Suzuki coupling of aroyl-MIDA boronate esters – A preliminary report on scope and limitations

Article abstract of DOI:10.1016/j.tetlet.2021.153147

Recent methodological reports for synthesizing acyl-MIDA boronate esters compel an investigation of their potential use as substrates in a standard Suzuki-Miyaura cross-coupling reaction. Here we report the production of benzophenones by C[sbnd]C cross coupling between a benzoyl-MIDA boronate ester and a multitude of aryl bromide substrates in adequate yields following optimization under ambient conditions outside of a glove box. Under these standard conditions, none of several acyl-MIDA boronate esters (in an alkyl series) serves as a competent coupling partner. The substrate scope is also limited by the finding that the corresponding trifluoroborates of both acyl- and aroyltrifluroborates are not suitable substrates. For reasons of availability and synthetic difficulty in procuring other aroyl-MIDA boronates, this preliminary study examines the reactivity of benzoyl-MIDA boronate with several aryl bromide substrates.

Full text of DOI:10.1016/j.tetlet.2021.153147

Tetrahedron Letters 74 (2021) 153147
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Suzuki coupling of aroyl-MIDA boronate esters – A preliminary report on
scope and limitations
⇑
Samson Lai, Noah Takaesu, Wen Xuan Lin, David M. Perrin
Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T-1Z1, Canada
a r t i c l e i n f o
a b s t r a c t
Article history:
Recent methodological reports for synthesizing acyl-MIDA boronate esters compel an investigation of
their potential use as substrates in a standard Suzuki-Miyaura cross-coupling reaction. Here we report
the production of benzophenones by CAC cross coupling between a benzoyl-MIDA boronate ester and
a multitude of aryl bromide substrates in adequate yields following optimization under ambient condi-
tions outside of a glove box. Under these standard conditions, none of several acyl-MIDA boronate esters
(in an alkyl series) serves as a competent coupling partner. The substrate scope is also limited by the find-
ing that the corresponding trifluoroborates of both acyl- and aroyltrifluroborates are not suitable sub-
strates. For reasons of availability and synthetic difficulty in procuring other aroyl-MIDA boronates,
this preliminary study examines the reactivity of benzoyl-MIDA boronate with several aryl bromide
substrates.
Received 26 January 2021
Revised 27 April 2021
Accepted 29 April 2021
Available online 12 May 2021
Keywords:
Acylboronate ester
Cross-coupling
Ketone
Acyl donor
Ó 2021 Elsevier Ltd. All rights reserved.
Introduction
[30–32], the aforementioned couplings have the advantage of cat-
alytic action by transition metals (e.g. Pd, Ni, In) under milder con-
Organoboronates are key substrates in metal-catalyzed cross
coupling reactions, most notably the Suzuki-Miyaura reaction [1].
Since its inception in 1979, numerous innovations in Suzuki-
Miyaura cross couplings [2,3] have expanded the applications of
this now-classic reaction to include a range of catalytic metals,
ligands and reaction sub-classes [4]. Over the past 4 decades, an
extensive array of organoboronates that include alkyl, aryl, hetero-
aryl, vinyl, and alkynyl boronates has been investigated as sub-
strates in various cross coupling reactions where the coupling
partner is typically an organobromide/iodide, but which may
now include sulfonate esters, nitrated organics, diazonium salts
[5], N-sulfonyl-aziridines, N-alkylpyridinium salts, and cyclo-
propanes [6].
Within this reaction manifold, ketones can be synthesized in
coupling reactions wherein organoboronates are caused to react
with electrophiles that include aroyl halides [7–10], aroyl- and acyl
anhydrides [11–16], and aroyl esters [17] as reviewed [18]. The
substrate scope of acyl donors now extends to acylimides
[19,20], thioesters, [21–23] and amides [24–29].
ditions that in turn improve functional group tolerance. In these
novel reactions, catalytic transition metals may play different roles.
Although typically, metals oxidatively insert into the acyl donor to
give an acyl-metal species, then transmetalate with the boronic
acid, and ultimately cross-couple via reductive elimination, such
does not necessarily hold in all cases; as a counter-example, in a
Cu-catalyzed ketonization of thioesters, Cu promotes desulfitative
coupling via Lewis-acid coordination, but without the standard
redox cycle of oxidative insertion or reductive elimination
[21,22]. Irrespective of the precise role of the catalytic metal, these
couplings all involve an electrophilic carbonyl attached to a leaving
group that is necessarily more electronegative than the carbon of
the acyl donor. In these cases, the organoboronate partner may
serve as a masked carbon nucleophile (Scheme 1a-g).
In stark contrast to all other acyl/aroyl donors, where the leav-
ing group e.g. NHR, OR, SR, imide, halogen etc., is more electroneg-
ative than carbon, acyl- and aroyl boronates, arguably are
‘‘umpoled” as they present reversed electronegativity. In the case
of nucleophilic acyl substitution, the boronate/borate is not
expected to depart either as a boryl anion or a borane (upon proto-
nation), and such a departure would be kinetically if not also ther-
modynamically unfavorable as it would generally defy
conventional notions of nucleofugacity in nucleophilic acyl substi-
tution reactions. Nevertheless, in a metal-mediated acylation reac-
tion, one could appreciate that acyl boronates might still undergo
In contrast to conventional methods such as Friedel-Crafts acy-
lation or the reaction of various acyl donors with standard
organometallic substrates e.g. Grignards and organo-zinc reagents
⇑
Corresponding author.
E-mail address: dperrin@chem.ubc.ca (D.M. Perrin).
https://doi.org/10.1016/j.tetlet.2021.153147
0040-4039/Ó 2021 Elsevier Ltd. All rights reserved.

S. Lai, N. Takaesu, Wen Xuan Lin et al.
Tetrahedron Letters 74 (2021) 153147
transmetalation, which could then undergo reductive elimination
resulting in cross-coupling as shown putatively in Scheme 2.
As far as organoboronates are concerned, acyl- and aroyl boro-
nates are relative newcomers to the realm of organoboronates.
First discovered by Nozaki [33,34] and made practicable by Molan-
der [35,36], several recent reports have increased synthetic acces-
sibility to the MIDA-acyl- and MIDA-aroyl boronate esters as well
as the corresponding trifluoroborate salts [37–51] and expanded
scope as recently reviewed [52]. Yet to date, the reactivity of
acyl/aroyl-boronates in a Suzuki-Miyaura type coupling reaction
remains altogether unknown, a void that this preliminary report
seeks to fill as we document the attempted Suzuki-Miyaura cou-
pling of MIDA boronates to various organohalides. In this first such
report of its kind, we identify major limitations in substrate scope
and briefly discuss the potential challenges with this reaction. This
reported success in certain cases and associated limitations are
worthy of note in guiding progress in this field.
Results and discussion
As MIDA-esters show greater solubility in organic solvents than
the corresponding trifluoroborates, and by certain measures are
considered to be more amenable to Suzuki-Miyaura coupling
[53,54], we focused on MIDA esters. In addition, in our hands the
corresponding aroyl/acyltrifluoroborates did not couple under
any conditions, which discouraged pursuit of otherwise commer-
cially available aroyltrifluoroborates that are easily synthesized
from aryl-Mg salts that routes that typically deliver the MIDA
esters [39] (see discussion). Hence, to begin, we explored condi-
tions starting with benzoyl-MIDA boronate 1 that we had previ-
ously prepared from phenylvinylboronate MIDA ester and report
yields under conditions noted in Table 1.
Initially, we hypothesized that benzoyl MIDA boronate ester
would react in accordance with standard Suzuki coupling proce-
dures starting with Pd(II) and a bulky phosphine ligand (XPhos)
(entry 2). We favored bulky phosphine ligands because of
enhanced rate of elimination and stabilization of Pd-arene interac-
tion (entry 3). Additionally, these types of ligands minimize adven-
titious oxidation by O2. We found that our target molecule 3a was
formed in 14% isolated yield from a Pd(OAc)2/XPhos-catalyzed
reaction (entry 2) starting with 1 and 4-bromobenzene. Although
low-yielding, this provided a benchmark for screening a multitude
of conditions to improve yields. Hence, we surveyed different types
of palladium sources (10 mol%) in the model reaction between
benzoyl-MIDA boronate ester and 4-bromobenzene in the pres-
ence of different bases (3–6 eq.) under open air conditions and in
a multitude of solvent conditions. From our results, Pd(0) sources
did not support coupling and only Pd(II) precatalysts afforded the
desired product. In our hands, the best results were obtained with
Pd(dppf)*CH2Cl2 (20 mol%) in the absence of any bulky phosphine
ligand. Yields increased with higher catalyst loading with a 10%
increase in yield observed when another 10 mol% of catalyst was
added. Of the commercially available palladium catalysts, PdCl2(-
dppf)*CH2Cl2 gave the most promising results.
Scheme 1. Previous reported synthetic methods for ketone synthesis (top) and this
work (bottom).
A screen of common bases showed that only potassium carbon-
ate (K2CO3) improved yields, while the others were less than opti-
mal. Organic bases such as triethylamine and DBU did not yield
any desired product (entry 9–10). Use of a biphasic mixture of
5:1 DCM/H2O also improved yields. Our rationale for this observa-
tion could be due to the fact that formation of the benzoylboronic
acid depends on aqueous solvolysis of the MIDA ester while the
actual coupling may take place in the organic phase.
Use of higher-boiling solvents e.g. 1,2-dichloroethane or chloro-
form gave little to no product in comparison to CH2Cl2 for reasons
that are not readily intuited. In our control studies, we show that
Scheme 2. Hypothetical mechanism for aroyl-MIDA-boronate ester coupling based
simply on standard Suzuki coupling.
2

S. Lai, N. Takaesu, Wen Xuan Lin et al.
Tetrahedron Letters 74 (2021) 153147
Table 1
Optimization of reaction conditions.
Entry
Cat. (x mol%)/ligand
Base
Additive
Solvent
Temperature (℃)
Yield (%)
1
2
3
4
5
6
7
8
Pd (10)
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
Cs2CO3
CuCO3*Cu(OH)2
NEt3
–
–
–
–
–
–
–
–
–
–
–
–
acetone–water
toluene-water
toluene-water
toluene-water
THF-water
THF-water
THF-water
THF-water
THF-water
90
90
90
90
RT
RT
RT
RT
90
90
60
60
60
60
60
60
60
–
14
2
5
32
–
–
–
–
–
36
68
52
24
25
–
Pd(OAc)2 (10)/XPhos
Pd(OAc)2 (10)/PCy3
Pd(OAc)2(10)/TTBP
PdCl2(dppf)*CH2Cl2(10)
PdCl2(dppf)*CH2Cl2(10)
PdCl2(dppf)*CH2Cl2(10)
PdCl2(dppf)*CH2Cl2(10)
PdCl2(dppf)*CH2Cl2(10)
PdCl2(dppf)*CH2Cl2(10)
PdCl2(dppf)*CH2Cl2 (20)
PdCl2(dppf)*CH2Cl2 (20)
PdCl2(dppf)*CH2Cl2 (10)
PdCl2(dppf)*CH2Cl2 (20)
PdCl2(dppf)*CH2Cl2 (20)
–
9
10
11
12
13
14
15
16
17
DBU
THF-water
THF-water
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
–
DCM-water
DCM-water
DCM-water
DCM-water
DCM-water
DCM-water
–
KFa
b
Cu(OAc)2
–
–
PdCl2(dppf)*CH2Cl2 (20)
–
All reactions were carried out with 0.1 mmol of 1 (1 equiv), 0.11 mmol of 2a (1.1 equiv), Base (6 equiv) 10–20% catalyst loading and 10% ligand loading as indicated above
with the indicated solvent systems (1 mL) for 2–3 h. Reported yields are isolated yields.
a
Added 0.2 mmol (2 equiv).
Added 0.2 mmol (2 equiv).
b
both base and metal catalyst are required as removal of either one
resulted in no product (entry 16–17). Yields were concentration
dependent; as the concentration of the reactants was decreased
(0.5 M), more biphenyl (byproduct) was produced (presumably
due to adventitious reaction with O2 from air) which significantly
lowered the yield of the desired benzophenone due to substrate
depletion. Nevertheless, sparging the solvents with argon prior to
reaction did not significantly improve the yield of the desired
benzophenone.
is also conceivable with the benzoyl boronic acid, it is thus indeed
puzzling as to why the benzoyl species underwent successful cou-
pling. Further studies would be required to address the solvolysis
Following this optimization study, we found that the benzoyl-
MIDA boronate ester 1 reacts well with different aryl bromides
2b-o (see Scheme 3). The majority of the aryl bromides are para
substituted groups 3c-n, but by comparing 3b and 3d, there is no
significant change in yield when the substrate is substituted at
the ortho position. A noteworthy observation is that coupling is rel-
atively rapid; TLC analysis showed total consumption of 1 within
2–3 h for all the substrates. This is compelling information as most
Suzuki-Miyaura reactions require hours, if not overnight, with a
sustained high temperature.
From the isolated yields, we observe that the presence of elec-
tron-withdrawing groups (2h-l, o), including a heteroaromatic
bromopyrimidine gave moderate to good yields while the presence
of electron-donating groups gave mixed results; 2b-g gave reason-
able yields however bromo-phenol 2m and bromo-aniline 2n gave
no detectable ketone. Although reasons for this are not immedi-
ately intuited, we speculate that the aniline could condense with
the aroyl-MIDA ester to form an imine, which has been observed
for 3n and this may serve to reduce yields.
In light of this modest success, several acyl-MIDA esters (alkyl
series) were subjected to the same reaction conditions above.
Unfortunately, none of these underwent Suzuki-Miyaura cross
coupling (Scheme 4).
While the basis for this failure remains entirely unclear, we
posit that upon MIDA solvolysis, the resulting acylboronic acid,
which is to date an elusive species that has never been isolated,
could undergo uncontrolled deborylation at rates that may com-
pete with either metal coordination or transmetalation. While such
Scheme 3. Preparation of biaryl ketones from coupling of benzoyl-MIDA boronate
ester and aryl bromides. 1 (1 eq.) and 2b-o (1.1 eq.) were used in the presence of
PdCl2(dppf)*CH2Cl2 (20 mol%) and 3.33 M K2CO3 (6 equiv) and mixing in DCM
(0.1 M). The reaction is heated to 60 °C. Isolated yields are reported. Yields are an
average of two experiments.
3

S. Lai, N. Takaesu, Wen Xuan Lin et al.
Tetrahedron Letters 74 (2021) 153147
nate esters was not readily achieved, we assert that aroyl MIDA
boronate would need to be procured as previously reported start-
ing with the aryl acetylene precursors followed by hydroboration,
BPin-BMIDA exchange, and then either ozonolysis or Upjohn dihy-
droxylation and Lemieux-Johnson oxidative cleavage [43,44]. By
applying these methodologies, we synthesized two different sub-
stituted benzoyl MIDA boronate esters, 6a-4-fluoro and 6b-4-tert
butyl (Scheme 5). Substrate 6a proved difficult in terms of solubi-
lization, which necessitated modification of the solvent system to
facilitate SMCC. By comparing substrates 7aa, 7ab and 7ac, there
is no significant change in yield with the differing aryl bromides.
Electronically, the anisole and benzonitrile groups did not influ-
ence the coupling capabilities when compared to bromobenzene.
For substrates 7ba, 7bb, and 7bc, there is some discernable differ-
ence between each other. Substrate 7ba displays has the same
yield 3c (Scheme 2) but for 7bb and 7bc, the electronics from the
aryl bromide may have made a difference. SMCC looks to heavily
favor electron-withdrawing aryl bromides more than the elec-
tron-donating ones.
Scheme 4. Acyl-MIDA boronate esters with 4-bromobenzonitrile as possible
Suzuki-Miyaura cross coupling partners.
rates of these substrates and to provide greater mechanistic insight
into this apparent discrepancy which we highlight here. It is note-
worthy that that majority of acylative coupling reports cited herein
have focused on aroyl donors and most note much higher yields for
these compared to aliphatic substrates. It is possible that in the
case of aliphatic substrates, b-hydride elimination may erode
yields compared to the aroyl substrates.
Given the general robustness of Suzuki-Miyaura coupling, we
speculate that this reaction is likely to tolerate electron-releasing
groups on the aryl ring as well, particularly since these sub-
stituents would be considered remote from the site of metal coor-
dination or insertion.
Of note, unlike other conventional Suzuki-Miyaura approaches,
this study was conducted under air- and water-tolerant conditions,
which we sought in terms of convenience. We recognize that the
use of highly reactive palladium catalyst species in conjunction
with inert glove-box conditions may further enhance yields and
may enable coupling to (non-aryl) acyl MIDA boronates. However,
given the utility of the Suzuki-Miyaura reaction outside of a glove
box, we constrained our focus to applications that are user-
friendly, scalable, and readily practicable.
We should also note that in our hands the benzoyltrifluorobo-
rate did not couple. The notable indolence of the corresponding
acyl/aroyltrifluoroborates to coupling is rationalized by recogniz-
ing the considerable kinetic stability of the acyltrifluoroborates to
hydrolysis [55], which is widely accepted to be required for cou-
pling [3,56–58]. While we appreciate that certain aroyl-trifluorob-
orates can be converted to the corresponding MIDA boronate esters
by treatment with MIDA-TMS diesters in the presence of BF3-OEt2
[42], when we treated p-cyanobenzoyl trifluoroborate or the p-ani-
soyl trifluoroborate, we observed no reaction in contrast to the
moderate yields (54–65%) that had previously been reported for
a very limited number of alkyl-substituted aroyl trifluoroborates
[42].
Such considerations notwithstanding, even if one were to
increase yields and expand the substrate scope further, the elabo-
ration of aryl acetylenes to aroyl-MIDA-boronates or accessing
them by converting the trifluoroborates in the presence of the
bis-TMS MIDA diester is likely to make this approach to ketone
synthesis considerably less efficient than if one were to simply
start with the corresponding aroyl ester or amide and couple to a
standard nucleophile.
In conclusion, we report the first example of a coupling an
aroyl-MIDA boronate ester. In so doing, we synthesized a variety
of asymmetric biaryl ketones via Pd-catalyzed cross coupling reac-
tions of benzoyl MIDA boronate ester and aryl bromides. Reactions
with non-aryl acylboronate MIDA esters are attempted as well but
yielded less than stellar results and further research must be done
to incorporate them into future experiments. More importantly,
this work expands the Suzuki-Miyaura cross coupling reaction to
include acylboronate as substrates for coupling, with current limi-
tations as noted herein.
Note added in proof
In the revision of this work, it became evident that Trofimova
et al. Org. Lett. 2021, 23, 9, 3294–3299 have published a similar
study that is consistent with the findings reported herein.
Since in our hands, the conversion of two commercially avail-
able aroyltrifluoroborates to the corresponding aroyl MIDA boro-
Declaration of Competing Interest
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
Acknowledgements
Funding from the Natural Sciences and Engineering Research
Council of Canada (NSERC) is acknowledged.
Appendix A. Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tetlet.2021.153147.
Scheme 5. Suzuki-Miyaura cross coupling of substituted benzoyl-MIDA boronate
esters with aryl bromides.
4

S. Lai, N. Takaesu, Wen Xuan Lin et al.
Tetrahedron Letters 74 (2021) 153147
[31] R.K. Dieter, Tetrahedron 55 (1999) 4177.
References
[32] Y.D. Zhang, T. Rovis, J. Am. Chem. Soc. 126 (2004) 15964.
[33] Y. Segawa, M. Yamashita, K. Nozaki, Science 314 (2006) 113.
[34] Y. Segawa, M. Yamashita, K. Nozaki, Angew. Chem. Int. Ed. 46 (2007) 6710.
[35] G.A. Molander, J. Raushel, N.M. Ellis, J. Org. Chem. 75 (2010) 4304.
[36] G.A. Molander, S.R. Wisniewski, J. Am. Chem. Soc. 134 (2012) 16856.
[37] M. Yamashita, Y. Suzuki, Y. Segawa, K. Nozaki, J. Am. Chem. Soc. 129 (2007)
9570.
[1] A. Biffis, P. Centomo, A. Del Zotto, M. Zeccal, Chem. Rev. 118 (2018) 2249.
[2] C. Seechurn, M.O. Kitching, T.J. Colacot, V. Snieckus, Angew. Chem. Int. Ed. 51
(2012) 5062.
[3] G.A. Molander, N. Ellis, Acc. Chem. Res. 40 (2007) 275.
[4] N. Miyaura, A. Suzuki, Chem. Rev. 95 (1995) 2457.
[5] M.B. Andrus, Y.D. Ma, Y.F. Zang, C. Song, Tetrahedron Lett. 43 (2002) 9137.
[6] A.F. Littke, C.Y. Dai, G.C. Fu, J. Am. Chem. Soc. 122 (2000) 4020.
[7] V.V. Bykov, D.N. Korolev, N.A. Bumagin, Russ. Chem. Bull. 46 (1997) 1631.
[8] M. Haddach, J.R. McCarthy, Tetrahedron Lett. 40 (1999) 3109.
[9] D.D. Martins, L.C.S. Aguiar, O.A.C. Antunes, J. Organomet. Chem. 696 (2011)
2845.
[10] D. Lee, T. Ryu, Y. Park, P.H. Lee, Org. Lett. 16 (2014) 1144.
[11] L.J. Goossen, K. Ghosh, Angew. Chem. Int. Ed. 40 (2001) 3458.
[12] B.W. Xin, Y.H. Zhang, K. Cheng, J. Org. Chem. 71 (2006) 5725.
[13] B.-W. Xin, Synth. Commun. 38 (2008) 2826.
[38] A.M. Dumas, J.W. Bode, Org. Lett. 14 (2012) 2138.
[39] G. Eros, Y. Kushida, J.W. Bode, Angew. Chem. Int. Ed. 53 (2014) 7604.
[40] Z. He, P. Trinchera, S. Adachi, J.D. St Denis, A.K. Yudin, Angew. Chem. Int. Ed. 51
(2012) 11092.
[41] J. Campos, S. Aldridge, Angew. Chem. Int. Ed. 54 (2015) 14159.
[42] H. Noda, J.W. Bode, Chem. Sci. 5 (2014) 4328.
[43] J. Taguchi, T. Ikeda, R. Takahashi, I. Sasaki, Y. Ogasawara, T. Dairi, N. Kato, Y.
Yamamoto, J.W. Bode, H. Ito, Angew. Chem. Int. Ed. 56 (2017) 13847.
[44] M.L. Lepage, S. Lai, N. Peressin, R. Hadjerci, B.O. Patrick, D.M. Perrin, Angew.
Chem. Int. Ed. 56 (2017) 15257.
[45] T. Shiro, A. Schuhmacher, M.K. Jackl, J.W. Bode, Chem. Sci. 9 (2018) 5191.
[46] S.Z.M. Liu, D.N. Wu, J.W. Bode, Org. Lett. 20 (2018) 2378.
[47] S.J. Lin, L. Wang, N. Aminoleslami, Y.T. Lao, C. Yagel, A. Sharma, Chem. Sci. 10
(2019) 4684.
[48] J. Taguchi, T. Takeuchi, R. Takahashi, F. Masero, H. Ito, Angew. Chem. Int. Ed. 58
(2019) 7299.
[49] D. Wu, N.A. Fohn, J.W. Bode, Angew. Chem. Int. Ed. 58 (2019) 11058.
[50] D. Wu, J. Taguchi, M. Tanriver, J.W. Bode, Angew. Chem. Int. Ed. 59 (2020)
16847.
[51] L.J. Cheng, S.L. Zhao, N.P. Mankad, Angew. Chem. Int. Ed., 6.
[52] A. Sterman, I. Sosic, S. Gobec, Z. Casar, ACS Omega 5 (2020) 17868.
[53] D.M. Knapp, E.P. Gillis, M.D. Burke, J. Am. Chem. Soc. 131 (2009) 6961.
[54] J.Q. Li, A.S. Grillo, M.D. Burke, Acc. Chem. Res. 48 (2015) 2297.
[55] Z.B. Liu, D. Chao, Y. Li, R. Ting, J. Oh, D.M. Perrin, Chem. Eur. J. 21 (2015) 3924.
[56] M. Butters, J.N. Harvey, J. Jover, A.J.J. Lennox, G.C. Lloyd-Jones, P.M. Murray,
Angew. Chem. Int. Ed. 49 (2010) 5156.
[14] X.-B. Shen, T.-T. Gao, J.-M. Lu, L.-X. Shao, Appl. Organomet. Chem. 25 (2011)
497.
[15] A. Yu, L. Shen, X. Cui, D. Peng, Y. Wu, Tetrahedron 68 (2012) 2283.
[16] Q. Chen, X.H. Fan, L.P. Zhang, L.M. Yang, Rsc Adv. 4 (2014) 53885.
[17] H. Tatamidani, F. Kakiuchi, N. Chatani, Org. Lett. 6 (2004) 3597.
[18] M. Blangetti, H. Rosso, C. Prandi, A. Deagostino, P. Venturello, Molecules 18
(2013) 1188.
[19] P. Lei, G.R. Meng, Y. Ling, J. An, S.P. Nolan, M. Szostak, Org. Lett. 19 (2017) 6510.
[20] M. Cui, Z.Y. Chen, T.T. Liu, H. Wang, Z. Zeng, Tetrahedron Lett. 58 (2017) 3819.
[21] L.S. Liebeskind, H. Yang, H. Li, Angew. Chem. Int. Ed. 48 (2009) 1417.
[22] J.M. Villalobos, J. Srogl, L.S. Liebeskind, J. Am. Chem. Soc. 129 (2007) 15734.
[23] P. Ghosh, B. Ganguly, E. Perl, S. Das, Tetrahedron Lett. 58 (2017) 2751.
[24] G.R. Meng, M. Szostak, Org. Lett. 17 (2015) 4364.
[25] J.E. Dander, N.K. Garg, Acs Catalysis 7 (2017) 1413.
[26] S.C. Shi, G.R. Meng, M. Szostak, Angew. Chem. Int. Ed. 55 (2016) 6959.
[27] N.A. Weires, E.L. Baker, N.K. Garg, Nat. Chem. 8 (2016) 75.
[28] X.Q. Liu, C.C. Hsiao, L. Guo, M. Rueping, Org. Lett. 20 (2018) 2976.
[29] J. Amani, R. Alam, S. Badir, G.A. Molander, Org. Lett. 19 (2017) 2426.
[30] M.K. Eberle, G.G. Kahle, Tetrahedron Lett. 21 (1980) 2303.
[57] A.J.J. Lennox, G.C. Lloyd-Jones, J. Am. Chem. Soc. 134 (2012) 7431.
[58] A.J.J. Lennox, G.C. Lloyd-Jones, Chem. Soc. Rev. 43 (2014) 412.
5