The first example of nickel-catalyzed silyl-Heck reactions: Direct activation of silyl triflates without iodide additives

Article abstract of DOI:10.1016/j.tet.2014.03.021

For the first time, nickel-catalyzed silyl-Heck reactions are reported. Using simple phosphine-supported nickel catalysts, direct activation of silyl triflates has been achieved. These results contrast earlier palladium-catalyzed systems, which require io

Full text of DOI:10.1016/j.tet.2014.03.021

Tetrahedron 70 (2014) 4250e4256
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The first example of nickel-catalyzed silyl-Heck reactions: direct
activation of silyl triflates without iodide additives
Jesse R. McAtee y, Sara E.S. Martin y, Andrew P. Cinderella, William B. Reid,
*
Keywan A. Johnson, Donald A. Watson
Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
For the first time, nickel-catalyzed silyl-Heck reactions are reported. Using simple phosphine-supported
nickel catalysts, direct activation of silyl triflates has been achieved. These results contrast earlier
palladium-catalyzed systems, which require iodide additives to activate silyl-triflates. These nickel-based
catalysts exhibit good functional group tolerance in the preparation of vinyl silanes, and unlike earlier
systems, allows for the incorporation of trialkylsilanes larger than Me3Si.
Received 14 January 2014
Received in revised form 4 March 2014
Accepted 7 March 2014
Available online 14 March 2014
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
the most reactive silyl triflate, trimethylsilyl triflate, fails to undergo
reaction under palladium-catalyzed conditions without added io-
Unsaturated organosilanes are potent nucleophiles and highly
useful intermediates in organic synthesis.1 Recently, we have
established the silyl-Heck reaction as a novel route to access both
allyl and vinyl silanes.2,3 This general method allows for the direct
silylation of terminal alkenes using silyl halides and transition
metal catalysts, in a reaction that we believe is analogous to clas-
sical Heck arylation (Fig. 1).4
Our previous work has focused exclusively on the use of
palladium-based catalysts in this transformation.2a,b In these pro-
cesses, we have found that the use of iodosilanes is required. These
can either be used directly or prepared in situ from silyl chlorides,
bromides, or triflates, and simple iodide salts.5 Significantly, even
dide. Siliconeoxygen bonds are known to be very strong, we at-
tribute this to the reluctance of palladium to insert into the SieOTf
bond.6
An active interest in our group is developing a catalyst capable
of engaging silyl halides other than iodosilanes in silyl-Heck type
reactions. This interest is fueled by the recognition that iodosilanes
are potent Lewis acids, and thus have attenuated functional group
compatibility. In addition, access to silyl iodides is limited, with
only Me3SiI being commercially available. In contrast, a much wider
variety of silyl chlorides and triflates can be purchased or readily
prepared, making methods that can directly utilize these reagents
attractive to develop.7
In cross-coupling chemistry of carbon electrophiles, nickel cat-
alysts have proven adept at the activation of strong carbon-
eheteroatom bonds (such as aryl ethers and carboxylates),
particularly in comparison to palladium catalysts.8 Despite the fact
that silyl bromides and iodides have been shown to oxidatively add
to a variety of late transition metal complexes, to our knowledge
such reactions involving nickel compounds have not been
described.3aee,9 Based upon the precedent with strong CeX bonds,
we decided to investigate silyl-Heck type reactions with nickel-
based catalysts.10
Herein, we report the first examples of nickel-catalyzed silyl-
Heck type reactions. We show that unlike in palladium-catalyzed
reactions, these nickel-catalyzed reactions are able to utilize silyl
triflate electrophiles without the need for iodide additives. Using
this system, a variety of styrene derivatives and related terminal
alkenes lacking allylic hydrogen atoms can be successfully trans-
formed into E-vinyl silanes. As significantly, for the first time, this
nickel-based catalyst system allows for the direct preparation of
Fig. 1. Proposed mechanism for silyl-Heck reaction.
* Corresponding author. E-mail address: dawatson@udel.edu (D.A. Watson).
These authors contributed equally to this publication.
y
0040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2014.03.021

J.R. McAtee et al. / Tetrahedron 70 (2014) 4250e4256
4251
Table 2
vinyl trialkylsilanes from trialkylsilyl electrophiles larger than tri-
Substrate scope with respect to styrene
methylsilane. We believe that this new catalytic system not only
provides promise for developing general base-metal catalysts for
this class of reaction, but also greatly expands the types of un-
saturated organosilanes that can be accessed using the silyl-Heck
reaction.
2. Results and discussion
To begin our investigation of nickel-catalyzed silyl-Heck re-
actions, we studied the reaction of 4-tert-butyl styrene with tri-
methylsilyl triflate (Me3SiOTf) without iodide additives (Table 1).
Consistent with our previous observations, palladium-based cata-
lysts provided only trace yield of desired vinyl silane 1 (entry 1). In
our hands, this outcome is not improved by variation of either
palladium pre-catalyst, nature of phosphine ligand, metal:ligand
ratio, solvent, or temperature (not shown). In contrast, a modest
screen of catalysts derived from Ni(COD)2 and phosphine ligands
revealed a significantly different outcome. Whereas catalysts
employing triaryl phosphines (entries 2 and 3) or mixed arylalkyl
phosphines (entries 4 and 5) were ineffective, moderately bulky
trialkyl phosphines provided highly active catalysts (entries 6e10).
Interestingly, however, there seems to be a steric limit with regard
to ligand size; the very bulky tBu3P was ineffective (entry 11).
Further optimization revealed that a highly effective catalyst was
t
obtained using BuPCy2 and Ni(COD)2 when a 1.5:1 ligand:metal
ratio was employed (entry 13).
Table 1
Identification of nickel-based catalyst
Entry
Pre-catalyst
Ligand (mol %)
Yield 1
1
2
3
4
5
6
7
8
(COD)Pd(CH2TMS)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
Ni(COD)2
tBuPPh2 (30)
PPh3 (30)
P(o-tol)3 (30)
tBuPPh2 (30)
Cy2PPh (30)
nBu3P (30)
0%
0%
0%
12%
11%
69%
57%
65%
71%
55%
7%
PCy3 (30)
PCyp3 (30)
tBuPCy2(30)
tBu2PCy (30)
tBu3P (30)
9
10
11
12
13
tBuPCy2 (20)
tBuPCy2 (15)
85%
90%
formation of ester 9 was not observed, and dimethylamino product
10 was formed in low yield. Strained rings, such as benzocyclobu-
tane (11), and steric bulk on the aromatic group ortho to the alkene
(12), however, were well tolerated. Some heterocyclic substrates
could also be silylated using this protocol. For example, silylation of
N-vinyl carbazole led to vinyl silane 13 in high yield.11 However, in
other cases, such as in the formation of benzofuran 14, yields
proved to be suboptimal. Finally, more complex vinyl silanes, such
as pinacol borane 15 and estradiol-derived 16, could also be
accessed using the nickel-catalyzed protocol. In the case of 15,
tricyclopentylphosphine (Cyp3P) proved to be a slightly more ef-
Using these optimized conditions, we studied the scope of the
nickel-catalyzed silyl-Heck reaction (Table 2). A variety of styrenyl
alkenes participate in the reaction. On preparative scale (1 mmol),
vinyl silane 1 was isolated in 82% yield. Likewise, unsubstituted
styrene could be silylated in 89% isolated yield under these con-
ditions (2). A variety of ethereal substrates were also tolerated,
including those with both electron-donating para-methoxy (3) and
electron-withdrawing meta-methoxy groups (4) in good yield (71%
and 76%, respectively). Silyl ethers (5) and dioxoles (6) were also
well tolerated. Aromatic fluorides proved amiable to the reaction
conditions; fluorinated vinyl styrene 7 was isolated in 66% yield.
Unfortunately, larger aromatic halogens were not compatible with
the silylation conditions. For example, the use of 4-chlorostyrene as
substrate led to a complex mixture of products without detectable
formation of desired vinyl styrene 8. Also problematic were highly
electron-deficient or electron-rich styrenes. For example, the
t
fective ligand than BuPCy2, demonstrating that some ligand opti-
mization might prove necessary in order to maximize vinyl silane
yield.12 Overall, while these yields are slightly lower and scope is
somewhat more limited than our previously reported palladium-
catalyzed silyl-Heck protocol involving Me3SiI, we believe that
this reaction enjoys sufficient substrate scope to make it a syn-
thetically viable alternative, particularly given the advantages of
using a nonprecious metal, nickel-based catalyst and a silyl triflate
as the silylating reagent.

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J.R. McAtee et al. / Tetrahedron 70 (2014) 4250e4256
As mentioned above, silyl triflates are much more abundant
catalyzed silyl-Heck reaction. Both phenyldimethyl and diphe-
nylmethyl vinyl silanes can be prepared in good yield in this way
(21 and 22). Finally, triethylsilyl triflate also participates in the re-
action; 23 was prepared in 65% yield. However, triisopropylsilyl
triflate appears to be too large (even under forcing conditions). As
the previously developed palladium-catalyzed reaction only toler-
ates Me3SiI (used directly or generated in situ), these results greatly
expand the types of electrophilic trialkylsilanes that can participate
in the silyl-Heck reaction.
In the case of reactions using larger silyl triflates (described in
Table 3), the major byproduct is alkene 25 (Fig. 2). We hypothesize
that this styrene dimer arises via a metal hydride-mediated Heck-
type pathway.15 Minor amounts of similar dimers are also observed
as byproducts in reactions using Me3SiOTf (Table 1); however,
formation of these dimers is less significant. These results suggest
that the dimerization pathway becomes more competitive with
increasing steric bulk of the silyl triflate, likely due to the difficulty
of oxidative addition.
than silyl iodides. We therefore wanted to investigate the scope of
the transformation with respect to the silyl triflate. We deemed this
to be a significant goal as vinyl silanes bearing groups other than
trimethylsilyl exhibit improved reactivity in a variety of trans-
formations. In particular, vinyl benzyl silanes are highly effective in
Hiyama cross-coupling,13 and those bearing aromatic functionality
on silicon are faster in both acylation and oxidation reactions.14 The
expansion of the silyl-Heck reaction to include these silanes would
allow direct preparation of these products from alkenes.
Initial investigations using tBuPCy2 and the above-optimized
conditions revealed that silyl triflates larger than trimethylsilyl
triflate do participate in the reaction. However, we rapidly identi-
fied the use of Cy3P with a ligand:metal ratio of 3:1 as an alternative
catalyst that provided generally higher yields with larger silanes.
Scope studies using 4-tert-butyl styrene and this latter catalyst
system are outlined in Table 3. Dimethylsilyl triflates containing
one primary alkyl group, such as nBuMe2SiOTf or BnMe2SiOTf
participate well under these conditions (17 and 18), providing
similar yields to Me3SiOTf. One secondary substituent, such as in
iPrMe2SiOTf, can also be tolerated without loss of yield (19).
However, a tertiary silyl substituent proved to be beyond the steric
limit under these conditions; using Cy3P as ligand, none of desired
vinyl silane 20 was observed using tBuMe2SiOTf (TBSOTf). However,
switching to the smaller ligand nBu3P and using elevated temper-
atures did allow for the formation of 20. Despite the modest yield,
this transformation is remarkable as it presumably involves oxi-
dative addition at a silicon center that bears a fully substituted
adjacent center (akin to a neopentylic carbon center). Silyl triflates
bearing aromatic groups are also good substrates for the nickel-
Fig. 2. Major byproduct from silyl-Heck reactions of larger silyl triflates.
3. Conclusions
For the first time, we have demonstrated a nickel-catalyzed
silyl-Heck reaction, the first demonstration of a first-row transi-
tion metal catalyst in this type of reaction. We have shown that
simple phosphine-supported nickel-based catalysts are not only
capable of silylating styrene derivatives, but are also capable of
promoting the reaction with silyl triflate reagents without the need
for in situ generation of silyl iodides. Moreover, good substrate
scope with respect to the alkene has been observed. More impor-
tantly, for the first time electrophilic trialkylsilanes bearing alkyl
groups larger than methyl have been shown to participate in Heck-
like reactions. These results provide promising leads for the further
development of silyl-Heck reactions using inexpensive catalysts
and silylating reagents.
Table 3
Substrate scope with respect to silyl triflate
4. Experimental section
4.1. General experimental details
Dioxane, tetrahydrofuran, and dichloromethane were dried on
alumina according to published procedures.16 Triethylamine was
distilled from CaH2 and then sparged with nitrogen. 2-
Dimethylaminoethanol was distilled under vacuum from anhy-
drous potassium carbonate and sparged with nitrogen. Tri-
fluoromethanesulfonic acid (TfOH) was distilled under vacuum and
stored under nitrogen in a Teflon-sealed vessel. Trimethylsilyl-,
triethylsilyl- (Oakwood Chemical), tert-butyldimethylsilyl- (Combi-
Blocks), and tri-iso-propylsilyl- (Gelest) trifluoromethanesulfonate
were distilled under vacuum and degassed prior to use. All hot
glassware was oven dried for a minimum of 4 h or flame-dried under
vacuum prior to use. All other substrates and reagents were pur-
chased in highest analytical purity from commercial suppliers.
Liquid substrates were sparged with nitrogen before use, and all
others were used as received. Column chromatography was per-
formed with 5e20
eluent reported
m
m or 40e63
in parentheses.
m
m silica gel (Silicycle) with the
Analytical thin-layer

J.R. McAtee et al. / Tetrahedron 70 (2014) 4250e4256
4253
chromatography (TLC) was performed on precoated glass plates and
visualized by UV or by staining with KMnO4.
purified using flash silica chromatography, eluting with the in-
dicated solvent noted in parenthesis.
4.4. Characterization data
4.2. Instrumentation
4.4.1. (E)-(4-(tert-Butyl)styryl)trimethylsilane (1). Following gen-
NMR spectra were obtained on a Bruker AV400 MHz FT-NMR
spectrometer equipped with a Bruker CryoPlatform (400 MHz 1H,
101 MHz 13C, and 376 MHz 19F) or on a Bruker AVIII 600 MHz FT-
NMR spectrometer (600 MHz 1H, 151 MHz 13C), in the indicated
deutero-solvent and were recorded at ambient temperatures.
Chemical shifts are reported in parts per million. 1H NMR were
calibrated using the residual protio-solvent as a standard. 13C
NMR spectra are calibrated using the deutero-solvent as a stan-
dard and were recorded using the attached proton test.17 19F
spectra are referenced to an external FCCl3 sample. IR spectra
were recorded on a Nicolet Magna 560 FTIR spectrometer as thin
films. GCeMS data was collected using an Agilent 6850 series GC
and 5973 MS detector. High resolution MS was attained on
a Waters GCT Premier spectrometer using electron impact ioni-
zation (EI).
eral procedure A: 1-tert-butyl-4-vinylbenzene (183
mL, 1 mmol),
tBuPCy2 (38 mg, 0.15 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N
(700 mL, 5 mmol), and Me3SiOTf (540 mL, 3 mmol) were reacted in
dioxane (2 mL) at 75 ꢀC for 24 h. The product was purified by flash
chromatography on silica gel (petroleum ether) and concentrated
in vacuo to yield 190 mg of 1 (82%) of a colorless oil. 1H NMR
(400 MHz, CDCl3)
d
7.38 (d, J¼8.7 Hz, 2H), 7.35 (d, J¼8.7 Hz, 2H),
6.85 (d, J¼19.1 Hz, 1H), 6.42 (d, J¼19.1 Hz, 1H), 1.31 (s, 9H), 0.14 (s,
9H); 13C NMR (101 MHz, CDCl3)
d 151.2, 143.4, 135.8, 128.6, 126.2,
125.6, 34.7, 31.4, ꢁ1.0; FTIR (cmꢁ1): 2957,1248, 986, 868, 838. HRMS
(EI) m/z, calcd for [C15H24Si]: 232.1647; found: 232.1668.
4.4.2. (E)-Trimethyl(styryl)silane (2). Following general procedure
A: styrene (115
(27.5 mg, 0.1 mmol), Et3N (700
m
L, 1 mmol), tBuPCy2 (38 mg, 0.15 mmol), Ni(COD)2
mL, 5 mmol), and Me3SiOTf (540 mL,
3 mmol) were reacted in dioxane (2 mL) at 75 ꢀC for 24 h. The
product was purified by flash chromatography on silica gel (pe-
troleum ether) and concentrated in vacuo to yield 158 mg of 2 (89%)
4.3. General procedures
of a colorless oil. 1H NMR (400 MHz, CDCl3)
d
7.44 (d, J¼7.0 Hz, 2H),
4.3.1. General procedure A. Reactions of alkenes with trimethylsilyl
trifluoromethanesulfonate: in a glovebox (N2 atmosphere), dicy-
clohexyl-tert-butylphosphine (15 mol %) and Ni(COD)2 (10 mol %)
were added to a two dram vial equipped with a stirbar. Solid al-
kenes were also added at this time. Dioxane and triethylamine
(5 equiv) were then added sequentially, followed by liquid alkene
(1 equiv) if applicable. The vial was sealed with a Teflon-lined
septum cap and removed from the glovebox. The reaction mix-
ture was stirred at room temperature until homogeneous. Trime-
thylsilyl trifluoromethanesulfonate (3 equiv) was then added via
syringe at room temperature with stirring. The vessel was then
heated in an oil bath at 75 ꢀC with stirring for 24 h. The reaction
was removed from the oil bath and cooled to room temperature.
The reaction vessel was then opened to air, and brine and diethyl
ether or hexanes were added. The brine layer was removed, and
the organic layer was washed twice with brine. The combined
aqueous layers were back-extracted twice with diethyl ether or
hexanes. The combined organic layers were dried over MgSO4 and
concentrated in vacuo. The product was purified using flash silica
chromatography, eluting with the indicated solvent noted in
parenthesis.
7.33 (t, J¼7.4 Hz, 2H), 7.25 (t, J¼7.2 Hz, 1H), 6.88 (d, J¼19.2 Hz, 1H),
6.48 (d, J¼19.1 Hz, 4H), 0.16 (s, 9H); 13C NMR (101 MHz, CDCl3)
d
143.7,138.5,129.7,128.7,128.1,126.5, ꢁ1.1; FTIR (cmꢁ1) 2955,1247,
988, 866, 843. HRMS (EI) m/z, calcd for [C11H16Si]: 176.1021; found:
176.1048.
4.4.3. (E)-(4-Methoxystyryl)trimethylsilane (3). Following general
t
procedure A: 4-vinyl-anisole (134
m
L, 1 mmol), BuPCy2 (38 mg,
0.15 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700 mL, 5 mmol),
and Me3SiOTf (540 mL, 3 mmol) were reacted in dioxane (2 mL) at
75 ꢀC for 24 h. The product was purified by flash chromatography
on silica gel (petroleum ether) and concentrated in vacuo to yield
146 mg of 3 (71%) as a white solid. 1H NMR (400 MHz, CDCl3)
d
7.38
(d, J¼8.8 Hz, 2H), 6.91e6.75 (m, 3H), 6.31 (d, J¼19.1 Hz, 1H), 3.81 (s,
3H), 0.14 (s, 9H); 13C NMR (101 MHz, CDCl3)
d 159.6, 143.1, 131.5,
127.7, 126.8, 114.0, 55.5, ꢁ1.0; FTIR (cmꢁ1) 2958, 1608, 1510, 1251,
1033, 993, 835, 798. HRMS (EI) m/z, calcd for [C12H18OSi]: 206.1127;
found: 206.1140.
4.4.4. (E)-(3-Methoxystyryl)trimethylsilane (4). Following general
t
procedure A: 3-vinyl-anisole (139
m
L, 1 mmol), BuPCy2 (38 mg,
0.15 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700 mL, 5 mmol),
4.3.2. General procedure B. Reactions of larger silyl triflates: in
a glovebox (N2 atmosphere), tricyclohexylphosphine (30 mol %)
and Ni(COD)2 (10 mol %) were added to a two dram vial equipped
with a stirbar. Dioxane, triethylamine (5 equiv), and 1-tert-butyl-4-
vinylbenzene (1 equiv) were then added, sequentially. The vial was
sealed with a Teflon-lined septum cap and removed from the glo-
vebox. The reaction mixture was stirred at room temperature until
homogeneous. The appropriate silyl trifluoromethanesulfonate
reagent (3 equiv) was then added via syringe at room temperature
with stirring. The vessel was then heated in an oil bath at 75 ꢀC with
stirring for 24 h, after which time N,N-dimethyl ethanolamine
(3 equiv) was added via syringe with stirring at 75 ꢀC. The vessel
was stirred at 75 ꢀC for approximately 1 min before stirring at room
temperature for approximately 15 min. The reaction vessel was
then opened to air, and hexanes and HCl (1 M aqueous) were added.
The HCl layer was removed, and the organic layer was washed
twice with HCl (1 M aqueous). The combined aqueous layers were
back-extracted with hexanes. The combined organic layers were
dried over MgSO4 and concentrated in vacuo. The product was
and Me3SiOTf (540 mL, 3 mmol) were reacted in dioxane (2 mL) at
75 ꢀC for 24 h. The product was purified by flash chromatography
on silica gel (5% Et2O:hexanes) and concentrated in vacuo to yield
159 mg of 4 (77%) as a colorless oil. 1H NMR (400 MHz, CDCl3)
d 7.27
(t, J¼7.8 Hz, 1H), 7.06 (d, J¼7.7 Hz, 1H), 7.01 (t, J¼2.0 Hz, 1H), 6.87 (d,
J¼19.2 Hz, 1H), 6.83 (dd, J¼2.7, 0.8 Hz, 1H), 6.50 (d, J¼19.1 Hz, 1H),
3.86 (s, 3H), 0.18 (s, 9H); 13C NMR (101 MHz, CDCl3)
d 159.9, 143.5,
139.9, 130.0, 129.6, 119.2, 114.0, 111.3, 55.5, ꢁ1.1; FTIR (cmꢁ1) 2954,
1263, 865, 838. HRMS (EI) m/z, calcd for [C12H18OSi]: 206.1127;
found: 206.1148.
4.4.5. (E)-tert-Butyldimethyl(3-(2-(trimethylsilyl)vinyl)phenoxy)si-
lane (5). Following general procedure A: tert-butyldimethyl(3-
vinylphenoxy)silane18 (234 mg,
1
mmol), tBuPCy2 (38 mg,
0.15 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700 mL, 5 mmol),
and Me3SiOTf (540 mL, 3 mmol) were reacted in dioxane (2 mL) at
75 ꢀC for 24 h. The product was purified by flash chromatography
on silica gel (petroleum ether) and concentrated in vacuo to yield
236 mg of 5 (77%) as a colorless oil. 1H NMR (400 MHz, CDCl3)
d 7.18

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J.R. McAtee et al. / Tetrahedron 70 (2014) 4250e4256
(t, J¼7.8 Hz, 1H), 7.04 (d, J¼7.7 Hz, 1H), 6.91 (t, J¼2.1 Hz, 6H), 6.80 (d,
J¼19.1 Hz, 1H), 6.73 (dd, J¼8.0, 2.3 Hz, 1H), 6.43 (d, J¼19.1 Hz, 1H),
0.99 (s, 9H), 0.20 (s, 6H), 0.15 (s, 9H); 13C NMR (101 MHz, CDCl3)
(2 mL) at 75 ꢀC for 24 h. The product was purified by flash chro-
matography on silica gel (petroleum ether) and concentrated in
vacuo to yield 248 mg of 13 (93%) as a white solid. 1H NMR
d
156.0, 143.5, 140.0, 129.7, 129.5, 119.9, 119.8, 118.0, 25.9, 18.4, ꢁ1.1,
(400 MHz, CDCl3)
d
8.07 (d, J¼7.8 Hz, 2H), 7.72 (d, J¼8.3 Hz, 2H), 7.48
ꢁ4.2; FTIR (cmꢁ1) 2956, 2859, 1575, 1280, 985, 838. HRMS (EI) m/z,
(ddd, J¼8.3, 7.2, 1.3 Hz, 2H), 7.38e7.27 (m, 3H), 6.04 (d, J¼17.2 Hz,
calcd for [C17H30OSi2]: 306.1835; found: 306.1819.
1H), 0.27 (s, 9H); 13C NMR (101 MHz, CDCl3)
d 139.4, 133.6, 126.3,
124.2, 120.8, 120.4, 113.5, 110.9, 77.2, ꢁ0.6; FTIR (cmꢁ1) 2953, 1610,
1447, 834, 751, 721. HRMS (EI) m/z, calcd for [C17H19NSi]: 265.1287;
found: 265.1262.
4.4.6. (E)-(2-(Benzo[d][1,3]dioxol-5-yl)vinyl)trimethylsilane
(6). Following general procedure A: 5-vinylbenzo[d][1,3]dioxole18
(148 mg, 1 mmol), tBuPCy2 (38 mg, 0.15 mmol), Ni(COD)2
(27.5 mg, 0.1 mmol), Et3N (700
m
L, 5 mmol), and Me3SiOTf (540
m
L,
4.4.11. (E)-Trimethyl(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)
styryl)silane (15). Following a modification to general procedure A:
4-pinacolatoboryl styrene19 (230 mg, 1 mmol), tricyclopentyl-
phosphine (72 mg, 0.3 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N
3 mmol) were reacted in dioxane (2 mL) at 75 ꢀC for 24 h. The
product was purified by flash chromatography on silica gel (hex-
anes) and concentrated in vacuo to yield 127 mg of 6 (57%) as
a colorless oil. 1H NMR (600 MHz, CDCl3)
d
7.00 (d, J¼1.8 Hz, 1H),
(700 mL, 5 mmol), and Me3SiOTf (540 mL, 3 mmol) were reacted in
6.86 (dd, J¼8.0, 1.7 Hz, 1H), 6.80e6.74 (m, 2H), 6.27 (d, J¼19.1 Hz,
dioxane (2 mL) at 75 ꢀC for 24 h. The product was purified by flash
chromatography on silica gel (3e15% CH2Cl2:hexanes) and con-
centrated in vacuo to yield 123 mg of 15 (41%) as a white solid. 1H
1H), 5.95 (s, 2H), 0.14 (s, 9H); 13C NMR (151 MHz, CDCl3)
d 148.2,
147.6, 143.1, 133.4, 127.4, 121.5, 108.3, 105.6, 101.2, ꢁ1.0; FTIR (cmꢁ1
)
2954, 2895, 1489, 1248, 866, 839. HRMS (EI) m/z, calcd for
NMR (600 MHz, CDCl3)
2H), 6.88 (d, J¼19.1 Hz,1H), 6.55 (d, J¼19.1 Hz,1H),1.35 (s,12H), 0.16
(s, 9H); 13C NMR (151 MHz, CDCl3)
143.7, 141.1, 135.2, 131.1, 125.8,
d
7.76 (d, J¼8.0 Hz, 2H), 7.43 (d, J¼8.0 Hz,
[C12H16O2Si]: 220.0920; found: 220.0933.
d
4.4.7. (E)-(4-Fluorostyryl)trimethylsilane (7). Following general
83.9, 25.0, ꢁ1.1 (the carbon attached to boron was not observed);
FTIR (cmꢁ1) 2953, 1607, 1358, 1141, 1090, 869. HRMS (EI) m/z, calcd
for [C17H27BO2Si]: 302.1873; found: 302.1893.
t
procedure A: 4-fluorostyrene (119
mL, 1 mmol), BuPCy2 (38 mg,
0.15 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700 mL, 5 mmol),
and Me3SiOTf (540 mL, 3 mmol) were reacted in dioxane (2 mL) at
75 ꢀC for 24 h. The product was purified by flash chromatography
4.4.12. tert-Butyldimethyl(((8R,9S,13S,14S,17S)-13-methyl-3-((E)-2-
(trimethylsilyl)vinyl)-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclo-
penta[a]phenanthren-17-yl)oxy)silane (16). Following general pro-
cedure A: tert-butyldimethyl(((8R,9S,13S,14S,17S)-13-methyl-3-
vinyl-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclopenta[a]phe-
on silica gel (hexanes) and concentrated in vacuo to yield 128 mg of
8 (66%) as a colorless oil. 1H NMR (400 MHz, CDCl3)
d 7.40 (ddt,
J¼8.3, 5.4, 2.5 Hz, 2H), 7.01 (app tt, J¼8.5, 1.9 Hz, 2H), 6.82 (d,
J¼19.1 Hz, 1H), 6.38 (d, J¼19.1 Hz, 1H), 0.15 (s, 9H); 13C NMR
t
(101 MHz, CDCl3)
d
162.7 (d, J¼247.3 Hz), 142.4 (s), 134.7 (s), 129.4
nanthren-17-yl)oxy)silane2b (396 mg, 1 mmol), BuPCy2 (38 mg,
(d, J¼2.2 Hz), 128.0 (d, J¼8.0 Hz), 115.5 (d, J¼21.5 Hz), ꢁ1.1 (s); 19F
0.15 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700
mL, 5 mmol),
NMR (376 MHz, CDCl3)
HRMS (EI) m/z, calcd for [C11H15FSi]: 194.0927; found: 194.0945.
d
ꢁ114.2; FTIR (cmꢁ1) 2956, 1507, 1248, 836.
and Me3SiOTf (540 mL, 3 mmol) were reacted in dioxane (2 mL) at
75 ꢀC for 24 h. The product was purified by flash chromatography
on silica gel (petroleum ether) and concentrated in vacuo to yield
283 mg of 16 (60%) as a white foam. 1H NMR (400 MHz, CDCl3)
4.4.8. (E)-(2-(Bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)vinyl)trime-
thylsilane
vinylbenzocyclobutene (130 mg,
0.15 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700
(11). Following
general
mmol), tBuPCy2 (38 mg,
L, 5 mmol),
mL, 3 mmol) were reacted in dioxane (2 mL) at
procedure
A:
4-
d
7.25e7.18 (m, 2H), 7.15 (s, 1H), 6.82 (d, J¼19.1 Hz, 1H), 6.40 (d,
1
J¼19.2 Hz, 1H), 3.64 (t, J¼8.2 Hz, 1H), 2.98e2.73 (m, 2H), 2.30 (dt,
J¼12.8, 3.0 Hz, 1H), 2.21 (td, J¼11.5, 11.0, 3.9 Hz, 1H), 2.08e1.79 (m,
3H), 1.76e1.59 (m, 1H), 1.59e1.09 (m, 7H), 0.89 (s, 9H), 0.74 (s, 3H),
0.14 (s, 9H), 0.04 (s, 3H), 0.03 (s, 3H); 13C NMR (101 MHz, CDCl3)
m
and Me3SiOTf (540
75 ꢀC for 24 h. The product was purified by flash chromatography
on silica gel (petroleum ether) and concentrated in vacuo to yield
157 mg of 11 (78%) as a colorless oil. 1H NMR (400 MHz, CDCl3)
d
143.6, 140.7, 137.0, 135.9, 128.5, 127.0, 125.7, 123.7, 81.9, 49.9, 44.7,
43.7, 38.8, 37.3, 31.1, 29.7, 27.4, 26.4, 26.0, 23.4, 18.3, 11.5, ꢁ1.0, ꢁ4.3,
ꢁ4.6; FTIR (cmꢁ1) 2926, 1248, 1095, 866, 836. HRMS (EI) m/z, calcd
for [C29H48OSi2]: 468.3244; found: 468.3259.
d
7.24 (d, J¼10.1 Hz, 1H), 7.18 (s, 1H), 7.00 (d, J¼7.5 Hz, 1H), 6.85 (d,
J¼19.1 Hz, 1H), 6.38 (d, J¼19.1 Hz, 1H), 3.16 (s, 4H), 0.14 (s, 9H); 13
C
NMR (101 MHz, CDCl3) d 146.2, 146.1, 144.7, 137.5, 127.8, 126.1, 122.7,
120.0, 29.6, 29.4, ꢁ1.0; FTIR (cmꢁ1) 2955, 2930, 1247, 985, 866, 837.
HRMS (EI) m/z, calcd for [C13H18Si]: 202.1178; found: 202.1194.
4.4.13. (E)-Butyl(4-(tert-butyl)styryl)dimethylsilane (17). Following
general procedure B: 1-tert-butyl-4-vinylbenzene (183
mL, 1 mmol),
Cy3P (84 mg, 0.3 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700
m
L,
4.4.9. (E)-(2,4-Dimethylstyryl)trimethylsilane (12). Following gen-
5 mmol), and n-butyldimethylsilyl trifluoromethanesulfonate7b
t
eral procedure A: 2,4-dimethystyrene (146
m
L, 1 mmol), BuPCy2
(790 mg, 3 mmol) were reacted in dioxane (2 mL) at 75 ꢀC for
(38 mg, 0.15 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700
mL,
24 h. N,N-Dimethyl ethanolamine (300 mL, 3 mmol) was added after
5 mmol), and Me3SiOTf (540
m
L, 3 mmol) were reacted in dioxane
reaction. The product was purified by flash chromatography on silica
(2 mL) at 75 ꢀC for 24 h. The product was purified by flash chro-
matography on silica gel (hexanes) and concentrated in vacuo to
yield 126 mg of 12 (62%) as a colorless oil. 1H NMR (400 MHz, CDCl3)
gel (petroleum ether) and concentrated in vacuo to yield 165 mg of
17 (60%) as a colorless oil. 1H NMR (600 MHz, CDCl3)
d 7.38 (d,
J¼8.4 Hz, 2H), 7.35 (d, J¼8.5 Hz, 2H), 6.85 (d, J¼19.2 Hz, 1H), 6.41 (d,
d
7.43 (d, J¼7.9 Hz,1H), 7.10 (d, J¼19.0 Hz,1H), 6.99 (d, J¼8.4 Hz,1H),
J¼19.1 Hz, 1H), 1.35e1.28 (m, 13H), 0.88 (t, J¼6.8 Hz, 3H), 0.64e0.59
6.96 (s, 1H), 6.33 (d, J¼19.0 Hz, 1H), 2.35 (s, 3H), 2.31 (s, 3H), 0.16 (s,
(m, 2H), 0.12 (s, 6H); 13C NMR (151 MHz, CDCl3)
d 151.2, 143.8,135.9,
9H); 13C NMR (101 MHz, CDCl3)
d
141.2, 137.6, 135.3, 134.9, 131.2,
127.8, 126.2,125.6, 34.8, 31.5, 26.7, 26.3,15.6,14.0, ꢁ2.8; FTIR (cmꢁ1
)
130.2, 127.0, 125.3, 21.3, 19.7, ꢁ1.0; FTIR (cmꢁ1) 2954, 1247, 987, 868,
842. HRMS (EI) m/z, calcd for [C13H20Si]: 204.1334; found: 204.1350.
2956, 1982, 986, 837. HRMS (EI) m/z, calcd for [C18H30Si]: 274.2117;
found: 274.2092.
4.4.10. (E)-9-(2-(Trimethylsilyl)vinyl)-9H-carbazole (13). Following
general procedure A: N-vinyl carbazole (193 mg, 1 mmol), tBuPCy2
4.4.14. (E)-Benzyl(4-(tert-butyl)styryl)dimethylsilane
(18). Following general procedure B: 1-tert-butyl-4-vinylbenzene
(38 mg, 0.15 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700
mL,
(183
mL, 1 mmol), Cy3P (84 mg, 0.3 mmol), Ni(COD)2 (27.5 mg,
5 mmol), and Me3SiOTf (540 L, 3 mmol) were reacted in dioxane
m
0.1 mmol), Et3N (700
mL, 5 mmol), and benzyldimethylsilyl

J.R. McAtee et al. / Tetrahedron 70 (2014) 4250e4256
4255
trifluoromethanesulfonate7a (895 mg, 3 mmol) were reacted in
dioxane (2 mL) at 75 ꢀC for 24 h. N,N-Dimethyl ethanolamine
were reacted in dioxane (1.5 mL) at 75 ꢀC for 24 h. N,N-Dimethyl
ethanolamine (225 L, 2.25 mmol) was added after reaction. The
m
(300
mL, 3 mmol) was added after reaction. The product was puri-
product was purified by flash chromatography on silica gel (2%e
fied by flash chromatography on silica gel (0e5% CH2Cl2:hexanes)
and concentrated in vacuo to yield 206 mg of 18 (67%) as a colorless
10% CH2Cl2:hexanes) and concentrated in vacuo to yield 198 mg of
22 (74%) as a colorless oil. 1H NMR (400 MHz, CDCl3)
d 7.59 (dd,
oil. 1H NMR (400 MHz, CDCl3)
d
7.36 (app s, 4H), 7.22 (t, J¼7.6 Hz,
J¼7.5, 1.8 Hz, 4H), 7.47e7.33 (m, 10H), 6.97 (d, J¼19.1 Hz, 1H), 6.73
2H), 7.08 (t, J¼7.4 Hz, 1H), 7.03 (app d, J¼7.3 Hz, 2H), 6.84 (d,
J¼19.2 Hz, 1H), 6.38 (d, J¼19.2 Hz, 1H), 2.21 (s, 2H), 1.33 (s, 9H), 0.13
(d, J¼19.0 Hz, 1H), 1.33 (s, 9H), 0.72 (s, 3H); 13C NMR (101 MHz,
CDCl3)
d 151.7, 147.1, 136.7, 135.5, 135.1, 129.4, 128.0, 126.5, 125.6,
(s, 6H); 13C NMR (101 MHz, CDCl3)
d
151.4, 144.6, 140.1, 135.7, 128.4,
123.9, 34.8, 31.4, ꢁ3.5; FTIR (cmꢁ1) 2961, 1427, 1111, 800, 699. HRMS
(EI) m/z, calcd for [C25H28Si]: 356.1960; found: 356.1955.
128.3, 126.4, 126.2, 125.6, 124.1, 34.8, 31.4, 26.3, ꢁ3.2; FTIR (cmꢁ1
)
2961, 1493, 832, 698. HRMS (EI) m/z, calcd for [C21H28Si]: 308.1960;
found: 308.1950.
4.4.19. (E)-(4-(tert-Butyl)styryl)triethylsilane (23). Following gen-
eral procedure B: 1-tert-butyl-4-vinylbenzene (183
mL, 1 mmol),
4.4.15. (E)-(4-(tert-Butyl)styryl)(isopropyl)dimethylsilane
Cy3P (84 mg, 0.3 mmol), Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N
(19). Following general procedure B: 1-tert-butyl-4-vinylbenzene
(700
(680
m
m
L, 5 mmol), and triethylsilyl trifluoromethanesulfonate
L, 3 mmol) were reacted in dioxane (2 mL) at 75 ꢀC for 24 h.
L, 3 mmol) was added after re-
(183
0.1 mmol), Et3N (700
fluoromethanesulfonate7a (750 mg, 3 mmol) were reacted in di-
oxane (2 mL) at 75 ꢀC for 24 h. N,N-Dimethyl ethanolamine (300
L,
mL, 1 mmol), Cy3P (84 mg, 0.3 mmol), Ni(COD)2 (27.5 mg,
m
L, 5 mmol), and isopropyldimethylsilyl tri-
N,N-Dimethyl ethanolamine (300
action. The product was purified by flash chromatography on silica
m
m
gel (petroleum ether) and concentrated in vacuo to yield 178 mg of
3 mmol) was added after reaction. The product was purified by
flash chromatography on silica gel (petroleum ether) and concen-
trated in vacuo to yield 157 mg of 19 (60%) as a colorless oil. 1H NMR
23 (65%) as a colorless oil. 1H NMR (400 MHz, CDCl3)
d 7.40 (d,
J¼8.6 Hz, 2H), 7.36 (d, J¼8.6 Hz, 2H), 6.88 (d, J¼19.3 Hz, 1H), 6.38 (d,
J¼19.3 Hz, 1H), 1.32 (s, 9H), 0.98 (t, J¼7.9 Hz, 9H), 0.65 (q, J¼7.9 Hz,
(400 MHz, CDCl3)
d
7.39 (d, J¼8.6 Hz, 2H), 7.36 (d, J¼8.4 Hz, 2H),
6H); 13C NMR (101 MHz, CDCl3)
d 151.2, 144.7, 135.9, 126.1, 125.6,
6.86 (d, J¼19.2 Hz, 1H), 6.41 (d, J¼19.2 Hz, 1H), 1.32 (s, 9H), 0.98 (d,
125.0, 34.7, 31.4, 7.6, 3.7; FTIR (cmꢁ1) 2954, 2874, 987, 788, 731.
J¼7.1 Hz, 6H), 0.93e0.80 (m, 1H), 0.10 (s, 6H); 13C NMR (101 MHz,
HRMS (EI) m/z, calcd for [C18H30Si]: 274.2117; found: 274.2093.
CDCl3)
d 151.2, 144.4, 135.9, 126.4, 126.2, 125.6, 34.7, 31.4, 17.8, 14.0,
ꢁ5.1; FTIR (cmꢁ1) 2955, 2863, 1267, 987, 839. HRMS (EI) m/z, calcd
Acknowledgements
for [C17H28Si]: 260.1960; found: 260.1968.
The University of Delaware (UD), the NSF (CAREER
CHE1254360), and the Research Corporation (Cottrell Scholars
Program) are gratefully acknowledged for funding and additional
support. SESM acknowledges graduate fellowship support from
NIH/NIGMS CBI Training Grant 5T32 GM 08550-16. NMR and other
data were acquired at UD on instruments obtained with the assis-
tance of NSF and NIH funding (NSF MRI CHE0421224 and
CHE1229234, NSF CRIF MU CHE0840401, NIH P20 GM103541).
4.4.16. (E)-tert-Butyl(4-(tert-butyl)styryl)dimethylsilane
(20). Following a modification of general procedure B: 1-tert-butyl-
4-vinylbenzene (183
Ni(COD)2 (27.5 mg, 0.1 mmol), Et3N (700
butyldimethylsilyl trifluoromethanesulfonate (690
were reacted in dioxane (1 mL) at 105 ꢀC for 24 h. N,N-Dimethyl
ethanolamine (300 L, 3 mmol) was added after reaction. The
m
L, 1 mmol), nBu3P (81 mg, 0.4 mmol),
mL, 5 mmol), and tert-
mL, 3 mmol)
m
product was purified by flash chromatography on silica gel (hex-
anes) and concentrated in vacuo to yield 86 mg of 20 (31%) as
Supplementary data
a colorless oil. 1H NMR (400 MHz, CDCl3)
d
7.39 (d, J¼8.6 Hz, 2H),
7.36 (d, J¼8.5 Hz, 2H), 6.87 (d, J¼19.2 Hz, 1H), 6.43 (d, J¼19.1 Hz,
Supplementary data associated with this article (NMR spectra of
products) can be found in the online version. Supplementary data
related to this article can be found at http://dx.doi.org/10.1016/
j.tet.2014.03.021.
1H), 1.32 (s, 9H), 0.91 (s, 9H), 0.11 (s, 6H); 13C NMR (101 MHz, CDCl3)
d
151.2, 144.7, 135.9, 126.2, 125.8, 125.6, 34.8, 31.4, 26.6, 17.0, ꢁ5.9;
FTIR (cmꢁ1) 2954, 2856, 1247, 987, 828. HRMS (EI) m/z, calcd for
[C18H30Si]: 274.2117; found: 274.2103.
References and notes
4.4.17. (E)-(4-(tert-Butyl)styryl)(phenyl)dimethylsilane
1. (a) Hosomi, A.; Endo, M.; Sakurai, H. Chem. Lett. 1976, 5, 941e942; (b) Masse, C.
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(183
0.1 mmol), Et3N (700
fluoromethanesulfonate7c (850 mg, 3 mmol) were reacted in di-
oxane (2 mL) at 75 ꢀC for 24 h. N,N-Dimethyl ethanolamine (300
L,
mL, 1 mmol), Cy3P (84 mg, 0.3 mmol), Ni(COD)2 (27.5 mg,
m
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3 mmol) was added after reaction. The product was purified by
flash chromatography on silica gel (petroleum ether) and concen-
trated in vacuo to yield 205 mg of 21 (70%) as a colorless oil. 1H NMR
(600 MHz, CDCl3)
7.37e7.33 (m, 5H), 6.93 (d, J¼19.1 Hz, 1H), 6.54 (d, J¼19.2 Hz, 1H),
1.32 (s, 9H), 0.42 (s, 6H); 13C NMR (151 MHz, CDCl3)
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d
7.58e7.55 (m, 2H), 7.39 (d, J¼8.4 Hz, 4H),
d
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calcd for [C20H26Si]: 294.1804; found: 294.1788.
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(137
(20.6 mg, 0.075 mmol), Et3N (529
nylmethylsilyl trifluoromethanesulfonate7c (780 mg, 2.25 mmol)
mL, 0.75 mmol), Cy3P (63 mg, 0.225 mmol), Ni(COD)2
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mL, 3.75 mmol), and diphe-

4256
J.R. McAtee et al. / Tetrahedron 70 (2014) 4250e4256
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