Palladium- and nickel-catalyzed carbon-carbon bond insertion reactions with alkylidenesilacyclopropanes

Article abstract of DOI:10.1021/om901042j

Palladium and nickel catalysts promoted highly selective carbon-carbon bond insertion reactions with di-tert-butyl-alkylidenesilacyclopropanes. Pd(PPh ₃)₄ was demonstrated to be the optimal catalyst, allowing for a variety of carbon-carbon π-bond insertion reactions. Depending on the nature of the carbon-carbon π bond, the insertion reaction proceeded with either direct insertion into the carbon(sp²)-silicon bond or allylic transposition. Ring-substituted alkylidenesilacyclopropanes required a nickel catalyst to afford insertion products. Using Ni(cod)₂ as the carbon-carbon bond insertion catalyst, new double alkyne insertion products and alkene isomerization products were observed.

Full text of DOI:10.1021/om901042j

Organometallics 2010, 29, 1661–1669 1661
DOI: 10.1021/om901042j
Palladium- and Nickel-Catalyzed Carbon-Carbon Bond Insertion
Reactions with Alkylidenesilacyclopropanes
Kay M. Buchner and K. A. Woerpel*
Department of Chemistry, University of California, Irvine, California 92697-2025
Received December 3, 2009
Palladium and nickel catalysts promoted highly selective carbon-carbon bond insertion reactions
withdi-tert-butyl-alkylidenesilacyclopropanes. Pd(PPh3)4 wasdemonstrated tobethe optimal catalyst,
allowing for a variety of carbon-carbon π-bond insertion reactions. Depending on the nature of the
carbon-carbon π bond, the insertion reaction proceeded with either direct insertion into the carbon-
(sp2)-silicon bond or allylic transposition. Ring-substituted alkylidenesilacyclopropanes required a
nickel catalyst to afford insertion products. Using Ni(cod)2 as the carbon-carbon bond insertion
catalyst, new double alkyne insertion products and alkene isomerization products were observed.
Introduction
diastereoselectivity. Electronic effects are examined and me-
chanistic considerations are discussed.
Strained-ring silanes undergo a variety of ring-expanding
reactions. For example, metal-catalyzed insertions with car-
bon-carbon π bonds have been reported for various three-1-12
and four-membered ring silacyclic compounds.13-17 These
reactions, however, suffer from low selectivity or limited sub-
strate scope.
In this article, we report selective and general metal-cata-
lyzed carbon-carbon π-bond insertion reactions with alkyli-
denesilacyclopropanes (3) derived from allenes (1, eq 1).18 We
also report the synthesis of a silacyclopropanederived from an
allene ether and its high reactivity that allows subsequent two-
atom ring-expansion reactions to occur with high regio- and
Results and Discussion
*Corresponding author. E-mail: kwoerpel@uci.edu.
(1) Seyferth, D.; Duncan, D. P.; Vick, S. C. J. Organomet. Chem.
1977, 125, C5–C10.
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D. P. J. Organomet. Chem. 1977, 135, C37–C44.
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Organometallics 1985, 4, 57–62.
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Attempted Synthesis of an Unsubstituted Alkylidenesila-
cyclopropane. An unactivated alkylidenesilacyclopropane
was desired for preliminary experiments. Unsubstituted
alkylidenesilacyclopropane 3a was formed by silylene trans-
fer to allene (1a), but it could not be isolated (eq 2).19 Because
monosubstituted alkylidenesilacyclopropane 3b can be iso-
lated (eq 3),18 it was employed in the initial carbon-carbon
bond insertion reactions.
(8) Saso, H.; Ando, W. Chem. Lett. 1988, 1567–1570.
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V.; Malacria, M.; Aubert, C. Organometallics 2007, 26, 819–830.
(17) Liu, J.; Sun, X.; Miyazaki, M.; Liu, L.; Wang, C.; Xi, Z. J. Org.
Chem. 2007, 72, 3137–3140.
(19) Silacyclopropane 3a was observed by 1H NMR spectroscopic
analysis of the crude reaction mixture. The yield was calculated relative
to an internal standard (PhSiMe3).
(18) Buchner, K. M.; Clark, T. B.; Loy, J. M. N.; Nguyen, T. X.;
Woerpel, K. A. Org. Lett. 2009, 11, 2173–2175.
r
2010 American Chemical Society
Published on Web 03/03/2010
pubs.acs.org/Organometallics

1662 Organometallics, Vol. 29, No. 7, 2010
Buchner and Woerpel
Table 1. Pd(0)-Catalyzed Carbon-Carbon Bond Insertion with
3b to Yield Si-C(sp2) Bond Cleavage Products
Table 2. Pd(0)-Catalyzed Carbon-Carbon Bond Insertion with
3b to Yield Allylic Transposition Products
a The stereo- and regiochemistry of the products were assigned by
NOE analyses. Details are provided as Supporting Information. b As
determined by 1H NMR spectroscopic analysis relative to an internal
standard (PhSiMe3). Isolated yields are shown in parentheses. c Formed
as a minor product in a 29:71 mixture with silacyclopentane 6. d Re-
quired heating at 70 °C to go to completion and was formed as a 56:44
mixture with dimeric material derived from 3b.
a As determined by 1H NMR spectroscopic analysis relative to an
internal standard (PhSiMe3). Isolated yields are shown in parentheses.
b Unstable toward isolation attempts.
Pd(0)-Catalyzed Insertion Reaction with a Monosubstituted
Alkylidenesilacyclopropane. To determine the potential of
metal-catalyzed carbon-carbon π-bond insertion reactions,
alkylidenesilacyclopropane 3b was tested with various sub-
strates in the presence of Pd(PPh3)4. For all reactions, two
equivalents of substrate were required for the reaction to
proceed to completion. Insertions of terminal alkynes into
substrate 3b afforded Si-C(sp2) bond cleavage products
selectively, as did the insertion of an allene (Table 1). Instead
of direct insertion, allylic transposition products were formed
in moderate yields in the presence of both internal alkynes and
terminal alkenes (Table 2). Many of the resultant silacyclo-
pentene and -pentane products exhibited moderate instability,
so they were difficult to purify. All reactions went to comple-
tion at ambient temperature, except for the reaction of
substrate 3b with 1-octene (entry 4), which required heating
at 70 °C. Attempts to react alkyl-substituted allenes, internal
alkenes, and sterically hindered internal alkynes with alkyli-
denesilacyclopropane 3b led to decomposition.
In addition to the observed allylic transposition products,
side products were observed for some of the reactions shown
in Table 2. Silacyclopentane 6 was observed as the major
product in entry 1. The formation of this product results
from the formal incorporation of a second equivalent of
alkylidenesilacyclopropane 3b in conjunction with di-tert-
butylsilylene extrusion.8,9 Dimeric material20,21 derived from
alkylidenesilacyclopropane 3b appeared when heating the
reaction mixture in entry 4.5,7,16,22,23 No reactions (including
decomposition and byproduct formation) were observed in
the absence of catalyst.
Pd(0)-Catalyzed Insertion Reaction with an Electronically
Activated Alkylidenesilacyclopropane. Alkylidenesilacyclo-
propane 3c was synthesized to investigate possible electronic
effects in the Pd(0)-catalyzed reactions. No silylene transfer
was observed R to the methoxy group, which is surprising
considering the electrophilic nature of the silver silylenoid
generated in situ.24,25 Control experiments demonstrated
that silylene transfer does not occur with enol ether 9
(Scheme 1), although it proceeded readily in the presence
of acetylenic ethers.26,27
(22) Ishikawa, M.; Sugisawa, H.; Kumada, M.; Higuchi, T.; Matsui,
K.; Hirotsu, K. Organometallics 1982, 1, 1473–1477.
(23) Ishikawa, M.; Fuchikami, T.; Kumada, M. J. Chem. Soc., Chem.
Commun. 1977, 352.
(24) Driver, T. G.; Woerpel, K. A. J. Am. Chem. Soc. 2003, 125,
10659–10663.
(20) The dimeric material could not be isolated due to its instability,
and its structure could not be determined in the reaction mixture. The
exact mass of the dimer was determined by HRMS (GC-MS). Addi-
tional details are provided as Supporting Information.
(25) Driver, T. G.; Woerpel, K. A. J. Am. Chem. Soc. 2004, 126, 9993–
10002.
(26) Clark, T. B.; Woerpel, K. A. Organometallics 2005, 24, 6212–
6219.
(21) Atwell, W. H. Organometallics 2009, 28, 3573–3586.
(27) Clark, T. B.; Woerpel, K. A. Org. Lett. 2006, 8, 4109–4112.

Article
Organometallics, Vol. 29, No. 7, 2010 1663
Scheme 1. Silacyclopropanation of Allene Ether 1c and a Control
Experiment with Enol Ether 8
Table 4. Pd(0)-Catalyzed Carbon-Carbon Bond Insertion with
3c to Yield Allylic Transposition Products
When subjected to the Pd(0)-catalyzed carbon-carbon
π-bond insertion reaction, alkylidenesilacyclopropane 3c
was shown to be more reactive than alkyl-substituted
analogue 3b while maintaining high regio- and diastereo-
selectivity. Terminal alkynes and allenes afforded Si-C(sp2)
bond cleavage products (Table 3), but internal alkynes
Table 3. Pd(0)-Catalyzed Carbon-Carbon Bond Insertion with
3c to Yield Si-C(sp2) Bond Cleavage Products
a As determined by 1H NMR spectroscopic analysis relative to an
internal standard (PhSiMe3). Isolated yields are shown in parentheses.
b Hydrolysis and elimination gave R,β,γ,δ-unsaturated acyl silane 5f0
upon attempted chromatography. Difficulties with purification pre-
vented accurate determination of the isolated yield. c Formed as a
68:32 mixture with dimeric material derived from 3c.
were also viable substrates in this reaction. Insertion with
1-octene proceeded to completion at ambient temperature
(Table 4, entry 4). Analogously to silacyclopropane 3b,
internal alkenes were unreactive, and a dimeric compound
derived from 3c was observed as a byproduct in the reaction
with 1-octene (Table 4, entry 4).20,21 Although alkylidene-
silacyclopropane 3c exhibited greater reactivity and sub-
strate scope, most of the insertion products were found to
be too unstable to isolate and purify.
In an effort to circumvent the isolation of the air-sensitive
alkylidenesilacyclopropane, a one-flask, two-step silacyclo-
propanation/π-bond insertion reaction (eq 4) was attem-
pted with alkylidenesilacyclopropane 3c in a manner similar
to carbonyl insertion reactions.18 Residual silver salts inhi-
bited the Pd(0)-catalyzed reaction, providing product 4e
in low yield. As a result, all further experiments were con-
ducted using isolated samples of alkylidenesilacyclopro-
panes.
a As determined by 1H NMR spectroscopic analysis relative to an
internal standard (PhSiMe3). Isolated yields are shown in parentheses.
b Hydrolysis gave R,β-unsaturated aldehyde 4h0 when subjected to
chromatography.
and terminal alkenes gave allylic transposition products
(Table 4). A sterically hindered internal alkyne (Table 4,
entry 2) and an alkyl-substituted allene (Table 3, entry 4)
Pd(0)-Catalyzed Insertion Reaction with Disubstituted
Alkylidenesilacyclopropanes. To extend these reactions to

1664 Organometallics, Vol. 29, No. 7, 2010
Buchner and Woerpel
Scheme 2. Pd(0)-Catalyzed Carbon-Carbon Bond Insertion
with 3d
center in the three-membered ring, which is necessary for
developing an asymmetric variant of this reaction, also
inhibited the reactivity of alkylidenesilacyclopropane 3d in
the Pd(0)-catalyzed reaction, alternative reaction conditions
were investigated.
Optimization and Catalyst Screen. Initial attempts to in-
crease the rate of the insertion reactions and avoid byproduct
formation by heating the reaction mixture resulted in in-
creased dimerization of the starting alkylidenesilacyclo-
propanes (eq 6).20,21 Control experiments with both alkyli-
denesilacyclopropanes 3b and 3c showed rapid dimerization
upon heating in the absence of substrate (eq 7) and suggested
that formation of dimeric material is a thermodynamically
favored process. An attempt to dimerize disubstituted alky-
lidenesilacyclopropane 3d resulted in decomposition of start-
ing material.
alkylidenesilacyclopropanes derived from chiral allenes,
alkylidenesilacyclopropane 3d was also subjected to the
Pd(0)-catalyzed insertion reaction (Scheme 2). Only the
reaction with phenylacetylene led to Si-C(sp2) bond clea-
vage product 4i as a mixture with silole byproduct 10.
Attempted insertion of 1-hexyne gave silole isomers 11a
and 11b exclusively. Silole product formation has been
reported for metal-catalyzed reactions of silacyclopro-
penes and -propanes, and regeneration of the starting
alkyne or alkene was observed.1,5,6,10-12 All other sub-
strates either gave no reaction or resulted in decomposi-
tion of the starting materials.
Steric and Electronic Effects in the Pd(0)-Catalyzed Inser-
tion Reactions. To investigate electronic effects, two elec-
tronically different alkynes were employed in the carbon-
carbon bond insertion reaction with alkylidenesila-
cyclopropane 3d. An electron-deficient terminal alkyne
required a longer reaction time compared to an electron-
rich alkyne (Scheme 3). Although a difference in reacti-
vity was observed, competitive silole formation was still
observed.
Scheme 3. Electronic Effects in the Pd(0)-Catalyzed
Carbon-Carbon Bond Insertion Reaction with 3d
Because heating the reactions led to an increase in both
byproduct formation and decomposition, alternative cata-
lysts were investigated. To find a more reactive catalytic
system that remained competent in the carbon-carbon
π-bond insertion reaction, we screened a variety of ligands
with metal catalysts at various temperatures.28 Most of
the catalyst studies were directed toward the reaction of
1-phenyl-1-propyne with alkylidenesilacyclopropane 3d in
an effort to develop an asymmetric version of the metal-
catalyzed carbon-carbon bond insertion reaction. Palla-
dium catalysts did not afford products in this reaction, and
all ligands examined were demonstrated to inhibit reactivity.
A control experiment demonstrated that steric effects were
responsible for the low reactivity of alkylidenesilacyclopro-
pane 3d. This substrate has both an increase in branching at
its allylic carbon and additional substitution of its three-
membered ring compared to alkylidenesilacyclopropane 3b.
The increased substitution on the ring, not the allylic branch-
ing, was found to impede insertion reactions. The insertion
reaction was repeated with alkylidenesilacyclopropane 3e
(eq 5), and the results were comparable with those obtained
for alkylidenesilacyclopropane 3d. Because the stereogenic
(28) Metals included in the screen were Pd(0), Pd(II), Ni(0), Ni(II),
Rh(I), and Pt(0). Also included were a variety of bimetallic systems with
gold catalysts. Ligands included a series of mono-, di-, and tridentate
ligands containing some combination of either phosphorous, nitrogen,
or oxygen chelation. Pd(PPh3)4 and Ni(cod)2 proved to be the best
catalysts in our catalytic system by consistently giving products in
modest to high yields. PdCl2(PPh3)2, Pt(PEt3)4, and [RhCl(CO)2]2 were
each observed to give products in low yields (<10%). All other catalysts
gave no reaction or decomposition of starting materials.

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Organometallics, Vol. 29, No. 7, 2010 1665
Only Ni(cod)2 gave an insertion product, although in mod-
erate yield (eq 8).
alkyne (eq 9).31 Alkene isomerization did not occur in the
absence of alkyne. The general applicability of alkylidenesi-
lacyclopropane 3d in the carbon-carbon π-bond insertion
reaction remains limited.
Ni(0)-Catalyzed Insertion Reaction with a Monosubstituted
Alkylidenesilacyclopropane. For comparison, monosubsti-
tuted alkylidenesilacyclopropane 3b was also examined in
the Ni(0)-catalyzed reaction (Table 5). As a result, the
Ni(0)-Catalyzed Insertion Reaction with a Disubstituted
Alkylidenesilacyclopropane. The scope of the Ni(0)-catalyzed
carbon-carbon π-bond insertion reaction was investi-
gated with alkylidenesilacyclopropane 3d. Reactivity was
observed with phenylacetylene, 1-phenyl-1-propyne, and
3-hexyne (Scheme 4). All other substrates (e.g., electron-rich
Table 5. Ni(0)-Catalyzed Carbon-Carbon Bond Insertion with 3b
Scheme 4. Ni(0)-Catalyzed Carbon-Carbon Bond Insertion
with 3d
a As determined by 1H NMR spectroscopic analysis relative to an
internal standard (PhSiMe3). Isolated yields are shown in parentheses.
b In the 1H NMR spectra of the reaction mixture, diagnostic peaks
corresponding to 14 overlapped with peaks from residual styrene,
making accurate determination of the NMR yield difficult.
a Formed as an 82:18 mixture of regioisomers with 4m0 (R1 = Me,
R2 = Ph). b Alkene migration occurred during purification to give silole
4n0 in 52% yield. Silacyclopentene 4n could be obtained in 10% yield if
purified in the presence of NEt3.
carbon-carbon bond insertion reaction gave Si-C(sp2)
bond cleavage product 4a with phenylacetylene (entry 1)
and allylic transposition product 5b with 3-hexyne (entry 2).
These products were analogous to those obtained in the
Pd(0)-catalyzed reaction. The insertion of styrene led to
acyclic product 14.1-3,8,32 Unlike the reaction with alkylidene-
silacyclopropane 3d, neither double insertion nor alkene
isomerization products were observed in any of the reactions.
In contrast to the Pd(0)-catalyzed reaction, no byproducts
were observed.
Reaction Mechanism. Although different products were
observed depending on either the substitution pattern of the
alkylidenesilacyclopropane or the π-bond substrate, all of the
carbon-carbon bond insertion reactions share similar mechan-
istic characteristics. Regiochemistry can best be explained by
insertion to a metal-silicon bond,33 and each reaction involves
oxidative addition and reductive elimination processes.
To explain the substrate-dependent product differentia-
tion that was observed in the Pd(0)-catalyzed reaction,
catalytic cycles are proposed (Schemes 5 and 6). Reversible
oxidative addition of alkylidenesilacyclopropane 3 provides
palladasilacyclobutane 15.2,3,5,10,12 For terminal alkynes
terminal alkynes, alkenes, and allenes) led to decomposition
of starting material. The increased reactivity exhibited by the
Ni(0) catalyst allowed for double insertion29,30 of phenyla-
cetylene to give a mixture of silacycloheptadienes 13a and
13b (Scheme 4a). If only one equivalent of phenylacetylene
were used, decomposition of starting materials was ob-
served. Alkyl-substituted internal alkynes led to Si-C(sp2)
bond cleavage products with isomerization of alkene geo-
metry (Scheme 4b).
For the latter two reactions, alkene isomerization from 3d
to 3d0 was observed prior to insertion of the corresponding
(29) Nickel-catalyzed incorporation of two equivalents of a terminal
alkyne has been reported for an acyclic example. See ref 30.
(30) Ananikov, V. P.; Orlov, N. V.; Kabeshov, M. A.; Beletskaya, I.
P.; Starikova, Z. A. Organometallics 2008, 27, 4056–4061.
(31) Nakao, Y.; Oda, S.; Yada, A.; Hiyama, T. Tetrahedron 2006, 62,
7567–7576.
(32) Seyferth, D.; Duncan, D. P.; Shannon, M. L.; Goldman, E. W.
Organometallics 1984, 3, 574–578.
(33) Braunstein, P.; Knorr, M. J. Organomet. Chem. 1995, 500, 21–38.

1666 Organometallics, Vol. 29, No. 7, 2010
Buchner and Woerpel
Scheme 5. Proposed Catalytic Cycle for the Pd(0)-Catalyzed
Carbon-Carbon π-Bond Insertion Reaction with Terminal
Alkynes
Scheme 7. Proposed Catalytic Cycle for the Ni(0)-Catalyzed
Carbon-Carbon π-Bond Insertion with 3d and Internal Alkynes
Scheme 6. Proposed Catalytic Cycle for the Pd(0)-Catalyzed
Carbon-Carbon π-Bond Insertion Reaction with Internal
Alkynes
alkynes, alkylidenesilacyclopropane 3d undergoes alkene
isomerization31 to generate 3d0. Oxidative addition and
migratory insertion afford nickelasilacyclohexene intermedi-
ate 21,42,43 which undergoes reductive elimination to yield
Si-C(sp2) bond cleavage product (E)-4. For double inser-
tion, a catalytic cycle is proposed (Scheme 8) comparable to
that depicted for the Pd(0)-catalyzed reaction in Scheme 5.
Oxidative addition by Ni(0) into alkylidenesilacyclopropane
3d gives nickelasilacyclobutane intermediate 22,6,7,44,45
which undergoes migratory insertion into the nickel-silicon
bond.42,43 A second insertion into the less sterically hindered
nickel-carbon(sp2) bond46 affords intermediate 24, which
reductively eliminates to yield product 13a. It is assumed that
Ni(0) facilitates the migratory insertion that, with Pd(0)
and allenes, migratory insertion into the palladium-silicon
bond3,8,10,12,14,17,34-36 affords intermediate 16. Reductive
elimination then provides product (Z)-4. Internal alkynes
and terminal alkenes are slow to undergo migratory in-
sertion37-40 with intermediate 15, so alkylidenesilacyclo-
propane 3 instead proceeds through a less favorable and
irreversible simultaneous allylic transposition and oxidative
addition to afford palladasilacyclobutane 17. Coordination
of an alkyne followed by migratory insertion would afford
palladasilacyclohexene 18. Reductive elimination from in-
termediate 18 leads to product 5. Previously, allylic trans-
position had not been observed for a carbon-carbon bond
insertion reaction with an alkylidenesilacyclopropane.8,9
For disubstituted alkylidenesilacyclopropane 3d, the Ni-
(0)-catalyzed reaction displayed an increase in reactivity41
that resulted in both alkene isomerization and double alkyne
insertion. A possible catalytic cycle to explain the former
process is depicted in Scheme 7. In the presence of internal
Scheme 8. Proposed Catalytic Cycle for the Ni(0)-Catalyzed
Carbon-Carbon π-Bond Insertion Reaction with 3d and
Phenylacetylene
(34) Osakada, K.; Tanabe, M. Bull. Chem. Soc. Jpn. 2005, 78, 1887–
1898.
(35) Tanabe, M.; Osakada, K. Chem.-Eur. J. 2004, 10, 416–424.
(36) Horn, K. A. Chem. Rev. 1995, 95, 1317–1350.
(37) Allen, A., Jr.; Lin, W. Organometallics 1999, 18, 2922–2925.
(38) Canovese, L.; Visentin, F.; Chessa, G.; Uguagliati, P.; Bandoli,
G. Organometallics 2000, 19, 1461–1463.
(42) Hirano, K.; Yorimitsu, H.; Oshima, K. Chem. Commun. 2008,
3234–3241.
(43) Hirano, K.; Yorimitsu, H.; Oshima, K. J. Am. Chem. Soc. 2007,
129, 6094–6095.
(44) Ishikawa, M.; Ohshita, J.; Ito, Y.; Iyoda, J. J. Am. Chem. Soc.
(39) Onozawa, S.-y.; Tanaka, M. Organometallics 2001, 20, 2956–
2958.
(40) Reddy, K. R.; Surekha, K.; Lee, G.-H.; Peng, S.-M.; Liu, S.-T.
1986, 108, 7417–7419.
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(46) The latter migratory insertion suffers from low regioselectivity,
which ultimately leads to products 13a and 13b in a 72:28 mixture. The
catalytic cycle is shown for the major regioisomer.
€

Article
Organometallics, Vol. 29, No. 7, 2010 1667
catalysis, would have been inhibited in the transformations
leading from intermediates 20 to 21 and from 23 to 24.41
The subtle substrate-ligand effects observed in the Ni(0)-
catalyzed reaction suggested that a more electron-rich
ligand (either π-bond substrate or alkylidenesilacyclo-
propane) would lead to an increase in reactivity. For the
Ni(0)-catalyzed reaction, we propose that hyperconjuga-
tion of σC-Me into π*CdC makes alkylidenesilacyclopro-
pane 3d a slightly better ligand for Ni(0) and allows for
unusual reactivity not observed for alkylidenesilacyclo-
propane 3b.
Conclusion. The reported insertion reactions with alkyli-
denesilacyclopropanes 3b, 3c, and 3d constitute general and
selective examples of metal-catalyzed carbon-carbon
π-bond insertion reactions into cyclic organosilicon com-
pounds. New reactivity was observed, and catalytic cycles
were proposed to explain these observations.
Silacyclopentane 4d:47 1H NMR (400 MHz, C6D6, distinctive
peaks) δ 6.29 (s, 1H), 5.63 (t, J = 7.2, 1H), 3.26 (s, 3H), 2.22 (q,
J = 7.1, 2H), 1.77 (s, 2H), 1.57 (s, 2H), 1.01 (s, 18H).
1
Silacyclopentene 4e: H NMR (400 MHz, C6D6) δ 7.38 (d,
J = 7.2, 2H), 7.21-7.16 (m, 3H), 6.21 (s, 1H), 5.83 (s, 1H), 3.06
(s, 3H), 1.93 (s, 2H), 1.09 (s, 18H); 13C NMR (125 MHz, C6D6) δ
163.8, 147.7, 141.8, 128.3, 127.2, 126.4, 124.3, 59.0, 31.6, 28.5,
19.4, 8.2; HRMS (ESI) m/z calcd for C20H31OSi (M þ H)þ
315.2144, found 315.2141.
Silacyclopentene 4f: 1H NMR (400 MHz, C6D6) δ 6.30 (s, 1H),
5.74 (s, 1H), 3.26 (s, 3H), 2.29 (t, J = 7.5, 2H), 1.82 (s, 2H), 1.59
(quint, J = 7.6, 2H), 1.35 (sext, J = 7.5, 2H), 1.07 (s, 18H), 0.92
(t, J = 7.4, 3H); 13C NMR (125 MHz, C6D6) δ 162.4, 143.9,
123.7, 122.3, 59.0, 32.1, 30.9, 28.5, 22.8, 19.2, 14.0, 7.9.
Silacyclopentane 4g: 1H NMR (500 MHz, C6D6) δ 6.11 (t, J =
2.0, 2H), 3.29 (s, 6H), 1.79 (d, J = 2.1, 4H), 1.01 (s, 18H); 13
NMR (125 MHz, C6D6) δ 138.0, 120.0, 58.8, 28.1, 19.0, 9.7.
C
Silacyclopentane 4h:47 1H NMR (400 MHz, C6D6, distinctive
peaks) δ 5.90 (t, J = 2.0, 1H), 3.26 (s, 3H), 1.95 (s, 3H), 1.82, (s,
3H), 1.75 (d, J = 2.0, 2H), 1.01 (s, 18H).
1
Silacyclopentene 4h0:48 mp 50-54 °C; H NMR (500 MHz,
Experimental Section
C6D6) δ 10.21 (s, 1H), 3.30-3.26 (m, 1H), 1.77 (s, 2H), 1.39 (s,
2H), 0.87 (s, 18H), 0.81 (d, J = 6.8, 6H); 13C NMR (125 MHz,
C6D6) δ 188.1, 168.9, 138.2, 28.2, 27.8, 20.9, 18.4, 13.5, 11.3; IR
(thin film) 2964, 2931, 2858, 1666, 1595, 1468 cm-1; HRMS
(ESI) m/z calcd for C16H31OSi (M þ H)þ 267.2144, found
267.2149.
General Procedures. General experimental details are pro-
vided as Supporting Information.
Palladium-Catalyzed Synthesis of Carbon-Carbon Bond In-
sertion Products. Method A (isolation). To a solution of
alkyne, alkene, or allene (2.0 mmol) and silacyclopropane 3
(1.0 mmol) in toluene (5 mL) was added Pd(PPh3)4 (0.060 g, 0.05
mmol). When the reaction had proceeded to completion as
determined by 1H NMR spectroscopic analysis, the reaction
mixture was filtered through SiO2 and concentrated in vacuo.
The resulting oil was purified by flash chromatography
(hexanes, 1:99 EtOAc/hexanes, or 0.5:1:98.5 NEt3/EtOAc/
hexanes) to afford carbon-carbon bond insertion products.
Unless otherwise indicated, all spectral data were obtained using
method A.
1
Silacyclopentene 4i: H NMR (500 MHz, C6D6) δ 7.41 (dd,
J = 7.6, 1.4, 2H), 7.21 (t, J = 7.3, 2H), 7.15 (td, J = 7.5, 1.7,
1H), 6.02 (s, 1H), 5.38 (d, J = 10.2, 1H), 2.46-2.39 (m, 2H),
1.78-1.54 (m, 8H), 1.42 (d, J = 7.8, 3H), 1.33-1.25 (m, 2H),
1.18 (s, 9H), 1.09 (s, 9H); 13C NMR (125 MHz, C6D6) δ 165.4,
149.1, 141.7, 133.9, 128.7, 128.1, 128.0, 127.3, 38.4, 33.6, 32.6,
29.6, 28.8, 25.99,49 25.95, 21.8, 21.6, 20.2, 18.5; IR (neat) cm-1
3076, 3021, 2929, 1538, 1470, 1363 cm-1; HRMS (GC-MS) m/z
calcd for C26H41Si (M þ H)þ 381.2978, found 381.2982.
Silacyclopentene 4j:50 1H NMR (400 MHz, C6D6, distinctive
peaks) δ 6.00 (s, 1H), 5.41 (d, J = 10.3, 1H), 3.37 (s, 3H), 1.41 (d,
J = 7.8, 3H); HRMS (GC-MS) m/z calcd for C27H43OSi (M þ
H)þ 411.3083, found 411.3093.
Method B (NMR observation). Alkyne, alkene, or allene
(0.254 mmol) was added to a solution of silacyclopropane 3
(0.550 mL, 0.127 mmol, 0.230 M solution of 3 and 0.0465 M
solution of PhSiMe3 in C6D6), followed by the addition of
Pd(PPh3)4 (0.007 g, 0.006 mmol). The progress of the reaction
was monitored and yields were determined by 1H NMR spectro-
scopic analysis (compared to the PhSiMe3 internal standard)
using a single scan.
Silacyclopentene 4k:50 1H NMR (400 MHz, C6D6, distinctive
peaks) δ 5.93 (s, 1H), 5.15 (d, J = 10.3, 1H), 1.36 (d, J = 7.8,
3H); HRMS (GC-MS) m/z calcd for C27H40F3Si (M þ H)þ
449.2851, found 449.2837.
Silacyclopentene 4l:47 1H NMR (400 MHz, C6D6, distinctive
peaks) δ 6.04 (s, 1H), 5.51 (t, J = 7.1, 1H), 2.34 (t, J = 7.3, 1H).
Silacyclopentene 4a: 1H NMR (500 MHz, CDCl3)
δ
7.35-7.25 (m, 5H), 5.96 (s, 1H), 5.41 (t, J = 7.2, 1H), 2.17 (q,
J = 7.1, 2H), 1.57 (s, 2H), 1.36-1.27 (m, 8H), 1.04 (s, 18H), 0.90
(t, J = 7.0, 3H); 13C NMR (125 MHz, CDCl3) δ 165.8, 143.7,
141.9, 129.9, 129.2, 128.5, 127.8, 127.0, 31.8, 30.0, 29.28, 29.26,
28.7, 22.7, 19.6, 14.2, 10.2; IR (neat) 3057, 2931, 2858, 1601,
1577, 1470 cm-1; HRMS (APCI) m/z calcd for C25H41Si (M þ
H)þ 369.2978, found 369.2975.
1
Silacyclopentene 5a: H NMR (400 MHz, C6D6) δ 7.21 (t,
J = 7.7, 2H), 7.11 (t, J = 7.5, 1H), 7.07 (d, J = 6.8, 2H), 5.90 (t,
J = 2.2, 1H), 5.73 (t, J = 2.5, 1H), 3.55-3.51 (m, 1H), 1.83 (d,
J = 2.2, 3H), 1.75-1.66 (m, 1H), 1.53-1.44 (m, 1H), 1.39-1.27
(m, 2H), 1.26-1.03 (m, 6H), 1.21 (s, 9H), 1.14 (s, 9H), 0.82 (t,
J = 7.0, 3H); 13C NMR (125 MHz, C6D6, distinctive peaks) δ
129.5, 129.1, 129.0, 128.3, 128.2, 126.9, 126.4, 123.1, 47.9, 36.0;
IR (neat) 3057, 2929, 2856, 1581, 1468, 1389 cm-1; HRMS (GC-
MS) m/z calcd for C26H43Si (M þ H)þ 383.3134, found
383.3145.
1
Silacyclopentene 4b: H NMR (500 MHz, C6D6) δ 5.89 (s,
1H), 5.78 (tt, J = 7.2, 2.3, 1H), 2.41 (appar t, J = 7.7, 2H), 2.28
(q, J = 7.3, 2H), 1.58 (quint, J = 7.6, 2H), 1.57 (s, 2H), 1.47
(sext, J = 7.5, 2H), 1.34-1.26 (m, 8H), 1.08 (s, 18H), 0.91 (t, J =
7.4, 3H), 0.90 (t, J = 7.0, 3H); 13C NMR (125 MHz, C6D6) δ
165.0, 143.3, 125.4, 124.6, 32.4, 31.1, 29.8, 29.6, 29.3, 29.2, 28.5,
28.5, 22.83, 22.77, 19.1, 14.0, 13.9, 10.1; IR (neat) 2957, 2856,
1543, 1469, 1363, 1141 cm-1; HRMS (GC-MS) m/z calcd for
C23H45Si (M þ H)þ 349.3290, found 349.3290.
Silacyclopentene 5b: 1H NMR (500 MHz, C6D6) δ 5.85 (t, J =
2.1, 1H), 5.68 (t, J = 2.4, 1H), 3.16 (br s, 1H), 2.48 (dq, J = 13.7,
7.5, 1H), 2.40-2.16 (m, 5H), 2.10, (quint, J = 7.2, 1H), 1.91 (dq,
J = 13.7, 7.5, 1H), 1.84-1.75 (m, 1H), 1.65-1.56 (m, 1H),
1.53-1.34 (m, 4H), 1.19 (s, 9H), 1.10 (s, 9H), 1.08 (appar t, J =
5.7, 3H), 0.96 (t, J = 7.5, 3H), 0.89 (t, J = 7.0, 3H); 13C NMR
(125 MHz, C6D6) δ 160.9, 151.9, 135.1, 122.4, 50.9, 32.1, 30.4,
29.4, 29.1, 28.8, 26.5, 25.4, 22.7, 21.4, 20.3, 20.0, 15.2, 14.0, 12.7;
Silacyclopentene 4c: 1H NMR (500 MHz, C6D6) δ 6.38
(s, 1H), 5.68 (t, J = 7.2, 1H), 4.36 (s, 2H), 3.97 (d, J = 2.4,
2H), 2.23 (q, J = 7.3, 2H), 2.00 (t, J = 2.4, 1H), 1.57 (s, 2H),
1.37-1.26 (m, 8H), 1.02 (s, 18H), 0.91 (t, J = 6.8, 3H); 13C
NMR (125 MHz, C6D6) δ 159.6, 141.6, 128.5, 125.2, 80.0, 74.3,
69.3, 57.1, 31.9, 29.7, 29.5, 29.3, 29.1, 28.4, 22.8, 19.1, 14.0, 10.2;
IR (neat) 2957, 2856, 2362, 1553, 1469, 1119 cm-1; HRMS (GC-
MS) m/z calcd for C23H41OSi (M þ H)þ 361.2927, found
361.2925.
(47) Spectrum for material obtained from method B.
(48) Obtained upon attempted chromatography of the desired pro-
duct.
(49) Corresponds to two chemically inequivalent carbons.
(50) Spectra for material obtained from method B.

1668 Organometallics, Vol. 29, No. 7, 2010
Buchner and Woerpel
IR (neat) 2960, 2857, 1580, 1469, 1387, 820 cm-1; HRMS
(GC-MS) m/z calcd for C23H45Si (M þ H)þ 349.3290, found
349.3296.
1470, 1387, 1190 cm-1; HRMS (GC-MS) m/z calcd for C24H31Si
(M þ H)þ 347.2195, found 347.2193. Anal. Calcd for C24H30Si:
C, 83.17; H, 8.72. Found: C, 83.09; H, 8.89.
Silacyclopentane 5c: 1H NMR (400 MHz, C6D6) δ 7.24-7.22
(m, 4H), 7.14-7.10 (m, 1H), 5.80 (t, J = 2.5, 1H), 5.65 (t, J =
2.7, 1H), 2.76 (td, J = 12.6, 6.4, 1H), 2.53 (dtd, J = 12.5, 4.7, 1.6,
1H), 1.68-1.60 (m, 1H), 1.53-1.44 (m, 1H), 1.39-1.30 (m, 2H),
1.26-1.16 (m, 8H), 1.11 (s, 9H), 1.09 (s, 9H), 0.83 (t, J = 6.9,
3H); 13C NMR (125 MHz, C6D6) δ 153.3, 147.8, 128.5, 127.1,
126.0, 121.2, 53.4, 49.2, 31.7, 30.0, 28.7, 28.5, 27.9, 24.7, 22.7,
19.6, 18.9, 18.7, 14.0; IR (neat) 3026, 2929, 2856, 1601, 1470,
1363 cm-1; HRMS (GC-MS) m/z calcd for C25H43Si (M þ H)þ
371.3134, found 371.3135. Anal. Calcd for C25H42Si: C, 81.00;
H, 11.42. Found: C, 80.87; H, 11.49.
Silole 11a: 1H NMR (500 MHz, C6D6) δ 5.74 (s, 2H), 2.25 (t,
J = 7.6, 4H), 1.51 (quint, J = 7.3, 4H), 1.34 (sext, J = 7.3, 4H),
1.18 (s, 18H), 0.91 (t, J = 7.4, 6H); 13C NMR (125 MHz, C6D6)
δ 162.7, 122.3, 32.8, 32.4, 29.0, 26.5, 22.6, 14.0; IR (neat) 2956,
2856, 1543, 1512, 1468, 1363 cm-1; HRMS (GC-MS) m/z calcd
for C20H39Si (M þ H)þ 307.2821, found 307.2824.
Silole 11b: 1H NMR (500 MHz, C6D6) δ 5.88 (s, 1H), 5.74 (s,
1H), 2.38 (t, J = 7.6, 2H), 2.21 (t, J = 7.3, 2H), 1.60-1.55 (m,
4H), 1.46 (sext, J = 7.4, 4H), 1.07 (s, 18H), 0.96 (t, J = 7.3, 3H),
0.91 (t, J = 7.4, 3H); 13C NMR (125 MHz, C6D6) δ 165.0, 143.5,
125.4, 124.3, 32.4, 31.8, 28.5, 26.2, 22.82, 22.78, 19.1, 18.9, 13.94,
13.92.
1
Silacyclopentane 5d: H NMR (500 MHz, C6D6) δ 5.78 (d,
Silole 12a:50 1H NMR (400 MHz, C6D6, distinctive peaks) δ
6.13 (s, 2H), 3.25 (s, 6H); HRMS (GC-MS) m/z calcd for
C26H35O2Si (M þ H)þ 407.2406, found 407.2391.
J = 2.2, 1H), 5.61 (d, J = 1.0, 1H), 2.33-2.27 (m, 1H),
2.00-1.92 (m, 2H), 1.84 (appar t, J = 11.8, 2H), 1.78-1.71
(m, 2H), 1.63-1.58 (m, 4H), 1.45-1.33 (m, 13H), 1.10 (s, 9H),
1.07 (s, 9H), 0.93-0.89 (m, 6H); 13C NMR (125 MHz, C6D6) δ
154.3, 120.3, 52.9, 41.3, 36.4, 32.1, 31.9, 30.4, 29.8, 28.7, 28.5,
27.5, 27.3, 24.2, 22.85, 22.82, 19.5, 18.7, 14.1, 14.0, 13.4; IR
(neat) 3041, 2927, 1468, 1387, 1363 cm-1; HRMS (GC-MS) m/z
calcd for C25H51Si (M þ H)þ 379.3760, found 379.3764.
Silacyclopentene 5e: 1H NMR (400 MHz, C6D6) δ 7.30-7.21
(m, 5H), 6.10 (dd, J = 2.9, 1.8, 1H), 5.78 (t, J = 2.5, 1H), 5.01 (q,
J = 1.9, 1H), 3.02 (s, 3H), 1.84 (d, J = 1.9, 3H), 1.17 (s, 9H), 1.08
(s, 9H); 13C NMR (125 MHz, C6D6) δ 156.5, 146.7, 139.4, 137.7,
128.7, 128.7, 126.7, 126.2, 87.6, 52.7, 29.0, 28.6, 20.2, 19.8, 17.5;
HRMS (ESI) m/z calcd for C21H32OSiNa (M þ Na)þ 351.2120,
found 351.2118.
Silole 12b:50. 1H NMR (400 MHz, C6D6, distinctive peaks) δ
6.09 (s, 2H); HRMS (GC-MS) m/z calcd for C26H29F6Si (M þ
H)þ 483.1943, found 483.1923.
Nickel-Catalyzed Synthesis of Carbon-Carbon Bond Inser-
tion Products. Method A (isolation). To a solution of alkyne,
alkene, or allene (2.0 mmol) and silacyclopropane 3 (1.0 mmol)
in toluene (5 mL) was added Ni(cod)2 (0.014 g, 0.05 mmol).
When the reaction had proceeded to completion as determined
1
by H NMR spectroscopic analysis, the reaction mixture was
filtered through SiO2 and concentrated in vacuo. The resulting
oil was purified by flash chromatography (hexanes) to afford
carbon-carbon bond insertion products. Unless otherwise in-
dicated, all of the spectral data were obtained using method A.
Method B (NMR observation). Alkyne, alkene, or allene
(0.254 mmol) was added to a solution of silacyclopropane 3
(0.550 mL, 0.127 mmol, 0.230 M solution of 3 and 0.0465 M
solution of PhSiMe3 in C6D6), followed by the addition of
Ni(cod)2 (0.002 g, 0.006 mmol). The progress of the reaction
was monitored, and yields were determined by 1H NMR
spectroscopic analysis (compared to the PhSiMe3 internal
standard) using a single scan.
Silacyclopentene 5f:47 1H NMR (400 MHz, C6D6, distinctive
peaks) δ 6.10 (s, 1H), 5.74 (s, 1H), 4.87 (s, 1H), 3.11 (s, 3H), 2.05
(t, J = 6.2, 2H).
1
Silacyclopentene 5f0: H NMR (500 MHz, C6D6, distinctive
peaks) δ 7.23 (s, 1H), 5.68 (d, J = 2.6, 1H), 5.42 (d, J = 2.3, 1H),
2.20 (t, J = 7.4, 2H), 1.58 (m, 2H), 1.07 (s, 18H), 0.83 (t, J = 7.0,
3H); 13C NMR (125 MHz, C6D6, distinctive peaks) δ 172.9,
157.2, 154.2, 144.3, 125.3, 35.6, 27.8, 24.9, 18.7, 13.7; HRMS
(ESI) m/z calcd for C17H30SiONa (M þ Na)þ 301.1964, found
301.1962.
Silacyclopentene 4m: 1H NMR (500 MHz, C6D6) δ 7.23-7.19
(m, 4H), 7.08-7.03 (m, 1H), 5.10 (dd, J = 9.7, 2.1, 1H), 2.74 (qt,
J = 10.2, 3.4, 1H), 2.19 (qd, J = 7.1, 2.1, 1H), 2.07 (s, 3H),
1.90-1.41 (m, 10H), 1.43 (d, J = 7.2, 3H), 1.11 (s, 9H), 1.09 (s,
9H); 13C NMR (125 MHz, C6D6) δ 155.2, 146.0, 145.1, 144.0,
128.7, 128.4, 128.2, 125.3, 37.5, 34.5, 34.2, 29.5, 29.3, 27.0, 26.2,
26.2, 26.1, 23.0, 20.5, 18.9, 14.4; IR (neat) 3020, 2925, 1597,
1541, 1468, 1365 cm-1; HRMS (GC-MS) m/z calcd for C27H43Si
(M þ H)þ 395.3134, found 395.3129.
1
Silacyclopentane 5g: H NMR (500 MHz, C6D6) δ 7.33 (d,
J = 7.1, 2H), 7.24 (t, J = 7.6, 2H), 7.14 (t, J = 7.3, 1H), 6.16 (t,
J = 2.9, 1H), 5.65 (t, J = 3.0, 1H), 4.04 (dt, J = 11.4, 2.7, 1H),
3.06 (s, 3H), 2.95 (ddd, J = 12.7, 11.5, 7.0, 1H), 1.050 (s, 9H),
1.045 (s, 9H), 0.89 (appar t, J = 6.8, 1H), 0.83 (dd, J = 15.2,
13.0, 1H); 13C NMR (125 MHz, C6D6) δ 149.5, 146.2, 128.3,
127.4, 126.2, 122.4, 91.2, 57.9, 50.0, 28.34, 28.33, 19.3, 18.7, 14.1;
IR (neat) 3059, 3028, 2931, 2858, 1470, 1105 cm-1; HRMS (ESI)
m/z calcd for C20H32OSiNa (M þ Na)þ 339.2120, found
339.2126.
Silacyclopentene 4m0: 1H NMR (400 MHz, C6D6, distinctive
peaks) δ 4.97 (d, J = 8.9, 1H).
Silacyclopentene 4n: H NMR (500 MHz, C6D6, distinctive
1
1
Silacyclopentane 5h: H NMR (400 MHz, C6D6, distinctive
peaks) δ 6.01 (t, J = 2.8, 1H), 5.57 (t, J = 3.2, 1H), 3.49 (dt, J =
11.2, 2.7, 1H), 3.34 (s, 3H), 1.03 (s, 9H), 1.01 (s, 9H); 13C NMR
(125 MHz, C6D6, distinctive peaks) δ 151.3, 121.2, 91.2, 56.9,
42.9, 35.9, 32.1, 27.4, 14.0; HRMS (APCI) m/z calcd for
C14H28OSi (M þ H)þ 325.2927, found 325.2932.
peaks) δ 4.90 (dd, J = 9.4, 2.1, 1H), 1.36 (d, J = 7.1, 3H), 1.10 (s,
9H), 1.09 (s, 9H); 13C NMR (125 MHz, C6D6) δ 160.9, 144.3,
142.4, 124.4, 37.4, 34.3, 34.2, 29.3, 29.0, 28.2, 23.1, 22.71, 22.68,
22.4, 20.0, 14.0, 13.8, 13.7; IR (neat) 2927, 2854, 1470, 1448,
1363, 820 cm-1; HRMS (GC-MS) m/z calcd for C22H45Si (M þ
H)þ 361.3290, found 361.3285.
Silacyclopentane 6: 1H NMR (500 MHz, C6D6) δ 5.78 (t, J =
1.5, 1H), 5.53 (t, J = 2.2, 1H), 5.26 (td, J = 7.2, 1.8, 1H),
2.97-2.95 (m, 1H), 2.44 (q, J = 6.8, 1H), 2.29 (q, J = 7.6, 1H),
2.25-2.12 (m, 3H), 1.81 (d, J = 15.6, 1H), 1.65-1.56 (m, 4H),
1.52-1.44 (m, 8H), 1.41-1.36 (m, 4H), 1.10 (s, 9H), 1.09 (s, 9H),
0.93-0.91 (m, 6H); 13C NMR (125 MHz, C6D6) δ 154.7, 142.6,
122.88, 122.86, 58.3, 36.6, 32.1, 31.9, 30.0, 29.5, 29.3, 29.0, 28.9,
28.5, 28.1, 27.5, 22.8, 20.0, 18.9, 14.03, 14.02, 11.3; IR (neat)
3037, 2927, 2856, 1468, 1389, 1363 cm-1; HRMS (GC-MS) m/z
calcd for C26H51Si (M þ H)þ 391.3760, found 391.3756.
Silole 10: mp 103-104 °C; 1H NMR (400 MHz, C6D6) δ
7.13-7.11 (m, 4H), 7.00-6.97 (m, 6H), 6.16 (s, 2H), 1.18
(s, 18H); 13C NMR (125 MHz, C6D6) δ 162.1, 141.3, 130.7,
128.01, 128.00, 126.8, 28.8, 19.3; IR (thin film) 3061, 2958, 1597,
1
Silacyclopentene 4n0: H NMR (500 MHz, C6D6) δ 2.35 (q,
J = 7.3, 2H), 2.34 (q, J = 7.5, 2H), 2.23 (d, J = 7.0, 2H), 1.96 (s,
3H), 1.79-1.37 (m, 11H), 1.16 (s, 18H), 1.14 (t, J = 7.6, 3H),
1.01 (t, J = 7.5, 3H); 13C NMR (125 MHz, C6D6) δ 157.9, 153.4,
134.7, 131.1, 39.1, 35.3, 33.7, 29.0, 26.6, 26.5, 22.6, 21.1, 19.3,
16.6, 15.3, 14.4; IR (neat) 2927, 2854, 1468, 1448, 1363, 820
cm-1; HRMS (GC-MS) m/z calcd for C24H45Si (M þ H)þ
361.3290, found 361.3287.
Silacycloheptadiene 13a: mp 64-67 °C; 1H NMR (500 MHz,
C6D6) δ 7.41-7.37 (m, 4H), 7.03 (s, 1H), 7.00 (appar t, J = 7.5,
4H), 6.90-6.85 (m, 2H), 6.58 (s, 1H), 5.21 (d, J = 9.9, 1H), 3.18
(q, J = 7.7, 1H), 2.42 (appar q, J = 10.8, 1H), 1.84-1.53 (m,
10H), 1.48 (d, J = 7.8, 3H), 1.21 (s, 9H), 1.15 (s, 9H); 13C NMR

Article
Organometallics, Vol. 29, No. 7, 2010 1669
(125 MHz, C6D6) δ 155.7, 144.3, 144.1, 140.6, 140.1, 136.0,
131.6, 129.0, 128.13, 128.06, 126.92,49 126.89, 126.8, 37.5, 34.4,
33.1, 30.6, 30.0, 28.6, 26.2, 26.0, 25.9, 23.0, 20.1, 17.1; IR
(thin film) 2926, 2854, 1599, 1566, 1470, 1444 cm-1; HRMS
(GC-MS) m/z calcd for C34H47Si (M þ H)þ 483.3447, found
483.3439.
126.48, 126.45, 123.7, 31.9, 29.7, 29.2, 28.8, 27.4, 22.7, 19.9, 14.0,
10.9; IR (neat) 3059, 2958, 1603, 1575, 1495, 1464 cm-1; HRMS
(GC-MS) m/z calcd for C25H43Si (M þ H)þ 371.3134, found
371.3130. Anal. Calcd for C25H42Si: C, 81.00; H, 11.42. Found:
C, 80.80; H, 11.61.
Silacycloheptadiene 13b: mp 68-70 °C; 1H NMR (500 MHz,
C6D6) δ 7.74 (d, J = 7.4, 2H), 7.47 (d, J = 7.0, 2H), 7.27-7.11
(m, 6H), 6.65 (s, 1H), 6.45 (s, 1H), 5.11 (d, J = 9.8, 1H), 3.33 (q,
J = 8.1, 1H), 2.56-2.48 (m, 1H), 1.73-1.57 (m, 10H), 1.22 (d,
J = 8.2, 3H), 1.18 (s, 9H), 1.13 (s, 9H); 13C NMR (125 MHz,
C6D6) δ 154.6, 147.1, 144.4, 141.2, 138.6, 131.7, 129.3, 128.3,
128.3, 128.2, 128.2, 127.4, 126.5, 126.2, 37.8, 32.0, 30.6, 28.7,
26.2, 26.0, 25.8, 22.4, 19.9, 17.3; IR (thin film) 3078, 2926, 1597,
1562, 1491, 1470 cm-1; HRMS (GC-MS) m/z calcd for C34H47Si
(M þ H)þ 483.3447, found 483.3445. Anal. Calcd for C34H46Si:
C, 84.58; H, 9.60. Found: C, 84.36; H, 9.75.
Acknowledgment. This research was supported by the
National Institute of General Medical Sciences of the
National Institutes of Health (GM-54909). K.M.B.
thanks the Department of Education (GAANN)
for a predoctoral fellowship. K.A.W. thanks Amgen
and Lilly for awards to support research. We thank
Dr. P. Dennison (UCI) for assistance with NMR spec-
troscopy, Dr. J. W. Ziller and M. K. Takase (UCI) for
X-ray crystallography, and Dr. J. Greaves and
S. Sorooshian (UCI) for mass spectrometry.
Diene 14: 1H NMR (400 MHz, C6D6) δ 7.37 (d, J = 7.9, 2H),
7.17 (d, J = 19.2, 1H), 7.13-7.06 (m, 3H), 6.60 (d, J = 19.3,
1H), 5.81 (appar q, J = 9.0, 1H), 5.43 (dt, J = 10.9, 7.7, 1H),
2.22 (q, J = 6.9, 2H), 1.93 (d, J = 9.0, 2H), 1.47-1.40 (m, 2H),
1.38-1.26 (m, 6H), 1.13 (s, 18H), 0.89 (t, J = 6.7, 3H); 13C
NMR (125 MHz, C6D6) δ 146.3, 138.6, 128.5, 128.1, 128.0,
Supporting Information Available: X-ray data for 13a, addi-
tional experimental procedures, spectroscopic and analytical
data. This material is available free of charge via the Internet at
http://pubs.acs.org.