RhIII-Catalyzed Olefination of 2-Aryloxypyridines Using 2-Pyridyloxyl as the Removable Directing Group

Article abstract of DOI:10.1002/ejoc.201500530

An efficient Rh^III-catalyzed trans selective ortho-olefination of 2-aryloxypyridines has been developed. The catalytic system is very effective for olefination of differently substituted 2-aryloxypyridines with acrylates, acrylamide and styrene

Full text of DOI:10.1002/ejoc.201500530

FULL PAPER
DOI: 10.1002/ejoc.201500530
RhIII-Catalyzed Olefination of 2-Aryloxypyridines Using 2-Pyridyloxyl as the
Removable Directing Group
Arun Jyoti Borah,[a] Guobing Yan,*[a] and Lianggui Wang[a]
Keywords: Homogeneous catalysis / Rhodium / Olefination / Nitrogen heterocycles / Regioselectivity
An efficient RhIII-catalyzed trans selective ortho-olefination
of 2-aryloxypyridines has been developed. The catalytic sys-
tem is very effective for olefination of differently substituted
2-aryloxypyridines with acrylates, acrylamide and styrenes
and exhibits broad compatibility with assorted olefinic cou-
pling partners. Although acrylates and acrylamide give rise
to trans-olefinated products in MeOH, styrenes provided the
trans products under solvent free reaction conditions. Inter-
estingly, in olefinations with ethyl acrylate, the aryloxypyrid-
ine compound bearing keto functionality at the ortho position
was found to undergo directing group cleavage to afford the
olefinated phenol product directly.
clearly warranted. The C–H activation of 2-aryloxypyridine
has been realized due to formation of favored six-membered
metallacyles.[6] RhIII has played a crucial role in catalyst
development for dehydrogenative ortho C–H olefination of
arenes bearing a diverse set of Lewis-basic directing groups
like anilides,[7] amides,[8] keto moieties,[8a] carbamates,[9] es-
ters,[10] oximes,[11] carboxylic acids[12] sulfoxides,[13] pyr-
azoles[14] and others. However reports of RhIII-catalyzed
alkenylations of arenes that exploit removable directing
groups remain scarce.[3i] Recently, Ackermann[3l] and Shi[3u]
have reported olefinations of 2-phenoxypyridines using RuII
and PdII catalysts, respectively. However, these methods are
limited to acrylates as the olefinic coupling partners. In con-
tinuation of arene olefination development using 2-pyrid-
yloxyl as the directing group, we have explored the efficacy
of Rh catalysts and found a RhIII catalyst that is very effec-
tive and compatible with a broad scope of olefins relative
to earlier protocols. In the present investigation, apart from
acrylates and acrylamide, we report our notable success
using styrenes as the olefinic coupling partners.
Introduction
Transition metal-catalyzed direct C–H bond activation/
functionalization has emerged as a powerful method for
construction of carbon–carbon bonds characterized by
economy of atoms and number of steps as well as features
of green chemistry.[1] Consequently, valuable polyfunctional
compounds can be synthesized expediently by this strategy.
Among these transformations, cross-dehydrogenative cou-
plings have emerged as increasingly powerful tools as they
oxidatively couple two different C–H bonds.[2] Notable ad-
vances have been achieved in this area primarily through
the use of Rh, Ru and Pd catalysts. The construction of C–
C bonds, especially the coupling of arenes with olefins via
a two-fold C–H activation process has drawn the attention
of chemists in recent years.[2] To control the regioselectivity
of the activation process, directing groups are usually intro-
duced. However, this approach may sometimes be restricted
in its effectiveness when the directing groups cannot be eas-
ily removed following the desired coupling. Hence, signifi-
cant effort has been focused on developing removable di-
recting groups.[3] Recently, a number of C–C bond forming
reactions assisted by the 2-pyridyloxyl group have been de-
veloped.[3f,3j–3m,3t–3x] Phenol derivatives, in particular, have
attracted significant attention in C–H bond functionaliza-
tion processes due to their broad synthetic utility.[4] Among
such derivatives, aryloxypyridine compounds exhibit impor-
tant bioactivities and are thereby drawing much attention in
the pharmaceutical field.[5] Hence, development of efficient
routes for structural modification of such compounds is
Results and Discussion
At the outset, reaction conditions were optimized using
2-phenoxypyridine (1a) and ethyl acrylate (2) as the model
substrates (Table 1). We initiated the coupling process using
[Cp*RhCl2]2 (5 mol-%) as the catalyst in the presence of
1 equiv. Cu(OAc)2·H2O as an oxidant and DCE as solvent
(Table 1, Entry 1). The reaction was carried out at 110 °C.
Only trace amounts of the desired coupled product forma-
tion were observed. However, we were pleased to get 33%
of ortho-olefinated product 3a in the presence of AgSbF6
as an additive (Table 1, Entry 2). In this reaction we also
recorded formation of trace di-olefinated product 3aЈ. This
result implied that in-situ generated cationic RhIII complex
[a] Department of Chemistry, Lishui University,
1, Xueyuan Road, Lishui 323000, Zhejiang Province,
P. R. China
E-mail: 0gbyan@tongji.edu.cn
http://www.lsu.edu.cn
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201500530
4782
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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New RhIII-Catalyzed Olefination of 2-Aryloxypyridines
plays a vital role in the coupling process. The installed ole- ferent substitution patterns was found to be compatible to
fin was in the E-form almost exclusively. The cationic RhIII the optimized coupling conditions; corresponding trans ole-
species enabled the desired olefination with moderate yield
in the presence of Cu(OAc)2·H2O (51% 3a, mono/di =
3.6:1, Table 1, Entry 3) revealing that the alkenylation pro-
cess is effective under oxidative conditions. Next, we exam-
Table 2. Scope of RhIII-catalyzed olefination process with acryl-
ates.[a]
ined the efficiency of different oxidants in DCE towards the
olefination process (Table 1, Entries 4–9). We were de-
lighted to find that the yield of singly olefinated product
improved to 65% with 1 equiv. of Cu(OAc)2 (mono/di =
3.6:1, Table 1, Entry 8). Lowering the amount of Cu(OAc)2
(0.5 equiv., Table 1, Entry 10) failed to change this effi-
ciency. Thus, in the next step, we planned to achieve im-
proved reaction selectivity (favoring mono-olefinated prod-
uct) by varying the solvent while using 0.5 equiv. of
Cu(OAc)2. Among the different solvents used in trial reac-
tions, MeOH (Table 1, Entry 13) was found to be ideal and
the mono-olefinated product was isolated in 70% yield
(mono/di = 5.4:1). On the basis of these data, we envisioned
optimal reaction conditions to call for 0.5 equiv. Cu(OAc)2
in MeOH at 110 °C. Lowering reaction temperature
(Table 1, Entry 16) and catalyst loading (Table 1, Entry 17)
provided comparatively lower yields. Additional experi-
ments have shown that, in absence of catalyst, no reaction
occurs (Table 1, Entry 18).
Table 1. Optimization of reaction conditions.[a]
Entry Additive Oxidant
(equiv.)
Solvent
Yields[b] [%]
3a, 3aЈ
1
2
3
4
5
6
7
8
–
Cu(OAc)2·H2O(1) 1,2-DCE
1,2-DCE
trace
AgSbF6
–
33, trace
51, 14
45, 10
54, 12
60, 23
26, trace
65, 18
trace
64, 18
53, 14
44, 20
70, 13
52, 29
AgSbF6 Cu(OAc)2·H2O(1) 1,2-DCE
AgSbF6 PhIOAc (1)
AgSbF6 AgOAc (1)
AgSbF6 Ag2O(1)
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
DMF
AgSbF6 K2S2O8 (1)
AgSbF6 Cu(OAc)2(1)
AgSbF6 Cu(OTf)2(1)
AgSbF6 Cu(OAc)2(0.5)
AgSbF6 Cu(OAc)2(0.5)
AgSbF6 Cu(OAc)2(0.5)
AgSbF6 Cu(OAc)2(0.5)
AgSbF6 Cu(OAc)2(0.5)
AgSbF6 Cu(OAc)2(0.5)
AgSbF6 Cu(OAc)2(0.5)
AgSbF6 Cu(OAc)2 (0.5)
9
10
11
12
13
14
15
16[c]
17[d]
18[e]
tAmOH
MeOH
PhMe
1,4-dioxane n.r.
MeOH
MeOH
MeOH
54, 16
60, 12
n.r.
–
Cu(OAc)2(0.5)
[a] Reaction condition:1a (0.2 mmol), ethyl acrylate (1.5 equiv.),
[RhCp*Cl2]2 (5 mol-%), AgSbF6 (20 mol-%), solvent (2.5 mL),
oxidant, 110 °C, 15 h. [b] Isolated yield. [c] Carried out at 90 °C.
[d] [RhCp*Cl2]2 (2.5 mol-%), AgSbF6 (10 mol-%). [e] Without Rh
catalyst; n.r.: no reaction.
With the optimized reaction conditions in hand, the
scope of substrates was investigated by using differently
substituted 2-aryloxypyridines (1) with ethyl acrylate as the
[a] Reaction condition: 1 (0.2 mmol), 2 (1.5 equiv.), [RhCp*Cl2]2
(5 mol-%), AgSbF6 (20 mol-%), MeOH (2.5 mL), Cu(OAc)2
(0.5 equiv.), 110 °C, 15 h. [b] Isolated yield. [c] Di-olefinated prod-
standard coupling partner (Table 2). A wide range of dif- uct. [d] Formation of the olefinated product was not detected.
Eur. J. Org. Chem. 2015, 4782–4787
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A. J. Borah, G. Yan, L. Wang
FULL PAPER
finated products were routinely obtained in moderate to Table 3. Scope of RhIII-catalyzed olefination with styrenes.[a]
high yields. Electrophilic functional groups like halogens,
esters, ketones and trifluoromethyl groups were found to be
very well tolerated. However the cyano functionality (1e)
correlated to reduced yield; only 32% mono-olefinated
product was obtained in this case. In case of unsubstituted
(1a) and para-substituted phenol derivatives (1b–e), the
selectivity for mono-olefination was not well-controlled and
di-olefinated products were also obtained to a lesser extent.
For ortho-substituted phenol derivatives (1f–h, 1k–l), the
olefinated products were isolated in very good yields (65–
80%). Interestingly, the compound bearing the keto func-
tionality at the ortho position (1l) was found to undergo
cleavage of the directing group under the reaction condi-
tions and provided the olefinated phenol directly with a
66% yield (3q). The olefinated product bearing the directing
group was not detected in this reaction and, at present, it
is not clear why the directing group is so readily cleaved
in this case. For meta-substituted phenol derivatives (1i–j),
olefination proceeded regioselectively at the sterically less
hindered ortho position providing only mono-olefinated
products. The present protocol was successfully extended to
other acrylates like methyl, butyl and benzyl acrylates and
provided the corresponding olefinated products (3l–n) in
high yields. We also investigated the versatility of the cata-
lytic system with N,N-dimethyacrylamide and acrylic acid.
Although the acrylamide, under the reaction conditions,
provided olefinated product in good yield (3o, 67%), the
use of acrylic acid failed to provide desired product 3p.
Relative to acrylates, styrenes are less active and hence,
challenging coupling partners when it comes to alkenylation
reactions. We were very pleased to find that the RhIII-cata-
lyst is very effective for olefination of styrene compounds.
Using the ortho-methyl-substituted phenol derivative, 1k
and styrene as the model coupling partner, we isolated just
20% of the olefinated product under the standard reaction
conditions developed for acrylates. In attempts to improve
coupling yields we employed solvent free conditions calling
for 10 mol-% catalyst at 120 °C and found these to be opti-
mal for the given coupling partners. Under these conditions,
the use of 0.2 mL of styrene afforded product 5a in 80%
[a] Reaction condition: 1k (0.2 mmol), 4 (0.2 mL), [RhCp*Cl2]2
(10 mol-%), AgSbF6 (40 mol-%), Cu(OAc)2 (0.5 equiv.), 120 °C,
yield and exclusively in the trans-form. Inspired by this suc- 24 h. [b] Isolated yield.
Scheme 1.
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New RhIII-Catalyzed Olefination of 2-Aryloxypyridines
cess, we extended our reaction to different liquid styrenes
and successfully isolated the corresponding trans-olefinated
products in moderate to excellent yield (5b–j, up to 91%).
Different styrene substituents were found to be very well
tolerated. Importantly however, the present protocol is lim-
ited to liquid styrenes (Table 3).
The styrene-based olefination conditions were also suc-
cessfully extended to other 2-aryloxypyridines (Scheme 1)
and anticipated products were isolated in excellent yields.
The meta-substituted phenol derivative (1i) provided mono-
olefinated product (5l) regioselectively at the sterically less
hindered ortho position. The trans configuration of ole-
finated products were unambiguously determined by X-ray
crystallography analysis using 5l as the representative exam-
ple (Figure 1).
Figure 1. ORTEP drawing of compound 5l.
The 2-pyridyl group can be removed using standardized
procedures.[3l,3u] Using the previously reported protocol we
have successfully cleaved the directing group from com-
pound 5a (Scheme 2) to deliver free phenol 5m (91%).
On the basis of literature, a plausible mechanistic path-
way has been proposed (Scheme 3) for the olefination de-
scribed herein.[10a,15] [RhCp*Cl2]2 dissociates initially into
an unsaturated monomeric species, which reacts with
AgSbF6 generating cationic RhIII species A. Electrophilic
species A is expected to readily coordinate the pyridine N-
atom of the substrate forming intermediate B. Sub-
Scheme 2. Removal of 2-pyridyl-based directing group from model
compound 5a.
sequently, a concerted metalation–deprotonation process at cies C. Olefin insertion into the carbon–RhIII bond gener-
the ortho position is envisioned to afford arylrhodium spe- ates rhodacycle D, from which β-hydride elimination pro-
Scheme 3. Proposed mechanism for RhIII-catalyzed olefination.
Eur. J. Org. Chem. 2015, 4782–4787
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A. J. Borah, G. Yan, L. Wang
FULL PAPER
vides the olefinated product E along with the [HRhIIICp*]-
SbF6 species. Reductive elimination of [HRhIIICp*]SbF6
species gives a RhI species, which is reoxidized to RhIII by
the action of Cu(OAc)2. Finally, the transiently reduced
copper is then air oxidized.
Acknowledgments
The authors thank the Natural Science Foundation of Zhejiang
Province (grant numbers LY12B02006 and LY13B020005) for fin-
ancial support.
[1] Selected reviews: a) V. Ritleng, C. Sirlin, M. Pfeffer, Chem. Rev.
2002, 102, 1731–1770; b) O. Daugulis, H.-Q. Do, D. Shabashov,
Acc. Chem. Res. 2009, 42, 1074–1086; c) A. A. Kulkarni, O.
Daugulis, Synthesis 2009, 4087–4109; d) X. Chen, K. M. Engle,
D. H. Wang, J. Q. Yu, Angew. Chem. Int. Ed. 2009, 48, 5094–
5115; Angew. Chem. 2009, 121, 5196; e) D. A. Colby, R. G.
Bergman, J. A. Ellman, Chem. Rev. 2010, 110, 624–655; f) T. W.
Lyons, M. S. Sanford, Chem. Rev. 2010, 110, 1147–1169; g) T.
Satoh, M. Miura, Chem. Eur. J. 2010, 16, 11212–11222; h)
C. L. Sun, B. J. Li, Z. J. Shi, Chem. Rev. 2011, 111, 1293–1314;
i) L. Ackermann, Chem. Rev. 2011, 111, 1315–1345; j) J. Wen-
cel-Delord, T. Dröge, F. Liu, F. Glorius, Chem. Soc. Rev. 2011,
40, 4740–4761; k) G. Song, F. Wang, X. Li, Chem. Soc. Rev.
2012, 41, 3651–3678; l) K. M. Engle, T.-S. Mei, M. Wasa, J.-Q.
Yu, Acc. Chem. Res. 2012, 45, 788–802; m) P. B. Arockiam, C.
Bruneau, P. H. Dixneuf, Chem. Rev. 2012, 112, 5879–5918.
[2] For selected reviews on cross-dehydrogenative C–H bond func-
tionalizations, see: a) C.-J. Li, Acc. Chem. Res. 2009, 42, 335–
344; b) C. J. Scheuermann, Chem. Asian J. 2010, 5, 436–451; c)
C. S. Yeung, V. M. Dong, Chem. Rev. 2011, 111, 1215–1292; d)
J. Le Bras, J. Muzart, Chem. Rev. 2011, 111, 1170–1214; e) F. W.
Patureau, J. Wencel-Delord, F. Glorius, Aldrichim. Acta 2012,
45, 31–41; f) S. A. Girard, T. Knauber, C.-J. Li, Angew. Chem.
Int. Ed. 2014, 53, 74–100; g) S. I. Kozhushkov, L. Ackermann,
Chem. Sci. 2013, 4, 886–896; h) Y. N. Wu, J. Wang, F. Mao,
F. Y. Kwong, Chem. Asian J. 2014, 9, 26–47.
Conclusions
In sum, we have developed a simple and efficient RhIII
-
catalyzed direct C–H olefination of arenes displaying a re-
movable directing group. The scope of the olefination pro-
cess is broad; differently substituted 2-aryloxypyridines ef-
fectively provide trans-olefinated products by virtue of their
coupling with acrylates, acrylamide and styrenes. The prod-
ucts were isolated in moderate to excellent yields. Acrylates
and acrylamide provide the desired olefinated products
when using MeOH as the optimized solvent. Compara-
tively, at a higher loading of catalyst under solvent free con-
ditions, styrenes provide the desired olefinated products in
excellent yields. Interestingly, during olefination with ethyl
acrylate, the aryloxypyridine compound bearing a keto
functionality at the ortho position was found to undergo
cleavage of the directing group and directly provided the
olefinated phenol. Products can be readily liberated from
the directing group using a previously reported protocol.
[3] For recent reviews on the use of removable directing groups,
see: a) C. Wang, Y. Huang, Synlett 2013, 24, 145–149; b) G.
Rousseau, B. Breit, Angew. Chem. Int. Ed. 2011, 50, 2450–2494;
Angew. Chem. 2011, 123, 2498. For illustrative examples of re-
movable directing groups: c) A. García-Rubia, R. G. Arrayás,
J. C. Carretero, Angew. Chem. Int. Ed. 2009, 48, 6511–6515;
Angew. Chem. 2009, 121, 6633; d) N. Chernyak, A. S. Dudnik,
C. Huang, V. Gevorgyan, J. Am. Chem. Soc. 2010, 132, 8270–
8272; e) D. Shabashov, O. Daugulis, J. Am. Chem. Soc. 2010,
132, 3965–3972; f) J. H. Chu, P. S. Lin, M. J. Wu, Organometal-
lics 2010, 29, 4058–4065; g) C.-H. Huang, B. Chattopadhyay,
V. Gevorgyan, J. Am. Chem. Soc. 2011, 133, 12406–12409; h)
M. Yu, Z. Liang, Y. Wang, Y. Zhang, J. Org. Chem. 2011, 76,
4987–4994; i) C. Wang, H. Chen, Z. Wang, J. Chen, Y. Huang,
Angew. Chem. Int. Ed. 2012, 51, 7242–7245; Angew. Chem.
2012, 124, 7354; j) S. Guin, S. K. Rout, A. Banerjee, S. Nandi,
B. K. Patel, Org. Lett. 2012, 14, 5294–5297; k) L. Ackermann,
E. Diers, A. Manvar, Org. Lett. 2012, 14, 1154–1157; l) W. B.
Ma, L. Ackermann, Chem. Eur. J. 2013, 19, 13925–13928; m)
M. Kim, S. Sharma, J. Park, M. Kim, Y. Choi, Y. Jeon, J. H.
Kwak, I. S. Kim, Tetrahedron 2013, 69, 6552–6559; n) L.-Q.
Zhang, S. Yang, X. Huang, J. You, F. Song, Chem. Commun.
2013, 49, 8830–8832; o) F.-J. Chen, S. Zhao, F. Hu, K. Chen,
Q. Zhang, S.-Q. Zhang, B.-F. Shi, Chem. Sci. 2013, 4, 4187–
4192; p) K. Chen, F. Hu, S.-Q. Zhang, B.-F. Shi, Chem. Sci.
2013, 4, 3906–3911; q) B. Urones, R. G. Arrayás, J. C. Carret-
ero, Org. Lett. 2013, 15, 1120–1123; r) X. Cong, J. You, J. Lan,
Chem. Commun. 2013, 49, 662–664; s) J. Yao, R. Feng, Z. Wu,
Z. Liu, Y. Zhang, Adv. Synth. Catal. 2013, 355, 1517–1522; t)
B. Liu, H. Z. Jiang, B. F. Shi, Org. Biomol. Chem. 2014, 12,
2538–2542; u) B. Liu, H.-Z. Jiang, B.-F. Shi, J. Org. Chem.
2014, 79, 1521–1526; v) C. Zhang, P. Sun, J. Org. Chem. 2014,
79, 8457–8461; w) W. Zhang, J. Zhang, S. Ren, Y. Liu, J. Org.
Chem. 2014, 79, 11508–11516; x) Y. Xu, P. Liu, S.-L. Li, P. Sun,
J. Org. Chem. DOI: 10.1021/jo5026095.
Experimental Section
General Procedure for the Olefination of 2-Aryloxypyridine (1) with
Acrylates 3a–q: A mixture of [RhCp*Cl2]2 (5 mol-%), AgSbF6
(20 mol-%) and substrate 1, (0.2 mmol) in MeOH (2.5 mL) was
placed in a Schlenk tube and then combined with ethyl acrylate
(1.5 equiv.) and Cu(OAc)2 (0.5 equiv., mmol). The reaction mixture
was allowed to stir for 15 h in a preheated oil bath at 110 °C. Reac-
tion progress was monitored by thin layer chromatography. The
reaction mixture was then cooled and passed through a short pad
of Celite and washed with EtOAc. Organic solvents were removed
under reduced pressure and the residue was purified by flash
chromatography using PE and EtOAc (4.5:1) as eluent.
General Procedure for the Olefination of 1k with Styrenes 5a–j: A
mixture of [RhCp*Cl2]2 (10 mol-%), AgSbF6 (40 mol-%), substrate
1k (0.2 mmol) and styrene compound 4 (0.2 mL) was placed in a
Schlenk tube and then combined with Cu(OAc)2 (0.5 equiv.). The
reaction mixture was allowed to stir for 24 h in a preheated oil
bath at 120 °C. The reaction mixture was then cooled and added
to EtOAc. The reaction mixture was passed through a short pad
of Celite and washed with EtOAc. Organic solvents were removed
under reduced pressure and the residue was purified by flash
chromatography using PE and EtOAc (5:0.2) as eluent. Products
5k and 5l were also prepared and isolated in similar fashion.
CCDC-1405844 (for 5l) contains the supplementary crystallo-
graphic 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.
Supporting Information (see footnote on the first page of this arti-
cle): Experimental procedures and characterization of all com-
pounds including crystallographic data for compound 5l.
[4] For selected references, see: a) T. A. Boebel, J. F. Hartwig, J.
Am. Chem. Soc. 2008, 130, 7534–7535; b) S. Gu, C. Chen, W.
4786
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New RhIII-Catalyzed Olefination of 2-Aryloxypyridines
Chen, J. Org. Chem. 2009, 74, 7203–7206; c) X. Zhao, C. S.
Yeung, V. M. Dong, J. Am. Chem. Soc. 2010, 132, 5837–5844;
d) B. Xiao, Y. Fu, J. Xu, T.-J. Gong, J.-J. Dai, J. Yi, L. Liu, J.
Am. Chem. Soc. 2010, 132, 468–469; e) B. Xiao, T.-J. Gong, Z.-
J. Liu, J.-H. Liu, D.-F. Luo, J. Xu, L. Liu, J. Am. Chem. Soc.
2011, 133, 9250–9253; f) L. Niu, H. Yang, R. Wang, H. Fu,
Org. Lett. 2012, 14, 2618–2621; g) H.-X. Dai, G. Li, X.-G.
Zhang, A. F. Stepan, J.-Q. Yu, J. Am. Chem. Soc. 2013, 135,
7567–7571; h) B. Li, J. Ma, Y. Liang, N. Wang, S. Xu, H. Song,
B. Wang, Eur. J. Org. Chem. 2013, 1950–1962; i) W. Liu, L.
Ackermann, Org. Lett. 2013, 15, 3484; j) C. Zhang, J. Ji, P.
Sun, J. Org. Chem. 2014, 79, 3200–3205.
[6]
a) D. J. de Geest, B. J. O’Keefe, P. J. Steel, J. Organomet. Chem.
1999, 579, 97–105; b) B. J. O’Keefe, P. J. Steel, Organometallics
2003, 22, 1281–1292.
F. W. Patureau, F. Glorius, J. Am. Chem. Soc. 2010, 132, 9982–
9983.
a) F. W. Patureau, T. Besset, F. Glorius, Angew. Chem. Int. Ed.
2011, 50, 1064–1067; Angew. Chem. 2011, 123, 1096; b) S. Rak-
shit, C. Grohmann, T. Besset, F. Glorius, J. Am. Chem. Soc.
2011, 133, 2350–2353.
a) T.-J. Gong, B. Xiao, Z.-J. Liu, J. Wan, J. Xu, D.-F. Luo, Y.
Fu, L. Liu, Org. Lett. 2011, 13, 3235–3237; b) C. Feng, T.-P.
Loh, Chem. Commun. 2011, 47, 10458–10460.
[7]
[8]
[9]
[5] a) F. Julémont, X. de Leval, C. Michaux, J.-F. Renard, J.-Y.
Winum, J.-L. Montero, J. Damas, J.-M. Dogné, B. Pirotte, J.
Med. Chem. 2004, 47, 6749–6759; b) C. W. am Ende, S. E.
Knudson, N. Liu, J. Childs, T. J. Sullivan, M. Boyne, H. Xu,
Y. Gegina, D. L. Knudson, F. Johnson, C. A. Peloquin, R. A.
Slayden, P. J. Tonge, Bioorg. Med. Chem. Lett. 2008, 18, 3029–
3033; c) M. A. Letavic, L. Aluisio, J. R. Atack, P. Bonaventure,
N. I. Carruthers, C. Dugovic, A. Everson, M. A. Feinstein,
I. C. Fraser, K. Hoey, X. Jiang, J. M. Keith, T. Koudriakova,
P. Leung, B. Lord, T. W. Lovenberg, K. S. Ly, K. L. Morton,
S. T. Motley, D. Nepomuceno, M. Rizzolio, R. Rynberg, K.
Sepassi, J. Shelton, Bioorg. Med. Chem. Lett. 2010, 20, 4210–
4214; d) X. Y. Song, W. M. Chen, L. Lin, C. H. Ruiz, M. D.
Cameron, D. R. Duckett, T. M. Kamenecka, Bioorg. Med.
Chem. Lett. 2011, 21, 7072–7075; e) H. Chao, H. Turdi, T. F.
Herpin, J. Y. Roberge, Y. Liu, D. M. Schnur, M. A. Poss, R.
Rehfuss, J. Hua, Q. Wu, L. A. Price, L. M. Abell, W. A. Schum-
acher, J. S. Bostwick, T. E. Steinbacher, A. B. Stewart, M. L.
Ogletree, C. S. Huang, M. Chang, A. M. Cacace, M. J. Arcuri,
D. Celani, R. R. Wexler, R. M. Lawrence, J. Med. Chem. 2013,
56, 1704–1714.
[10]
a) S. H. Park, J. Y. Kim, S. Chang, Org. Lett. 2011, 13, 2372–
2375; b) B. C. Chary, S. Kim, Org. Biomol. Chem. 2013, 11,
6879–6882.
[11] A. S. Tsai, M. Brasse, R. G. Bergman, J. A. Ellman, Org. Lett.
2011, 13, 540–542.
[12] a) K. Ueura, T. Satoh, M. Miura, Org. Lett. 2007, 9, 1407–
1409; b) S. Mochida, K. Hirano, T. Satoh, M. Miura, Org.
Lett. 2010, 12, 5776–5779; c) S. Mochida, K. Hirano, T. Satoh,
M. Miura, J. Org. Chem. 2011, 76, 3024–3033.
[13] K. Nobushige, K. Hirano, T. Satoh, M. Miura, Org. Lett. 2014,
16, 1188–1191.
[14] N. Umeda, K. Hirano, T. Satoh, M. Miura, J. Org. Chem. 2009,
74, 7094–7099.
[15] a) Y. Boutadla, O. Al-Duaij, D. L. Davies, G. A. Griffith, K.
Singh, Organometallics 2009, 28, 433–440; b) D. R. Stuart, P.
Alsabeh, M. Kuhn, K. Fagnou, J. Am. Chem. Soc. 2010, 132,
18326–18339; c) N.-J. Wang, S.-T. Mei, L. Shuai, Y. Yuan, Y.
Wei, Org. Lett. 2014, 16, 3040–3043.
Received: April 26, 2015
Published Online: June 15, 2015
Eur. J. Org. Chem. 2015, 4782–4787
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4787