Monodentate chiral N-heterocyclic carbene-palladium-catalyzed asymmetric Suzuki-Miyaura and Kumada coupling

Article abstract of DOI:10.1055/s-0033-1338864

N-Heterocyclic carbene ligands derived from C₂-symmetric diamine with naphthyl side chains are introduced as chiral monodentate ligands, and their palladium complexes (NHC)Pd(cin)Cl are prepared. These compounds exist as a mixture of diastereomers, and the palladium complexes can be successfully separated. When used in the asymmetric Suzuki-Miyaura and Kumada coupling, chiral biaryls can be obtained in high yield and moderate selectivity. Georg Thieme Verlag Stuttgart New York.

Full text of DOI:10.1055/s-0033-1338864

CLUSTER
▌1215
cluster
Monodentate Chiral N-Heterocyclic Carbene–Palladium-Catalyzed Asymme-
tric Suzuki–Miyaura and Kumada Coupling
NHC–Pd-Catalyzed Asymmetric Suzuki–Miyaura Coupling
Linglin Wu,a,b Alvaro Salvador,a,b Arnold Ou,b Ming Wen Shi,b Brian W. Skelton,c Reto Dorta*a,b
a
Organisch-chemisches Institut, Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
b
School of Chemistry and Biochemistry, University of Western Australia, 35 Stirling Highway, 6009 Crawley, Australia
Fax +61(8)64887330; E-mail: reto.dorta@uwa.edu.au
c
Centre for Microscopy, Characterisation and Analysis, University of Western Australia, 6009 Crawley, Australia
Received: 01.05.2013; Accepted after revision: 08.05.2013
line-2,3-diyl)-based phosphine served as highly enantio-
Abstract: N-Heterocyclic carbene ligands derived from C2-sym-
selective ligand (up to 95% ee) in the Suzuki–Miyaura
metric diamine with naphthyl side chains are introduced as chiral
coupling reaction to form axially chiral biarylphosphinic
monodentate ligands, and their palladium complexes
(NHC)Pd(cin)Cl are prepared. These compounds exist as a mixture
esters.10i
of diastereomers, and the palladium complexes can be successfully
separated. When used in the asymmetric Suzuki–Miyaura and
attention in the passed two decades and are now consid-
Kumada coupling, chiral biaryls can be obtained in high yield and
N-Heterocyclic carbenes (NHC) have received enormous
ered as ligands of choice for various (asymmetric) catalyt-
moderate selectivity.
ic reactions.11 In the context of cross-coupling reactions,
Key words: monodentate chiral NHC, palladium, asymmetric
catalysis, Suzuki–Miyaura coupling, Kumada coupling
monodentate NHC have been intensively studied by dif-
ferent research groups and they have demonstrated re-
markably
high
activity
promoting
these
transformations.11c,12 The capacity of NHC has been illus-
trated not only in cross-coupling reactions but also in dif-
ferent asymmetric transformations.13 However, little
attention has been given to asymmetric cross-coupling re-
actions using chiral NHC as the ligands. To the best of our
knowledge, there are only two reports to date detailing the
use of chiral NHC ligands to promote asymmetric cross-
coupling reactions. In 2010, Labande disclosed the first
example of asymmetric Suzuki–Miyaura coupling with
palladium complexes bearing chelating, planar chiral fer-
rocenyl phosphine–NHC ligands.14 However, only low
enantioselectivities were achieved (less than 40% ee) in
this transformation using aryl bromides as the electro-
philes. Recently, Zhang and co-workers prepared two pal-
ladium complexes of a chelating NHC ligand derived
from 1,2-cyclohexanediamine and employed them to cat-
alyze the asymmetric Suzuki–Miyaura couplings of aryl
bromides with arylboronic acids in good yields and mod-
erate enantioselectivities (up to 61% ee).15 Up to now,
there are no reports on asymmetric cross-coupling using
monodentate NHC as the ligand, and NHC ligands have
so far not been used for the asymmetric Kumada cross-
coupling (Scheme 1).
Axially chiral biaryls are common and decisive structure
motifs in bioactive compounds1 and form the basis for
some of the most effective chiral ligands, such as the well-
known BINAP2 and BINOL3 ligands. Modern cross-
coupling reactions4 (i.e., Suzuki–Miyaura coupling and
Kumada coupling) have opened a direct and convenient
route to such axially chiral biaryl molecules, and these
coupling reactions are particularly valuable for obtaining
unsymmetric biaryls, which cannot be readily obtained by
other catalytic asymmetric reactions. The first successful
atroposelective cross-coupling was reported by Hayashi
in the late 1980s using aryl halides and aryl Grignard re-
agents as the coupling partners (Kumada coupling) and
chiral ferrocenylphosphine/Ni as the catalyst.5 Following
this seminal work, related phosphine ligands were exam-
ined in the Kumada coupling but gave only low to moder-
ate enantioselectivities.6 Until now, there are various
reports of asymmetric Suzuki–Miyaura and Kumada cou-
pling using chiral phosphine ligands.7 The earliest reports
of asymmetric cross-coupling of aryl halides and aryl bo-
ron reagents were disclosed by Cammidge8 and
Buchwald9 using ferrocene- and binaphthyl-derived phos-
phines, respectively. Since then, a variety of chiral ligands
have been examined for the asymmetric Pd-catalyzed Su-
zuki–Miyaura coupling reaction.10 Remarkably, in 2008
Lassaletta disclosed a new class of chiral bishydrazone li-
gands derived from C2-symmetric hydrazines for the
asymmetric Suzuki–Miyaura coupling, providing the bia-
ryls in high selectivities (up to 98% ee).10e Recently,
Suginome showed that a helically chiral poly(quinoxa-
Our group has developed a new type of monodentate
NHC ligands with a chiral N-heterocycle and naphthyl
side chains. These compounds exist as a mixture of diaste-
reomers and their palladium complexes showed different
selectivity in asymmetric intramolecular α-arylation reac-
tions.16 Recently, we were able to access a single NHC
diastereomer by introduction of a cyclooctyl group onto
the 2-position of the naphthyl side chain, and the palladi-
um cinnamyl complex (Scheme 2, complex A) gave ex-
cellent results in a new α-arylation protocol that allows the
direct synthesis of 3-aryl-3-fluoro-oxindoles.17
SYNLETT 2013, 24, 1215–1220
Advanced online publication: 17.05.2013
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
DOI: 10.1055/s-0033-1338864; Art ID: ST-2013-R0404-C
© Georg Thieme Verlag Stuttgart · New York

1216
L. Wu et al.
CLUSTER
X
B(OH)2
R4
R1
R2
R1
R3
R2
R4
R3
Pd/chiral monodentate NHC?
conditions
+
X
MgBr
R1
R2
R1
R3
R2
R4
R3
R4
Pd/chiral NHC?
conditions
+
X = Cl, Br
Scheme 1 Asymmetric Suzuki–Miyaura and Kumada coupling
Scheme 2 NHC–Pd complexes tested in this study
When the complex (Ra,Ra)-A was used to catalyze the light, the (Sa,Sa)-C diastereomer, which orients the 2-
Suzuki–Miyaura coupling between 1-bromo-2-me- alkyl chains of the naphthyl wingtips opposite to the phe-
thoxynaphthalene and 1-naphthylboronic acid, high nyl groups of the N-heterocyclic backbone, promoted this
yields of the product were obtained. However, only low reaction efficiently affording the tri-ortho-substituted bia-
enantioselectivity (25%) was observed (Table 1, entry 1). ryl in excellent yield (91%) and moderately good enanti-
We therefore decided to modify the structure of the NHC oselecvitity (60% ee, Table 1, entry 4). When 1-bromo-2-
ligand. When the bulky and acyclic 4-heptyl moiety was methylnaphthalene instead of 1-bromo-2-methoxynaph-
introduced to the 2-position of the naphthyl group, a new thalene was used, a slightly lower ee was observed (Table
NHC salt (Scheme 2, compound B) was generated, and a 1, entry 5). Screening of the solvent revealed that toluene
mixture of three diastereomers were observed in a ratio of is the best choice and that ethereal solvents and dichloro-
38:28:34 (Sa,Sa/Ra,Ra/Ra,Sa). While the separation of methane gave lower enantioselectivities (Table 1, entries
these three diastereomeric salts turned out to be impossi- 6–9). The catalyst showed little reactivity in hexane (Ta-
ble, we successfully separated the corresponding palladi- ble 1, entry 10). Optimization of the base showed that
um cinnamyl complexes C via silica gel chromatography. NaOt-Bu gave much lower yields and enantiomeric ex-
The structure of one of the isomers [(Ra,Sa)-C] was un- cesses compared to KOt-Bu (Table 1, entry 11), while the
ambiguously confirmed by single-crystal X-ray crystal- use of LiOt-Bu and KHMDS led to the recovery of the
lography.18 All of the three complexes were starting material (Table 1, entries 12 and 13).
independently tested in the asymmetric Suzuki–Miyaura
With the optimized conditions in hand [2 mol% of the cat-
coupling. To our surprise, the Ra,Ra isomer [(Ra,Sa)-C],
alyst (Sa,Sa)-C, toluene as solvent and KOt-Bu as base],
which was the isomer showing the best enantiomeric dis-
different substrates were tested, and the results are sum-
marized in Table 2. In most of the cases, excellent yields
were obtained by using 2 mol% of the (Sa,Sa)-C precata-
lyst. The coupling of 1-bromo-2-methylnaphthalene and
crimination in the intramolecular asymmetric α-arylation
giving oxindoles,16a,b,17 again gave low enantioselectivity
(Table 1, entry 2). In contrast, isomer (Ra,Sa)-C showed
increased reactivity in this transformation while giving es-
1-naphthylboronic acid afforded the product in excellent
sentially racemic product (Table 1, entry 3). To our de-
Synlett 2013, 24, 1215–1220
© Georg Thieme Verlag Stuttgart · New York

CLUSTER
NHC–Pd-Catalyzed Asymmetric Suzuki–Miyaura Coupling
1217
Table 1 Optimization of Reaction Conditions for the Suzuki–Miyaura Couplinga
Br
B(OH)2
R
Pd cat. (2 mol%)
R
+
base, solvent (0.125 M)
r.t., 16 h
R = OMe, Me
(1.5 equiv)
Entry
Pd catalyst
R
Base
Solvent
Yield (%)b
ee (%)c
1
2
A
OMe
OMe
OMe
OMe
Me
KOt-Bu
KOt-Bu
KOt-Bu
KOt-Bu
KOt-Bu
KOt-Bu
KOt-Bu
KOt-Bu
KOt-Bu
KOt-Bu
NaOt-Bu
LiOt-Bu
KHMDS
toluene
toluene
toluene
toluene
toluene
THF
90
55
25
22
8
(Ra,Ra)-C
(Ra,Sa)-C
(Sa,Sa)-C
(Sa,Sa)-C
(Sa,Sa)-C
(Sa,Sa)-C
(Sa,Sa)-C
(Sa,Sa)-C
(Sa,Sa)-C
(Sa,Sa)-C
(Sa,Sa)-C
(Sa,Sa)-C
3
93
4
91
60
51
40
50
37
35
n.d.
35
n.d.
n.d.
5
94
6
Me
92
7
Me
DME
83
8
Me
dioxane
CH2Cl2
hexane
toluene
toluene
toluene
94
9
Me
92
10
11
12
13
Me
<20
43
Me
Me
<15
<10
Me
a Conditions: aryl bromide (0.125 mmol, 1 equiv), 1-naphthylboronic acid (1.5 equiv), base (2.5 equiv), Pd complex (2 mol%), solvent (1 mL),
25 °C, 16 h.
b Isolated yield.
c Determined by HPLC.
yield and 51% ee (Table 2, entry 1). Increasing the amount catalyst (Sa,Sa)-C promoted the asymmetric Kumada
of boronic acid, base, and catalyst loading decreased the coupling smoothly giving the chiral biaryls in good yields
reactivity and selectivity (Table 2, entry 2). The use of but relatively low selectivities (Table 3). For instance, the
(Ra,Ra)-C or the in situ generated catalyst {mixture of in situ generated 2-methoxynaphthylmagnesium bromide
isomers of B with [Pd(cinnamyl)(μ-Cl)]2} lowered the en- is coupled with 1-bromonaphthalene at room temperature
antioselectivity (Table 2, entries 3 and 4) as well. The aryl affording the chiral binaphthyl product in 81% yield and
chloride analogue could serve as the electrophile, al- 48% ee (Table 3, entry 1). In this case, switching the nu-
though the yields and enantiomeric exesses decreased cleophile and electrophile with respect to each other re-
compared to the bromides (Table 2, entry 1 vs. 5, 7 vs. 8). duced the reactivity and selectivity, but again the absolute
Switching the electrophile and nucleophile of entry 1 had configuration of the product was maintained, as already
no effect on the yield and the enantiomeric exess de- seen in the Suzuki–Miyaura coupling mentioned above
creased only marginally from 51% to 46% (Table 2, entry (Table 3, entry 2). Using aryl chloride retained the selec-
1 vs. 6). Interestingly, the absolute configuration of the tivity, although the yield of the product decreased dramat-
product was retained (both S).10e Introduction of a substit- ically from 81% to 40% (Table 3, entry 3 vs. 1). Replacing
uent on the 7-position of the naphthalene electrophile 1-bromonaphthalene with 2-methylphenylbromide low-
seems to be very deleterious to the selectivity (Table 2, ered both the yield and enantiomeric excess (Table 3, en-
entry 7 vs. 9). One example of ortho-substituted phenyl- try 4 vs. 1). The yield was improved with slight heating
bromide was examined, and the product 2-methyl-1-(2- (50 °C), however, with a deleterious effect on the enanti-
methylphenyl)naphthalene was obtained in good yield oselectivity (31% ee, Table 3, entry 5). Changing the elec-
(83%) but low enantiomeric excess (28%, Table 2, entry trophile to the corresponding chloride did not alter the
10).19
outcome in terms of reactivity and selectivity (Table 3, en-
try 6). When a sterically more demanding nucleophile was
employed (2-methylnaphthylmagnesium bromide), the
enantioselectivity decreased (27% ee, Table 3, entry 7 vs.
1).
With the promising results from the asymmetric Suzuki–
Miyaura coupling in hand, we turned our attention to an-
other versatile coupling – the Kumada coupling. Our pre-
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 1215–1220

1218
L. Wu et al.
CLUSTER
In conclusion, we report the synthesis of a new NHC li- es incorporating these ligands were obtained after simple
gand with a chiral N-heterocycle and naphthyl side chains chromatography. One of the resulting compounds
substituted by 4-heptyl groups in the 2-position. The im- [(Sa,Sa)-C] was tested in the asymmetric Suzuki–Miyau-
idazolinium salts showed the existence of three different ra and Kumada coupling that formed chiral biaryls in high
isomers in such NHC structures. Pure palladium complex- yields and low to moderate enantioselectivities. This rep-
Table 2 Substrate Scope of the Asymmetric Suzuki–Miyaura Couplinga
(Sa,Sa)-C (2 mol%)
ArB(OH)2
ArAr
ArX
+
KOt-Bu, toluene
r.t., 16 h
Entry
ArX
ArB(OH)2
Ar–Ar
Yield (%)b
ee (%)c
Br
B(OH)2
1
2
3
4
94
90
85
95
51 (S)
43 (S)d
30 (S)e
27 (S)f
Me
Me
Me
B(OH)2
Cl
Br
Br
Me
5
6
66
93
91
70
86
83
33 (S)
46 (S)
60 (R)
50 (R)
12
B(OH)2
Me
Me
B(OH)2
B(OH)2
B(OH)2
B(OH)2
OMe
OMe
7
Cl
OMe
OMe
8
Br
MeO
OMe
MeO
OMe
9
Br
Me
Me
Me
Me
10
28
a Conditions: ArX (0.125 mmol, 1 equiv), ArB(OH)2 (1.5 equiv), KOt-Bu (2.5 equiv), (Sa,Sa)-C (2 mol%), toluene (1 mL), 25 °C, 16 h.
b Isolated yield.
c Determined by HPLC. The absolute configuration was assigned by comparison with literature data.
d ArB(OH)2 (2.5 equiv), KOt-Bu (3.5 equiv), (Sa,Sa)-C (5 mol%).
e (Ra,Ra)-C (2 mol%), 50 °C.
f B (5 mol%), [Pd(cinnamyl) (μ-Cl)]2 (2.5 mol%).
Synlett 2013, 24, 1215–1220
© Georg Thieme Verlag Stuttgart · New York

CLUSTER
NHC–Pd-Catalyzed Asymmetric Suzuki–Miyaura Coupling
1219
resents the first example of asymmetric coupling giving steric crowding and/or might not be able to accommodate
chiral biaryls by using a monodentate NHC ligand. That the substrates via π-stacking as proposed by Lassaletta
precatalysts [(Ra,Ra)-A] and [(Ra,Ra)-C] failed in this re- and co-workers.10e Studies aimed at increasing the enantio-
action warrants further mechanistic studies and might be selectivities via fine-tuning of the NHC structure are
due to the fact that these NHC structures show a higher under way.
Table 3 Substrate Scope of the Asymmetric Kumada Couplinga
(Sa,Sa)-C (2 mol%)
+
ArX
ArAr
ArMgBr
toluene
16 h
Entry
1
ArMgBr
ArX
Temp. (°C)
Ar–Ar
Yield (%)b
ee (%)c
MgBr
Br
Br
Cl
OMe
OMe
r.t.
81
48 (R)
MgBr
MgBr
MgBr
MgBr
MgBr
MgBr
OMe
2d
50
50
r.t.
50
50
r.t.
72
40
51
71
77
78
37 (R)
41 (R)
39
OMe
OMe
OMe
3
Br
Br
Cl
OMe
Me
OMe
OMe
OMe
Me
Me
Me
4
OMe
Me
5d
6d
7
31
OMe
Me
Me
Br
31
Me
27 (S)
a Conditions: ArMgBr (0.25 mmol, 1 equiv), ArX (1.0 or 2.0 equiv), (Sa,Sa)-C (2 mol%), THF (2 ml), 16 h.
b Isolated yield.
c Determined by HPLC. The absolute configuration was assigned by comparison with literature data.
d Conditions: 2.0 equiv of halide were used.
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 1215–1220

1220
L. Wu et al.
CLUSTER
Org. Lett. 2010, 12, 5546. (j) Yamamoto, T.; Akai, Y.;
Acknowledgment
Nagata, Y.; Suginome, M. Angew. Chem. Int. Ed. 2011, 50,
8844. (k) Tang, W.; Patel, N. D.; Xu, G.; Xu, X.; Savoie, J.;
Ma, S.; Hao, M. H.; Keshipeddy, S.; Capacci, A. G.; Wei,
X.; Zhang, Y.; Gao, J. J.; Li, W.; Rodriguez, S.; Lu, B. Z.;
Yee, N. K.; Senanayake, C. H. Org. Lett. 2012, 14, 2258.
(11) (a) Nolan, S. P. N-Heterocyclic Carbenes in Synthesis;
Wiley-VCH: Weinheim, 2006. (b) N-Heterocyclic Carbenes
in Transition Metal Catalysis; Vol. 21; Glorius, F., Ed.;
Springer: Berlin, 2007. (c) Diez-Gonzalez, S.; Nolan, S. P.
Chem. Rev. 2009, 109, 3612. (d) N-Heterocyclic Carbenes
in Transition Metal Catalysis and Organocatalysis; Vol. 32;
Cazin, C. S. J., Ed.; Springer: Dordrecht, 2010.
(12) (a) Kantchev, E. A. B.; O’Brien, C. J.; Organ, M. G. Angew.
Chem. Int. Ed. 2007, 46, 2768. (b) Marion, N.; Nolan, S. P.
Acc. Chem. Res. 2008, 41, 1440. (c) Würtz, S.; Glorius, F.
Acc. Chem. Res. 2008, 41, 1523.
(13) For reviews, see: (a) César, V.; Bellemin-Laponnaz, S.;
Gade, L. H. Chem. Soc. Rev. 2004, 33, 619. (b) Wang, F.;
Liu, L.; Wang, W.; Li, S.; Shi, M. Coord. Chem. Rev. 2012,
256, 804. (c) Benhamou, L.; Chardon, E.; Lavigne, G.;
Bellemin-Laponnaz, S.; César, V. Chem. Rev. 2011, 111,
2705.
L.W. thanks the Swiss National Foundation (SNF) for a PhD fel-
lowship. The University of Zurich and the University of Western
Australia are acknowledged for funding. Access to the facilities at
the Centre for Microscopy, Characterisation and Analysis, Univer-
sity of Western Australia, is kindly acknowledged.
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett.SnoIufproig
m
iotSrat
ungIifoop
r
t
References
(1) Bringmann, G.; Günther, C.; Ochse, M.; Schupp, O.; Tasler,
S. Biaryls in Nature In Progess in the Chemistry of Organic
Natural Products; Vol. 82; Herz, W.; Falk, H.; Kirby, G. W.;
Moore, R. E., Eds.; Springer: Vienna, 2001, 1–249.
(2) (a) Berthod, M.; Mignani, G.; Woodward, G.; Lemaire, M.
Chem. Rev. 2005, 105, 1801. (b) Li, Y. M.; Kwong, F. Y.;
Yu, W. Y.; Chan, A. S. C. Coord. Chem. Rev. 2007, 251,
2119.
(3) (a) Chen, Y.; Yekta, S.; Yudin, A. K. Chem. Rev. 2003, 103,
3155. (b) Brunel, J. M. Chem. Rev. 2007, 107, PR1.
(4) de Meijere, A.; Diederich, F. In Metal-Catalyzed Cross-
Coupling Reactions; Wiley-VCH: Weinheim, 2004, 2nd ed..
(5) (a) Hayashi, T.; Hayashizaki, K.; Kiyoi, T.; Ito, Y. J. Am.
Chem. Soc. 1988, 110, 8153. (b) Hayashi, T.; Hayashizaki,
K.; Ito, Y. Tetrahedron Lett. 1989, 30, 215.
(6) (a) Frejd, T.; Klingstedt, T. Acta Chem. Scand. 1989, 43,
670. (b) Terfort, A.; Brunner, H. J. Chem. Soc., Perkin
Trans. 1 1996, 1467. (c) Dahlenburg, L.; Kurth, V. Inorg.
Chim. Acta 2001, 319, 176.
(7) For selected reviews, see: (a) Bringmann, G.; Mortimer, A.
J. P.; Keller, P. A.; Gresser, M. J.; Garner, J.; Breuning, M.
Angew. Chem. Int. Ed. 2005, 44, 5384. (b) Wallace, T. W.
Org. Biomol. Chem. 2006, 4, 3197. (c) Ogasawara, M.;
Watanabe, S. Synthesis 2009, 1761.
(14) Debono, N.; Labande, A.; Manoury, E.; Daran, J.; Poli, R.
Organometallics 2010, 29, 1879.
(15) Shigeng, G.; Tang, J.; Zhang, D.; Wang, Q.; Chen, Z.; Weng,
L. J. Organomet. Chem. 2012, 700, 223.
(16) (a) Luan, X.; Mariz, R.; Robert, C.; Gatti, M.; Blumentritt,
S.; Linden, A.; Dorta, R. Org. Lett. 2008, 10, 5569. (b) Luan,
X.; Wu, L.; Drinkel, E.; Mariz, R.; Gatti, M.; Dorta, R. Org.
Lett. 2010, 12, 1912. For other work on such naphthyl-
substituted NHC, see: (c) Luan, X.; Mariz, R.; Gatti, M.;
Costabile, C.; Poater, A.; Cavallo, L.; Linden, A.; Dorta, R.
J. Am. Chem. Soc. 2008, 130, 6848. (d) Gatti, M.; Vieille-
Petit, L.; Luan, X.; Mariz, R.; Drinkel, E.; Linden, A.; Dorta,
R. J. Am. Chem. Soc. 2009, 131, 9498. (e) Vieille-Petit, L.;
Luan, X.; Gatti, M.; Blumentritt, S.; Linden, A.; Clavier, H.;
Nolan, S. P.; Dorta, R. Chem. Commun. 2009, 3783.
(f) Vieille-Petit, L.; Luan, X.; Mariz, R.; Blumentritt, S.;
Linden, A.; Dorta, R. Eur. J. Inorg. Chem. 2009, 1861.
(g) Vieille-Petit, L.; Clavier, H.; Linden, A.; Blumentritt, S.;
Nolan, S. P.; Dorta, R. Organometallics 2010, 29, 775.
(h) Wu, L.; Drinkel, E.; Gaggia, F.; Capolicchio, S.; Linden,
A.; Falivene, L.; Cavallo, L.; Dorta, R. Chem. Eur. J. 2011,
17, 12886. (i) Gatti, M.; Wu, L.; Drinkel, E.; Gaggia, F.;
Blumentritt, S.; Linden, A.; Dorta, R. ARKIVOC 2011, (vi),
176.
(17) Wu, L.; Falivene, L.; Drinkel, E.; Grant, S.; Linden, A.;
Cavallo, L.; Dorta, R. Angew. Chem. Int. Ed. 2012, 51, 2870.
(18) CCDC 936764 [(Ra,Sa)-C)] contains the supplementary
crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge
Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
(19) The Suzuki–Miyaura coupling using the corresponding aryl
iodide (2-iodotoluene) gave very similar results (81% yield,
27% ee).
(8) (a) Cammidge, A. N.; Crépy, K. V. L. Chem. Commun.
2000, 1723. (b) Cammidge, A. N.; Crépy, K. V. L.
Tetrahedron 2000, 1723.
(9) Yin, J.; Buchwald, S. L. J. Am. Chem. Soc. 2000, 122,
12051.
(10) For selected examples, see: (a) Mikami, K.; Miyamoto, T.;
Hatano, M. Chem. Commun. 2004, 2082. (b) Willis, M. C.;
Powell, L. H. W.; Claverie, C. K.; Watson, S. J. Angew.
Chem. Int. Ed. 2004, 43, 1249. (c) Genov, M.; Almrín, A.;
Espinet, P. Chem. Eur. J. 2006, 12, 9346. (d) Sawai, K.;
Tatumi, R.; Nakahodo, T.; Fujihara, H. Angew. Chem. Int.
Ed. 2008, 47, 6017. (e) Bermejo, A.; Ros, A.; Fernandez, R.;
Lassaletta, J. M. J. Am. Chem. Soc. 2008, 130, 15798.
(f) Uozumi, Y.; Matsuura, Y.; Arakawa, T.; Yamada, Y. M.
A. Angew. Chem. Int. Ed. 2009, 48, 2708. (g) Shen, X.;
Jones, G. O.; Watson, D. A.; Bhayana, B.; Buchwald, S. L.
J. Am. Chem. Soc. 2010, 132, 11278. (h) Urbaneja, X.;
Mercier, A.; Besnard, C.; Kundig, E. P. Chem. Commun.
2011, 47, 3739. (i) Zhang, S.; Wang, Z.; Xu, M.; Lin, G.
Synlett 2013, 24, 1215–1220
© Georg Thieme Verlag Stuttgart · New York
graphical abstract