0.2
1:0.6
1:0.9
1:0.3
1:0.4
-
1:0
1:0.1
1:0
-
toluene
hexane
DCM
MeCN
DMF
-
1:0:3.6
8
9
1:0.05:1.5
1:3.1:3.5
0:0:1
1:0:1
1:0:0.3
-
-
10
11
12
13
14
15
16
TMSCle
-
50
-
-
-
-
70 (69)
71 (67)
70
80(75)
62i
TMSCle
1:0:0.4
TMSCle, MeCNf
1:0.22:0.22
1:0:0.25
1:3.6:0.07
TMSCle, MeCNg
-
1:0
1:0
MeCNh
aUsing 0.2 mmol 1a and 1 mL DCA solution in ether (1 M). b“-” Represents using only ether as a
solvent; otherwise, a 1:1 solvent:ether mixture was used. c 1H NMR yield using CH2Br2 as an
d
e
internal standard; isolated yield of 3b indicated in brackets. Reaction time was 24 h. Using an
f
g
h
additional 0.68 equiv TMSCl. Using 0.5 mL MeCN. Using 0.1 mL MeCN. DCA 2 was
prepared in a solution of MeCN. iIsolated yield of 4a.
As changing the solvent led to no improvement in the conversion to 3b, we next screened
several additives to evaluate their effectiveness in both reducing the decomposition of 1b and the
formation of 3b´ (see ESI for additional details). When substoichiometric amounts of exogenous
TMSCl were used as an additive,22 the yield of product 3b was increased to 50% (Entry 11).
1
More significantly, 3b´ was no longer detected by H NMR analysis. Because acetophenone 5
was still observed as the major byproduct, we next decreased the reaction temperature in an

attempt to slow decomposition of 1b; however, no improvement in the yield of 3b was observed
(see ESI for details). We reasoned that if the decomposition of 1b to 5 was faster than addition
across DCA (2), increasing the reaction temperature could favor the formation of 3b. Indeed,
increasing the reaction temperature to 80 oC, led to 69% isolated yield of 3b, and reduction in the
formation of 5 (Entry 12); however, small amounts of 3b´ were formed. Applying exogenous
TMSCl as an additive to the higher temperature conditions both reduced decomposition of 1b
and prevented the formation of 3b´ (Entry 13 versus entries 11 and 12).
As a final attempt to decrease the decomposition of 1b, we considered mixed solvent
systems. While the polar solvent MeCN gave the greatest yield of protonated 4b, the use of
MeCN also led to decreased formation of 5 (Entry 9 vs entries 6-8). Via a detailed screening of
MeCN as a co-solvent (see ESI for additional details), we found that adding 10% MeCN gave
the best isolated yield of 3b when used in conjunction with TMSCl at 80 oC (Entry 15; optimized
o
Conditions A). Finally, using DCA (2) as a solution in MeCN at 80 C led to the greatest
conversion to trisubstituted olefin 4b (Entry 16; optimized Conditions B). All screening reactions
and subsequent studies on the scope of the reaction were performed on a 0.2 mmol scale, though
we found that we could increase the scale to 0.5 mmol and 1 mmol, with little effect on the yield,
and could decrease the catalyst loading to 5 mol% with only a small decrease in the isolated
yield of 3b. However, in consideration of the safety issue of DCA at high temperature, we did
not pursue increasing the scale of the reaction further.
The addition of nucleophiles across DCA is well-known to produce trans-
dichloroolefins.9c, 13d However, to unambiguously confirm the geometry of the olefin, we treated
products 3b and 4b with 2,4-dinitrophenylhydrazine (DNP); the derivatives 3b-DNP and 4b-

DNP were crystalline, and we confirmed the anti-geometry by single crystal X-ray diffraction
(Fig. 1). The geometry of other adducts 3 and 4 were assigned by analogy.
NO2
NO2
NH
N
Cl
TMS
Cl
3b-DNP
NO2
NO2
NH
N
Cl
H
Cl
4b-DNP
Figure 1. Thermal ellipsoid representations, 50 % probability, of the 2,4-dinitrophenylhydrazine
adducts of 3b and 4b. Most protons omitted for clarity.
With these optimized conditions in hand, we investigated the scope of this catalytic
Nakamura-type reaction under both Conditions A and B (Table 2). We found that the addition of
the silyl enol ethers 1 across DCA 2 generally proceeded smoothly, and the tetrasubstituted
olefins 3 were isolated in moderate yields.23 The products bearing electron-rich groups (3c, 3d,
3e) were generally isolated in higher yields than those containing electron-withdrawing groups
(3f, 3g, 3h). The α-tetralone derived substrate 3i was isolated in moderate yield, as were alkyl
methyl ketone based substrates 3j and 3k. The application of Conditions B were somewhat less
general. α-Vinylated acetophenone derivatives with electron-donating groups (4c, 4d, 4e) were
isolated in good yields, as was the p-chloro analogue 4f. While the p-bromo compound was

1
observed via crude H NMR spectroscopy, we were unable to isolate 4g due to decomposition
1
during column chromatography. Similarly, tetralone adduct 4i appeared to have formed via H
NMR analysis of the crude material, but was unstable and decomposed upon column
chromatography. We were unable to confirm formation of either m-trifluoromethyl acetophenone
adduct 4h or t-butyl methyl ketone derivative 4j, though adamantyl derivative 4k was isolated in
good yield.
Table 2. Substrate scope for the addition of silyl enol ethers 1c-1k to dichloroacetylene 2 under
Conditions A to give tetrasubstituted olefins 3c-3k or trisubstituted olefins 4c-4f, 4k under
Conditions B.a,b
O
Cl
O
Cl
OTMS
R2
AgOTf (10 mol%)
80 °C, 48 h
TMS
H
R1
or
R1
R1
R2 Cl
R2 Cl
Cl
Cl
3c-3k
4c-4f, 4k
Conditions B
2
, 1 M in solvent
(~5 equiv)
1c-1m
(1 equiv)
Conditions Ac
10:1 Et2O:MeCN
MeCN
O
Cl
O
Cl
R
O
Cl
R
R
Cl
65%, , R = TMS
Cl
Cl
MeO
Me
MeO
F3C
OMe
3c
59%, , R = TMS
4c
76%, , R = H
3d
3e
52%, , R = TMS
4e
69%, , R = H
4d
72%, , R = H
O
Cl
O
Cl
O
Cl
R
R
R
Cl
Cl
Cl
Br
Cl
3f
3g
3h
56%, , R = TMS
42%, , R = TMS
28%, , R = TMS
4f
d 4g
e 4h
45%, , R = H
--
, R = H
--
, R = H
O
Cl
O
Cl
O Cl
Me
Me
R
R
R
Me
Cl
Cl
Cl
3i
3j
3k
38%, , R = TMS
30%, , R = TMS
42%, , R = TMS
d 4i
e 4j
4k
--
, R = H
--
, R = H
71%, , R = H
aUsing 0.2 mmol scale for the reaction. bYields of isolated, analytically pure material. c0.67 equiv
d
1
of TMSCl was added. Product was identified by H NMR analysis of the crude reaction
e
1
mixture, but decomposed upon column chromatography. Product not identified by H NMR
analysis of the crude reaction mixture.

Interestingly, we observed partial C(sp2)-H silylation when some silyl enol ethers were
exposed to the silver catalyst and DCA (Scheme 2). Tetrasubstituted olefins 3l and 3l’ were
isolated in 42% and 30% yields, respectively. The thiophene based silyl enol ether 1m led to
tetrasubstituted olefins 3m and 3m’, in 50% and 14% isolated yields. The mechanism for the
formation of 3l’ and 3m’ is unclear at this point. Typical C-H silylation reactions occur from
hydrosilanes,24 and the regioselectivity is surprising, given that carbonyl groups typically direct
silylation to occur ortho to themselves.25 While detailed studies to elucidate the mechanism are
warranted, it appears that under the standard conditions, an unknown reactive silyl source is
being formed in situ, as exposing a ketone to the silver catalyst and chlorotrimethylsilane did not
lead to C-H silylation (Scheme 2, equation A, bottom).
Finally, we varied both the substituents on the silyl enol ether and the exogenous silyl
source to study their influence on the reaction outcome under Conditions A (Scheme 3). The
parent trimethylsilyl enol ether gave the adduct 3b-TMS in 75% yield. The slightly more bulky
triethylsilyl 1b-TES yielded the tetrasubstituted olefin 3b-TES in 43% yield. The very bulky
tert-butyldimethylsilyl enol ether 1b-TBS was unreactive under the standard conditions, but the
dimethylphenylsilyl enol ether 1b-DMPS led to tetrasubstituted olefin 3b-DMPS in 39% yield.
Most interestingly, when we exposed trimethylsilyl enol ether 1b-TMS to the silver catalyst,
DCA, and chlorotriethylsilane, the TMS group was preferentially incorporated into the olefin
over TES, giving more than twice 3b-TMS over 3b-TES (Scheme 3, equation B). This further
supports our supposition that the silyl enol ether is a reactive silyl source under these conditions.

O
Cl
O
Cl
(A)
Conditions A
TMS TMS
F
TMS
Cl
Cl
Cl
Cl
OTMS
F
F
3l
3l'
42%,
30%,
O
Cl
O
Cl
F
H
TMS
F
H
Conditions B
4l
38%,
not detected
O
AgOTf (10 mol%)
CH3
no reaction
TMSCl (1 equiv)
10:1 Et2O:MeCN
F
(B)
OTMS
O
Cl
O
Cl
Conditions A
TMS
TMS
TMS
Cl
3m
Cl
3m'
S
S
S
50%,
14%,
Scheme 2. C(sp2)-H silylation was observed in the reaction of p-fluoroacetophenone (A) and 3-
thiophene (B) derived silyl enol ethers with DCA.
As a simple mechanistic picture, it seems likely that the π bond in DCA is activated by
silver triflate,26 followed by attack of the silyl enol ether to form a putative vinylsilver species
with an anti-geometry.27 We postulate that in a non-polar solvent, the disassociated silyl group
from the silyl enol ether remains closely associated with the organosilver species, and quenches
it to yield the tetrasubstituted olefin 3. However, in a polar solvent, the ion pair can separate, and
the vinylsilver complex is quenched by adventitious water to give the trisubstituted olefins 4.
The observed reactivity is unique to that of DCA, as other alkynes, including methyl propiolate,
dimethyl acetylenedicarboxylate, and phenylacetylene remain unreactive under these conditions.

A
Cl
Cl
(
)
O[Si]
O
Cl
AgOTf (10 mol%)
[Si]Cl (0.67 equiv)
[Si]
Cl
Et2O:MeCN (10:1)
80 °C, 48 hr
(1M in ether)
(1 equiv)
1b-TMS
1b-TES
1b-TBS
2a
3b-TMS
3b-TES
3b-TBS
, 75% yield
, 43% yield
, 0% yield
3b-DMPS
, 39% yield
1b-DMPS
Cl
Cl
OTMS
O
Cl
B
(
)
O
Cl
AgOTf (10 mol%)
TESCl (0.67 equiv)
TES
TMS
Cl
Cl
Et2O:MeCN (10:1)
80 °C, 48 hr
3b
58%
3b-TES
2
1b
(1 equiv)
22%
(~5 equiv)
C
(
)
OTMS
Cl
O
Cl
Cl
O
O
Cl
Cl
Ag
Ag
[Si]
Cl
AgOTf
Cl
Cl
Cl
Cl
I
II
favored in
non-polar media
favored in
polar media
O
TMS
H
3b
4b
Scheme 3. Varying internal (A) and exogenous (B) [Si] source. (C) Simplified proposed
mechanism.
In conclusion, we report here a Nakamura-type reaction between silyl enol ethers and
DCA, which can generate either tri- or tetrasubstituted olefins, controlled by a simple switch of
the solvent. Both sets of products contain highly functionalizable handles, and are useful
building blocks to form more complex olefin compounds. Furthermore, we have discovered
interesting silyl transfer processes, for which the mechanisms are a current line of investigation
and will be reported in due course.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the internet. Further catalyst
optimization screening data, synthetic details and characterization data, and crystallographic data
(PDF). Copies of 1H and 13C NMR spectra (PDF).
AUTHOR INFORMATION

Corresponding Author
* Email: lgeary@unr.edu
Present Address
†Westlake University, Hangzhou, China.
Author Contributions
The manuscript was written through contributions of all authors.
ACKNOWLEDGMENT
The University of Nevada, Reno, and the National Institute of General Medical Sciences of the
National Institutes of Health under award number R15GM120738 are acknowledged for partial
support of this research.
References
1.
Chem. Rev. 2007, 107, 4698-4745.
2. (a) Rocha, D. H. A.; Pinto, D. C. G. A.; Silva, A. M. S. Applications of the Wittig
Flynn, A. B.; Ogilvie, W. W. Stereocontrolled Synthesis of Tetrasubstituted Olefins.
Reaction on the Synthesis of Natural and Natural-Analogue Heterocyclic Compounds. Eur. J.
Org. Chem. 2018, 2018, 2443-2457; (b) McNulty, J.; McLeod, D.; Das, P.; Zepeda-Velázquez,
C. Wittig Reactions of Trialkylphosphine-Derived Ylides: New Directions and Applications in
Organic Synthesis. Phosphorus, Sulfur Silicon Relat. Elem. 2015, 190, 619-632.
3.
(a) Blakemore, P. R. The Modified Julia Olefination: Alkene Synthesis Via the
Condensation of Metallated Heteroarylalkylsulfones with Carbonyl Compounds. J. Chem. Soc.,
Perkin Trans. 1 2002, 2563-2585; (b) Marko, I. E.; Pospisil, J. Synthesis of Alkenes by Julia,
Julia-Kocienski, and Related Sulfur-Based Alkenations. Sci. Synth. 2010, 47a, 105-160; (c)
Gueyrard, D. Extension of the Modified Julia Olefination on Carboxylic Acid Derivatives: Scope
and Applications. Synlett 2018, 29, 34-45.
4.
(a) Barrett, A. G. M.; Hill, J. M.; Wallace, E. M.; Flygare, J. A. Recent Studies on the
Peterson Olefination Reaction. Synlett 1991, 764-770; (b) van Staden, L. F.; Gravestock, D.;
Ager, D. J. New Developments in the Peterson Olefination Reaction. Chem. Soc. Rev. 2002, 31,
195-200.
5.
(a) Mori, M. Regio- and Stereoselective Synthesis of Tri- and Tetrasubstituted Alkenes
by Introduction of Co2 and Alkylzinc Reagents into Alkynes. Eur. J. Org. Chem. 2007, 2007,
4981-4993; (b) Negishi, E.-i.; Huang, Z.; Wang, G.; Mohan, S.; Wang, C.; Hattori, H. Recent
Advances in Efficient and Selective Synthesis of Di-, Tri-, and Tetrasubstituted Alkenes Via Pd-
Catalyzed Alkenylation−Carbonyl Olefination Synergy. Acc. Chem. Res. 2008, 41, 1474-1485.

6.
(a) Nagaki, A.; Matsuo, C.; Kim, S.; Saito, K.; Miyazaki, A.; Yoshida, J. Angew. Chem.
Int. Ed. 2012, 51, 3245-3248. (b) Nakao, Y.; Hiyama, T. Chem. Soc. Rev. 2011, 40, 4893-4901.
(c) Denmark, S. E.; Liu, J. H.-c. Angew. Chem. Int. Ed. 2010, 49, 2978-2986. (d) Ma, D.; Cai, Q.
Acc. Chem. Res. 2008, 41, 1450-1460. (e) Shi, J.-c.; Negishi, E.-i. J. Organomet. Chem. 2003,
687, 518-514. (f) Littke, A. F.; Dai, C.; Fu, G. C. J. Am. Chem. Soc. 2000, 122, 4020-4028. (g)
Fleming, I.; Barbero, A.; Walter, D. Chem. Rev. 1997, 97, 2063-2192. (h) Miyaura, N.; Suzuki,
A. Chem. Rev. 1995, 95, 2457-2483.
7.
(8) (a) Organ, M. G.; Cooper, J. T.; Rogers, L. R.; Soleymanzadeh, F.; Paul, T. J. Org.
Chem. 2000, 65, 7959-7970. (b) Organ, M. G.; Ghasemi, H. J. Org. Chem. 2004, 69, 695–700.
(c) Organ, M. G.; Ghasemi, H.; Valente, C. Tetrahedron 2004, 60, 9453-9461. (d) Organ, M. G.;
Arvanitis, E. A.; Villani, A.; Majkut, Y.; Hynes, S. Tetrahedron Lett. 2003, 44, 4403-4406. (e)
Organ, M. G.; Arvanitis, E. A.; Dixon, C. E.; Cooper, J. T. J. Am. Chem. Soc. 2002, 124, 1288-
1294.
8.
(a) Gredicak, M.; Jeric, I. The Sonogashira Cross-Coupling Reaction of Alkenyl
Chlorides with Aliphatic Acetylenes. Synlett 2009, 1063-1066; (b) MacNaughtan, M. L.; Gary, J.
B.; Gerlach, D. L.; Johnson, M. J. A.; Kampf, J. W. Cross-Metathesis of Vinyl Halides. Scope
and Limitations of Ruthenium-Based Catalysts. Organometallics 2009, 28, 2880-2887; (c)
Tikad, A.; Hamze, A.; Provot, O.; Brion, J.-D.; Alami, M. Suzuki Coupling Reactions of (E)-
and (Z)-Chloroenynes with Boronic Acids: Versatile Access to Functionalized 1,3-Enynes. Eur.
J. Org. Chem. 2010, 725-731; (d) Schevenels, F.; Marko, I. E. Efficient and Connective
Assembly of Highly Functionalized Benzofurans Using O-Hydroxyphenones and
Dichloroethylene. Org. Lett. 2012, 14, 1298-1301; (e) Matsuda, T.; Suzuki, K.; Miura, N.
Rhodium-Catalyzed Cross-Coupling of Alkenyl Halides with Arylboron Compounds. Adv.
Synth. Catal. 2013, 355, 3396-3400; (f) Umana, C. A.; Cabezas, J. A. Palladium-Catalyzed One-
Pot Conversion of Aldehydes and Ketones into 4-Substituted Homopropargyl Alcohols and 5-
En-3-Yn-1-Ols. J. Org. Chem. 2017, 82, 9505-9514; (g) Zhao, G.; Bignon, J.; Levaique, H.;
Dubois, J.; Alami, M.; Provot, O. One-Pot Synthesis of 2-Styrylindoles from Ortho-Substituted
Chloroenynes. J. Org. Chem. 2018, 83, 15323-15332.
9.
(a) Geary, L. M.; Hultin, P. G. Modular Construction of 2-Substituted Benzo[B]Furans
from 1,2-Dichlorovinyl Ethers. Org. Lett. 2009, 11, 5478-5481; (b) Geary, L. M.; Hultin, P. G.
2-Substituted Benzo[b]furans from (E)-1,2-Dichlorovinyl Ethers and Organoboron Reagents:
Scope and Mechanistic Investigations into the One-Pot Suzuki Coupling/Direct Arylation. Eur.
J. Org. Chem. 2010, 5563-5573; (c) Geary, L. M.; Hultin, P. G. Palladium-Catalyzed Modular
Assembly of Electron-Rich Alkenes, Dienes, Trienes, and Enynes from (E)-1,2-Dichlorovinyl
Phenyl Ether. J. Org. Chem. 2010, 75, 6354-6371.
10.
Asymmetric Oxo-Diels-Alder Reactions. Tetrahedron: Asymm. 2017, 28, 1506-1556.
11. (a) Hilt, G.; Janikowski, J.; Hess, W. Meta-Directing Cobalt-Catalyzed Diels-Alder
Taheri kal Koshvandi, A.; Heravi, M. M. Applications of Danishefsky’s Dienes in
Reactions. Angew. Chem., Int. Ed. 2006, 45, 5204-5206; (b) Erver, F.; Kuttner, J. R.; Hilt, G.
Multidirectional Cobalt-Catalyzed Diels-Alder/1,4-Hydrovinylation Sequences. J. Org. Chem.
2012, 77, 8375-8385.
12.
(a) Hilt, G.; Smolko, K. I.; Lotsch, B. V. Cobalt(I)-Catalyzed Neutral Diels-Alder
Reactions of Oxygen-Functionalized Acyclic 1,3-Dienes with Alkynes. Synlett 2002, 1081-1084;
(b) Kuttner, J. R.; Warratz, S.; Hilt, G. Straightforward Synthesis of Nonconjugated Cyclohex-3-
Enone and Conjugated 4-Methylenecyclohex-2-Enone Derivatives. Synthesis 2012, 44, 1293-

1303; (c) Kuttner, J. R.; Hilt, G. Synthesis of Acyclic Polycarbonyl Compounds Via Ozonolysis
of Cyclohexa-1,4-Dienes. Synthesis 2015, 47, 1170-1180.
13.
(a) Kende, A. S.; Benechie, M.; Curran, D. P.; Fludzinski, P.; Swenson, W.; Clardy, J.
The Dichlorovinylation of Enolates. Tetrahedron Lett. 1979, 19, 4513-4516; (b) Kende, A. S.;
Fludzinski, P. Chloroacetylenes as Michael Acceptors. I. Mechanism of Enolate
Dichlorovinylation. Tetrahedron Lett. 1982, 23, 2369-2372; (c) Kende, A. S.; Fludzinski, P.
Chloroacetylenes as Michael Acceptors. Ii. Direct Ethynylation and Vinylation of Tertiary
Enolates. Tetrahedron Letters 1982, 23, 2373-2376; (d) Kende, A. S.; Fludzinski, P.; Hill, J. H.
Chloroacetylenes as Michael Acceptors. 3. Mechanism and Synthetic Utility of Enolate
Reactions with Halogenated Olefins and Chloroacetylenes. J. Am. Chem. Soc. 1984, 106, 3551-
3562.
14.
(a) Nishimoto, Y.; Moritoh, R.; Yasuda, M.; Ba-ba, A. Angew. Chem. Int. Ed. 2009, 48,
4577-4580. (b) Itoh, Y.; Tsuji, H.; Yamagata, K.-c.; Endo, K.; Tanaka, I.; Nakamura, M.;
Nakamura, E. J. Am. Chem. Soc. 2008, 130, 17161-17167. (c) Nakamura, M.; Endo, K.;
Nakamura, E. J. Am. Chem. Soc. 2003, 125, 13002-13003. (d) Yamaguchi, M.; Tsukagoshi, T.;
Arisawa, M. J. Am. Chem. Soc. 1999, 121, 4074-4075.
15.
(a) Huang, J.; Bunel, E.; Faul, M. M. Palladium-Catalyzed α-Vinylation of Carbonyl
Compounds. Org. Lett. 2007, 9, 4343-4346; (b) Taylor, A. M.; Altman, R. A.; Buchwald, S. L.
Palladium-Catalyzed Enantioselective α-Arylation and α-Vinylation of Oxindoles Facilitated by
an Axially Chiral P-Stereogenic Ligand. J. Am. Chem. Soc. 2009, 131, 9900-9901; (c) Ankner,
T.; Cosner, C. C.; Helquist, P. Palladium- and Nickel-Catalyzed Alkenylation of Enolates. Chem.
- Eur. J. 2013, 19, 1858-1871; (d) Grigalunas, M.; Ankner, T.; Norrby, P.-O.; Wiest, O.;
Helquist, P. Palladium-Catalyzed Alkenylation of Ketone Enolates under Mild Conditions. Org.
Lett. 2014, 16, 3970-3973.
16.
(a) Trofimov, B. A.; Schmidt, E. Y.; Zorina, N. V.; Ivanova, E. V.; Ushakov, I. A.
Transition-Metal-Free Superbase-Promoted Stereoselective Α-Vinylation of Ketones with
Arylacetylenes: A General Strategy for Synthesis of ,-Unsaturated Ketones. J. Org. Chem.
2012, 77, 6880-6886; (b) Schmidt, E. Y.; Ivanova, E. V.; Semenova, N. V.; Tatarinova, I. V.;
Ushakov, I. A.; Trofimov, B. A. Base-Catalyzed α-Vinylation of Ketones with Acetylenes as a
Key Step in One-Pot Synthesis of Pyrazolines and Pyrazoles. Mendeleev Commun. 2015, 25,
131-132.
17.
Sproul, K. C.; Chalifoux, W. A. Highly Regio- and Diastereoselective Formation of
Tetrasubstituted (Z)-1,2-Dihaloalkenes from the Halogenation of Trimethylsilyl Alkynes with
ICl. Org. Lett. 2015, 17, 3334-3337.
18.
Yauchi, Y.; Ide, M.; Shiogai, R.; Chikugo, T.; Iwasawa, T. Regio- and Stereoselective
Synthesis of Vicinal (Z)-Dihaloalkenylsilanes from Silyl Ethynylarenes. Eur. J. Org. Chem.
2015, 938-943.
19.
Dichloroacetylene is a known explosive. The addition of diethyl ether minimizes the risk
of explosion, and while we have not experienced any incidents either using it in situ, or distilling
it, caution is highly recommended. See ESI for more details.
20.
21.
Isolated yields of 3 decreased after the DCA was stored for longer than one week.
We suspect that 3b´ is the geometrical isomer of 3b. However, we were unsuccessful in
all attempts to isolate and fully characterize it; all compounds 3 and 4 were isolated as
stereoisomerically pure compounds.
22.
Further increasing the amount of TMSCl to superstoichiometric amounts gave no further
improvement

23.
24.
In some cases, small amounts of the protiated olefin 4 could be detected by TLC.
Cheng, C.; Hartwig, J. F. Catalytic Silylation of Unactivated C–H Bonds. Chem. Rev.
2015, 115, 8946-8975.
25.
Fumitoshi, K.; Mitsutaka, M.; Motohiro, S.; Takahide, F.; Naoto, C.; Shinji, M.;
Naoyuki, F.; Yoshio, S. A New Synthetic Route to Heteroarylsilanes Via Ruthenium-Catalyzed
C-H/SiR3 Coupling. Chem. Lett. 2000, 29, 750-751.
26.
Fang, G.; Bi, X. Silver-Catalysed Reactions of Alkynes: Recent Advances. Chem. Soc.
Rev. 2015, 44, 8124-8173.
27.
Wong, V. H. L.; Hor, T. S. A.; Hii, K. K. Silver-Catalysed Intramolecular
Hydroamination of Alkynes with Trichloroacetimidates. Chem. Commun. 2013, 49, 9272-9274.
Cl
H
Cl
TMS
Cl
O
O
OTMS
10 mol% AgOTf
10 mol% AgOTf
R
Cl
R
R
Cl
Cl
Cl
Cl
1 M in Et2O
1 M in MeCN
10 examples
28-75% yield
7 examples
45-76% yield
Silver catalyzed proto- and sila-Nakamura-type α-vinylation of silyl enol
ethers with dichloroacetylene. Divergent formation of stereochemically
pure tri- and tetrasubstituted olefins.
Lun Li,† Kimberly A. Wasik, Brian J. Frost, and Laina M. Geary*
University of Nevada, Reno, Department of Chemistry, Reno, Nevada, 89557, USA.
Highlights:
-
-
-
-
-
Silver catalyzed activation of dichloroacetylene towards addition
Highly trans selective addition of enol ether across dichloroacetylene
Silyl versus proton transfer controlled via solvent
Highly functionalized tri- and tetrasubstituted alkenes selectively obtained
Unusual C-H silylation observed in select cases
Declaration of interests

☒ The authors declare that they have no known competing financial interests or personal
relationships that could have appeared to influence the work reported in this paper.
☐The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests: