Gold-Catalyzed syn-1,2-Difunctionalization of Ynamides via Nitrile Activation

Article abstract of DOI:10.1021/acs.orglett.8b03830

Developed is an unprecedented Au(I)-catalyzed syn-1,2-difunctionalization of ynamides with 2-aminobenzonitriles via nitrile activation. The coupling between ynamides and 2-aminobenzonitriles is explicitly regioselective, providing a straightforward access to 2,4-diamino-substituted quinolines. Density functional theory (DFT) study provides insightful information and rationalizes the reaction pathway. It shows how the synergy between ynamide π-activation and nitrile σ-coordination by the Au(I) catalyst makes the cyclization viable.

Full text of DOI:10.1021/acs.orglett.8b03830

Letter
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
pubs.acs.org/OrgLett
Gold-Catalyzed syn-1,2-Difunctionalization of Ynamides via Nitrile
Activation
Rajeshwer Vanjari,† Shubham Dutta, Manash P. Gogoi, Vincent Gandon,*
†
†
,¥,‡
,
†
and Akhila K. Sahoo*
†
School of Chemistry, University of Hyderabad, Hyderabad, Telangana India-500046
¥
Institut de Chimie Molec
Paris-Saclay, Batiment 420, 91405 Orsay cedex, France
Laboratoire de Chimie Moleculaire (LCM), CNRS UMR 9168, Ecole Polytechnique, Universite
1128 Palaiseau cedex, France
́
ulaire et des Mater
́
iaux d’Orsay (ICMMO), CNRS UMR 8182, Universite
́
Paris-Sud, Universite
́
̂
‡
́
́
Paris-Saclay, route de Saclay,
9
*
S Supporting Information
ABSTRACT: Developed is an unprecedented Au(I)-cata-
lyzed syn-1,2-difunctionalization of ynamides with 2-amino-
benzonitriles via nitrile activation. The coupling between
ynamides and 2-aminobenzonitriles is explicitly regioselective,
providing a straightforward access to 2,4-diamino-substituted
quinolines. Density functional theory (DFT) study provides
insightful information and rationalizes the reaction pathway. It
shows how the synergy between ynamide π-activation and nitrile σ-coordination by the Au(I) catalyst makes the cyclization
viable.
itrogen heteroarenes are widely present in natural
nucleophile at the α-position of a keteniminium species,
obtained in situ from an ynamide under the influence of a gold
catalyst, followed by the β-attack of the resulting vinyl-[Au]
species to an unsaturated-heteroatom motif, is a challenging
endeavor (Scheme 1C).
N
products, molecules of pharmaceutical importance, and
1
materials of various significance. The ynamide motif has been
broadly used for the construction of such complex N-
2
heterocycles. In this context, gold-catalyzed transformations
of ynamides have proven efficient, highly selective, and are
synthetically relevant. Notably, the cyclization/cycloisomeriza-
tion of yne-surrogates under homogeneous Au catalysis has led
to novel synthetic transformations that allow the construction
Intrigued by the significant challenges involved in the
multiple activation of π-bonds, we planned a reaction of
ynamides with 2-aminobenzonitriles (having a nucleophilic
amine moiety and a weakly coordinating CN group) in the
presence of a Au(I) catalyst. We envisaged that the attack of
3
of diverse molecular scaffolds. Generally, the cyclization of
4
5
diynes proceeds via a vinyl carbocation or a gold-vinylidene
the NH group at the α-position of the Au-activated ynamide
2
intermediate through π-coordination and dual σ- and/or π-
coordination of the alkyne moieties, followed by the attack of a
nucleophile, respectively (Scheme 1A). For example, cycliza-
tion of terminal alkyne tethered ynamides/diynes involves
gold-vinylidene intermediate (developed by Hashmi′s and
would be favored over that of the nitrile. The hydroamination
and protodeauration would provide a helically chiral nitrile-
10
gold complex D. Finally, intramolecular enamine addition to
the nitrile-gold ligated species, followed by the imine/enamine
tautomerism would produce unusual 2,4-diamino-substituted
quinolines (a core structure present in various natural
5
Gagosz′s groups; Scheme 1A, path a). In the yne-tethered
ynamide series, nucleophile-promoted attack of the ynamide to
11
products), as shown in eq 1. The current demonstration is
the activated alkyne via vinyl carbocation is demonstrated
6
synthetically different from previously described Au-catalyzed
transformations of ynamides involving nitriles in the sense that
the −CN species here acts as an electrophile and not as a
(
path b). A recent report by Gagosz et al. based on
intermolecular dimerization of ynamides followed by intra-
molecular C−H attack to a vinyl-carbocation intermediate
12
nucleophile.
(
Scheme 1B, right), and the demonstration of Hashmi’s on
To accomplish the envisaged process, ynamide 1a was
reacted with 2-aminobenzonitrile 2a in the presence of various
Au-catalysts (Table 1). To our delight, product 3a was formed
in 53% yield when the reaction was conducted with
Ph PAuNTf (1.0 mol %) in 1,2-dichloroethane (DCE) at
intermolecular trapping of a gold carbene with an ynamide
Scheme 1B, left), provides a direct access to novel
(
7
heterocycles. The Au-catalyzed hydroamination of anilines
8
with ynamides (developed by Skrydstrup′s and Liu′s groups),
and the intramolecular trapping of vinyl-[Au] species,
generated from aniline attack to ynamides, by alkynes, have
3
2
9
also been reported. Within this context, trying to devise an
Received: November 30, 2018
intermolecular method based on the concomitant attack of a
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.8b03830
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 1. (A and B) Cyclization Methods of Ynamides; (C)
Intermolecular syn-1,2-Difunctionalization of Ynamides
room temperature (rt) for 7 h (Table 1, entry 1). At 80 °C, the
yield was improved to 86% (Table 1, entry 2). The reaction in
acetone or toluene was equally efficient (Table 1, entries 3 and
4
9
). The best solvent proved to be 1,4-dioxane, providing 3a in
3% yield at 80 °C (Table 1, entry 5), or in 85% yield at 50 °C
(
Table 1, entry 6). Of note, the nature of the ligated gold
species substantially influenced the outcome. The product
yield was diminished when JohnPhos and CyJohnPhos ligated
Au-catalysts were employed (44%, Table 1, entry 7; 38%,
Table 1, entry 8). Similarly, the use of IPr- or IMes-derived
catalysts gave 3a in 24% and 58% yield, respectively (Table 1,
entries 9 and 10). Not surprisingly, the use of copper and
palladium catalysts did not yield the desired product (Table 1,
entries 11 and 12), whereas 3a was isolated in 11% yield when
the reaction was performed with AgNTf (Table 1, entry 13).
2
The scope of this Au(I)-catalyzed reaction between
ynamides and 2-aminobenzonitrile 2a was then surveyed
(
Schemes 2 and 3). Under the optimized condition (Table 1,
entry 5), the ynamides having aryl motifs [electron-neutral,
electron-rich (p-Ph, p-OMe), electron-poor (p-F, p-NO , p-
2
CHO)] at the ynamide terminus furnished the desired 2,4-
diamino-substituted quinolines 3a−3g in good yields in most
cases. The N-Me/Bn protected ynamides effectively partici-
Scheme 2. Scope I: Reaction of Ynamides (1) with 2-
a
Aminobenzonitrile (2a)
a
Table 1. Optimization of Reaction Conditions
b
entry
catalyst
solvent
yield of 3a (%)
c
1
2
3
4
5
6
7
8
9
0
1
2
3
Ph PAuNTf
ClCH CH Cl
53
3
2
2
2
2
2
2
Ph PAuNTf
3
ClCH CH Cl
86
79
82
93
2
2
Ph PAuNTf
3
acetone
Ph PAuNTf
3
toluene
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
Ph PAuNTf
3
2
d
Ph PAuNTf
85
3
2
JohnPhosAu(MeCN)SbF6
CyJohnPhosAuNTf2
IprAuNTf2
IMesAuNTf2
Cu(OAc)2
44
38
24
58
0
1
1
1
1
Pd(OAc)2
AgNTf2
0
11
a
Reaction conditions: 1a (0.3 mmol, 1.0 equiv), 2a (1.2 equiv),
b
catalyst (1.0 mol %), solvent (1 M) at 80 °C for 7 h. Isolated yield.
c
d
a
At room temperaure (rt). 50 °C.
Reaction conditions: 1a (1.0 equiv), 2a (1.2 equiv), Au-cat (1.0
mol %), 1,4-dioxane (1 M) at 80 °C for 7 h. Isolated yield.
B
DOI: 10.1021/acs.orglett.8b03830
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Scheme 3. Scope II: Reactivity of Various N-Protected
Ynamides with 2a
Scheme 4. Scope III: Screening of 2-Aminobenzonitriles
(2)
a
a
a
Reaction conditions: 1 (1.0 equiv), 2 (1.2 equiv), Au-cat (1.0
mol %), 1,4-dioxane (1 M) at 80 °C for 7 h. Isolated yield.
a
Reaction conditions: 1 (1.0 equiv), 2 (1.2 equiv), Au-cat (1.0 mol
%), 1,4-dioxane (1 M) at 80 °C for 7 h. Isolated yield.
Scheme 5. Mechanistic Experiments
pated. Similarly, the reaction of ynamides displaying ortho-
substituted aryls with 2a provided 3h (73%) and 3i (32%).
The π-extended 1-naphthyl-substituted quinoline 3j was also
successfully constructed. Quinolines 3k−3m were accessed
from multisubstituted aryl-bearing ynamides. Disappointingly,
the 2-thienyl-substituted quinoline 3n was formed only in
trace, which is a possible consequence from the quench of the
Au-catalyst. Alkyl- and alkenyl-bearing ynamides showed
moderate reactivity with 2a, delivering 3o and 3p in 40%
and 26% yield, respectively. Gratifyingly, this transformation
was scalable with no change in yield: 1.29 g of 3a was obtained
from 1.0 g of 1a and 0.5 g of 2a.
deuterated-2a (70% D) under the standard conditions
provided 3a with 40% deuterium incorporation; the proton
source from 2a is thus confirmed (eq 3 in Scheme 5).
Sulfonamide-substituted heterocycles are widely present in
13
the molecules of biological importance. In this context,
transformation of various N-sulfonyl protected ynamides using
To further explore the mechanistic details of the reaction of
ynamide 1a with 2-aminobenzonitrile (2a), DFT computations
were executed at the M06/def2-QZVP(Au)-6-311+G(2d,p)//
B3LYP/LANL2DZ(Au)-6-31G(d,p) level of theory (see the
Supporting Information for details). Complex A, which results
2a was probed (Scheme 3). Accordingly, several 4-amino-2-N-
sulfonyl protected 3-phenyl quinolines 3q−3u [having N-Bn-
n
SO Bu/SO Bn/SO C H -p-CF /SO C H -p-Br/SO -β-naph-
2
2
2
6
4
3
2
6
4
2
thyl] and 3v [N-cyclopropyl-SO Ph] were synthesized. In
2
+
addition, the carbamate derivative 3w was prepared, albeit in
moderate yield compared to sulfonyls.
We next explored the generality of the transformation by
reacting 1a with various 2-aminobenzonitriles having sub-
stituents at different positions of the arene periphery (Scheme
from the coordination of AuL to ynamide 1a and 2a, were
selected as reference for the free energies of system [AB]
(Figure 1). The geometry of this complex is actually closer to a
σ-ketiminium species than a π-complex (see the SI). The trans-
hydroamination of 1a with 2a was first modeled. This step
requires a low free energy of activation of 17.0 kcal/mol and is
endergonic by 15.2 kcal/mol. In fact, iminium C shows two
elements of chirality, because of its helicity and the C−N axis
connecting the alkene and the amide fragment. Thus,
diastereomer C′ displaying the same helix but an inverted
4
). Thus, the reaction of 5-Cl/4-Cl/4-Me-substituted 2-
aminobenzonitriles with 1a delivered the corresponding highly
substituted quinolines 4a−4c. Unfortunately, the reaction with
a nitro-substituted 2-aminobenzonitrile was unsuccessful, a
likely consequence of the strong electron-withdrawing nature
of the nitro group that reduces the nucleophilicity of the amine
moiety. The desired quinoline 4e (73%) was accessed from 2-
amino-6-fluorobenzonitrile. The strong coordination ability of
the pyridine scaffold did not hamper the reaction, delivering 4f
in 47% yield.
9
C−N axis can be defined. It is more stable than C, by 6.2
kcal/mol, but slightly slower to form. The transformation of C’
into the final product has been computed and the
corresponding energy profile is presented in the Supporting
Information. The protodeauration from intermediate C is
exergonic, providing the nitrile-gold complex D lying at −19.6
kcal/mol on the potential energy surface (PES). Next,
intramolecular enamine addition to the helically and axially
chiral nitrile-gold ligated species gives E. This step is
endergonic by 10.2 kcal/mol and requires 20.7 kcal/mol of
To get some insight into the reaction pathway, a few control
experiments were designed. The coupling of 2-aminobenzyl-
cyanide 5 with 1a provided the uncyclized product 6 (eq 2 in
Scheme 5); this ascertains the plausible involvement of
hydroamination/enamine intermediates. The reaction of N-
C
DOI: 10.1021/acs.orglett.8b03830
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Figure 1. Free-energy profile (ΔG353, kcal/mol, L = dimethylJohnPhos).
free energy of activation. The diastereomer I, obtained through
enamine/iminium tautomerism of D (this step requires an
unknown proton shuttle to avoid the symmetry-forbidden
intramolecular 1,3-H shift, it thus cannot be computed), is
more stable than D by 0.4 kcal/mol. The cyclization of I
demands 20.1 kcal/mol free energy of activation and provides
J, which is a diastereomer of E. This cyclization I → J imposes
a different sense of rotation around the chiral C−N axis,
compared to D → E; thus, E and J are diastereomers. The
imine/enamine tautomerism of E/J gives pyridinium species F,
lying at −46.0 kcal/mol on the PES. Finally, protodeauration
of F leads to the amine-gold complex G (−40.3 kcal/mol), or
the pyridine-gold complex H (−54.5 kcal/mol). The formation
of H is thus more favorable. Overall, the transformation of the
catalytic system is robust, showcasing broad scope, and
tolerates various functional groups. The mechanistic details
are rationalized by DFT calculations.
ASSOCIATED CONTENT
Supporting Information
■
*
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.8b03830.
Experimental procedures and methods, substrate syn-
thesis and isolated product characterization, analytical
data, computational details, coordinates and energy of
the computed species (PDF)
[
AB] system to H is strongly exergonic by 54.5 kcal/mol.
Accession Codes
On the basis of this DFT study, the transformation begins
CCDC 1870573 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
with the attack of amine to the gold ketiniminium species (I),
obtained in situ via selective π-coordination with the Au(I)
catalyst and generates enamine intermediate II (which exists as
14
cis and trans diastereomers). The intramolecular enamine
attack to the activated CN moiety then provides III. Finally,
aromatization of III and the proto-deauration of IV leads to
the desired quinoline product 3 and regenerating the Au(I)
AUTHOR INFORMATION
Corresponding Authors
■
1
4
catalyst.
We have herein demonstrated an Au(I)-catalyzed direct
coupling of ynamides with 2-aminobenzonitriles for the
synthesis of 2,4-diamino-substituted quinolines. This trans-
formation highlights the syn-1,2-difunctionalization of ynamide
through the intramolecular 6-exo-dig cyclization of ketene
aminal to the σ-coordinated nitrile moiety by Au(I). The
*
E-mail address: vincent.gandon@u-psud.fr (V. Gandon).
E-mail addresses: akhilchemistry12@gmail.com, akssc@
*
uohyd.ac.in (A. K. Sahoo).
ORCID
Rajeshwer Vanjari: 0000-0002-5816-5305
D
DOI: 10.1021/acs.orglett.8b03830
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
Toste, F. D. J. Am. Chem. Soc. 2008, 130, 4517. (d) Hashmi, A. S. K.;
Braun, I.; Rudolph, M.; Rominger, F. Organometallics 2012, 31, 644.
Vincent Gandon: 0000-0003-1108-9410
Akhila K. Sahoo: 0000-0001-5570-4759
Notes
(
1
e) Odabachian, Y.; Le Goff, X. F.; Gagosz, F. Chem. - Eur. J. 2009,
5, 8966. (f) Hashmi, A. S. K.; Braun, I.; Nosel, P.; Schadlich, J.;
Wieteck, M.; Rudolph, M.; Rominger, F. Angew. Chem., Int. Ed. 2012,
1, 4456. (g) Tsupova, S.; Hansmann, M. M.; Rudolph, M.;
Rominger, F.; Hashmi, A. S. K. Chem. - Eur. J. 2017, 23, 5716.
h) Wang, Y.; Yepremyan, A.; Ghorai, S.; Todd, R.; Aue, D. H.;
Zhang, L. Angew. Chem., Int. Ed. 2013, 52, 7795. (i) Tsupova, S.;
The authors declare no competing financial interest.
5
ACKNOWLEDGMENTS
■
(
We thank UoH, CEFIPRA (Grant No. 5505-2), UPE-II, and
PURSE for financial support. R.V. thanks SERB-NPDF, S.D.
and M.P.G. thank CSIR India for fellowships. V.G. thanks
CNRS, UPS, and Ecole Polytechnique for financial support.
̌
Rudolph, M.; Rominger, F.; Hashmi, A. S. K. Chem. - Eur. J. 2017, 23,
12259. (j) Bucher, J.; Wurm, T.; Taschinski, S.; Sachs, E.; Ascough,
D.; Rudolph, M.; Rominger, F.; Hashmi, A. S. K. Adv. Synth. Catal.
2
(
2
2
017, 359, 225.
6) (a) Nayak, S.; Ghosh, N.; Prabagar, B.; Sahoo, A. K. Org. Lett.
015, 17, 5662. (b) Ghosh, N.; Nayak, S.; Sahoo, A. K. Chem. - Eur. J.
013, 19, 9428.
7) For selected examples, see: (a) Kramer, S.; Odabachian, Y.;
REFERENCES
■
(
2
1) (a) Li, A. N.; Wang, T. Y.; Gong, L. Z.; Zhang, L. Chem. - Eur. J.
015, 21, 3585. (b) Zhu, S.; Wu, L.; Huang, X. J. Org. Chem. 2013,
(
78, 9120. (c) Pan, Y.; Chen, G.-W.; Shen, C.-H.; He, W.; Ye, L.-W.
Overgaard, J.; Rottlander, M.; Gagosz, F.; Skrydstrup, T. Angew.
Chem., Int. Ed. 2011, 50, 5090. (b) Rettenmeier, E.; Schuster, A. M.;
Rudolph, M.; Rominger, F.; Gade, C. A.; Hashmi, A. S. K. Angew.
Chem., Int. Ed. 2013, 52, 5880. (c) Mukherjee, A.; Dateer, R. B.;
Chaudhuri, R.; Bhunia, S.; Karad, S. N.; Liu, R.-S. J. Am. Chem. Soc.
Org. Chem. Front. 2016, 3, 491. (d) Prechter, A.; Henrion, G.; Faudot
dit Bel, P. F.; Gagosz, F. Angew. Chem., Int. Ed. 2014, 53, 4959.
(
e) Xiao, Y.; Zhang, L. Org. Lett. 2012, 14, 4662.
2) (a) Dunetz, J. R.; Danheiser, R. L. J. Am. Chem. Soc. 2005, 127,
776. (b) Martínez-Esperon, M. F.; Rodriguez, D.; Castedo, L.; Saa,
(
5
́
́
2
(
011, 133, 15372.
8) (a) Kramer, S.; Dooleweerdt, K.; Lindhardt, A. T.; Rottlander,
C. Org. Lett. 2005, 7, 2213. (c) Theunissen, C.; Metayer, B.; Lecomte,
M.; Henry, N.; Chan, H.-C.; Compain, G.; Gerard, P.; Bachmann, C.;
Mokhtari, N.; Marrot, J.; Martin-Mingot, A.; Thibaudeau, S.; Evano,
G. Org. Biomol. Chem. 2017, 15, 4399. (d) Evano, G.; Coste, A.;
Jouvin, K. Angew. Chem., Int. Ed. 2010, 49, 2840. (e) DeKorver, K. A.;
Li, H.; Lohse, A. G.; Hayashi, R.; Lu, Z.; Zhang, Y.; Hsung, R. P.
Chem. Rev. 2010, 110, 5064. (f) Prabagar, B.; Ghosh, N.; Sahoo, A. K.
Synlett 2017, 28, 2539. (g) Mallick, R. K.; Prabagar, B.; Sahoo, A. K. J.
̈
M.; Skrydstrup, T. Org. Lett. 2009, 11, 4208. (b) Singh, R. R.; Liu, R.
S. Adv. Synth. Catal. 2016, 358, 1421.
(9) During the preparation of this manuscript, related work
appeared: (a) Rode, N. D.; Arcadi, A.; Di Nicola, A.; Marinelli, F.;
Michelet, V. Org. Lett. 2018, 20, 5103. (b) Zhao, X.; Song, X.; Jin, H.;
Zeng, Z.; Wang, Q.; Rudolph, M.; Rominger, F.; Hashmi, A. S. K.
Adv. Synth. Catal. 2018, 360, 2720.
Org. Chem. 2017, 82, 10583. (h) Zhao, Q.; Leon
Campeau, D.; Daenen, M.; Gagosz, F. Angew. Chem., Int. Ed. 2018,
7, 13603. (i) Wang, Y.; Lin, J.; Wang, X.; Wang, G.; Zhang, X.; Yao,
B.; Zhao, Y.; Yu, P.; Lin, B.; Liu, Y.; Cheng, M. Chem. - Eur. J. 2018,
4, 4026. (j) Zhou, B.; Li, L.; Zhu, X. Q.; Yan, J. Z.; Guo, Y. L.; Ye, L.
́
Rayo, D. F.;
(
1
(
10) Tanaka, K.; Takeishi, K.; Noguchi, K. J. Am. Chem. Soc. 2006,
28, 4586.
11) (a) Musiol, R.; Jampilek, J.; Buchta, V.; Silva, L.; Niedbala, H.;
5
Podeszwa, B.; Palka, A.; Majerz Maniecka, K.; Oleksyn, B.; Polanski, J.
Bioorg. Med. Chem. 2006, 14, 3592. (b) McCormick, J. L.; Mckee, T.
C.; Cardellina, J. H., II; Boyd, M. R. J. Nat. Prod. 1996, 59, 469.
2
W. Angew. Chem., Int. Ed. 2017, 56, 4015. (k) Shen, W.-B.; Xiao, X.-
Y.; Sun, Q.; Zhou, B.; Zhu, X.-Q.; Yan, J.-Z.; Lu, X.; Ye, L.-W. Angew.
Chem., Int. Ed. 2017, 56, 605. (l) Li, L.; Chen, X.-M.; Wang, Z.-S.;
Zhou, B.; Liu, X.; Lu, X.; Ye, L.-W. ACS Catal. 2017, 7, 4004.
(
(
12) Karad, S. N.; Liu, R.-S. Angew. Chem., Int. Ed. 2014, 53, 9072.
13) (a) Thiele-Bruhn, S. J. J. Plant Nutr. Soil Sci. 2003, 166, 145.
(
b) Supuran, C. T.; Casini, A.; Scozzafava, A. Med. Res. Rev. 2003, 23,
35. (d) Pandya, R.; Murashima, T.; Tedeschi, L.; Barrett, A. G. M. J.
Org. Chem. 2003, 68, 8274.
14) See the Supporting Information (SI).
(
m) Wang, G.; You, X.; Gan, Y.; Liu, Y. Org. Lett. 2017, 19, 110.
5
(3) (a) Hashmi, A. S. K. Chem. Rev. 2007, 107, 3180. (b) Li, Z.;
Brouwer, C.; He, C. Chem. Rev. 2008, 108, 3239. (c) Arcadi, A. Chem.
Rev. 2008, 108, 3266. (d) Corma, A.; Leyva-Perez, A.; Sabater, M.
(
Chem. Rev. 2011, 111, 1657. (e) Miro,
016, 116, 11924. (f) Zhang, L. Acc. Chem. Res. 2014, 47, 877.
g) Pflasterer, D.; Hashmi, A. S. K. Chem. Soc. Rev. 2016, 45, 1331.
h) Yang, X.; Wu, T.; Phipps, R. J.; Toste, F. D. Chem. Rev. 2015, 115,
26. (i) O’Connor, T. J.; Toste, F. D. ACS Catal. 2018, 8, 5947.
́
J.; del Pozo, C. Chem. Rev.
2
(
(
̈
8
(
j) Kim, S.; Rojas-Martin, J.; Toste, F. D. Chem. Sci. 2016, 7, 85.
(k) Campbell, M. J.; Toste, F. D. Chem. Sci. 2011, 2, 1369. (l) Pan, F.;
Shu, C.; Ye, L.-W. Org. Biomol. Chem. 2016, 14, 9456. (m) Wang, X.-
N.; Yeom, H.-S.; Fang, L.-C.; He, S.; Ma, Z.-X.; Kedrowski, B. L.;
Hsung, R. P. Acc. Chem. Res. 2014, 47, 560. (n) DeKorver, K. A.; Li,
H.; Lohse, A. G.; Hayashi, R.; Lu, Z.; Zhang, Y.; Hsung, R. P. Chem.
Rev. 2010, 110, 5064. (o) Evano, G.; Coste, A.; Jouvin, K. Angew.
Chem., Int. Ed. 2010, 49, 2840.
(
4) (a) Wurm, T.; Bucher, J.; Duckworth, S. B.; Rudolph, M.;
Rominger, F.; Hashmi, A. S. K. Angew. Chem., Int. Ed. 2017, 56, 3364.
b) Odabachian, Y.; Le Goff, X. F.; Gagosz, F. Chem. - Eur. J. 2009,
5, 8966. (c) Zi, W.; Toste, F. D. J. Am. Chem. Soc. 2013, 135, 12600.
d) Mukherjee, A.; Dateer, R. B.; Chaudhuri, R.; Bhunia, S.; Karad, S.
(
1
(
N.; Liu, R.-S. J. Am. Chem. Soc. 2011, 133, 15372. Xu, W.; Wang, G.;
Xie, X.; Liu, Y. Org. Lett. 2018, 20, 3273. (e) Shen, W.-B.; Zhou, B.;
Zhang, Z.-X.; Yuan, H.; Fang, W.; Ye, L.-W. Org. Chem. Front. 2018,
5
(
, 2468.
5) (a) Tokimizu, Y.; Wieteck, M.; Rudolph, M.; Oishi, S.; Fujii, N.;
Hashmi, S. K.; Ohno, H. Org. Lett. 2015, 17, 604. (b) Hashmi, A. S.
K.; Frost, T. M.; Bats, J. W. J. Am. Chem. Soc. 2000, 122, 11553.
(c) Cheong, P. H.-Y.; Morganelli, P.; Luzung, M. R.; Houk, K. N.;
E
DOI: 10.1021/acs.orglett.8b03830
Org. Lett. XXXX, XXX, XXX−XXX