Silicon Grignard Reagents as Nucleophiles in Transition-Metal-Catalyzed Allylic Substitution

Article abstract of DOI:10.1055/s-0037-1610309

A broad range of transition-metal catalysts is shown to promote allylic substitution reactions of allylic electrophiles with silicon Grignard reagents. The procedure was further elaborated for CuI as catalyst. The regioselectively is independent of the leaving group for primary allylic precursors, favoring α over γ. The stereochemical course of this allylic transposition was probed with a cyclic system, and anti -dia-stereoselectivity was obtained.

Full text of DOI:10.1055/s-0037-1610309

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2018, 50, A–G
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W. Xue, M. Oestreich
Feature
Synthesis
Silicon Grignard Reagents as Nucleophiles in Transition-Metal-
Catalyzed Allylic Substitution
Weichao Xue
catalyst
R3SiMgX
R1
R4
R1
R4
R4
R3Si R1
Martin Oestreich*
+
R2
LG
R2
SiR3
R2
THF
0 °C for 1 h
R3
R3
R3
Institut für Chemie, Technische Universität Berlin,
Strasse des 17. Juni 115, 10623 Berlin, Germany
martin.oestreich@tu-berlin.de
several transition-metal catalysts
broad range of leaving groups
various silicon Grignard reagents
Published as part of the 50 Years SYNTHESIS –
Golden Anniversary Issue
Received: 24.09.2018
Accepted: 28.09.2018
Published online: 22.10.2018
DOI: 10.1055/s-0037-1610309; Art ID: ss-2018-z0648-fa
Copper-catalyzed allylic substitution with R3SiBpin or (R3Si)2Zn
α-selectivity
R1
SiR3
w/ LG = OC(O)Me, OC(O)Ph,
OC(O)OEt, OC(O)NHPh
Refs 3a and 4a
copper catalysis
Abstract A broad range of transition-metal catalysts is shown to pro-
mote allylic substitution reactions of allylic electrophiles with silicon
Grignard reagents. The procedure was further elaborated for CuI as cat-
alyst. The regioselectively is independent of the leaving group for pri-
mary allylic precursors, favoring α over γ. The stereochemical course of
this allylic transposition was probed with a cyclic system, and anti-dia-
stereoselectivity was obtained.
R1
γ
α
LG
R3SiBpin
or
(R3Si)2Zn
SiR3
γ-selectivity
R1
w/ LG = OP(O)(OEt)2, Br, Cl
Refs 3, 4c, and 4d
Our approach to the preparation of silicon Grignard reagents
Key words allylic substitution, copper, Grignard reagents, silicon
R3SiLi
MgBr2
R3SiMgX·2LiX
(1 M inTHF)
Mg
(1 M in THF)
at 66 °C
Br
(0.5 M)
Br
THF, Δ
THF, Δ
Allylic silanes are an often-used class of silicon reagents
and continue to be widely applied in synthesis.1 Several
methods are available that provide reliable access to these
compounds.2–6 One established methodology is by transi-
tion-metal-catalyzed allylic substitution of allylic precur-
sors with silicon (pro)nucleophiles such as Si–Si2 and Si–B3
compounds as well as zinc4 reagents. Examples with copper
complexes as catalysts pertinent to the present study are
summarized in Scheme 1 (top). The reverse approach, that
is, the nucleophilic displacement at silicon electrophiles
with carbon nucleophilic, is far less general.5
We recently developed a robust method for the prepara-
tion of bench-stable solutions of silicon Grignard reagents 1
(Scheme 1, bottom).7 These had essentially been not avail-
able previously,8 and we decided to assess their suitability
as silicon nucleophiles in allylic substitution reactions, par-
ticularly with emphasis on the influence of the leaving
group on the regioselectivity. Herein, we describe the appli-
cation of silicon Grignard reagents to allylic substitution re-
actions catalyzed by manganese, iron, cobalt, nickel, copper,
and palladium salts.
1
1a: R3Si = Me2PhSi
1b: R3Si = MePh2Si
1c: R3Si = Ph3Si
1d: R3Si = t-BuPh2Si 1e: R3Si = t-Bu(Me)Ph2Si 1f: R3Si = (Et2N)Ph2Si
additional salts omitted for clarity (X = Cl and Br)
Scheme 1 Copper-catalyzed allylic substitution with silicon (pro)nucle-
ophiles (top; LG: leaving group) and preparation of silicon Grignard re-
agents (bottom)
these catalysts enabled the reaction, affording the linear
allylic silane α-(E)-3a in near-quantitative yields using
NiBr2·glyme, CuI, and CuCN; however, MnBr2, FeCl3, and
CoCl2 furnished the desired product in somewhat lower
yields. Also, (E)-2a underwent silylation in the presence of
PdCl2 (entry 7). In all these reactions, the thermodynami-
cally favored α-regioisomer was formed with high α/γ ratio.
The yield remained high when 2 mol% of CuI were em-
ployed. A blank experiment without catalyst gave no con-
version (entry 8).
With the ligand-free, copper-catalyzed procedure in
hand, we probed the effect of various leaving groups [(E)-
2a–i → α-(E)-3a and γ-3a, Table 2]. Next to model substrate
(E)-2a, E-cinnamyl alcohols activated as carboxylate [as in
(E)-2b], carbonates [as in (E)-2c and (E)-2d], carbamate [as
in (E)-2e], and phosphate [as in (E)-2f] participated well in
We started our investigation by exploring the coupling
reaction of commercially available E-cinnamyl acetate [(E)-
2a] and Me2PhSiMgX 1a (Table 1). At the beginning, several
first-row metal salts were employed as catalysts (5 mol%)
without additional ligands (Table 1, entries 1–6). Any of
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–G

B
W. Xue, M. Oestreich
Feature
Synthesis
Table 1 Selected Examples of the Catalyst Screeninga
Table 2 Investigation of Leaving Groupsa
catalyst
(5 mol%)
CuI
(2 mol%)
Me2PhSiMgX
1a (1.2 equiv)
Me2PhSiMgX
1a (1.2 equiv)
SiMe2Ph
SiMe2Ph
Ph
OC(O)Me
(E)-2a
Ph
SiMe2Ph
Ph
SiMe2Ph
α-(E)-3a
Ph
LG
THF
0 °C for 1 h
THF
0 °C for 1 h
Ph
Ph
(E)-2a–i
α-(E)-3a
α/γb
γ-3a
γ-3a
Entry
Catalyst
E/Z of α-3ab
Yield (%)b of 3a
Entry LG
Substrate E/Z of α-3ab α/γb
Yield of 3a (%)b
1
2
3
4
5
6
7
8
MnBr2
FeCl3
99:1
99:1
99:1
99:1
99:1
99:1
97:3
–
96:4
98:2
99:1
98:2
99:1
99:1
95:5
–
67
1
2
3
4
5
6
7
8
9
OC(O)Me
OC(O)Ph
(E)-2a
(E)-2b
(E)-2c
(E)-2d
(E)-2e
(E)-2f
(E)-2g
(E)-2h
(E)-2i
99:1
97:3
99:1
99:1
99:1
95:5
96:4
97:3
–
99:1
99:1
96:4
97:3
99:1
94:6
91:9
96:4
–
95
79
85
CoCl2
NiBr2·glyme
CuI
81
OC(O)OMe
OC(O)OEt
OC(O)NHPh
OP(O)(OEt)2
Cl
94
94
92
95 (95)c
95
88
CuCN
PdCl2
87
80
91
none
trace
Br
93
a Reactions performed on a 0.50 mmol scale.
OH
trace
b Yield is for the mixture of isomers and was determined by GLC analysis
with tetracosane as an internal standard.
c With CuI (2 mol%).
a Reactions performed on a 0.50 mmol scale.
b Yield is for the mixture of isomers and was determined by GLC analysis
with tetracosane as an internal standard.
this silylation (Table 2, entries 1–6); yields were generally
high and α/γ ratios and E/Z selectivities were good. Cinnam-
yl halides (E)-2g and (E)-2h were also included into the sur-
vey (entries 7 and 8), again leading to high yields but to
slightly diminished regioselectivities. This outcome, that is
α-selectivity for all tested leaving groups, stands in stark
contrast to earlier findings in copper-catalyzed allylic sub-
stitution with Si–B compounds3 and silicon zinc reagents4
(see Scheme 1, top). As expected, the allylic substitution did
not occur with free cinnamyl alcohol [(E)-2i] (entry 9).
This allylic substitution was then applied to a variety of
primary allylic precursors using Me2PhSiMgX 1a (Scheme
2). In accordance with the previous observations (Tables 1
and 2), isomerically pure geranyl acetate (E)-4a and neryl
acetate (Z)-4a reacted cleanly to produce allylic silanes α-
(E)-8a and α-(Z)-8a, respectively, with exclusive preserva-
tion of the double bond geometry and excellent α/γ selec-
tivity. Allylic bromide (E)-5h underwent silylation equally
well, however, with reduced regio- and diastereoselectivi-
Biographical Sketches
Weichao Xue (born in 1989 in
Gong (Shanghai, 2015). He then
moved to Berlin to pursue doc-
toral research funded by the
also a member of the Berlin
Graduate School of Natural
Sciences and Engineering (BIG-
NSE) of the Cluster of Excellence
Unifying Concepts in Catalysis of
Pingdingshan/China)
studied
Chemistry at Henan University
(2008–2012) and Shanghai Uni-
versity (2012–2015). He ob-
tained his bachelor’s degree
with Feng Shi (Kaifeng, 2012)
and master’s degree with Hegui
China
Scholarship
Council
(2015–2019). Currently, he is a
Ph.D. candidate in the group of
Martin Oestreich at the Tech-
nische Universität Berlin. He is
the
Deutsche
Forschungs-
gemeinschaft.
Martin Oestreich (born in
1971 in Pforzheim/Germany) is
Professor of Organic Chemistry
at the Technische Universität
Berlin. He received his diploma
degree with Paul Knochel (Mar-
burg, 1996) and his doctoral de-
gree with Dieter Hoppe
(Münster, 1999). After a two-
year postdoctoral stint with Lar-
ry E. Overman (Irvine, 1999–
2001), he completed his habili-
tation with Reinhard Brückner
(Freiburg, 2001–2005) and was
appointed as Professor of Or-
ganic Chemistry at the West-
fälische
Wilhelms-Universität
Münster (2006–2011). He also
held visiting positions at Cardiff
University in Wales (2005), The
Australian National University in
Canberra (2010), and Kyoto
University (2018).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–G

C
W. Xue, M. Oestreich
Feature
Synthesis
ties. As expected, simple primary allylic electrophiles such
as 6a and 7h were converted into corresponding silylated
products in good yields.
was formed predominantly, which is different from litera-
ture precedence.4a,9 To further distinguish between anti-SN′
and syn-SN′ mechanisms, cyclic allylic carboxylate syn-16a
was synthesized and subjected to the standard condition
(Scheme 3, eq 3).10 Indeed, syn-16a was converted into
anti-17a with complete inversion of the stereochemical in-
formation. This result is consistent with related copper-
promoted allylic substitutions.3f,4a,11
Continuing with allyl methyl carbonate (18c), different
silicon Grignard reagents 1 were subjected to the standard
setup (Scheme 4). Similar to Me2PhSiMgX 1a, yields are
generally excellent for regularly used MePh2Si (from 1b)
and Ph3Si (from 1c) as well as more hindered t-BuPh2Si
(from 1d) and t-Bu(Me)PhSi (from 1e). The same result was
obtained with heteroatom-substituted silicon nucleophile
1f, containing Tamao’s silicon anion.12
CuI
(2 mol%)
Me2PhSiMgX
R1
R1
1a (1.2 equiv)
R2
LG
Me
R2
SiMe2Ph
THF
0 °C for 1 h
R3
4–7
R3
α-8a–α-11a
Me
Me
Me
Me
Me
SiMe2Ph
SiMe2Ph
α-(Z)-8a: 91%
α-(E)-8a: 87%
(α/γ = 99: 1, E/Z = 99:1)
from (E)-4a w/ LG = OC(O)Me
(α/γ = 99:1, E/Z = 1:99)
from (Z)-4a w/ LG = OC(O)Me
Me
SiMe2Ph
SiMe2Ph
Me
SiMe2Ph
Me
CuI
α-10a: 95%
(α/γ = 99:1)
α-(E)-9a: 90%
(α/γ = 82:18, E/Z = 87:13)
from (E)-5h w/ LG = Br
α-11a: 86%
from 7h w/ LG = Br
(2 mol%)
R3SiMgX
1 (1.2 equiv)
from 6a w/ LG = OC(O)Me
OC(O)OMe
SiR3
19a–f
THF
0 °C for 1 h
18c
Scheme 2 Copper-catalyzed allylic substitution of primary allylic pre-
cursors with silicon Grignard reagents. Yields are for the mixture of iso-
mers, and regiochemical and diasteromeric ratios were confirmed by 1H
NMR analysis.
SiMe2Ph
19a: 95%
SiMePh2
SiPh3
19c: 89%
19b: 91%
Sit-BuPh2
19d: 82%
Sit-Bu(Me)Ph
19e: 91%
Si(OEt)Ph2
19f: 86%a
Unlike primary allylic sources that engage in an SN path-
way with high regiocontrol, the regiochemical situation is
different for secondary substrates. Cyclic 13a was obtained
in high yield starting from the secondary bromide 12h
(Scheme 3, eq 1). Acyclic 14b was transformed into γ-(Z)-
15a with excellent γ-selectivity, corresponding to an SN′
mechanism (Scheme 3, eq 2). Interestingly, the Z-isomer
Scheme 4 Copper-catalyzed allylic substitution of allylic precursor 18c
with silicon Grignard reagents. Yields are for the mixture of isomers,
and ratios were determined by 1H NMR analysis. a EtOH/NH4Cl added
after reaction.
Considering the challenges associated with the con-
struction of silicon-stereogenic silanes,13 we attempted an
enantioselective version of this allylic substitution in the
presence of chiral ligands (Scheme 5). The reaction of race-
mic t-Bu(Me)PhSiMgX 1e and allylic precursor 18c was
chosen as a model reaction. Several catalytic systems were
tested but neither led to the asymmetric induction at the
silicon atom.
CuI
(2 mol%)
Me2PhSiMgX
1a (1.2 equiv)
(1)
THF
0 °C for 1 h
Me2PhSi
13a: 84%
Br
12h
CuI
(2 mol%)
Me2PhSiMgX
1a (1.2 equiv)
Me
Me
catalyst/ligand
(5 mol%)
t-Bu(Me)PhSiMgX
1e (1.2 equiv)
(2)
(3)
THF
0 °C for 1 h
OC(O)Ph
14b
Me2PhSi
γ-(Z)-15a: 91%
(α/γ = 3:97, E/Z = 37:63)
OC(O)OMe
Sit-Bu(Me)Ph
THF
0 °C for 1 h
18c
19e
CuI
(2 mol%)
Me2PhSiMgX
1a (1.2 equiv)
Me
Me
CuBr
(R,R)-QuinoxP
85%, 0% ee
PdCl2
(R)-methyl-BoPhoz
THF
0 °C for 1 h
61%, 0% ee
OC(O)Me
Me2PhSi
FeCl3
syn-16a
(d.r. = 96:4)
anti-17a: 95%
(d.r.= 97:3)
NiBr2·glyme
(R,R)-Ph-pybox
81%, 0% ee
(1R,2R)-N,N,N',N'-tetramethyl-
cyclohexane-1,2-diamine
73%, 0% ee
Scheme 3 Copper-catalyzed allylic substitution of secondary allylic
precursors with silicon Grignard reagents. Yields are for the mixture of
isomers, and regiochemical and diasteromeric ratios were confirmed by
1H NMR analysis.
Scheme 5 Attempted enantioselective allylic substitution of allylic car-
bonate 18c with t-Bu(Me)PhSiMgX (1e)
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–G

D
W. Xue, M. Oestreich
Feature
Synthesis
To summarize, we have disclosed here a practical meth-
od for the synthesis of allylic silanes from readily accessible
allylic precursors and easy-to-handle silicon Grignard re-
agents. Several metal salts can promote this transformation
in moderate to excellent yields without the need of added
ligand. The leaving-group scope is broad, comprising the
usual oxygen leaving groups as well as halides.
over 10 min at this temperature. R3SiMgX·2LiX solution formed was
cooled to r.t. The concentration of R3SiMgX·2LiX (~0.5 M in THF, full
conversion) was determined by titration against I2 (Knochel’s meth-
od).17 The homogeneous R3SiMgX·2LiX solution could be stored in a
Schlenk flask purged with N2 at 2–8 °C in a fridge.
The color of the R3SiMgX·2LiX solution depends on the substitution at
the silicon atom: Me2PhSiMgX·2LiX 1a (purple), MePh2SiMgX·2LiX 1b
(light purple), Ph3SiMgX·2LiX 1c (brown), t-BuPh2SiMgX·2LiX 1d
(light green), t-Bu(Me)PhSiMgX·2LiX 1e (light purple), (Et2N)Ph2SiMg-
Br·2LiX 1f (gray).
All reactions were performed in flame-dried glassware using conven-
tional Schlenk techniques under a static pressure of N2, unless other-
wise stated. Liquids and solutions were transferred with syringes. CuI
(anhyd CuI, 99%, ABCR), other metal salts, and chiral ligands were
purchased from commercial suppliers and used as received. Allylic
precursors 2a, 2g, 2h, 2i, (E)-4a, (Z)-4a, 6a, 7h, 12h, and 18c are com-
mercially available. Compounds 2b,4c 2c,4c 2e,4c 2f,4c (E)-5h,4c 14b,14
and syn-16a10 were synthesized according to the reported procedure,
and all spectroscopic data matched those reported. THF was dried
over Na or K/benzophenone and distilled prior to use. Technical grade
solvents for extraction or chromatography (cyclohexane, CH2Cl2,
EtOAc, and n-pentane) were distilled prior to use. Analytical TLC was
performed on silica gel 60 F254 glass plates from Merck. Flash column
chromatography was performed on silica gel 60 (40–63 μm, 230–400
mesh, ASTM) from Grace using the indicated solvents. 1H, 13C, and 29Si
DEPT NMR spectra were recorded in CDCl3 on Bruker AV400 and
AV500 instruments. Chemical shifts are reported in parts per million
(ppm) and are referenced to the residual solvent resonance as the in-
Copper-Catalyzed Allylic Substitution with R3SiMgX 1; General
Procedure 2 (GP 2)
A flame-dried Schlenk flask equipped with a stir bar was charged
with CuI (1.9 mg, 0.010 mmol, 2.0 mol%). The flask was evacuated and
backfilled with N2 (3 ×) followed by the addition of THF (1 mL). After
stirring for 10 min at r.t., the indicated allylic precursor (0.50 mmol,
1.0 equiv) was added, and the solution was brought to 0 °C. Then, the
corresponding R3SiMgX 1 (0.60 mmol, 1.2 equiv) was added over 1
min. After 1 h, the reaction was quenched with sat. aq NH4Cl (5 mL).
CH2Cl2 (20 mL) was added for extraction, and the CH2Cl2 layer was
washed with brine (20 mL) and H2O (20 mL). The aqueous phase was
extracted with CH2Cl2 (2 × 20 mL). The combined organic phases were
dried (anhyd Na2SO4), filtered, and the solvents were evaporated un-
der reduced pressure. Purification of the residue by flash column
chromatography on silica gel with indicated solvent as eluent afford-
ed the silylated product.
(E)-Cinnamyldimethyl(phenyl)silane [α-(E)-3a]
ternal standard (CHCl3: δ = 7.26 for 1H NMR and CDCl3: δ = 77.0 for 13
C
NMR). 29Si is referenced in compliance with the unified scale for NMR
chemical shifts as recommended by the IUPAC stating the chemical
shift relative to BF3·Et2O, CCl3F and Me4Si.15 Data are reported as fol-
lows: chemical shift, multiplicity (standard abbreviations), coupling
constant (Hz), and integration. Gas liquid chromatography (GLC) was
performed on a Varian 430-GC gas chromatograph equipped with a
Varian FactorFour Capillary column (30 m × 0.25 mm, 0.25 μm film
thickness). Enantiomeric excesses were determined by analytical
high-performance liquid chromatography (HPLC) analysis on an Agi-
lent Technologies 1290 Infinity instrument with a chiral stationary
phase using Daicel Chiralcel OJ-RH, (MeCN/H2O mixtures as solvent).
Melting points were determined using a Leica Galen III melting point
apparatus. Mass spectra (MS) were obtained from the Analytical Fa-
cility at the Institut für Chemie, Technische Universität Berlin.
Prepared from (E)-cinnamyl acetate [(E)-2a; 88 mg, 0.50 mmol] ac-
cording to GP 2 with Me2PhSiMgX 1a at 0 °C. Purification by flash col-
umn chromatography on silica gel using n-pentane afforded α-(E)-3a
as a colorless oil; yield: 120 mg (95%, contaminated with 1,1,2,2-te-
tramethyl-1,2-diphenyldisilane); Rf = 0.60 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 0.31 (s, 6 H), 1.90 (d, J = 6.5 Hz, 2 H),
6.16–6.26 (m, 2 H), 7.12–7.17 (m, 1 H), 7.24–7.26 (m, 4 H), 7.35–7.38
(m, 3 H), 7.49–7.55 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = –3.3, 23.0, 125.6, 126.3, 127.1, 127.8,
128.4, 128.9, 129.1, 133.6, 138.4, 138.5.
29Si DEPT NMR (99 MHz, CDCl3): δ = –4.1.
HRMS (EI): m/z [M]+ calcd for C17H20Si: 252.1334; found: 252.1332.
The spectroscopic data are in accordance with those reported.4c
Preparation of R3SiMgX 1; General Procedure 1 (GP 1)
(E)-Geranyldimethyl(phenyl)silane [α-(E)-8a]
At 0 °C, the required chlorosilane (24.0 mmol, 1.0 equiv) was added to
a flame-dried Schlenk flask charged with activated Li chunks (666
mg, 96.0 mmol, 4.0 equiv) suspended in THF (20 mL), and the result-
ing suspension was stirred at this temperature overnight under N2 at-
mosphere to give R3SiLi. The concentration of R3SiLi (~1.0 M in THF,
approximately 80–90% conversion) was determined by titration
against diphenylacetic acid (Kofron’s method).16 A flame-dried two-
necked round-bottomed flask charged with a magnetic stir bar and
equipped with a water condenser is connected to a Schlenk line and
purged with N2. The flask was charged with Mg turnings (292 mg,
12.0 mmol, 1.2 equiv) followed by the addition of THF (10 mL) and
was then heated to 66 °C. 1,2-Dibromoethane (1.88 g, 10.0 mmol, 1.0
equiv) was quickly added via syringe, and the reaction mixture was
heated at reflux for 3 h at high water-flow rate to afford MgBr2 (1.0 M
in THF at 66 °C). Then, the corresponding R3SiLi solution (10 mmol,
1.0 equiv) was subsequently added dropwise to the MgBr2 solution
Prepared from (E)-geranyl acetate [(E)-4a; 98 mg, 0.50 mmol] accord-
ing to GP 2 with Me2PhSiMgX 1a at 0 °C. Purification by flash column
chromatography on silica gel using n-pentane afforded α-(E)-8a as a
colorless oil; yield: 119 mg (87%); Rf = 0.65 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 0.26 (s, 6 H), 1.50 (s, 3 H), 1.61 (s, 3 H),
1.64 (d, J = 8.6 Hz, 2 H), 1.69 (s, 3 H), 1.97–2.02 (m, 2 H), 2.03–2.10 (m,
2 H), 5.09 (tt, J = 6.7, 1.4 Hz, 1 H), 5.17 (tq, J = 8.6, 1.4 Hz, 1 H), 7.31–
7.38 (m, 3 H), 7.49–7.55 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = –3.3, 15.8, 17.67, 17.69, 25.7, 26.9,
40.0, 119.6, 124.6, 127.7, 128.8, 131.2, 133.1, 133.6, 139.3.
29Si DEPT NMR (99 MHz, CDCl3): δ = –3.8.
HRMS (EI): m/z [M]+ calcd for C18H28Si: 272.1955; found: 272.1952.
The spectroscopic data are in accordance with those reported.4a
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–G

E
W. Xue, M. Oestreich
Feature
Synthesis
(Z)-Neryldimethyl(phenyl)silane [α-(Z)-8a]
29Si DEPT NMR (99 MHz, CDCl3): δ = –5.0.
HRMS (EI): m/z [M]+ calcd for C12H18Si: 190.1172; found: 190.1164.
The spectroscopic data are in accordance with those reported.18
Prepared from (Z)-neryl acetate [(Z)-4a; 98 mg, 0.50 mmol] according
to GP 2 with Me2PhSiMgX 1a at 0 °C. Purification by flash column
chromatography on silica gel using n-pentane afforded α-(Z)-8a as a
colorless oil; yield: 124 mg (91%); Rf = 0.65 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 0.26 (s, 6 H), 1.60 (s, 3 H), 1.65 (d, J =
8.6 Hz, 2 H), 1.69 (s, 6 H), 1.94–2.02 (m, 4 H), 5.07–5.13 (m, 1 H), 5.17
(t, J = 8.6 Hz, 1 H), 7.33–7.38 (m, 3 H), 7.49–7.54 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = –3.2, 17.3, 17.6, 23.4, 25.7, 26.4, 31.7,
119.7, 124.6, 127.7, 128.8, 131.4, 133.6, 133.9, 139.3.
29Si DEPT NMR (99 MHz, CDCl3): δ = –4.2.
HRMS (EI): m/z [M]+ calcd for C18H28Si: 272.1955; found: 272.1952.
The spectroscopic data are in accordance with those reported.4a
Dimethyl(cyclohex-2-en-1-yl)(phenyl)silane (13a)
Prepared from 3-bromocyclohexene (12h; 81 mg, 0.50 mmol) accord-
ing to GP 2 with Me2PhSiMgX 1a at 0 °C. Purification by flash column
chromatography on silica gel using n-pentane afforded 13a as a color-
less oil; yield: 91 mg (84%); Rf = 0.75 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 0.28 (s, 3 H), 0.29 (s, 3 H), 1.43–1.53
(m, 2 H), 1.63–1.70 (m, 1 H), 1.74–1.82 (m, 2 H), 1.88–2.03 (m, 2 H),
5.60–5.69 (m, 2 H), 7.31–7.39 (m, 3 H), 7.50–7.56 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = –4.8 (SiCH3), –4.6 (SiCH3), 22.5, 23.8,
25.0, 25.6, 125.9, 127.5, 127.7, 128.9, 133.9, 138.3.
(3-Cyclohexylallyl)dimethyl(phenyl)silane (9a)
29Si DEPT NMR (99 MHz, CDCl3): δ = –2.5.
HRMS (EI): m/z [M]+ calcd for C14H20Si: 216.1334; found: 216.1327.
The spectroscopic data are in accordance with those reported.9
Prepared from (E)-(3-bromoprop-1-en-1-yl)cyclohexane [(E)-5h; 102
mg, 0.50 mmol] according to GP 2 with Me2PhSiMgX 1a at 0 °C. Purifi-
cation by flash column chromatography on silica gel using n-pentane
afforded 9a as a colorless oil; yield: 116 mg (90%, mixture of all iso-
mers). The ratio of different isomers was confirmed by 1H NMR analy-
sis.
Dimethyl(but-2-en-1-yl)(phenyl)silane (15a)
Prepared from but-3-en-2-yl benzoate (14b; 88 mg, 0.50 mmol) ac-
cording to GP 2 with Me2PhSiMgX 1a at 0 °C. Purification by flash col-
umn chromatography on silica gel using n-pentane afforded 15a as a
colorless oil; yield: 87 mg (91%, mixture of all isomers). The ratio of
different isomers was confirmed by 1H NMR analysis; Rf = 0.70 (n-
pentane).
α-(E)-9a
Rf = 0.70 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 0.26 (s, 6 H), 1.03–1.25 (m, 5 H), 1.61–
1.71 (m, 8 H), 5.19–5.25 (m, 1 H), 5.29–5.38 (m, 1 H), 7.33–7.37 (m, 3
H), 7.49–7.54 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = –3.4, 21.6, 26.1, 26.2, 33.5, 41.0, 122.7,
γ-(Z)-15a
127.6, 128.8, 133.7, 136.0, 139.1.
29Si DEPT NMR (99 MHz, CDCl3): δ = –4.7.
HRMS (EI): m/z [M]+ calcd for C17H26Si: 258.1798; found: 258.1786.
1H NMR (500 MHz, CDCl3): δ = 0.26 (s, 6 H), 1.51 (d, J = 6.0 Hz, 3 H),
1.73 (d, J = 8.6 Hz, 2 H), 5.34–5.43 (m, 2 H), 7.33–7.38 (m, 3 H), 7.46–
7.57 (m, 2 H).
29Si DEPT NMR (99 MHz, CDCl3): δ = –3.8.
Prenyldimethy(phenyl)silane (α-10a)
γ-(E)-15a
Prepared from prenyl acetate (6a; 64 mg, 0.50 mmol) according to GP
2 with Me2PhSiMgX 1a at 0 °C. Purification by flash column chroma-
tography on silica gel using n-pentane afforded α-10a as a colorless
oil; yield: 97 mg (95%); Rf = 0.70 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 0.29 (s, 6 H), 1.61–1.68 (m, 5 H), 5.25–
5.46 (m, 2 H), 7.33–7.38 (m, 3 H), 7.46–7.57 (m, 2 H).
29Si DEPT NMR (99 MHz, CDCl3): δ = –4.6.
1H NMR (500 MHz, CDCl3): δ = 0.26 (s, 6 H), 1.50 (s, 3 H), 1.63 (d, J =
8.6 Hz, 2 H), 1.69 (s, 3 H), 5.16 (tt, J = 8.6, 1.4 Hz, 1 H), 7.31–7.38 (m, 3
H), 7.49–7.55 (m, 2 H).
The spectroscopic data are in accordance with those reported.9
anti-Dimethyl(5-methylcyclohex-2-en-1-yl)(phenyl)silane (anti-
17a)
13C NMR (125 MHz, CDCl3): δ = –3.2, 17.6, 17.7, 25.7, 119.3, 127.6,
128.8, 129.5, 133.6, 139.3.
29Si DEPT NMR (99 MHz, CDCl3): δ = –3.8.
HRMS (EI): m/z [M]+ calcd for C13H20Si: 204.1329; found: 204.1329.
The spectroscopic data are in accordance with those reported.9
Prepared from syn-5-methylcyclohex-2-en-1-yl acetate (syn-16a; 77
mg, 0.50 mmol) according to GP 2 with Me2PhSiMgX 1a at 0 °C. Purifi-
cation by flash column chromatography on silica gel using n-pentane
afforded anti-17a as a colorless oil; yield: 109 mg (95%, mixture of all
isomers). The ratio of different isomers was confirmed by 1H NMR
analysis; Rf = 0.50 (n-pentane).
Dimethyl(2-methylallyl)(phenyl)silane (α-11a)
1H NMR (500 MHz, CDCl3): δ = 0.29 (s, 3 H), 0.30 (s, 3 H), 0.88 (d, J =
6.4 Hz, 3 H), 1.41–1.48 (m, 1 H), 1.58–1.72 (m, 3 H), 1.82–1.87 (m, 1
H), 2.01–2.07 (m, 1 H), 5.55–5.59 (m, 1 H), 5.61–5.65 (m, 1 H), 7.33–
7.37 (m, 3 H), 7.49–7.54 (m, 2 H).
13C NMR (125 MHz, CDCl3): δ = –4.13 (SiCH3), –4.08 (SiCH3), 21.2,
24.9, 26.2, 31.2, 33.0, 124.3, 127.2, 127.7, 128.9, 133.9, 138.5.
29Si DEPT NMR (99 MHz, CDCl3): δ = –2.6.
HRMS (EI): m/z [M]+ calcd for C15H22Si: 230.1491; found: 230.1492.
The spectroscopic data are in accordance with those reported.3f
Prepared from 3-bromo-2-methylpropene (7h; 68 mg, 0.50 mmol)
according to GP 2 with Me2PhSiMgX 1a at 0 °C. Purification by flash
column chromatography on silica gel using n-pentane afforded α-11a
as a colorless oil; yield: 82 mg (86%); Rf = 0.70 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 0.32 (s, 6 H), 1.62 (s, 3 H), 1.78 (s, 2 H),
4.47–4.50 (m, 1 H), 4.59–4.62 (m, 1 H), 7.32–7.39 (m, 3 H), 7.50–7.57
(m, 2 H).
13C NMR (125 MHz, CDCl3): δ = –2.9, 25.2, 25.7, 108.8, 127.7, 128.9,
133.6, 139.1, 143.3.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–G

F
W. Xue, M. Oestreich
Feature
Synthesis
Allyldimethyl(phenyl)silane (19a)
Allyl(tert-butyl)(methyl)(phenyl)silane (19e)
Prepared from allyl methyl carbonate (18c; 58 mg, 0.50 mmol) ac-
cording to GP 2 with Me2PhSiMgX 1a at 0 °C. Purification by flash col-
umn chromatography on silica gel using n-pentane afforded 19a as a
colorless oil; yield: 84 mg (95%); Rf = 0.65 (n-pentane).
Prepared from allyl methyl carbonate (18c; 58 mg, 0.50 mmol) ac-
cording to GP 2 with t-Bu(Me)PhSiMgX 1e at 0 °C. Purification by
flash column chromatography on silica gel using n-pentane afforded
19e as a colorless oil; yield: 99 mg (91%); Rf = 0.65 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 0.29 (s, 6 H), 1.76 (d, J = 8.6 Hz, 2 H),
4.82–4.92 (m, 2 H), 5.73–5.83 (m, 1 H), 7.33–7.39 (m, 3 H), 7.49–7.55
(m, 2 H).
13C NMR (125 MHz, CDCl3): δ = –3.5, 23.7, 113.4, 127.7, 129.0, 133.6,
134.6, 138.7.
HPLC-analysis: OJ-RH (Dacial), MeCN/H2O = 65:35, 0.2 mL/min, λ =
210 nm, tR = 47.9, 51.1 min.
1H NMR (500 MHz, CDCl3): δ = 0.28 (s, 3 H), 0.90 (s, 9 H), 1.81–1.87
(m, 1 H), 1.93–1.99 (m, 1 H), 4.78–4.82 (m, 1 H), 4.86–4.92 (m, 1 H),
5.71–5.82 (m, 1 H), 7.31–7.44 (m, 3 H), 7.48–7.55 (m, 2 H).
29Si DEPT NMR (99 MHz, CDCl3): δ = –4.7.
13C NMR (125 MHz, CDCl3): δ = –8.6, 17.4, 18.7, 26.8, 113.6, 127.5,
128.9, 134.7, 135.0, 136.0.
29Si DEPT NMR (99 MHz, CDCl3): δ = 1.5.
HRMS (EI): m/z [M]+ calcd for C14H22Si: 218.1485; found: 218.1482.
HRMS (EI): m/z [M]+ calcd for C11H16Si: 176.1021; found: 176.1018.
The spectroscopic data are in accordance with those reported.18
Allyl(methyl)diphenylsilane (19b)
Allyl(ethoxy)diphenylsilane (19f)
Prepared from allyl methyl carbonate (18c; 58 mg, 0.50 mmol) ac-
cording to GP 2 with MePh2SiMgX 1b at 0 °C. Purification by flash col-
umn chromatography on silica gel using n-pentane afforded 19b as a
colorless oil; yield: 108 mg (91%); Rf = 0.55 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 0.56 (s, 3 H), 2.08 (d, J = 8.6 Hz, 2 H),
4.85–4.95 (m, 2 H), 5.75–5.85 (m, 1 H), 7.33–7.40 (m, 6 H), 7.51–7.56
(m, 4 H).
13C NMR (125 MHz, CDCl3): δ = –4.8, 22.1, 114.2, 127.8, 129.2, 134.1,
134.5, 136.6.
29Si DEPT NMR (99 MHz, CDCl3): δ = –9.6.
HRMS (EI): m/z [M]+ calcd for C16H18Si: 238.1178; found: 238.1172.
The spectroscopic data are in accordance with those reported.19
Prepared from allyl methyl carbonate (18c; 58 mg, 0.50 mmol) ac-
cording to GP 2 with (Et2N)Ph2SiMgX 1f at 0 °C. Afterwards, anhyd
EtOH (1 mL) and NH4Cl (55 mg, 2.0 mmol) was added, and the reac-
tion mixture was stirred overnight. Purification by flash column chro-
matography on silica gel using n-pentane afforded 19f as a colorless
oil; yield: 115 mg (86%); Rf = 0.30 (n-pentane).
1H NMR (500 MHz, CDCl3): δ = 1.22 (t, J = 7.1 Hz, 3 H), 2.18 (dt, J = 7.8,
1.4 Hz, 2 H), 3.81 (q, J = 7.1 Hz, 2 H), 4.88–4.98 (m, 2 H), 5.80–5.90 (m,
1 H), 7.35–7.44 (m, 6 H), 7.59–7.64 (m, 4 H).
13C NMR (125 MHz, CDCl3): δ = 18.4, 21.9, 59.5, 115.0, 127.8, 129.9,
133.1, 134.70, 134.73.
29Si DEPT NMR (99 MHz, CDCl3): δ = –8.6.
HRMS (EI): m/z [M – C3H5]+ calcd for C14H15OSi: 227.0887; found:
227.0889.
The spectroscopic data are in accordance with those reported.21
Allyltriphenylsilane (19c)
Prepared from allyl methyl carbonate (18c; 58 mg, 0.50 mmol) ac-
cording to GP 2 with Ph3SiMgX 1c at 0 °C. Purification by flash column
chromatography on silica gel using n-pentane afforded 19c as a white
solid; yield: 134 mg (89%); mp 90.0–90.8 °C; Rf = 0.35 (n-pentane).
Funding Information
1H NMR (500 MHz, CDCl3): δ = 2.40 (d, J = 7.8 Hz, 2 H), 4.87–4.98 (m, 2
H), 5.81–5.92 (m, 1 H), 7.33–7.44 (m, 9 H), 7.50–7.55 (m, 6 H).
13C NMR (125 MHz, CDCl3): δ = 21.8, 115.1, 127.8, 129.5, 133.8, 134.6,
135.7.
This research was supported by the China Scholarship Council (pred-
octoral fellowship to W.X., 2015–2019) and the Deutsche Forschungs-
gemeinschaft (Oe 249/15-1). M.O. is indebted to the Einstein
29Si DEPT NMR (99 MHz, CDCl3): δ = –13.8.
Foundation Berlin for an endowed professorship.
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HRMS (EI): m/z [M]+ calcd for C21H20Si: 300.1334; found: 300.1330.
The spectroscopic data are in accordance with those reported.19
Supporting Information
Supporting information for this article is available online at
Allyl(tert-butyl)diphenylsilane (19d)
https://doi.org/10.1055/s-0037-1610309.
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Prepared from allyl methyl carbonate (18c; 58 mg, 0.50 mmol) ac-
cording to GP 2 with t-BuPh2SiMgX 1d at 0 °C. Purification by flash
column chromatography on silica gel using n-pentane afforded 19d as
a colorless oil; yield: 115 mg (82%); Rf = 0.65 (n-pentane).
References
1H NMR (500 MHz, CDCl3): δ = 1.07 (s, 9 H), 2.08 (dt, J = 8.6, 1.4 Hz, 2
H), 4.78–4.82 (m, 1 H), 4.88–4.93 (m, 1 H), 5.71–5.82 (m, 1 H), 7.33–
7.41 (m, 6 H), 7.59–7.64 (m, 4 H).
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–G

G
W. Xue, M. Oestreich
Feature
Synthesis
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2018, 50, A–G