Ir-Catalyzed Asymmetric and Regioselective Hydrogenation of Cyclic Allylsilanes and Generation of Quaternary Stereocenters via the Hosomi-Sakurai Allylation

Article abstract of DOI:10.1002/chem.201704684

A number of cyclic dienes containing the allylsilane moiety were prepared by a Birch reduction and subjected to iridium-catalyzed regioselective and asymmetric hydrogenation, which provided chiral allylsilanes in high conversion and enantiomeric excess (up to 99 % ee). The compounds were successively used in the Hosomi–Sakurai allylation with various aldehydes employing TiCl₄ as Lewis acid, providing adducts with two additional stereogenic centers in excellent diastereoselectivity.

Full text of DOI:10.1002/chem.201704684

A Journal of
Accepted Article
Title: Ir-Catalyzed Asymmetric and Regioselective Hydrogenation of
Cyclic Allylsilanes and Generation of Quaternary Stereocenters
via the Hosomi-Sakurai Allylation
Authors: Wangchuk Rabten, Cristiana Margarita, Lars Eriksson, and
Pher G. Andersson
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201704684
Link to VoR: http://dx.doi.org/10.1002/chem.201704684
Supported by

10.1002/chem.201704684
Chemistry - A European Journal
FULL PAPER
Ir-Catalyzed Asymmetric and Regioselective Hydrogenation of
Cyclic Allylsilanes and Generation of Quaternary Stereocenters
via the Hosomi-Sakurai Allylation
Wangchuk Rabten,[a] Cristiana Margarita,[a] Lars Eriksson,[b] and Pher G. Andersson*[a]
Dedication ((optional))
Abstract: A number of cyclic dienes containing the allylsilane moiety
were prepared via Birch reduction and subjected to iridium-catalyzed
regioselective and asymmetric hydrogenation, which provided chiral
allylsilanes in high conversion and enantiomeric excess (up to 99 %
ee). The compounds were successively used in the Hosomi-Sakurai
allylation with various aldehydes employing TiCl4 as Lewis acid,
providing adducts with two additional stereogenic centers in
excellent diastereoselectivity.
diastereomeric ratios were achieved and in some cases only a
single diastereoisomer was obtained. Later, Shea reported a
bridgehead cyclic allylsilane that gave rise to single
diastereomers when employed in analogous transformations
(Scheme 1b).[9b] Nonetheless, only the relative stereochemistry
of the products was controlled in both cases since the starting
materials were prepared in racemic form. In order to control
absolute stereochemistry, it can be anticipated to install a
stereochemically defined chiral center distal or proximal to the
allysilane moiety. Additionally, if the reagent bears double
substitution on the γ-carbon, it would generate a chemically
challenging stereodefined quaternary center in the adducts
(Scheme 2).
Introduction
Allylsilanes are very versatile reagents, which possess high
thermal stability and rather low sensitivity to moisture and
oxygen. They are relatively inert towards a range of synthetic
O
OH
OH
R’
H
R
R’
R’
+
H
R
R
a
b
methodologies
such
as
oxidation,
reduction
and
Si(CH3)2Ph
hydrogenation,[1] yet they react smoothly with aldehydes and
ketones in presence of Lewis acids. This transformation has
been reported by Hosomi and Sakurai in 1976[2] and has been
thoroughly studied and applied in synthesis since, allowing
stereoselective carbon-carbon bond formation. The method has
been employed as a key step in the total synthesis of many
complex natural products,[3] such as (+)-Tetronomycin[4] and
Lycopodium alkaloids.[5]
CO2H
Ph
Si
O
O
O
R
R
H
H
H
OH
Ph
Scheme 1. Work by Organ (a) and Shea (b) group.
In the past few decades the focus has been oriented on enantio-
and regioselective synthesis for many chemical transformations.
This lead to the development of various chiral Lewis[6] and
Brønsted acids[7] as well as to the use of optically active
allylsilanes[8] to direct the stereochemical outcome when
introducing two or more stereogenic centers in the target
molecules.
Results and Discussion
Recently we have reported the Ir-catalyzed asymmetric and
regioselective hydrogenation of carbocyclic
olefins.[10]
Henceforth we envisioned that the introduction of a silyl group
Numerous reports on chiral acyclic allylsilanes appeared in the
literature,[8d] but few on cyclic allylsilanes.[9] Organ and co-
workers reported the example of Sakurai allylation with cyclic
silanes bearing a stereogenic center, reacting with various
electrophiles in presence of TiCl4 (Scheme 1a).[9a] High
Birch
reduction
Asymmetric
Hydrogenation
Si
Si
Si
R1
R1
R1
R2
R2
R2
1
2
3
Hosomi-Sakurai
allylation
R1
R2
R3
OH
4
[a]
[b]
W. Rabten, C. Margarita, Prof. P. G. Andersson
Department of Organic Chemistry, Stockholm University
Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden
E-mail: Pher.Andersson@su.se
Scheme 2. General procedure for the synthesis of compounds 4.
Assoc. Prof. Lars Eriksson
Department of Physical, Inorganic and Structural Chemistry,
Stockholm University, Svante Arrhenius väg 16C, SE-10691
Stockholm, Sweden
could afford chiral cyclic allylsilanes upon asymmetric
monohydrogenation, which would be useful substrates for the
stereoselective Hosomi-Sakurai reaction to obtain further
functionalized cyclohexane structures.
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
This article is protected by copyright. All rights reserved.

10.1002/chem.201704684
Chemistry - A European Journal
FULL PAPER
The prochiral allylsilanes turned out to be easily generated from
the reduction of benzyl silanes (1, Scheme 2). The formed
cyclohexadienes (2) are suitable substrates for the initial
installation of a stereogenic center using the iridium catalyzed
asymmetric monohydrogenation.
excess (88-98% ee, Table 1, entries 6 and 7). Most ligand
structures afforded mixtures of the hydrogenated product (3a)
and volatile compounds, probably by causing the
protodesilylation of the allylic substrate and its further
hydrogenation (Scheme 3). Dimethoxy catalyst v was found to
prevent this issue, most likely due to its decreased acidity and
was then chosen to further study the solvent effect. A screening
was carried out, showing that CH2Cl2, benzene and toluene
gave comparable results (97-98% ee, Table 1, entries 7-9).
However, the use of α,α,α-trifluorotoluene enabled a cleaner
reaction, with full conversion and 99% ee (entry 10).
+
+
+
-
-
-
BArF
BArF
BArF
Ph
P
Ph
P
Ph
P
Ph
Ph
Ph
Ir
Ir
Ir
N
N
N
F
N
N
S
iii
ii
i
+
Table 1. Optimization of the reaction conditions for the asymmetric
hydrogenation of 2a.[a]
+
-
-
BArF
BArF
Ph
P
Ph
P
Ph
Ph
Ir
Ir
N
N
Ir cat. (0.5 mol%)
H2 (10 bar)
O
Si
Si
N
N
O
rt, 18 h
*
iv
v
2a
Entry
3a
conv.(%)[b] ee (%)[c]
Figure 1. Catalysts used in this study.
cat.
solvent
CH2Cl2
CH2Cl2
CH2Cl2
additive
-
-
1
2
3
i
70
90
99
80
65
70
ii
ii
Dimethyl substituted silane 2a (Table 1) was chosen as model
substrate for the hydrogenation catalyst screening. Iridium N,P-
catalysts containing thiazole i and imidazole ii ligands (Figure 1)
were evaluated, as they had been previously found to be the
PVP
CH2Cl2
KHCO3
4
ii
99
71
CH2Cl2
CH2Cl2
CH2Cl2
Benzene
Toluene
-
-
-
-
-
-
5
6
iii
iv
v
75
92
95
93
97
99
34
88
98
97
97
99
most
efficient
classes
for
the
hydrogenation
of
cyclohexadienes.[10b] The ligand was found to have great
influence on the hydrogenation outcome, especially in presence
of the acid-sensitive allylsilane group.[11] The catalyst containing
a thiazole ring had been reported to be more acidic compared to
the imidazole,[11b] and lead to lower conversion to the desired
product (Table 1, entries 1 and 2). The imidazole catalyst ii was
chosen and we studied the effect of basic additives (PVP and
KHCO3); they granted improvement of the reaction outcome with
a slight increment in the enantioselectivity (70-71% ee, entries 3
and 4).
7
v
8
v
9
v
α,α,α-trifluorotoluene
10
[a] Reaction conditions: 0.05 mmol substrate, 0.5 mol% catalyst, 0.5 mL of
solvent, 10 bar of H2, 18 h, rt. [b] Conversion determined by 1H NMR
spectroscopy. [c] Enantiomeric excess determined by GC analysis using a
chiral stationary phase.
Protodesilylation
Hydrogenation
Si
Si
With the best conditions defined, the hydrogenation was
extended to analogous cyclic silanes. The substrate scope
included the variation of the alkyl chain length and its position on
the ring. The results from the asymmetric hydrogenation of these
substrates are summarized in Table 2. Catalyst v performed
excellently in the reduction regardless of the substitution pattern.
Hydrogenations occurred with high conversion, allowing the
isolation of the optically active allylsilanes in good to excellent
yield (70-96%). Substrates having ethyl and n-butyl groups on
the 4 or 5 position tended to give slightly lower enantioselectivity
92-94% ee (Table 2, entries 1, 2, 5 and 6). Having an isobutyl
group on the 4 position didn’t affect the enantioselectivity, giving
99% ee (Table 2, entry 3). Similarly, when the methyl substituent
was replaced with ethyl and n-butyl on the 2 position of the
tetrasubstituted allylsilane, excellent enantioselectivity 99% ee
(Table 2, entries 7 and 8) was still obtained.
2a
3a
6
Hydrogenation
7
Scheme 3. Possible protodesilylation pathway generating undesired
byproducts.
Thus, electronic properties of the aromatic substituent on the
imidazole ligand were examined. When an electron-withdrawing
group (Figure 1, catalyst iii) was installed, it led to low
conversion and enantiomeric excess (34% ee, entry 5). The
increase in electronic density from the 2,4-dimethyl group
(Figure 1, catalyst iv) to the more electron-donating 2,4-
dimethoxy group (Figure 1, catalyst v) contributed to improve the
conversion (92 to 95%) and to reach excellent enantiomeric
The obtained chiral β,γ-substituted allylsilanes could then be
employed in the Hosomi-Sakurai reaction, generating a sterically
This article is protected by copyright. All rights reserved.

10.1002/chem.201704684
Chemistry - A European Journal
FULL PAPER
demanding quaternary center in the homoallylic alcohol adduct.
The initial reactivity optimization studies employed the dimethyl
allylsilane 3a as model substrate and benzaldehyde as standard
electrophile. Screening of different Lewis acids showed that
TiCl4 was the appropriate choice in order to have a selective
reaction (Table 3). SnCl4 promoted the allylation as well,
although producing higher amounts of side-products and
showing opposite diastereoselectivity (entry 2)[12]. SiCl4 resulted
mainly in the desilylation (6) of the starting material. The use of
BF3•Et2O did not afford the desired product and generated
complex reaction mixtures.
was kept at -78 °C with a dry ice/acetone cooling bath for 1h.
The use of 3Å molecular sieves aided to increase the yield to
68% (Table 3, entry 6).
It was then necessary to investigate the diastereoselectivity of
the reaction. The final allylation product bears three stereogenic
centers, which can give rise to a maximum of four possible
diastereoisomers. Stereoselectivity is dictated by the allylsilane
preferred mode of attack, in which the incoming aldehyde is
antiperiplanar to the allyl nucleophile and minimizing steric
repulsion between the larger group on the aldehyde and the
ring[1] (Figure 2). This leads to two possible facial attacks either
from top or bottom of the cyclohexyl ring. The attack on the top
face gives rise to energetically more stable chair-like transition
states TS1a and TS1b compared to the bottom attack, which
forms a more energy demanding boat-like transition state TS2.
Table 2. Substrate scope of the asymmetric hydrogenation of cyclic
allylsilanes.[a]
Ir cat. v (0.5 mol%)
H2 (10 bar)
Si
Si
R1
R1
α,α,α-trifluorotoluene
Table 3. Screening of Lewis acids for the Hosomi-Sakurai allylation.[a]
R2
R2
rt, 18 h
Yield (%)[c] ee (%)[d]
Substrate
Product[b]
Entry
Lewis acid,
PhCHO
Si
Ph
OH
Ph
+
Si
Si
CH2Cl2
- 78 °C, 1h
OH
1
2
84
84
92
93
3a
8a
8a’
Et
Et
(relative stereochemistry)
2b
2c
3b
3c
3d
Yield (%)[c]
34
dr [b]
Entry
Lewis acid
additive
Si
Si
Si
Si
TiCl4
-
-
1
2
5:1
n-Bu
n-Bu
SnCl4
SiCl4
1:6
20
-
-
-
-
-
-
-
3
4
5
3
4
5
6
7
8
96
70
87
89
70
95
99
99
93
94
99
98
BF3.Et2O
TBAF
-
i-Bu
i-Bu
2d
2e
-
TiCl4
6
5:1
68
3Å MS
Si
Si
3e
Et
Et
Si
Si
[a] Reaction conditions: 0.15 mmol substrate, 1.1 eq. Lewis acid, 1.1 eq.
PhCHO, 1.5 mL of CH2Cl2, 1 h, -78 °C. [b] Diastereomeric ratio determined by
1H NMR spectroscopy. [c] Isolated yield.
2f
2g
2h
2i
3f
n-Bu
n-Bu
Si
Si
Thus, trans adducts are obtained as major product when
substitution is present on the 4 position, which is in accordance
with Organ’s work, however cis adducts were obtained when it is
on the 5 position. This was confirmed from single crystal X-ray
crystallography of two individual compounds 8a and 8e (Figure
3). It was observed the formation of only two diastereoisomers,
whose ratio was optimized by further varying the reaction
conditions. It was in fact found that the diastereomeric ratio
arising from the reaction of cyclic allylsilane 3a with
benzaldehyde is highly concentration-dependent (Table 4). This
called for an investigation of the concentration effects of the
individual reagents. The concentration of TiCl4 and
benzaldehyde was evaluated independently while keeping the
3g
Si
Si
Si
Et
Et
3h
Si
n-Bu
n-Bu
3i
[a] Reaction conditions: 0.05 mmol substrate, 0.5 mol% catalyst, 0.5 mL of
solvent, 10 bar of H2, 18 h, rt. [b] Predicted absolute configuration for the major
product. [c] Isolated yield. [d] Enantiomeric excess determined by GC analysis
using a chiral stationary phase.
allylsilane’s
concentration
constant.
A
decrease
in
diastereoselectivity was observed in presence of excess
benzaldehyde (Table 4, entry 5), while the use of excess TiCl4
resulted in rather dramatic increase of the stereoselectivity
It is also known that TBAF can be used to initiate fluoride-
promoted allylations, however we observed no such reactivity for
the investigated cyclic silanes. TiCl4 was then chosen to
continue the selectivity optimization. The solvent of choice for
the transformation is dichloromethane, and the reaction mixture
This article is protected by copyright. All rights reserved.

10.1002/chem.201704684
Chemistry - A European Journal
FULL PAPER
the dimethyl silane 3a, and the results are shown in Table 5. The
use of cyclohexanecarboxaldehyde afforded homoallylic alcohol
8aa as
Unfavored
Si
Si
Ph
Si
Ph
Si
Ph
H
H
Ph
H
Table 4. Concentration dependence in the Hosomi-Sakurai allylation.
H
O
O
O
O
TiCl4
Cl4Ti
TiCl4
Cl4Ti
TiCl4
PhCHO
Favored
Si
Ph
OH
4-Subsituted
Ph
+
Cl4Ti
H
CH2Cl2
- 78 °C, 1h
O
Cl4Ti
H
OH
6
3
Ph
Si
Ph
O
5
4
1
2
3a
8a
8a’
Ph
H
Ph
OH
(relative stereochemistry)
O
8a
Si
Si
Cl4Ti
Above
dr [a]
Entry
1
Allylsilane (M)
0.03
Benzaldehyde (M)
TiCl4 (M)
0.03
trans
Major
TS 1a
0.03
3:1
Si
4-Subsituted
6
Si
Ph
1
2
5
H
2
3
4
5
6
0.10
0.22
0.60
0.30
0.30
0.10
0.26
0.73
0.60
0.30
0.10
0.26
0.73
0.30
0.60
5:1
12:1
30:1
2:1
4
Ph
OH
Si
3
Cl4Ti
H
O
8a’
Cl4Ti
Cl4Ti
H
O
Cl4Ti
O
Ph
Ph
cis
Minor
Below
TS 2
H
5-Subsituted
O
Ph
6
Cl4Ti
O
Si
Ph
H
5
1
45:1
H
2
4
Ph
OH
3
Ph
8e
O
Si
Cl4Ti
Si
cis
Major
TS 1b
Above
[a] Diastereomeric ratio determined by 1H NMR spectroscopy
a single diastereoisomer (Table 5, entry 1). The isobutyl- and
ethyl-substituted compounds 8ab and 8ac were obtained with
high ratios of 24:1 and 46:1, respectively (Table 5, entries 2 and
3). Using isobutyraldehyde 8ad resulted in a less selective
Figure 2. Proposed transition states for the formation of 8a and 8e.
allylation, with
a dr of 9:1 (Table 5, entry 4). When
cyclopentanecarboxaldehyde was employed, the product 8ae
was again obtained in excellent diastereoselectivity (49:1, Table
5, entry 5). The substrate scope was then extended to differently
substituted cyclic silanes. High stereoselectivity was reached in
most cases (Table 5, entries 6-9). Changing substituent at the 4
position from methyl to isobutyl group (8d) didn’t affect the dr
(24:1, Table 5, entry 6).
Further switching the position of the methyl substituent (8e) did
not alter the observed dr either, and a ratio of 31:1 was reached
(table 5, entry 7). The ethyl-substituted product 8f (Table 5, entry
8) could be isolated as a single diastereoisomer and the n-butyl-
substituted counterpart 8g (table 5, entry 9) was obtained with a
dr of 34:1.
8a
8e
Figure 3. Crystal structure of compounds 8a and 8e.
(Table 4, entry 6). Under optimized conditions, the Hosomi-
Sakurai allylation was tested against range of carbon
electrophiles. A number of aliphatic aldehydes were reacted with
a
This article is protected by copyright. All rights reserved.

10.1002/chem.201704684
Chemistry - A European Journal
FULL PAPER
imidazole-based iridium catalyst v. The more electron donating
ligand was found to be crucial for both reactivity and
stereoselectivity. The chiral allylsilanes were successfully
employed in Hosomi-Sakurai allylations giving rise to two new
stereogenic centers in high diastereoselectivity. The developed
methodology grants the generation of multiple stereocenters on
the cyclohexane ring in few steps, starting from achiral materials
and introducing additional functional groups for further synthetic
transformations. Furthermore, this is to the best of our
knowledge, the first example to be reported on the asymmetric
synthesis of cyclic chiral allylsilanes by means of iridium
catalysis.
Table 5. Substrate scope for the Hosomi-Sakurai allylation.[a]
TiCl4
R3CHO
R1
R2
R1
R2
Si
*
3
*
R
R3
*
R1
+
CH2Cl2, 3Å MS
- 78 °C, 1h
R2
OH
OH
3a-g
8a-g
Yield (%)[b]
8a’-g’
dr [c]
Entry
Product
single stereoisomer
observed
Cy
1
65
8aa OH
i-Bu
2
3
4
32
40
56
24:1
46:1
9:1
Experimental Details
OH
8ab
General procedure for asymmetric hydrogenations
Et
OH
8ac
A vial was charged with substrate (0.17 mmol) and Ir-complex (0.5 mol%).
α,α,α-trifluorotoluene (1 mL) was added and the vial was placed in a
high-pressure hydrogenation apparatus. The reactor was purged three
times with Ar, then purged with H2 filled to 10 bar with H2. The reaction
was stirred at room temperature for 16 h before the H2 pressure was
released and the solvent was removed in vacuo. The crude product was
purified through dry silica gel with pentane as eluent. Conversions were
determined by 1H NMR spectroscopy and ee values were determined
using chiral GC or SFC. Racemates were prepared using the racemic
version of the iridium catalyst.
i-Pr
OH
OH
8ad
8ae
5
42
49:1
Ph
OH
6
7
8
9
30
42
69
37
24:1
31:1
General procedure for Hosomi-Sakurai reactions
i-Bu
8d
The procedure for the Hosomi-Sakurai allylation was adapted from the
literature.[9a] To a mixture of allylsilane (0.35 mmol) and aldehyde (0.42
mmol) in anhydrous DCM (0.6 mL) 10 mg of activated molecular sieves
(3Å) were added. The reaction vessel was sealed and the mixture
Ph
OH
8e
8f
degassed with argon for about 10 min, simultaneously cooling down to
-
Et
78 °C in a dry ice/acetone bath. After approximately 15 min of vigorous
stirring, freshly distilled TiCl4 (0.42 mmol) was added dropwise over 15
min. The reaction mixture was stirred for 1 h, then removed from the
cooling bath and quenched immediately with saturated aqueous NaHCO3.
The aqueous layer was extracted with Et2O three times, dried over
anhydrous Na2SO4 and concentrated under reduced pressure. The crude
product was purified by column chromatography on silica gel using a
gradient of 2% to 4% Et2O in pentane as eluent.
single stereoisomer
observed
Ph
OH
n-Bu
Ph
OH
34:1
8g
The complete experimental section can be found in the supporting
information, including compound characterization data, copies of NMR
spectra and chromatogram.
[a] Reaction conditions: 0.30 mmol substrate, 1.1 eq. TiCl4, 1.1 eq. aldehyde,
0.5 mL of CH2Cl2, 1 h, -78 °C. [b] Isolated yield. The lower yields are most
likely due to protodesilylation and loss of volatile byproducts. [c]
Diastereomeric ratio and relative stereochemistry determined by 1H NMR
spectroscopy.
Acknowledgements
We hereby acknowledge the Stiftelsen Olle Engkvist
Byggmästare for supporting this work.
Conclusions
In conclusion, the highly enantioselective preparation of chiral
cyclic allylsilanes could be accomplished by means of N,P-
iridium catalyzed asymmetric hydrogenation. The optically active
allylsilanes were obtained in excellent ee’s (92-99%) with
isolated yields of 70–96%, employing the recently developed
Keywords: Asymmetric monohydrogenation • Allylsilane •
Regioselectivity • Allylation • Iridium-catalyzed
This article is protected by copyright. All rights reserved.

10.1002/chem.201704684
Chemistry - A European Journal
FULL PAPER
[1]
P. V. Ramachandran, D. R. Nicponski, P. D. Gagare, in Comprehensive
Organic Synthesis II (Second Edition), Elsevier, Amsterdam, 2014, pp.
72-147.
2006, 2385-2387; (d) C. E. Masse, J. S. Panek, Chem. Rev. 1995, 95,
1293-1316.
[9]
(a) M. G. Organ, D. D. Winkle, J. Huffmann, J. Org. Chem. 1997, 62,
5254-5266; (b) R. Lauchli, J. M. Whitney, L. Zhu, K. J. Shea, Org. Lett.
2005, 7, 3913-3916; (c) J. W. Han, T. Hayashi, Tetrahedron:
Asymmetry 2010, 21, 2193-2197.
[2]
[3]
A. Hosomi, H. Sakurai, Tetrahedron Lett. 1976, 17, 1295-1298.
(a) E. Langkopf, D. Schinzer, Chem. Rev. 1995, 95, 1375-1408; (b) S.
R. Chemler, W. R. Roush, in Modern Carbonyl Chemistry, Wiley-VCH
Verlag GmbH, 2007, pp. 403-490.
[10] (a) A. Paptchikhine, K. Itto, P. G. Andersson, Chem. Commun. 2011,
47, 3989-3991; (b) B. K. Peters, J. Liu, C. Margarita, W. Rabten, S.
Kerdphon, A. Orebom, T. Morsch, P. G. Andersson, J. Am. Chem. Soc.
2016, 138, 11930-11935.
[4]
[5]
[6]
K. Hori, N. Hikage, A. Inagaki, S. Mori, K. Nomura, E. Yoshii, J. Org.
Chem. 1992, 57, 2888-2902.
C. H. Heathcock, E. F. Kleinman, E. S. Binkley, J. Am. Chem. Soc.
1982, 104, 1054-1068.
[11] The effect of the ligand on the acidity of the iridium hydride catalyst has
been studied and verified earlier. It has also been observed that the use
of electron donating ligands can prevent acid sensitive groups from
decomposing during the reaction. (a) Y. Zhu, Y. Fan, K. Burgess, J. Am.
Chem. Soc. 2010, 132, 6249-6253; (b) J.-Q. Li, J. Liu, S. Krajangsri, N.
Chumnanvej, T. Singh, P. G. Andersson, ACS Catalysis 2016, 6, 8342-
8349; (c) J. Liu, S. Krajangsri, T. Singh, G. De Seriis, N. Chumnanvej,
H. Wu, P. G. Andersson, J. Am. Chem. Soc. 2017, 139, 14470-14475.
[12] SnCl4 is known to undergo transmetallation in presence of an allylsilane.
(a) M. Wadamoto, H. Yamamoto, J. Am. Chem. Soc. 2005, 127, 14556-
14557; (b) A. Yanagisawa, H. Kageyama, Y. Nakatsuka, K. Asakawa, Y.
Matsumoto, H. Yamamoto, Angew. Chem. Int. Ed. 1999, 38, 3701-
3703; (c) K. Mikami, S. Matsukawa, Tetrahedron Lett. 1994, 35, 3133-
3136.
[7]
[8]
(a) M. Sai, H. Yamamoto, J. Am. Chem. Soc. 2015, 137, 7091-7094; (b)
D. Kampen, A. Ladépêche, G. Claßen, B. List, Adv. Synth. Catal. 2008,
350, 962-966; (c) N. Momiyama, H. Nishimoto, M. Terada, Org. Lett.
2011, 13, 2126-2129; (d) T. Akiyama, Chem. Rev. 2007, 107, 5744-
5758.
The resultant allystannane can be therefore involved in
a cyclic
transition state, which generates the opposite stereoselectivity
compared to the anti-periplanar open transition state;M. A. Biamonte, in
Name Reactions for Homologations, John Wiley & Sons, Inc., 2009, pp.
539-574.
(a) J. S. Panek, M. Yang, J. S. Solomon, J. Org. Chem. 1993, 58, 1003-
1010; (b) M. E. Maier, B. Schöffling, Tetrahedron Letters 1990, 31,
3007-3010; (c) J. D. Sellars, P. G. Steel, M. J. Turner, Chem. Commun.
This article is protected by copyright. All rights reserved.

10.1002/chem.201704684
Chemistry - A European Journal
FULL PAPER
Entry for the Table of Contents (Please choose one layout)
Layout 1:
FULL PAPER
Text for Table of Contents
Author(s), Corresponding Author(s)*
Page No. – Page No.
Title
((Insert TOC Graphic here: max.
width: 5.5 cm; max. height: 5.0 cm))
Layout 2:
FULL PAPER
Author(s), Corresponding Author(s)*
Page No. – Page No.
Title
Text for Table of Contents
This article is protected by copyright. All rights reserved.