Iridium-catalyzed, diastereoselective dehydrogenative silylation of terminal alkenes with (TMSO)2MeSiH

Article abstract of DOI:10.1002/anie.201304084

Ligands' choice: The title reaction was achieved under mild conditions with low catalyst loading. The diastereoselectivity of the reaction can be controlled by choosing the appropriate ancillary ligand (see scheme; coe=cyclooctene). The silylation product

Full text of DOI:10.1002/anie.201304084

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DOI: 10.1002/anie.201304084
À
C H Functionalization
Iridium-Catalyzed, Diastereoselective Dehydrogenative Silylation of
Terminal Alkenes with (TMSO)2MeSiH**
Chen Cheng, Eric M. Simmons, and John F. Hartwig*
Vinylsilanes and vinylboranes are versatile synthetic inter-
mediates that can be constructed through catalytic function-
We report herein the dehydrogenative silylation of
terminal alkenes with (TMSO)2MeSiH, a silane that is
commercially available in bulk quantities, catalyzed by
iridium complexes of 3,4,7,8-tetramethyl-1,10-phenanthroline
(Me4Phen), together with subsequent cross-coupling and
oxidation of the vinylsilane products. The reaction is highly
selective for the Z vinylsilane. Isotope labeling suggests that
the reaction occurs by insertion of the alkene, rather than
[1,2]
À
alization of C H bonds with boron and silicon reagents.
The majority of borylations of alkenes to form vinylboronates
as the major product require cyclic alkenes, vinylarenes, or
specific substituted alkenes (vinyl ethers and allyltrimethyl-
silane);[3] therefore methods for the alternative dehydrogen-
À
ative silylation of terminal alkenyl C H bonds are desirable.
À
Current methods for the preparation of vinylsilanes include
the silyl-Heck reaction,[4] alkyne hydrosilylation,[5] direct
dehydrogenative silylation of alkenes,[6] and manipulation of
direct C H activation, and the stereoselectivity of the process
can be reversed by conducting the reaction with a hindered,
chelating nitrogen ligand.
compounds with existing C Si bonds;[7] each of these methods
To begin to develop the dehydrogenative silylation with
a silane suitable for synthetic purposes, we surveyed the
reactions of allylcyclohexane (4a) with several inexpensive
and readily available siloxysilanes, such as trisiloxane
(TMSO)2MeSiH,[12] in the presence of norbornene (nbe) as
hydrogen acceptor and a series of catalysts. The reaction of
this silane with 4a catalyzed by [{Ir(cod)OMe}2] and Me4Phen
formed the Z vinylsilane 4b in 82% yield with a Z/E isomer
ratio of 90:10 (Table 1, entry 6). The alkene geometry was
assigned based on the J-coupling value of the vinylic protons
(14.3 Hz for 4b versus 18.6 Hz for the independently pre-
pared E isomer 4c, see below). Reaction with the more
sterically-hindered silane (TMSO)3SiH occurred with slightly
higher diastereoselectivity but required a higher temperature
(1008C; Table 1, entry 7) and longer time, whereas reactions
with smaller silanes, such as (TMSO)Me2SiH or Et3SiH,
exhibited higher turnover rates but lower diastereoselectivity
(Table 1, entries 8 and 9).
Among the ligands examined, 3,4,7,8-tetramethyl-1,10-
phenathroline (Me4Phen) generated the catalyst that reacted
with the highest activity and diastereoselectivity.[13] Reactions
conducted with phosphine- or nitrogen-based ligands, other
than phenanthroline or bipyridine derivatives, resulted in
poor yields of the vinylsilane (see the Supporting Informa-
tion). Reactions conducted with the hydroxy-bridged bi-
nuclear dimer [{Ir(coe)2OH}2][14] as the catalyst precursor
(Table 1, entry 14) occurred faster than those conducted with
the related complexes [{Ir(coe)2Cl}2] (Table 1, entry 13) and
[{Ir(cod)OMe}2] (Table 1, entry 6), presumably because of the
lack of strongly coordinating ligands and thus faster gener-
ation of the catalytically active species.[15] Furthermore, the
choice of solvent influenced the yield, but not the diastereo-
selectivity (Table 1, entries 10–12 and the Supporting Infor-
mation). Finally, the same reaction conducted without the
sacrificial hydrogen acceptor nbe gave the vinylsilane product
in 49% yield, along with 50% propylcyclohexane (Table 1,
entry 15), showing that nbe is critical for inhibiting substrate
hydrogenation (see below).
À
suffers from a number of drawbacks, including the require-
ment of an excess of the alkene, limitation to vinylarenes, or
the production of the more readily-accessible E vinylsilane as
the major product.
Recently, Lu and Falck reported the Z-selective silylation
of terminal alkenes with Et3SiH in the presence of the
iridium/di-tert-butylbipyridine catalyst developed by our
group for the borylation of arenes.[8] However, the lack of
electronegative atoms attached to the silicon atom prevents
the products from being substrates for the Tamao oxidation or
Hiyama–Denmark coupling reactions.[9] Unfortunately, silyl-
ation reactions often occur in lower yields with silanes, such as
alkoxysilanes, bearing electronegative atoms than with tri-
alkylsilanes. Because the alkoxysilyl group is electron with-
drawing, the hydride is less hydridic.[10] In addition, the rates
of side reactions, such as hydrosilylation, silane dehydrocou-
pling, and silane redistribution, are affected by the identity of
the substituents on the silanes.[6b,11] Therefore, reactions with
a silane containing a silicon–heteroatom bond are unlikely to
parallel directly the reactions of trialkylsilanes. We hypothe-
sized that the dehydrogenative silylation could be made more
practical by conducting the reactions with a tertiary hydro-
silane containing bulky siloxy groups and that the catalysts we
À
recently developed for the silylation of aliphatic C H
bonds[2f] could make the dehydrogenative silylation faster
than the redistribution reactions of a hydrosilane containing
one or more electronegative groups.
[*] C. Cheng, Dr. E. M. Simmons, Prof. J. F. Hartwig
Department of Chemistry, University of California
Berkeley, CA 94720 (USA)
E-mail: jhartwig@berkeley.edu
[**] We thank the NSF (CHE-1213409) for financial support and Johnson
Matthey for a gift of [{Ir(cod)OMe}2]. We thank Leslie Bienen of C3
Science for assistance in manuscript preparation. TMS=trimeth-
ylsilyl.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201304084.
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Table 1: Survey of conditions for terminal alkene silylation.[a]
Entry Ligand
[Ir] Solvent Silane
1[c] THF
Yield
[%][b]
Z/E[b]
1
Phen
(TMSO)2MeSiH 58
85:15
–
2
3
bpy
1
1
1
1
1
1
1
1
1
1
1
THF
THF
THF
THF
THF
THF
THF
THF
(TMSO)2MeSiH
–
dtbpy[d]
(TMSO)2MeSiH 78
(TMSO)2MeSiH 19
(TMSO)2MeSiH 82
(TMSO)2MeSiH 82
(TMSO)3SiH
(TMSO)Me2SiH 75
Et3SiH 85
85:15
83:17
86:14
90:10
92:8
82:18
79:21
86:14
90:10
91:9
4
5
6
(MeO)2Phen[e]
4-MePhen
Me4Phen[f]
Me4Phen
Me4Phen
Me4Phen
Me4Phen
Me4Phen
Me4Phen
Me4Phen
Me4Phen
7[g]
8
83
9
10
11
12
13
14[i]
heptane (TMSO)2MeSiH 86
MeTHF (TMSO)2MeSiH 74
CH2Cl2 (TMSO)2MeSiH 19
2[h] THF
3[j] THF
(TMSO)2MeSiH 77
(TMSO)2MeSiH 83
(TMSO)2MeSiH 49
88:12
90:10
82:18
15[k] Me4Phen
1
THF
[a] For detailed reaction conditions, see the Supporting Information.
[b] Determined by GC. [c] [{Ir(cod)OMe}2]. [d] 4,4’-di-tert-butyl-2,2’-
bipyridine. [e] 4,7-dimethoxy-1,10-phenanthroline. [f] 3,4,7,8-tetramethyl-
1,10-phenanthroline. [g] Reaction conducted at 1008C for 7 days.
Reaction at 508C gave no product. [h] [{Ir(coe)2Cl}2]. [i] Reaction run for
8 h. [j] [{Ir(coe)2OH}2]. [k] No nbe was added. bpy=4,4’-bipyridine,
Phen=1,10-phenanthroline, TMS=trimethylsilyl.
Scheme 1. Scope of alkene silylation with (TMSO)2MeSiH. Yields are
With certain alkenes, the reactions in the presence of
1.1 equiv of silane and nbe led to substantial substrate
hydrogenation that lowered the yields of the desired vinyl-
silane products. One substrate especially prone to hydro-
genation is 4-phenyl-1-butene (5a). At full conversion, the
desired product 5b was produced in only 68% yield (see the
Supporting Information, Table S2, entry 1). However, when
the reaction was conducted at higher concentration of nbe
(3 equiv) hydrogenation of the starting alkene was greatly
reduced, and the yield of the vinylsilane product was
increased to 84% (see the Supporting Information,
Table S2, entry 5).
Under the conditions developed for the reaction of 5a
(see the Supporting Information, Table S2, entry 5), reactions
with various terminal alkenes afforded the corresponding
vinylsilanes in good yields with high diastereoselectivity
favoring the Z product (Scheme 1). A variety of functional
groups were tolerated, such as epoxide (7b), ketone (9b),
ester (6b), amide (17b and 18b), alcohol (11b), aryl iodide
(15b), and internal alkene (10b). Higher catalyst loading or
a higher temperature was needed for substrates containing
coordinating groups, such as a tertiary amine or nitrile, but the
corresponding vinylsilanes were obtained in good yields. This
reaction system does not lead to the conversion of internal
alkenes, 1,1-disubstituted alkenes, or terminal alkenes with
of the isolated products. Z/E ratios were determined by NMR
spectroscopy. [a] 1 mol% of [{Ir(coe)2OH}2] and 3 mol% of ligand
were used. [b] Reaction was heated at 658C. [c] 4-MePhen was used
instead of Me4Phen as ligand. [d] Yield determined by GC. The crude
product was directly subjected to oxidation (see below). coe=cyclooc-
tene.
substituents on the a carbon, such as 2-methyl-1-pentene or 3-
methyl-1-pentene. This limitation in scope is likely due to the
steric demand at the metal center.
Cross-coupling reactions of aryl electrophiles with vinyl-
silanes in which the silyl group is SiMe(OTMS)2 have only
been reported once with TBAF as the activator.[5g] However,
the presence of two heteroatoms on the silicon atom made it
possible for these materials to undergo Hiyama–Denmark
cross-coupling in the absence of a fluoride activator.[9c]
Indeed, we found that reactions conducted with catalytic
amounts of Pd(OAc)2 and chelating phosphine ligand DPE-
Phos and KOTMS as activator in THF gave vinylarene
products in good yields with retention of the diastereomeric
ratio. Although vinylarenes can be accessed from terminal
alkenes through the Heck reaction[16] or direct arene vinyl-
ation,[17] the method we report here produces the Z isomer as
the major product, whereas the Heck reaction produces the
E isomer. Alternative routes by Suzuki coupling require the
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Z vinylhalide or vinylboronate, which are difficult to
access.[16e]
As shown in Scheme 2, the Ir-catalyzed silylation of
terminal alkenes with (TMSO)2MeSiH provides an alterna-
À
tive method for the arylation of vinyl C H bonds by a one-pot
Scheme 3. One-pot aldehyde synthesis from alkenes. Yields are over
two steps and are of the isolated products. [a] 1 mol% of [{Ir-
(coe)2OH}2] and 3 mol% of ligand were used for the silylation.
TBAF=tetra-n-butylammonium fluoride.
Table 2: Surveying conditions for the E-selective alkene silylation.[a]
Entry Ligand
Equiv of nbe Equiv of Silane Yield [%][b] Z/E[b]
1
2
3
4
5
6
7
8
2-MePhen
2-EtPhen
2-MeOPhen 1.1
2-PhPhen
2-ClPhen
2,9-Me2Phen 1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
2.0
3.8
70
27
nd
5
15
11
64
54
7:93
11:89
nd
1.1
1.1
nd
82:18
89:11
9:91
12:88
Scheme 2. One-pot synthesis of vinylarenes from alkenes. Yields are of
À
the isolated products based on 0.8 equiv of Ar I. E/Z ratios were
2-MePhen
2-MePhen
2.0
3.8
determined by GC or NMR spectroscopy. [a] Bromobenzene (1.1 equiv)
was used instead of an aryl iodide. Yield is based on the starting
alkene. DPEPhos=bis(2-diphenylphosphinophenyl)ether.
[a] For reaction conditions see the Supporting Infomation. [b] Deter-
mined by GC. nd=not determined.
procedure involving silylation and coupling. Under these
conditions, various aryl iodides and an aryl bromide are all
suitable electrophilic coupling partners.
In addition to the cross-coupling with aryl iodide electro-
philes, we developed conditions for the oxidation of the
vinylsilanes in the presence of aqueous H2O2 and 4.4 equiv-
alents of TBAF in a mixture of THF and methanol to give the
corresponding aldehydes. The reaction requires 4 equivalents
Scheme 4, m/z = 299.1, MÀCH3). However, the yields and the
selectivity for the E isomer were high. Reactions conducted
with other 2-substituted phenanthrolines (Table 2) in which
the substituents are larger than a methyl group occurred more
À
of TBAF, presumably because of the presence of 4 Si O
bonds in the starting material.[18] Scheme 3 shows a series of
aldehydes prepared through a one-pot silylation and oxida-
tion sequence starting with terminal alkenes. This protocol
leads to the formation of aldehyde products with regioselec-
tivity complementing the Wacker oxidation of alkenes and
avoids the need for two oxidation steps to convert an
alkylborane into the aldehyde.
While studying the effects of ligands on the diastereose-
lectivity of alkene silylation, we discovered that the reaction
conducted with 2-methyl-1,10-phenanthroline[19] (2-MePhen)
as the ligand gave the E vinylsilane as the major product (Z/
E = 7:93; Table 2, entry 1). The yield of the E vinylsilane was
lower than the yield of the Z vinylsilane obtained from
reactions with Me4Phen as ligand; the major side products are
hydrogenated starting material and silylated nbe (“Si-nbe”;
Scheme 4. Scope of the E-selective alkene silylation. Reaction condi-
tions: Method A: [{Ir(cod)OMe}2] (0.5 mol%), 2-MePhen (1.7 mol%),
alkene (2.0 mmol), and silane (1.0 mmol) in 0.4 mL THF. Method B:
[{Ir(cod)OMe}2] (0.5 mol%), 2-MePhen (1.7 mol%), alkene
(1.0 mmol), nbe (1.1 mmol), and silane (1.1 mmol) in 0.4 mL THF.
[a] Yield of the isolated product from method A based on silane.
[b] Z/E ratios were determined by NMR spectroscopy. [c] Yield of the
isolated product from method B based on alkene.
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slowly (Table 2, entries 2 and 4) than those with 2-MePhen,
whereas reactions conducted with 2,9-dialkyl-1,10-phenan-
throlines gave predominantly the Z vinylsilane in poor yields
(Table 2, entry 6 and the Supporting Information). Reactions
run with higher concentrations of nbe led to increased
Second, the ratios of the rates for separate reactions of 1-
octene and [1,1-D2]oct-1-ene conducted with Me4Phen or 2-
MePhen as ligand are 1.7 and 1.5, respectively. This small
kinetic isotope effect suggests that the reaction does not occur
À
by initial, irreversible oxidative addition of the vinyl C H
À
À
production of Si nbe, but the yields of the desired product
bond and that the C H bond cleavage step is similar for
did not increase (Table 2, entries 7 and 8).
reactions catalyzed by the two systems.
The reactions of several alkenes to form E vinylsilanes
with high diastereoselectivity are summarized in Scheme 4.
For the reactions of nonpolar alkenes (4 and 8), 2 equivalents
of alkenes were used. One equivalent of the alkene serves as
the hydrogen acceptor under these conditions to facilitate
product purification.[20] High ratios of E to Z isomers were
observed, and the reaction tolerated electrophilic function-
ality.
Finally, and most definitively, the reaction of trans-[1-
D]oct-1-ene under the conditions that favor formation of the
Z vinylsilane gave the major Z product containing hydrogen
at the vinylic position [Eq. (1)]. Similarly, the reaction of cis-
The resulting E vinylsilanes can be transformed to Z vi-
nylbromides (Scheme 5). Addition of bromine to the alkene
forms the 1,2-dibromoalkylsilane; reaction of the dibromide
generated in situ with base gives the Z vinylbromide.
[1-D]oct-1-ene led to the vinylsilane product containing
deuterium at the trans position [Eq. (2)]. These labeling
studies support a mechanism involving syn insertion of the
alkene into the iridium–silyl bond, followed by b-hydrogen
elimination from a syn coplanar conformation of the silylalkyl
intermediate (Scheme 6).
Scheme 5. Transformation of E vinylsilanes.
The vinylsilanes also can be converted to stereochemically
defined dienes. We studied the E vinylsilane to identify
À
conditions for the conversion of the C H functionalization
product to dienes. Reaction of an E vinylsilane with an
E vinylbromide in the presence of Pd(OAc)2 and DPEphos
with KOTMS as base generated the diene stereospecifically.
Analogous procedures are suitable for the conversion of
Z vinylsilanes to Z,E -dienes.[21] Such dienes that lack steric or
electronic deactivation of one of the two alkenes are difficult
to produce by cross metathesis.[22,23]
Mechanistic studies suggest that the dehydrogenative
silylation of alkenes occurs by a pathway distinct from arene
silylation and does not occur by direct insertion of iridium
À
into the vinyl C H bond. First, the reactions that give
Scheme 6. Proposed catalytic cycle for the dehydrogenative silylation.
predominately the Z vinylsilane proceed without nbe as the
acceptor (Table 1, entry 15), whereas the reaction with 2-
MePhen as ligand strongly favors the E vinylsilane product
even in the presence of nbe (Table 2, entry ). This observation
contrasts with published results of reactions involving trie-
thylsilane; in these cases no catalytic reaction was observed in
the absence of nbe, and nbe was proposed to promote the
selectivity for the Z isomer.[8,24] Our data suggest that the
diastereoselectivity of the reactions with the siloxysilane is
influenced more by the ligand than by the hydrogen acceptor.
In summary, we have discovered a diastereoselective
intermolecular silylation of terminal alkenes with a siloxysi-
lane to give either E or Z vinylsilanes depending on the ligand
employed. These vinylsilane products are suitable for further
functionalization, including cross-coupling and oxidation. The
one-pot silylation and Hiyama coupling sequence provides an
alternative strategy to the Wittig olefination and Heck
reaction for the synthesis of cis-1,2-substituted alkenes,
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Kuninobu, T. Nakahara, H. Takeshima, K. Takai, Org. Lett.
2013, 15, 426 – 428.
whereas the silylation/oxidation sequence complements the
regioselectivity of the Wacker process and is shorter than the
combination of hydroboration, oxidation to the alcohol, and
further oxidation to the aldehyde. The nature of the active
silylating species and the origin of difference in diastereo-
selectivity between 2-MePhen and Me4Phen ligands are
currently under investigation.
[3] a) A. Caballero, S. Sabo-Etienne, Organometallics 2007, 26,
1191 – 1195; b) A. Kondoh, T. F. Jamison, Chem. Commun. 2010,
46, 907 – 909; c) M. Murata, K. Kawakita, T. Asana, S. Watanabe,
Y. Masuda, Bull. Chem. Soc. Jpn. 2002, 75, 825 – 829; d) N.
Selander, B. Willy, K. J. Szabꢁ, Angew. Chem. 2010, 122, 4145 –
4147; Angew. Chem. Int. Ed. 2010, 49, 4051 – 4053.
[4] J. R. McAtee, S. E. S. Martin, D. T. Ahneman, K. A. Johnson,
D. A. Watson, Angew. Chem. 2012, 124, 3723 – 3727; Angew.
Chem. Int. Ed. 2012, 51, 3663 – 3667.
Experimental Section
[5] a) Y. Na, S. Chang, Org. Lett. 2000, 2, 1887 – 1889; b) S. V.
Maifeld, M. N. Tran, D. Lee, Tetrahedron Lett. 2005, 46, 105 –
108; c) B. M. Trost, Z. T. Ball, J. Am. Chem. Soc. 2005, 127,
17644 – 17655; d) S. E. Denmark, W. Pan, Org. Lett. 2002, 4,
4163 – 4166; e) C. S. Aricꢁ, L. R. Cox, Org. Biomol. Chem. 2004,
2, 2558 – 2562; f) S. E. Denmark, D. Wehrli, Org. Lett. 2000, 2,
565 – 568; g) G. Berthon-Gelloz, J.-M. Schumers, G. De Bo, I. E.
Markꢁ, J. Org. Chem. 2008, 73, 4190 – 4197.
[6] a) K. Hirano, H. Yorimitsu, K. Oshima, J. Am. Chem. Soc. 2007,
129, 6094 – 6095; b) Y. Jiang, O. Blacque, T. Fox, C. M. Frech, H.
Berke, Chem. Eur. J. 2009, 15, 2121 – 2128; c) R. S. Tanke, R. H.
Crabtree, Organometallics 1991, 10, 415 – 418; d) A. M.
Lapointe, F. C. Rix, M. Brookhart, J. Am. Chem. Soc. 1997,
119, 906 – 917; e) F. Kakiuchi, Y. Tanaka, N. Chatani, S. Murai, J.
Organomet. Chem. 1993, 456, 45 – 47; f) M. J. Fernꢂndez, M. A.
Esteruelas, M. S. Jimꢃnez, L. A. Oro, Organometallics 1986, 5,
1519 – 1520; for review, see: B. Marciniec, Coord. Chem. Rev.
2005, 249, 2374 – 2390.
A representative procedure for silylation of 4a: In a nitrogen-
atmosphere glovebox, THF (0.4 mL) was added to a 4 mL vial
containing [{Ir(coe)2OH}2] (4.3 mg, 0.005 mmol) and Me4Phen
(3.5 mg, 0.015 mmol), and the mixture was stirred at room temper-
ature for 5 min. (TMSO)2MeSiH (668 mg, 3.0 mmol) was added to the
dark brown suspension, and the solution was stirred at room
temperature for 5 min. Norbornene (282 mg, 3.0 mmol) and 4a
(124 mg, 1.0 mmol) were added subsequently, the vial was sealed, and
the solution was stirred at room temperature for 30 min and then
heated at 508C for 20 h. The volatiles were removed in vacuo, and the
residue was purified by flash column chromatography (hexanes) to
1
give 4b as colorless oil (320 mg, 93% yield, Z/E = 90:10). H NMR
(500 MHz, CDCl3): d = 6.35–6.27 (m, 1H), 5.35 (d, J = 14.3 Hz, 1H),
2.11 (t, J = 7.1 Hz, 2H), 1.76–1.62 (m, 6H), 1.38–1.28 (m, 1H), 1.28–
1.09 (m, 3H), 0.98–0.84 (m, 2H), 0.14–0.07 ppm (m, 21H). 13C NMR
(126 MHz, CDCl3): d = 149.14 (s), 127.74 (s), 41.10 (s), 38.37 (s), 33.38
(s), 26.76 (s), 26.55 (s), 2.25 (s), 2.05 ppm (s). HRMS (EI +) calcd for
[C15H33O2Si3]+ (MÀCH3): 329.1788, found: 329.1793.
[7] a) K. Takai, Y. Kataoka, T. Okazoe, K. Utimoto, Tetrahedron
Lett. 1987, 28, 1443 – 1446; b) D. M. Hodgson, P. J. Comina,
Tetrahedron Lett. 1994, 35, 9469 – 9470; c) K. Itami, T. Nokami, J.
Yoshida, Org. Lett. 2000, 2, 1299 – 1302; d) J. McNulty, P. Das,
Chem. Commun. 2008, 1244 – 1245; e) K. K. Murthi, R. G.
Salomon, Tetrahedron Lett. 1994, 35, 517 – 520; f) S. E. Den-
mark, S. Fujimori, J. Am. Chem. Soc. 2005, 127, 8971 – 8973;
g) B. M. Trost, M. U. Frederiksen, J. P. N. Papillon, P. E. Har-
rington, S. Shin, B. T. Shireman, J. Am. Chem. Soc. 2005, 127,
3666 – 3667; h) B. M. Trost, M. R. Machacek, Z. T. Ball, Org.
Lett. 2003, 5, 1895 – 1898; i) C. Pietraszuk, H. Fischer, M.
Kujawa, B. Marciniec, Tetrahedron Lett. 2001, 42, 1175 – 1178;
j) S. E. Denmark, S.-M. Yang, Org. Lett. 2001, 3, 1749 – 1752.
[8] B. Lu, J. Falck, J. Org. Chem. 2010, 75, 1701 – 1705.
[9] a) K. Tamao, N. Ishida, M. Kumada, J. Org. Chem. 1983, 48,
2120 – 2122; b) K. Tamao, N. Ishida, T. Tanaka, M. Kumada,
Organometallics 1983, 2, 1694 – 1696; c) S. E. Denmark, R. C.
Smith, W.-T. T. Chang, J. M. Muhuhi, J. Am. Chem. Soc. 2009,
131, 3104 – 3118; d) S. E. Denmark, J. M. Kallemeyn, J. Am.
Chem. Soc. 2006, 128, 15958 – 15959.
Received: May 13, 2013
Published online: July 16, 2013
Keywords: alkene functionalization · cross-coupling ·
.
dehydrogenative silylation · homogeneous catalysis · iridium
[1] a) I. Fleming, J. Dunoguꢀs, R. Smithers in Organic Reactions,
Vol. 2 (Eds.: A. S. Kende, et al.), Wiley, New York, 1989, pp. 57 –
193; b) T.-Y. Luh, S.-T. Liu in The Chemistry of Organic Silicon
Compounds, Vol. 2 (Eds.: Z. Rappoport, Y. Apeloig), Wiley,
New York, 2003; c) H. C. Brown, S. K. Gupta, J. Am. Chem. Soc.
1972, 94, 4370 – 4371; d) H. C. Brown, T. Hamaoka, N. Ravin-
dran, J. Am. Chem. Soc. 1973, 95, 5786 – 5788; e) H. C. Brown, T.
Hamaoka, N. Ravindran, J. Am. Chem. Soc. 1973, 95, 6456 –
À
6457; for reviews on catalytic C H bond functionalization with
boron and silicon reagents, see: f) J. F. Hartwig, Acc. Chem. Res.
2012, 45, 864 – 873; g) I. A. I. Mkhalid, J. H. Barnard, T. B.
Marder, J. M. Murphy, J. F. Hartwig, Chem. Rev. 2010, 110, 890 –
931; h) F. Kakiuchi, N. Chatani, Adv. Synth. Catal. 2003, 345,
1077 – 1101; i) J. F. Hartwig, Chem. Soc. Rev. 2011, 40, 1992 –
2002.
[10] a) D. C. Apple, K. A. Brady, J. M. Chance, N. E. Heard, T. A.
Nile, J. Mol. Catal. 1985, 29, 55 – 64; b) R. N. Haszeldine, R. V.
Parish, R. J. Taylor, J. Chem. Soc. Dalton Trans. 1974, 2311 –
2315.
[11] a) K. Ezbiansky, P. I. Djurovich, M. LaForest, D. J. Sinning, R.
Zayes, D. H. Berry, Organometallics 1998, 17, 1455 – 1457;
b) B. J. Truscott, A. M. Z. Slawin, S. P. Nolan, Dalton Trans.
2013, 42, 270 – 276.
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[2] For silylation of aromatic and aliphatic C H bonds, see: a) N.
Tsukada, J. F. Hartwig, J. Am. Chem. Soc. 2005, 127, 5022 – 5023;
b) M. Murata, N. Fukuyama, J.-i. Wada, S. Watanabe, Y. Masuda,
Chem. Lett. 2007, 36, 910 – 911; c) T. Ishiyama, K. Sato, Y. Nishio,
N. Miyaura, Angew. Chem. 2003, 115, 5504 – 5506; Angew. Chem.
Int. Ed. 2003, 42, 5346 – 5348; d) T. Saiki, Y. Nishio, T. Ishiyama,
N. Miyaura, Organometallics 2006, 25, 6068 – 6073; e) E. M.
Simmons, J. F. Hartwig, J. Am. Chem. Soc. 2010, 132, 17092 –
17095; f) E. M. Simmons, J. F. Hartwig, Nature 2012, 483, 70 – 73;
g) A. Kuznetsov, Y. Onishi, Y. Inamoto, V. Gevorgyan, Org. Lett.
2013, 15, 2498 – 2501; h) A. Kuznetsov, V. Gevorgyan, Org. Lett.
2012, 14, 914 – 917; i) T. Ureshino, T. Yoshida, Y. Kuninobu, K.
Takai, J. Am. Chem. Soc. 2010, 132, 14324 – 14326; j) Y.
[12] For an example of Pt-catalyzed arene silylation with this silane,
see Ref. [2b].
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[13] Notably, Me4Phen is also the best ligand for aliphatic C H
borylation. See: C. W. Liskey, J. F. Hartwig, J. Am. Chem. Soc.
2012, 134, 12422 – 12425.
[14] D. A. Ortmann, H. Werner, Z. Anorg. Allg. Chem. 2002, 628,
1373 – 1376.
[15] For example, product 11b was obtained in only 27% yield with
[{Ir(cod)OMe}2] as the catalyst precursor and 71% yield with
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same loading of [{Ir(coe)2OH}2] at 508C after 20 h (1.1 equiv of
nbe and silane).
[21] For example, reaction of 4b with (E)-b-bromostyrene gives the
coupled product in high yield with retention of the Z geometry
[16] a) R. F. Heck, J. P. Nolley, Jr., J. Org. Chem. 1972, 37, 2320 –
2322; b) K. S. Yoo, C. H. Yoon, J. W. Jung, J. Am. Chem. Soc.
2006, 128, 16348 – 16393; c) Y. C. Jung, R. K. Mishra, C. H.
Yoon, K. W. Jung, Org. Lett. 2003, 5, 2231 – 2234; d) H. J. Li, L.
Wang, Eur. J. Org. Chem. 2006, 5101 – 5102; e) G.-P. Lu, K. R.
Voigtritter, C. Cai, B. H. Lipshutz, J. Org. Chem. 2012, 77, 3700 –
3703.
(see the Supporting Information for details):
[17] D.-H. Wang, K. M. Engle, B.-F. Shi, J.-Q. Yu, Science 2010, 327,
315 – 319.
[18] Reactions with KFor CsF instead of TBAFas the fluoride source
gave no conversion even at 608C (see the Supporting Informa-
tion).
[22] R. B. Miller, T. Reichenbach, Tetrahedron Lett. 1974, 15, 543 –
546.
[19] R. A. Poole, G. Bobba, M. J. Cann, J.-C. Frias, D. Parker, R. D.
Peacock, Org. Biomol. Chem. 2005, 3, 1013 – 1024.
[23] a) T. W. Funk, J. Efskind, R. H. Grubbs, Org. Lett. 2005, 7, 187 –
190; b) G. Moura-Letts, D. P. Curran, Org. Lett. 2007, 9, 5 – 8.
[24] We found that reaction of oct-1-ene with Et3SiH catalyzed by
0.5% [{Ir(cod)OMe}2] and 1.5% Me4Phen in the absence of nbe
gave an equimolar mixture of triethyl-1-octenyl-silane and
octane at complete conversion.
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[20] The side product Si nbe can be difficult to separate from the
desired silylation product that contains no polar functional
group by silica column chromatography, whereas the low-
molecular weight hydrogenation product can be simply removed
in vacuo.
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