Palladium-Catalyzed Carbonylative Coupling of Aryl Iodides with Alkenylaluminum Reagents

Article abstract of DOI:10.1021/acs.orglett.9b02923

A highly reactive catalytic system for the carbonylative coupling of aryl iodides with alkenylaluminum reagents has been developed. Various β-substituted γ,δ-unsaturated ketones were produced under mild conditions in good to excellent yields even under ppm level of palladium catalyst. Notably, this also represents the first example on carbonylative transformation of alkenylaluminum compounds. Additionally, by the addition of zinc salt, the selectivity of the product can be modified.

Full text of DOI:10.1021/acs.orglett.9b02923

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Palladium-Catalyzed Carbonylative Coupling of Aryl Iodides with
Alkenylaluminum Reagents
Bo Chen and Xiao-Feng Wu*
Department of Chemistry, Zhejiang Sci-Tech University, Xiasha Campus, Hangzhou 310018, People’s Republic of China
Leibniz-Institut fur Katalyse e. V. an der Universitat Rostock, Albert-Einstein-Straße 29a, 18059 Rostock, Germany
̈
̈
S
* Supporting Information
ABSTRACT: A highly reactive catalytic system for the carbon-
ylative coupling of aryl iodides with alkenylaluminum reagents has
been developed. Various β-substituted γ,δ-unsaturated ketones were
produced under mild conditions in good to excellent yields even
under ppm level of palladium catalyst. Notably, this also represents
the first example on carbonylative transformation of alkenylalumi-
num compounds. Additionally, by the addition of zinc salt, the
selectivity of the product can be modified.
As attracted by the advantages of organoaluminum
compounds and also in order to fill the mentioned gap, we
become interested to develop a new carbonylative coupling
procedure with alkenylaluminums. Initial investigations were
carried out with iodobenzene and (E)-diisobutyl(oct-1-en-1-
yl)aluminum which was prepared by oct-1-yne with
diisobutylaluminum hydride (DIBAL-H) as the model
substrates. To our delight, the target (E)-3-hexyl-1-phenyl-
undec-4-en-1-one can be successfully obtained with Pd(PPh3)4
as the catalyst in THF at 60 °C for 16 h under 10 bar CO with
50% yield (Table 1, entry 1). Next, a set of solvents were
tested, and decreased yields of 3aa were achieved (Table 1,
entries 2−5). Notably, 45% yield of the desired product can
still be obtained by using Pd(OAc)2 and PPh3 as the catalyst
system (Table 1, entry 6). The combination of Pd/C and PPh3
can further increase the reaction outcome to 53% yield (Table
1, entry 7). The yield was able to be further improved to 60%
when DPEphos was used as the ligand among all the tested
systems (Table 1, entries 8−12). The model system was tested
at 80 and 100 °C as well. The best results can be obtained by
performing the reaction at 80 °C (Table 1, entry 13), whereas
a slightly reduced yield of the target product was produced by
performing the reaction at 100 °C (Table 1, entry 14).
Interestingly, we found that decreasing the pressure of CO to 2
bar can further increase the yield (Table 1, entry 15). The
reaction can be performed under 1 bar of carbon monoxide as
well; however, considering the boiling point of solvent is lower
than the reaction temperature, we decided to continue with 2
bar of CO for following studies. It is important to mention that
the yield of the final product is maintained with prolonged
reaction time, and decreased yield was obtained with short
reaction time (10 h) because of the low conversion of
iodobenzene.
rganoaluminum reagents are a class of organometallic
Ocompounds with several attractive advantages, including
low cost, low toxicity, ready availability, and broad tolerance of
various important functional groups which benefit from the
low ionic character of the carbon−aluminum bond.1 As
expected, these features have been recognized by various
research groups. In 1976, Negishi’s group reported the first
example on using organoaluminum compounds in transition-
metal-catalyzed cross-coupling reactions.2 In the subsequent
decades, many cross-coupling reactions with organoaluminum
compounds have been reported.3 Notably, in 2010, Knochel’s
group reported a novel procedure for the preparation of
organoaluminum reagents by directly inserting aluminum
powder into Ar−X (X = I, Br) bonds in the presence of a
catalytic amount of selected metallic chlorides (TiCl4, BiCl3,
InCl3, or PbCl2) together with LiCl as the promotor. The
formed organoaluminum reagents were applied in palladium-
catalyzed cross-coupling and acylation reactions.3i More
recently, Uchiyama’s group performed a systematic study on
nickel-catalyzed cross-coupling reactions of organoaluminum
reagents with various electrophiles for new C−C bond
formation.4 Among the various organoaluminum compounds,
alkenylaluminum compounds are attractive as they can be
easily prepared from the corresponding alkynes by hydro-
alumination with aluminum hydrides such as DIBAL-H.5 They
are attractive reagents for new C−C bond formation and
meanwhile introduce a new alkenyl group into the products.
Furthermore, since its discovery by Heck and co-workers in
1970s, palladium-catalyzed coupling reaction of aryl halides
with CO and various nucleophiles has been widely used both
in academia and industry for the production of carbonyl-
containing compounds.6 Even though many novel palladium-
catalyzed carbonylation reactions have been developed and
applied, to our surprise, no example on using alkenylaluminum
as the nucleophiles in carbonylation has been realized to date.
Received: August 17, 2019
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.9b02923
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Letter
†
Table 1. Selected Results of the Optimization of the
Reaction Conditions
Scheme 1. Substrate Scope of Various Aryl Iodides
a
b
entry
catalyst
ligand
solvent
yield %
1
2
3
4
5
6
7
8
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(OAc)2
Pd/C
Pd/C
Pd/C
Pd/C
Pd/C
-
-
-
-
-
THF
dioxane
PhCl
DMF
DCE
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
50
17
35
22
43
45
53
trace
53
5
PPh3
PPh3
-
Xantphos
DPPE
PCy3
DPEphos
DPEphos
DPEphos
DPEphos
9
10
11
12
13
14
20
60
78
69
Pd/C
Pd/C
Pd/C
Pd/C
d
e
d
,f
c
15
80 (76 )
a
Reaction conditions: 1a (0.5 mmol), 2a (1.25 mmol in hexane),
catalyst (1 mol %), ligand (1 mol % for bidentate ligand, 2 mol % for
monophosphine ligand), solvent (1.0 mL), 10 bar CO, 60 °C, 16 h.
b
c
d
e
f
NMR yield. Isolated yield. 80 °C. 100 °C. 2 bar CO.
With the optimal reaction conditions in hand, we explored
the scope of this carbonylative cascade reaction. First, we
tested the generality of aryl iodides for this reaction. As shown
in Scheme 1, iodobenzene with electron-donating or -with-
drawing substituents can be well tolerated and delivers the
desired products in good to excellent yields (3aa−3qa).
Notably, monoketone and diketone product could be achieved,
respectively, by controlling the equivalent of alkenylaluminum
added (3la, 3ma). Additionally, carbonylative cascade
reactions with heterocyclic and polycyclic iodides also proceed
smoothly and gave the target products in moderate yields
(3ra−3ta). Then we tested some functional group substituted
iodobenzenes including ester, cyano, alkenyl, alkynyl, azido,
indole, and sulfonyl groups which may be sensitive to
alkenylaluminum. Gratifyingly, for these compounds, the
reaction could also give the expected products in good to
excellent yields (3ua−3aba).
Subsequently, we examined different types of alkenylalumi-
num reagents for this carbonylative cascade reaction (Scheme
2). Several aliphatic alkenylaluminum reagents which were
prepared by reacting aliphatic alkynes with DIBAL-H
proceeded well to afford the desired products in moderate to
good yield (3ab−3ah). Aromatic alkenylaluminum compounds
can be tolerated as well, and moderate yields of the
corresponding products can be isolated (3ai−3ak). Interest-
ingly, diene aluminum compounds can also work well in this
reaction and gave the desired product in 72% yield (3al).
When indole-substituted alkenylaluminum reagent was sub-
jected to the reaction conditions, a 64% yield of the
corresponding product was achieved (3am). It is also
interesting to mention that attempting to produce a mixed 3-
R-5-R′-type enone product from two different alkenyl reagents
was unsuccessful. The reaction leads to no selectivity.
Additionally, we tried to prepare cis-alkenylaluminum reagent,
†
Reaction conditions: 1 (0.5 mmol), 2a (1.25 mmol in hexane which
is prepared by oct-1-yne with DIBAL-H), Pd/C (1 mol %), DPEphos
(1 mol %), THF (1.0 mL), 2 bar CO, 80 °C, 16 h, isolated yields.
a
1,4-Diiodobenzene (0.25 mmol).
but failed. However, according to previous works on alkenes,7
cis or trans should have no effect on the outcome of this
reaction.
To gain some insight into the reaction pathway, control
experiments were performed (Scheme 3). Under identical
conditions but using alternative metals such as Fe, Ni, Co, Cu,
and others as catalysts, no desired product 3aa could been
B
DOI: 10.1021/acs.orglett.9b02923
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Scheme 2. Substrate Scope of Various Alkenylaluminum
Compounds
Scheme 3. Control Experiments
†
†
Scheme 4. Carbonylative Synthesis of Ketones
†
Reaction conditions: 1a (0.5 mmol), 2 (1.25 mmol in hexane which
were prepared by corresponding alkynes with DIBAL-H), Pd/C (1
mol %), DPEphos (1 mol %), THF (1.0 mL), 2 bar CO, 80 °C, 16 h,
isolated yields.
detected. This indicates the unique role of palladium catalyst in
this reaction. Using (E)-styrylboronic acid which was a
common alkenylation reagent instead of alkenylaluminum
compound, no reaction occurred under our standard
conditions. It implied alkenylaluminum possessed specific
activity in this reaction. Finally, the cross-coupling compound
4a could be achieved almost quantitatively when combining
(E)-chalcone with (E)-diisobutyl(oct-1-en-1-yl)aluminum in
THF at room temperature for 0.5 h (Scheme 3, eq a). The
reaction also proceeds when benzoyl chloride was applied in
the presence of palladium catalyst (Scheme 3, eq b vs eq c).
Interestingly, when Zn(OAc)2 was added into our model
system, the selectivity can be modified, and an 82% yield of 3-
methyl-1-phenylbutan-1-one was isolated under CO pressure
(30 bar). In the variation of aryl iodide substrates, good yields
and good functional groups tolerance can be obtained
(Scheme 4). The substrates that failed with aluminum reagent
can proceed well under these conditions. In our control
experiments, we found that transmetalation occurred between
zinc salt and aluminum reagent primarily and was then
catalyzed by palladium to give the final product (Scheme 3, eq.
d−f).
†
Reaction conditions: 1 (0.5 mmol), 2a (0.6 mmol in hexane),
Pd(PPh3)4 (1 mol %), Zn(OAc)2 (0.6 mmol), THF (1.0 mL), 30 bar
CO, 80 °C, 16 h, isolated yields. 1,4-Diiodobenzene (0.5 mmol), 2a
(1.2 mmol), Zn(OAc)2 (1.2 mmol).
a
On the basis of our results and literature,8−10 a plausible
reaction pathway is proposed in Scheme 5. First the oxidative
addition of aryl iodide to palladium provides the arylpalladium
complex A, which is followed by migratory insertion of carbon
monoxide giving the acylpalladium complex B. This acylpalla-
dium B will undergo transmetalation with the alkenylalumi-
C
DOI: 10.1021/acs.orglett.9b02923
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Letter
concentration), and good yield of the product 3aa was
Scheme 5. Proposed Reaction Mechanism
obtained with very high TON up to 15600 (Scheme 6).
Scheme 6. Gram-Scale Synthesis
Interestingly, these two selectivities can be combined in one
reaction as well (Scheme 7). By using 1,4-diiodobenzene as the
Scheme 7. Tandem Synthesis
substrate, after the first step reaction, Zn(OAc)2 (1 mmol) was
added to the reaction vial, and then the reaction was placed
back under 30 bar of carbon monoxide at 80 °C for 16 h;
subsequently, 43% of the designed product 6 can be isolated.
In conclusion, we have developed a general and convenient
palladium-catalyzed cascade carbonylation procedure for the
synthesis of β-substituted γ,δ-unsaturated ketones. Started
from readily available aryl iodides and alkenylaluminum
reagents, the desired products were obtained in good yields
in general. Various iodides with different functional groups
were transformed to the corresponding products under mild
conditions. To the best of our knowledge, this is the first
procedure for the carbonylation of alkenylaluminums, which
can even be performed under ppm level of palladium catalyst.
Additionally, by the addition of zinc salt, the selectivity of the
product can modified.
num compound to form the complex C, which will undergo
reductive elimination to form the key enone intermediate D.
Meanwhile the active palladium species will be regenerated and
ready for the next catalytic cycle. At the same time, the formed
α,β-unsaturated ketone D undergoes 1,4-Michael addition to
give the final obtained product E. For the formation of product
5, the in situ production of organozinc reagent occurred.
The developed procedures for the organometallic related
carbonylative coupling reactions usually require loading 1−10
mol % of catalysts.6 Therefore, the discovery of more effective
conditions, for the organometallic carbonylation under low
catalyst loading conditions (less than 0.1 mol %), would be a
considerable advantage for industrial applications and also for
sustainable development. Hence, we tested different catalyst
loading conditions as shown in Table 2. Notably, we found
even 0.01 mol % Pd(PPh3)4 was enough to catalyze this
reaction. Additionally, the practicability of the presented
methodology was demonstrated with a 5 mmol scale reaction
in the presence of 0.005 mol % palladium catalyst (1 ppm
GENERAL PROCEDURE
■
Under an argon atmosphere, a 4 mL screwcap vial was charged
with Pd/C (1 mol %), DPEphos (1 mol %), iodobenzene (0.5
mmol), toluene (1 mL), and an oven-dried stirring bar and
then injected with alkenylaluminum solutions which were
prepared by corresponding alkynes with DIBAL-H. The vial
was closed by a Teflon septum and a phenolic cap and
connected to the atmosphere through a needle. Then the vial
was fixed in an alloy plate and put into Paar 4560 series
autoclave (300 mL). At room temperature, the autoclave is
flushed with carbon monoxide for three times, and 2 bar of
carbon monoxide was charged. The autoclave was placed on a
heating plate equipped with magnetic stirring and an
aluminum block. The reaction was heated at 80 °C for 16 h.
Afterward, the autoclave was cooled to room temperature, and
the pressure was carefully released. After removal of the solvent
under reduced pressure, pure product was obtained by column
chromatography on silica gel (eluent: pentane/ethyl acetate
30:1).
a
Table 2. Catalyst Loading Variation
b
entry
catalyst loading
0.1 mol % Pd(PPh3)4
0.1 mol % Pd(PPh3)4 and 1 mol % PPh3
0.01 mol % Pd(PPh3)4
0.01 mol % Pd(PPh3)4 and 1 mol % PPh3
0.001 mol % Pd(PPh3)4 and 1 mol % PPh3
0.0001 mol % Pd(PPh3)4 and 1 mol % PPh3
yield
1
2
3
4
5
6
81%
88%
22%
86%
10%
2%
a
Reaction conditions: 1a (0.5 mmol), 2a (1.25 mmol in hexane which
is prepared by oct-1-yne with DIBAL-H), THF (1.0 mL), 2 bar CO,
b
80 °C, 16 h. NMR yields.
D
DOI: 10.1021/acs.orglett.9b02923
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Organic Letters
Letter
Aryl Aluminium Reagents: A Protecting-group-free Strategy Attaining
Remarkable Rate Enhancement and Diastereoinduction. Chem.
Commun. 2012, 48, 9376−9378. (h) Biradar, D. B.; Gau, H.-M.
Simple and Efficient Nickel-catalyzed Cross-coupling Reaction of
Alkynylalanes with Benzylic and Aryl Bromides. Chem. Commun.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.9b02923.
■
S
2011, 47, 10467−10469. (i) Blumke, T.; Chen, Y.-H.; Peng, Z.;
̈
Knochel, P. Preparation of Functionalized Organoaluminiums by
Direct Insertion of Aluminium to Unsaturated Halides. Nat. Chem.
2010, 2, 313−318. (j) Terao, J.; Nakamura, M.; Kambe, N. Non-
catalytic Conversion of C-F Bonds of Benzotrifluorides to C-C Bonds
using Organoaluminium Reagents. Chem. Commun. 2009, 6011−
6012. (k) Cooper, T.; Novak, A.; Humphreys, L. D.; Walker, M. D.;
Woodward, S. User-Friendly Methylation of Aryl and Vinyl Halides
and Pseudohalides with DABAL-Me3. Adv. Synth. Catal. 2006, 348,
686−690. (l) Wang, B.; Bonin, M.; Micouin, L. Palladium-Catalyzed
Cross-Coupling of Aryl Electrophiles with Dimethylalkynylaluminum
Reagents. Org. Lett. 2004, 6, 3481−3484. (m) Schumann, H.;
General comments, analytic data, and NMR spectra for
products (PDF)
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: Xiao-Feng.Wu@catalysis.de
ORCID
Xiao-Feng Wu: 0000-0001-6622-3328
Funding
̈
Kaufmann, J.; Schmalz, H.-G.; Bottcher, A.; Gotov, B. Pd-Catalyzed
Cross-Coupling of Haloarenes and Chloroarene-Cr(CO)3 Complexes
with Stabilized Vinyl- and Allylaluminium Reagents. Synlett 2003,
1783−1788. (n) Lipshutz, B. H.; Mollard, P.; Pfeiffer, S. S.; Chrisman,
W. A Short, Highly Efficient Synthesis of Coenzyme Q10. J. Am. Chem.
Soc. 2002, 124, 14282−14283.
(4) Ogawa, H.; Yang, Z.-K.; Minami, H.; Kojima, K.; Saito, T.;
Wang, C.; Uchiyama, M. Revisitation of Organoaluminum Reagents
Affords a Versatile Protocol for C-X (X = N, O, F) Bond-Cleavage
Cross-Coupling: A Systematic Study. ACS Catal. 2017, 7, 3988−
3994.
(5) (a) Akiyama, K.; Gao, F.; Hoveyda, A. H. Stereoisomerically
Pure Trisubstituted Vinylaluminum Reagents and their Utility in
Copper-Catalyzed Enantioselective Synthesis of 1,4-Dienes Contain-
ing Z or E Alkenes. Angew. Chem., Int. Ed. 2010, 49, 419−423.
(b) Gao, F.; McGrath, K. P.; Lee, Y.; Hoveyda, A. H. Synthesis of
Quaternary Carbon Stereogenic Centers through Enantioselective
Cu-Catalyzed Allylic Substitutions with Vinylaluminum Reagents. J.
Am. Chem. Soc. 2010, 132, 14315−14320. (c) May, T. J.; Dabrowski,
J. A.; Hoveyda, A. H. Formation of Vinyl-, Vinylhalide- or Acyl-
Substituted Quaternary Carbon Stereogenic Centers through NHC-
Cu-Catalyzed Enantioselective Conjugate Additions of Si-Containing
Vinylaluminums to β-Substituted Cyclic Enones. J. Am. Chem. Soc.
C.B. thanks the Chinese Scholarship Council (CSC) for
financial support.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The analytical support of Dr. W. Baumann, Dr. C. Fisher, S.
Buchholz, and S. Schareina (all in LIKAT) is gratefully
acknowledged.
REFERENCES
■
(1) (a) Negishi, E.-i.; Takahashi, T.; Baba, S.; Van Horn, D. E.;
Okukado, N. Nickel- or Palladium-catalyzed Cross Coupling. 31.
Palladium- or Nickel-catalyzed Reactions of Alkenylmetals with
Unsaturated Organic Halides as a Selective Route to Arylated
Alkenes and Conjugated Dienes: Scope, Limitations, and Mechanism.
J. Am. Chem. Soc. 1987, 109, 2393−2401. (b) Negishi, E.-i. Palladium-
or Nickel-catalyzed Cross Coupling. A New Selective Method for
Carbon-Carbon Bond Formation. Acc. Chem. Res. 1982, 15, 340−348.
(c) Ku, S.-L.; Hui, X.-P.; Chen, C.-A.; Kuo, Y.-Y.; Gau, H.-M.
AlAr3(THF): Highly Efficient Reagents for Cross-Couplings with Aryl
Bromides and Chlorides Catalyzed by the Economic Palladium
Complex of PCy3. Chem. Commun. 2007, 3847−3849. (d) Zweifel,
G.; Miller, J. A. In Organic Reactions; Dauben, W. G., Ed.; Wiley: New
York, 1984.
2011, 133, 736−739. (d) Cottet, P.; Muller, D.; Alexakis, A. Copper-
̈
Catalyzed Asymmetric Conjugate Addition of Alkenyl- and
Alkylalanes to α,β-Unsaturated Lactams. Org. Lett. 2013, 15, 828−
831. (e) Takimoto, M.; Hou, Z. Cu-Catalyzed Formal Methylative
and Hydrogenative Carboxylation of Alkynes with Carbon Dioxide:
Efficient Synthesis of α,β-Unsaturated Carboxylic Acids. Chem. - Eur.
J. 2013, 19, 11439−11445. (f) McGrath, K. P.; Hoveyda, A. H. A
Multicomponent Ni-, Zr-, and Cu-Catalyzed Strategy for Enantiose-
lective Synthesis of Alkenyl-Substituted Quaternary Carbons. Angew.
Chem., Int. Ed. 2014, 53, 1910−1914.
(2) Baba, S.; Negishi, E.-i. A Novel Stereospecific Alkenyl-Alkenyl
Cross-Coupling by a Palladium- or Nickel-catalyzed Reaction of
Alkenylalanes with Alkenyl halides. J. Am. Chem. Soc. 1976, 98, 6729−
6731.
(3) (a) Shrestha, B.; Thapa, S.; Gurung, S. K.; Pike, R. A. S.; Giri, R.
General Copper-Catalyzed Coupling of Alkyl-, Aryl-, and Alkynyla-
luminum Reagents with Organohalides. J. Org. Chem. 2016, 81, 787−
802. (b) Minami, H.; Saito, T.; Wang, C.; Uchiyama, M.
Organoaluminum-Mediated Direct Cross-Coupling Reactions.
Angew. Chem., Int. Ed. 2015, 54, 4665−4668. (c) Chen, X.; Zhou,
L.; Li, Y.; Xie, T.; Zhou, S. Synthesis of Heteroaryl Compounds
through Cross-Coupling Reaction of Aryl Bromides or Benzyl Halides
with Thienyl and Pyridyl Aluminum Reagents. J. Org. Chem. 2014, 79,
230−239. (d) Klatt, T.; Groll, K.; Knochel, P. Generation of
Functionalized Aryl and Heteroaryl Aluminum Reagents by Halogen-
lithium Exchange. Chem. Commun. 2013, 49, 6953−6955. (e) An-
drews, P.; Latham, C. M.; Magre, M.; Willcox, D.; Woodward, S.
ZrCl2(η-C5Me5)2-AlHCl2η(THF)2: Efficient Hydroalumination of
Terminal Alkynes and Cross-coupling of the Derived Alanes. Chem.
(6) (a) Brennfuhrer, A.; Neumann, H.; Beller, M. Palladium-
̈
Catalyzed Carbonylation Reactions of Aryl Halides and Related
Compounds. Angew. Chem., Int. Ed. 2009, 48, 4114−4133. (b) Peng,
J.-B.; Geng, H.-Q.; Wu, X.-F. The Chemistry of CO: Carbonylation.
Chem. 2019, 5, 526−552.
(7) Wu, X.-F.; Fang, X.; Wu, L.; Jackstell, R.; Neumann, H.; Beller,
M. Transition-Metal-Catalyzed Alkynes: A Personal Account. Acc.
Chem. Res. 2014, 47, 1041−1053.
(8) Zhao, K.; Shen, L.; Shen, Z.-L.; Loh, T.-P. Transition Metal-
catalyzed Cross-coupling Reactions using Organoindium Reagents.
Chem. Soc. Rev. 2017, 46, 586−602.
(9) Echavarren, A. M.; Stille, J. K. Palladium-catalyzed Carbonylative
Coupling of Aryl Triflates with Organostannanes. J. Am. Chem. Soc.
1988, 110, 1557−1565.
(10) (a) Ireland, R. E.; Wipf, P. Carboalumination of 1-Alkynes and
in situ Transmetalation to Higher order Cyanocuprates. Stereospecific
Synthesis of Tri- and Disubstituted Olefins by Conjugate Addition to
Enones. J. Org. Chem. 1990, 55, 1425−1426. (b) Wipf, P.; Smitrovich,
J. H.; Moon, C. Transmetalation Reactions of Alkenylalanes: Copper-
Commun. 2013, 49, 1488−1490. (f) Groll, K.; Blumke, T. D.; Unsinn,
̈
A.; Haas, D.; Knochel, P. Direct Pd-Catalyzed Cross-Coupling of
Functionalized Organoaluminum Reagents. Angew. Chem., Int. Ed.
2012, 51, 11157−1161. (g) Kawamura, S.; Kawabata, T.; Ishizuka, K.;
Nakamura, M. Iron-catalysed Cross-coupling of Halohydrins with
E
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catalyzed Conjugate Addition to Enones. J. Org. Chem. 1992, 57,
3178−3186.
F
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