Zirconium-Catalyzed Synthesis of Alkenylaminoboranes: From a Reliable Preparation of Alkenylboronates to a Direct Stereodivergent Access to Alkenyl Bromides

Article abstract of DOI:10.1021/acs.orglett.0c00908

A simple procedure has been optimized for the preparation of alkenylaminoborane from alkynes using diisopropylaminoborane and HZrCp₂Cl. Coupled with a magnesium-catalyzed dehydrogenation, it allowed for the use of air- and moisture-stable diisopropylamine. This synthesis has been extended to a one-pot sequence leading directly to bromoalkenes with controlled stereochemistry. As such, it provides an easy, scalable, cheap process to access alkenylboronates and both (E)- and (Z)-bromoalkenes from commercially available alkynes.

Full text of DOI:10.1021/acs.orglett.0c00908

pubs.acs.org/OrgLett
Letter
Zirconium-Catalyzed Synthesis of Alkenylaminoboranes: From a
Reliable Preparation of Alkenylboronates to a Direct
Stereodivergent Access to Alkenyl Bromides
́
Melodie Birepinte, Virginie Liautard, Laurent Chabaud, and Mathieu Pucheault*
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ABSTRACT: A simple procedure has been optimized for the preparation of alkenylaminoborane from alkynes using
diisopropylaminoborane and HZrCp2Cl. Coupled with a magnesium-catalyzed dehydrogenation, it allowed for the use of air-
and moisture-stable diisopropylamine. This synthesis has been extended to a one-pot sequence leading directly to bromoalkenes with
controlled stereochemistry. As such, it provides an easy, scalable, cheap process to access alkenylboronates and both (E)- and (Z)-
bromoalkenes from commercially available alkynes.
lkenylboron derivatives are versatile building blocks1
Scheme 1. Relevant Precedent Examples in the Literature
2
Atraditionally used in Suzuki−Miyaura or Chan−Lam−
Evans cross-coupling reactions. Recently, they have been
elegantly used in metal-free halide-mediated carbon−carbon
bond formation.3 Similarly to most arylboron derivatives,
alkenylboronates can be obtained by the addition of the
corresponding Grignard or lithiated compounds to trialkox-
yboranes or other boron-centered electrophiles. However, the
difficult preparation of vinylmetal and the low stability of the
carbon−boron bond as borate usually lead to significantly
lower yields than for the corresponding aromatic derivatives.
Alternatively, transition-metal-catalyzed borylation of alkenyl-
halides or triflates is more efficient but somehow limited by the
accessibility of starting materials, prepared in one or two steps
from commercially available reagents. The reaction scope
could nonetheless be widened by using dehydrogenative
coupling of alkenes with boranes, which is often easier on
styrenyl derivatives. Hence, alkyne hydroboration remains the
most reliable, high-yielding, and robust access to alkenylbor-
anes.4 Over the last 50 years, many boranes have been used in
this reaction, mostly, 9-BBN, (ipc)2BH, Cy2BH, pinacolborane,
and catecholborane.5 Depending on the substrates, the
Received: March 11, 2020
reaction can be sluggish and unselective, which led to the
development of catalysts based on transition metal complexes
of Rh,6−8 Ir,9,10 Ru,11−13 Co,14−16 Al,17,18 Fe,19−22 Cu,23,24
Mg,25,26 or Zr (Scheme 1-1).27 The resulting product function
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solely depends on the hydroboration reagent nature and often
requires a tricky selective postfunctionalization to be used in
the next synthetic steps.
hexyne proceeded at 70 °C with 100% conversion in MTBE
(Scheme 3a). The reaction was also quite efficient in THF and
Aminoorganoboranes, on the other hand, are likely to be
easily transformed in most common boronic acid derivatives
using simple workup procedures and represent a more versatile
synthon family.28,29 Access to these compounds has widely
been described.28,30−36 For alkenyl analogues, only palladium-
catalyzed borylation of vinyltriflates and vinyl halides37 has
been reported. Indeed, diisopropylaminoborane is unreactive
in direct hydroboration of alkenes or alkynes, due to its poor
Lewis acidity. This reagent is isoelectronic from diisopropyle-
thene and one of the few aminoboranes that exists under
monomeric form in solution.38 So far, hydroboration of alkyne
using aminoborane has only been described with 40% yield
using unstable pyrroloborane.39 Amine borane complexes and
alkynes can react intramolecularly (Scheme 1-4)40 using gold
catalysts (Scheme 1-3)41 or using borenium intermediates42
generated with stoichiometric I2 or HNTf2 (Scheme 1-2).43 In
most cases, using organometallic catalysis with the alkyne/
amine borane combination usually leads to hydrogen release,
which is directly used in the semihydrogenation of the
alkyne.44,45 As zirconocenes have been shown to dehydrogen-
ate amine borane complexes leading to poly(aminoborane) or
poly(iminoborane),46 an extra challenge was determining
conditions under which the alkyne would react faster with
zirconium hydride than the borane.
Scheme 3. Hydroboration Using Various Borane Sources
MTBE (Supporting Information Table 1, entries 1−3), as the
reaction was complete after 16 h. In MTBE, either the reaction
time or the catalyst loading could be reduced without a
significant loss in conversion and yield (Supporting Informa-
tion Table 1, entries 6−13).
One of the downsides of DIPOB is related to its relative
instability toward air and moisture, requiring distillation prior
to use. These limitations could be bypassed by inducing in situ
dehydrogenation of the corresponding diisopropylaminebor-
ane complex (DIPAB). Direct reaction with DIPAB was
unsuccessful (Scheme 3b). However, as described previously,28
DIPAB dehydrogenation could be performed at room
temperature using as little as 5 mol % of PhMgBr, among
other Mg complexes (Scheme 2A).51−53 We, therefore,
attempted to sequentially add PhMgBr and, after 5 min,
Schwartz reagent (Scheme 3c). Solvent and catalyst loading
variation were performed (Supporting Information Table 2).
The quantity of Schwartz reagent should be greater than the
one required for dehydrogenation. Hence if 5% of PhMgBr is
used, 10 to 12% of HZrCp2Cl would ensure reproducible
results, and the product was isolated in 92% yield. Noticeably,
amine borane complexes have been known to participate in
transition-metal-catalyzed reaction with multiple carbon−
carbon bonds, but usually as hydrogen sources, leading to
alkanes,54,55 not hydroboration reagents.
Mechanistically, we hypothesized that hydrozirconation of
alkyne followed by reaction with di-iso-propylaminoborane
(DIPOB) would lead to alkenylaminoborohydride via σ-bond
metathesis or intermolecular addition followed by direct
hydride transfer (Scheme 2B). The addition of organo-
Scheme 2. Proposed Catalytic Cycles
If the reaction could be run using in situ dehydrogenation
followed by the hydroboration itself, remaining Grignard has
led during the scoping study to side reactions and generally
lower yields than those obtained with pure DIPOB. The study
was therefore pursued using the aminoborane, keeping in mind
that careful optimization of stoichiometry between PhMgBr
and HZrCp2Cl could prevent side reactions to occur on some
trickier substrates. An example will be given of this in the last
part of this study with the in situ bromination.
After having checked that conversions were complete on
most simple substrates (Scheme 4), we found that the reaction
worked equally well on 1-methylbutynol provided that 2 equiv
of DIPOB was used. Only aniline and methylester were found
to be incompatible with the reaction conditions (Scheme 4).
As some substrates were less reactive, a 4 h reaction time was
kept as a standard. The versatility of the reaction was proven
using classical workup procedures on a few substrates in order
to obtain the various boron derivatives (29 examples, Scheme
5), which could easily be accessed from alkenylaminoboranes:
1,5-diazaborolanes using 1,8-diaminonaphthalene (Scheme
5A) and boronic esters using pinacol (Scheme 5B) or
neopentyl glycol (Scheme 5C). In the case of Bdan, the
purification over silica gel led to yield diminution. However,
zirconium reagents has been found to proceed only on
chloroboranes only using Pd and Ni complexes.47−50 In this
reaction, despite the high Lewis acidity of the chloroborane, no
direct addition of organozirconium was observed.47 However,
initial tests showed that vinylzirconium was reacting quite
efficiently on DIPOB, and the resulting compound was a
mixture of the vinylaminoborane and Schwartz reagent. The
putative intermediate alkenylaminoborohydride was not
observed to strengthen the σ-bond metathesis pathway, and
the zirconium hydride was regenerated completely. As a result,
it triggered the possibility of a catalytic version of the reaction,
assuming the reaction conditions would be compatible with
the hydrozirconation of alkyne. Indeed using 1.1 equiv of
DIPOB and 12 mol % of ZrCp2HCl, the hydroboration of
B
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(4n), phthalimide (4l, 5l), silylether (4j, 5j), and silane (4m).
As witnessed by the reaction on enyne (4i, 5i), the
hydroboration of carbon−carbon double bonds was not
observed, even on nonconjugated substrates bearing multiple
functionalities such as lynestrenol (4p). To date, mestranol,
despite displaying no potentially problematic functional group,
failed to react even using 20 mol % of catalyst at a higher
temperature.
Scheme 4. Synthesis of Alkenylaminoboranes
As previously mentioned, the reaction can be performed
directly on air-stable amine borane complexes. 4-Phenylbut-1-
yne was converted to the corresponding boronate in 96% yield
on a 10 mmol scale over the course of 4 reactions performed in
a single pot (dehydrogenation using PhMgBr, Zr-catalyzed
hydroboration, dehydrocoupling with MeOH, and trans-
esterification with the neopentylglycol or pinacol, Scheme 6).
On substituted propargyl alcohol (fluorenol and lynestrenol),
the reaction works equally well, affording the neopentylglycol
boronates in 92% and 88% yield, respectively.
The tandem dehydrogenation−hydroboration process was
then extended to the formation of vinyl bromide. These
compounds are highly useful building blocks for cross-coupling
reactions, and classical preparation methods usually afford
configurationally more stable (E)-bromoolefins.56 After opti-
mization (see Supporting Information), we found that a
methanolysis followed by a treatment with CuBr2 in a
THF:H2O mixture was leading to the (E)-bromoolefin
(Scheme 7A), whereas a direct addition of Br2, followed by a
basic methanolysis using MeONa, provided mostly the (Z)-
the alkenyldiazaborolane was still isolated in 53−93% yield
depending on the starting material. The reaction tolerates
chloride (3h), substituted phenyl rings (3d, 3e, 3f), and
silylated alcohols (3j). Ene-yne is fairly reactive, affording
borylated diene in 53% yield. In general, substitution by an
alkyl chain led to the best isolated yields (3a, 3b, 3g, 3h, 3j, 3k,
and 3l). For pinacolboronate and neopentylglycol boronates,
yields are generally higher (63−98%) due to the lower
propensity of protodeborylation during purification. Group
tolerance is very similar, and the reaction is efficient in the
presence of alcohols (4c, 5n, 5o), chlorides (4h, 5h), bromides
Scheme 5. Synthesis of Alkenyldiazaborolanes
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((E)-6d and (Z)-6d; (E)-6e and (Z)-6e), products were
isolated in good yields, but selectively was displaced in favor of
the (E)-olefin due to further isomerization into the most stable
isomer under the reaction conditions.
Scheme 6. Reaction Extension Using in Situ
Dehydrogenation
Overall, di-iso-propylaminoborane, which is unreactive
toward alkene and alkyne, was found to be a good
hydroboration reagent when combined with HClZrCp2 used
as a catalyst. The reaction was optimized on various substrates,
including alcohols and halides, which could be incompatible
with classical hydroboration conditions. Depending on the
workup conditions, the resulting alkenylaminoboranes could
be transformed into the corresponding borinic acid derivatives
(diaminoboranes or boronates) but also into bromoolefins by
displacement of the boron atom by bromine. The last reaction
could, at will, provide both bromoalkene stereoisomers without
requiring isolation of the boron intermediate. Finally, as
DIPAB is air and moisture stable, this hydroboration reagent
could advantageously replace more reactive boranes which are
often quite sensitive.
bromoolefin (Scheme 7B). The reaction could also be
performed starting from DIPOB and the alkyne, but the in
situ dehydrogenation usually provided better results by
avaoiding the manipulation of sensitive aminoborane. With
this stereodivergent method in hand, we prepared 19 different
bromoolefins with a very good control of stereochemistry in
the case of (E)-isomers (E:Z ratio >94:6) (Scheme 7A).
Similarly, when the resulting olefin is not bound to an sp2
carbon, the (Z)-isomers were isolated with almost perfect
control of the stereochemistry (Z:E ratio >94:6). For dec-1,9-
diyne, both (E)-6g and (Z)-6g isomers were isolated in good
yields and good stereoselectivity, 56% (E:Z 98:2) and 84%
(Z:E 96:4), respectively. In most cases, alkyl-derived
bromoolefins were obtained in good yields ((E)-6b and (Z)-
6b; (E)-6h and (Z)-6h; and (E)-6k and (Z)-6k). The reaction
is mostly limited by the product volatility as witnessed by the
impracticality of obtaining a pure sample of (Z)-bromobutene
and (Z)-bromohexene (Z)-6a despite a complete conversion
and a >80% NMR yield. The problem was similar to TBDMS-
acetylene products ((E)-6m and (Z)-6m), for which the
selectivity was close to perfect (>99:1), but yields were
deceivingly low (41% and 46%, respectively). For enyne
products ((E)-6i and (Z)-6i), as well as styrenyl bromides
ASSOCIATED CONTENT
■
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* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.0c00908.
1
Experimental procedure and H, 11B, 13C NMR and
HRMS of compounds (PDF)
AUTHOR INFORMATION
■
Corresponding Author
́
Mathieu Pucheault − Institut des Sciences Moleculaires, UMR
́
5255, CNRS, Universite de Bordeaux 33405 Talence, France;
orcid.org/0000-0002-7001-2803;
Email: mathieu.pucheault@u-bordeaux.fr
Scheme 7. Stereodivergent Access to Bromoolefins
D
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(20) Nakajima, K.; Kato, T.; Nishibayashi, Y. Org. Lett. 2017, 19
(16), 4323−4326.
(21) Gorgas, N.; Alves, L. G.; Stoger, B.; Martins, A. M.; Veiros, L.
́
́
Melodie Birepinte − Institut des Sciences Moleculaires, UMR
̈
́
5255, CNRS, Universite de Bordeaux 33405 Talence, France
F.; Kirchner, K. J. Am. Chem. Soc. 2017, 139 (24), 8130−8133.
(22) Zhang, L.; Peng, D.; Leng, X.; Huang, Z. Angew. Chem., Int. Ed.
2013, 52 (13), 3676−3680.
́
Virginie Liautard − Institut des Sciences Moleculaires, UMR
5255, CNRS, Universite de Bordeaux 33405 Talence, France
Laurent Chabaud − Institut des Sciences Moleculaires, UMR
5255, CNRS, Universite de Bordeaux 33405 Talence, France;
́
́
(23) Semba, K.; Fujihara, T.; Terao, J.; Tsuji, Y. Chem. - Eur. J. 2012,
18 (14), 4179−4184.
́
orcid.org/0000-0002-2590-8707
(24) Bidal, Y. D.; Lazreg, F.; Cazin, C. S. J. ACS Catal. 2014, 4 (5),
1564−1569.
Complete contact information is available at:
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(25) Li, J.; Luo, M.; Sheng, X.; Hua, H.; Yao, W.; Pullarkat, S. A.;
Xu, L.; Ma, M. Org. Chem. Front. 2018, 5 (24), 3538−3547.
(26) Magre, M.; Maity, B.; Falconnet, A.; Cavallo, L.; Rueping, M.
Angew. Chem., Int. Ed. 2019, 58 (21), 7025−7029.
(27) Pereira, S.; Srebnik, M. Organometallics 1995, 14 (7), 3127−
3128.
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
(28) Marciasini, L. D.; Richard, J.; Cacciuttolo, B.; Sartori, G.;
Birepinte, M.; Chabaud, L.; Pinet, S.; Pucheault, M. Tetrahedron
2019, 75 (2), 164−171.
Notes
(29) Wood, J. L.; Marciasini, L.; Vaultier, M.; Pucheault, M. Synlett
2014, 25, 551−555.
The authors declare no competing financial interest.
(30) Marciasini, L. D.; Vaultier, M.; Pucheault, M. Tetrahedron Lett.
2014, 55 (10), 1702−1705.
ACKNOWLEDGMENTS
■
́
This work was funded by the Universite de Bordeaux and the
(31) Guerrand, H. D. S.; Marciasini, L. D.; Jousseaume, M.; Vaultier,
M.; Pucheault, M. Chem. - Eur. J. 2014, 20 (19), 5573−5579.
(32) Guerrand, H. D. S.; Marciasini, L. D.; Gendrineau, T.; Pascu,
O.; Marre, S.; Pinet, S.; Vaultier, M.; Aymonier, C.; Pucheault, M.
Tetrahedron 2014, 70 (36), 6156−6161.
̀
́
CNRS. M.B. thanks the Ministere de l’Enseignement Super-
ieur, de la Recherche et de l’Innovation for a fellowship. V.L.
thanks AST Innovations for funding.
(33) Pascu, O.; Marciasini, L.; Marre, S.; Vaultier, M.; Pucheault,
M.; Aymonier, C. Nanoscale 2013, 5 (24), 12425−12431.
(34) Marciasini, L. D.; Richy, N.; Vaultier, M.; Pucheault, M. Adv.
Synth. Catal. 2013, 355 (6), 1083−1088.
(35) Gendrineau, T.; Marre, S.; Vaultier, M.; Pucheault, M.;
Aymonier, C. Angew. Chem., Int. Ed. 2012, 51 (34), 8525−8528.
(36) Euzenat, L.; Horhant, D.; Ribourdouille, Y.; Duriez, C.; Alcaraz,
G.; Vaultier, M. Chem. Commun. 2003, 18, 2280−2281.
(37) Euzenat, L.; Horhant, D.; Brielles, C.; Alcaraz, G.; Vaultier, M.
J. Organomet. Chem. 2005, 690 (11), 2721−2724.
(38) Robertson, A. P. M.; Leitao, E. M.; Jurca, T.; Haddow, M. F.;
Helten, H.; Lloyd-Jones, G. C.; Manners, I. J. Am. Chem. Soc. 2013,
135 (34), 12670−12683.
(39) Pasumansky, L.; Haddenham, D.; Clary, J. W.; Fisher, G. B.;
Goralski, C. T.; Singaram, B. J. Org. Chem. 2008, 73 (5), 1898−1905.
(40) Yuan, K.; Suzuki, N.; Mellerup, S. K.; Wang, X.; Yamaguchi, S.;
Wang, S. Org. Lett. 2016, 18 (4), 720−723.
(41) Wang, Q.; Motika, S. E.; Akhmedov, N. G.; Petersen, J. L.; Shi,
X. Angew. Chem., Int. Ed. 2014, 53 (21), 5418−5422.
(42) De Vries, T. S.; Prokofjevs, A.; Vedejs, E. Chem. Rev. 2012, 112
(7), 4246−4282.
(43) Clay, J. M.; Vedejs, E. J. Am. Chem. Soc. 2005, 127 (16), 5766−
5767.
REFERENCES
■
(1) Vaultier, M.; Pucheault, M. Science of Synthesis; Houben Weyl -
Thieme Verlag VCH, 2012; Vol. 6.
(2) Miyaura, N., Organoboron Compounds. In Cross-Coupling
Reactions; Miyaura, N., Ed.; Springer Berlin/Heidelberg: 2002; Vol.
219, pp 11−59.
(3) Leonori, D.; Aggarwal, V. K. Angew. Chem., Int. Ed. 2015, 54 (4),
1082−1096.
(4) Zaidlewicz, M.; Wolan, A.; Budny, M. 8.24 Hydrometallation of
CC and CC Bonds. Group 3. In Comprehensive Organic Synthesis II,
2nd ed.; Knochel, P., Ed.; Elsevier: Amsterdam, 2014; pp 877−963.
(5) Barbeyron, R.; Benedetti, E.; Cossy, J.; Vasseur, J.-J.; Arseniyadis,
S.; Smietana, M. Tetrahedron 2014, 70 (45), 8431−8452.
(6) Pereira, S.; Srebnik, M. Tetrahedron Lett. 1996, 37 (19), 3283−
3286.
(7) Ohmura, T.; Yamamoto, Y.; Miyaura, N. J. Am. Chem. Soc. 2000,
122 (20), 4990−4991.
(8) Carreras, L.; Serrano-Torne, M.; van Leeuwen, P. W. N. M.;
Vidal-Ferran, A. Chem. Sci. 2018, 9 (15), 3644−3648.
(9) Knorr, J. R.; Merola, J. S. Organometallics 1990, 9 (12), 3008−
3010.
(10) Iwadate, N.; Suginome, M. Org. Lett. 2009, 11 (9), 1899−1902.
(11) Burgess, K.; Jaspars, M. Organometallics 1993, 12 (10), 4197−
4200.
́
(44) Vasilikogiannaki, E.; Titilas, I.; Vassilikogiannakis, G.; Stratakis,
M. Chem. Commun. 2015, 51 (12), 2384−2387.
(45) Fu, S.; Chen, N.-Y.; Liu, X.; Shao, Z.; Luo, S.-P.; Liu, Q. J. Am.
Chem. Soc. 2016, 138 (27), 8588−8594.
(46) Helten, H.; Dutta, B.; Vance, J. R.; Sloan, M. E.; Haddow, M.
F.; Sproules, S.; Collison, D.; Whittell, G. R.; Lloyd-Jones, G. C.;
Manners, I. Angew. Chem., Int. Ed. 2013, 52, 437−440.
(47) Daini, M.; Suginome, M. Chem. Commun. 2008, 41, 5224−
5226.
(12) Sundararaju, B.; Fu
(52), 14050−14054.
(13) Gunanathan, C.; Holscher, M.; Pan, F.; Leitner, W. J. Am.
Chem. Soc. 2012, 134 (35), 14349−14352.
(14) Obligacion, J. V.; Neely, J. M.; Yazdani, A. N.; Pappas, I.;
Chirik, P. J. J. Am. Chem. Soc. 2015, 137 (18), 5855−5858.
(15) Guo, J.; Cheng, B.; Shen, X.; Lu, Z. J. Am. Chem. Soc. 2017, 139
(43), 15316−15319.
̈
rstner, A. Angew. Chem., Int. Ed. 2013, 52
̈
(48) Daini, M.; Suginome, M. J. Am. Chem. Soc. 2011, 133, 4758−
4761.
(16) Ben-Daat, H.; Rock, C. L.; Flores, M.; Groy, T. L.; Bowman, A.
C.; Trovitch, R. J. Chem. Commun. 2017, 53 (53), 7333−7336.
(17) Yang, Z.; Zhong, M.; Ma, X.; Nijesh, K.; De, S.; Parameswaran,
P.; Roesky, H. W. J. Am. Chem. Soc. 2016, 138 (8), 2548−2551.
(18) Bismuto, A.; Thomas, S. P.; Cowley, M. J. Angew. Chem., Int.
Ed. 2016, 55 (49), 15356−15359.
(49) Daini, M.; Yamamoto, A.; Suginome, M. J. Am. Chem. Soc.
2008, 130, 2918−2919.
(50) Daini, M.; Yamamoto, A.; Suginome, M. Asian J. Org. Chem.
2013, 2, 968−976.
(51) Spielmann, J.; Bolte, M.; Harder, S. Chem. Commun. 2009, 45,
6934−6936.
(19) Espinal-Viguri, M.; Woof, C. R.; Webster, R. L. Chem. - Eur. J.
2016, 22 (33), 11605−11608.
E
https://dx.doi.org/10.1021/acs.orglett.0c00908
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
pubs.acs.org/OrgLett
Letter
(52) Liptrot, D. J.; Hill, M. S.; Mahon, M. F.; MacDougall, D. J.
Chem. - Eur. J. 2010, 16 (28), 8508−8515.
(53) Hill, M. S.; Hodgson, M.; Liptrot, D. J.; Mahon, M. F. Dalton
Trans 2011, 40 (30), 7783−7790.
(54) Sloan, M. E.; Staubitz, A.; Lee, K.; Manners, I. Eur. J. Org.
Chem. 2011, 2011 (4), 672−675.
(55) Revunova, K.; Nikonov, G. I. Dalton Trans 2015, 44 (3), 840−
866.
(56) Kabalka, G. W.; Mereddy, A. R. Organometallics 2004, 23 (19),
4519−4521.
F
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