Reductive cross-coupling of conjugated arylalkenes and aryl bromides with hydrosilanes by cooperative palladium/copper catalysis

Article abstract of DOI:10.1002/anie.201511975

A method for the reductive cross-coupling of conjugated arylalkenes and aryl bromides with hydrosilanes by cooperative palladium/copper catalysis was developed, thus resulting in the highly regioselective formation of various 1,1-diarylalkanes, including a biologically active molecule. Under the applied reaction conditions, high levels of functional-group tolerance were observed, and the reductive cross-coupling of internal alkynes with aryl bromides afforded trisubstituted alkenes. Forming a Co-op: A method for the reductive cross-coupling of conjugated arylalkenes or internal alkynes and aryl bromides with hydrosilanes using cooperative palladium/copper catalysis was developed. The resulting 1,1-diarylalkanes and trisubstituted alkenes were isolated with high regio- and stereoselectivity. Under the applied reaction conditions, high levels of functional-group tolerance were observed.

Full text of DOI:10.1002/anie.201511975

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International Edition: DOI: 10.1002/anie.201511975
German Edition: DOI: 10.1002/ange.201511975
Alkenes
Reductive Cross-Coupling of Conjugated Arylalkenes and Aryl
Bromides with Hydrosilanes by Cooperative Palladium/Copper
Catalysis
Kazuhiko Semba,* Kenta Ariyama, Hong Zheng, Ryohei Kameyama, Shigeyoshi Sakaki,* and
Yoshiaki Nakao*
Abstract: A method for the reductive cross-coupling of
conjugated arylalkenes and aryl bromides with hydrosilanes
by cooperative palladium/copper catalysis was developed, thus
resulting in the highly regioselective formation of various 1,1-
diarylalkanes, including a biologically active molecule. Under
the applied reaction conditions, high levels of functional-group
tolerance were observed, and the reductive cross-coupling of
internal alkynes with aryl bromides afforded trisubstituted
alkenes.
Cross-coupling reactions of aryl halides with 1-arylalkyl
metal species represent a convenient method to prepare 1,1-
diarylalkanes,[4] which are often found in biologically active
compounds.[5] 1-Arylalkylmetal reagents such as organoboron
and organosilicon compounds are conventionally prepared by
the transition metal catalyzed hydrometallation of styrenes.[6]
The resulting 1-arylalkylmetal reagents are subsequently
purified and used for the cross-coupling with aryl halides.
Sigman and co-workers then developed reductive cross-
coupling reactions of styrenes with arylstannanes[7a] or
arylboronic esters[7b] in the presence of iPrOH as a hydrogen
source to afford 1,1-diarylethanes via an alkylpalladium
species [Eq. (3)]. However, in these reactions, the scope
with respect to the alkenes is limited to vinylarenes, and in
many cases the main-group aryl nucleophiles have to be
prepared from the corresponding aryl halides. Herein, we
report the reductive cross-coupling of conjugated arylalkenes
and aryl bromides with hydrosilanes by cooperative palla-
dium/copper catalysis [Eq. (4)].[8,9] This reaction furnishes
a variety of 1,1-diarylalkanes in a highly regioselective
manner from the palladium-catalyzed coupling of the 1-
arylalk-1-ylcopper species generated in situ by catalytic
hydrocupration[10] of arylalkenes with aryl halides.[11]
T
ransition metal catalyzed cross-coupling reactions of alkyl
and alkenyl organometallic reagents represent a powerful
method for the alkylation and alkenylation, respectively, of
organic electrophiles.[1] The hydrometallation of alkenes and
alkynes is an atom-efficient and practical way to prepare alkyl
and alkenyl metal reagents, respectively, because a variety of
main-group metal hydrides, alkenes, and alkynes are readily
available.[2] However, these organometallic nucleophiles are
usually presynthesized and often purified prior to subsequent
cross-coupling reactions [Eq. (1)], and such processes gen-
erally involve multistep operations. In contrast, cross-cou-
pling reactions based on organometallic nucleophiles gener-
ated by hydrometallation of alkenes and alkynes with
a catalytic amount of transition-metal hydrides in situ can
be more step-economical, because this process requires just
a single operation, and isolation of the organometallic
reagents is not necessary [Eq. (2)].[3]
To evaluate the validity of Equation (4), we carried out
cross-coupling reaction of the alkylcopper 1a, which is
prepared from hydrocupration of styrene (2a), with p-
bromoanisole (3a) in the presence of Pd(OAc)2/tricyclopen-
tylphosphane (PCyp3) [Equation (5); see Equation (S1) in the
Supporting Information].[12] As a result, 4a was obtained in
98% yield. This result encouraged us to develop a catalytic
reaction.
[*] Dr. K. Semba, K. Ariyama, R. Kameyama, Prof. Dr. Y. Nakao
Department of Material Chemistry, Graduate School of Engineering
Kyoto University
Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan)
E-mail: semba.kazuhiko.5n@kyoto-u.ac.jp
nakao.yoshiaki.8n@kyoto-u.ac.jp
Dr. H. Zheng, Prof. Dr. S. Sakaki
Fukui Institute for Fundamental Chemistry, Kyoto University
Sakyo-ku, Kyoto 606-8103 (Japan)
After optimization of various reaction parameters,[12] we
found that in the presence of Pd(OAc)2 (1.0 mol%), PCyp3
(2.0 mol%), (SIPr)CuCl (10 mol%), and LiOtBu (1.2 mmol),
the reductive cross-coupling of 2a with 3a and HSi(OEt)3
afforded 1,1-diarylalkane 4a in 94% yield with concomitant
E-mail: sakaki.shigeyoshi.47e@st.kyoto-u.ac.jp
Supporting information for this article can be found under:
http://dx.doi.org/10.1002/anie.201511975.
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Table 1: Reductive cross-coupling of arylalkenes with aryl bromides and
HSi(OEt)3.
Entry
1
2
3
Yield [%][a]
2a
3a
60 (4a)
formation of small amounts of ethylbenzene (5a) and anisole
(6a) [Eq. (6)]. In the absence of Pd(OAc)2, Pd(OAc)2/PCyp3,
or (SIPr)CuCl under otherwise identical reaction conditions,
4a was not formed. These results clearly demonstrate that the
cooperative palladium/copper catalysis is indispensable for
the present reaction.
2
PhBr (3b)
52 (4b)
52 (4c)
61 (4d)
76 (4e)
3[b]
2b
2b
2b
4
5[c]
6
2a
81 (4 f)
7[c,d]
3b
3b
3b
71 (4a)
85 (4g)
71 (4h)
8[e]
The reaction of 2a and 3a could be scaled up to 0.60 mmol
with respect to 2a, and 4a was isolated in 60% yield (Table 1,
entry 1). The substrate scope was examined by using various
styrene derivatives (2a–h) and aryl bromides (3a–g) as shown
in Table 1. In all cases, the reactions proceeded in a highly
regioselective manner (> 20:1) to afford a range of 1,1-
diarylalkanes. In some cases, the reactivity of [(MeIPr)CuCl]
was observed to be superior to that of [(SIPr)CuCl]
(entries 8–13). When electron-rich or electron-deficient aryl
bromides were employed, the corresponding 1,1-diarylal-
kanes were obtained in moderate to good yields (entries 1–5).
The presence of an ortho substituent on the aryl bromide did
not affect the yield and regioselectivity (entry 6). Moreover,
4-methoxystyrene (2c), 3-trifluoromethylstyrene (2d), and 2-
vinylnaphthalene (2e) reacted in good yield (entries 7–9).
Notably, the biologically active 1,1-diarylethane 4i[5c] was
obtained in 85% yield (entry 10). However, not only vinyl-
arenes, but also internally conjugated arylalkenes are viable
substrates for reaction conditions similar to the standard ones
(entries 11–13). A modest yield was observed for trans-
stilbene (2 f) and trans-1-phenyl-1-propene (2g), whereas the
1,1-diaryloctane 4l was obtained in 81% yield from (E)-1-
aryl-1-octene (2h). Various functional groups such as F, CF3,
NEt2, OTBS, and CO2R remained unaffected under the
applied reaction conditions. Other alkenes such as cis-
stilbene, indene, a-methylstyrene, or 1-octene did not afford
9[e]
10[e]
2e
85 (4i)
11[c,d,e]
3b
3b
48 (4j)
46 (4k)
12[d,e]
13[e]
3b
81 (4l)
[a] Yield of isolated product. [b] Used 0.60 mmol 3c. [c] Used 1.2 mmol
alkene and 0.60 mmol aryl bromide. [d] Used 0.50 mol% Pd(OAc)2 and
1.0 mol% PCyp3. [e] Used 10 mol% [(MeIPr)CuCl] instead of [(SIPr)CuCl].
TBS=tert-butyldimethylsilyl.
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These results imply that a three-coordinated palladium
complex, which would be generated through dissociation of
PCyp3 from 8a, is reactive for the transmetallation. In the
catalytic reaction, a less sterically hindered phosphane such as
P(nPr)3 did not afford 4n [Eq. (8)], probably because P(nPr)3
stabilizes the corresponding four-coordinated palladium com-
plex, thus making it unreactive for the transmetallation. In
fact, transmetallation between {[P(nPr)3]2Pd(p-biphenyl)-
(Br)} and 1a was sluggish at 608C for 15 hours [Eq. (S3)].[12]
To determine the stereochemistry of the transmetallation,
[D]-1b was prepared by syn addition of copper deuteride,
which was generated from [(MeIPr)CuCl], LiOtBu, and
D2SiPh2, to 2g [Eq. (9)].[14] The cross-coupling reaction of
[D]-1b with 3a in the presence of Pd(OAc)2/PCyp3 gave [D]-
4o in a stereospecific manner [Eq. (10)].
Scheme 1. Proposed reaction mechanism.
the corresponding cross-coupling products under the standard
reaction conditions.
A plausible mechanism for this reaction, consisting of
individual palladium- and copper-catalyzed cycles, is outlined
in Scheme 1. Initially, the copper hydride 12 is generated from
the copper alkoxide 11 and HSi(OEt)3 (step e). The regiose-
lective hydrocupration of the 1-arylalkene with 12 then
affords the alkylcopper 1 [step f; Eq. (S1)]. Transmetallation
of 1 with [(PCyp3)2Pd(Ar)Br] (8), which is generated from the
oxidative addition of 3 across [Pd(PCyp3)2] (7), is followed by
a reductive elimination from the three-coordinated palladium
species 9 to afford 4 and 10 (steps b and c).[13] The copper
alkoxide 11 is then regenerated from [(NHC)CuBr] (10) and
LiOtBu (step d).
To gain some insight into the reaction mechanism, the
reaction of 2a with 3b was monitored by 31P NMR spectros-
copy. During the course of the reaction, [(PCyp3)2Pd(Br)Ph]
(8a) was the only species observed by 31P NMR spectroscopy
[Eq. (S2)].[12] Thus, 8a is likely a resting state in the palladium
cycle. The stoichiometric reaction of 8a and 1a afforded 4m
in 88% yield, and [(MeIPr)CuBr] was isolated in 69% yield
[Eq. (7)]. In contrast, addition of PCyp3 retarded the reaction.
Excess PCyp3 also hampered the catalytic reaction [Eq. (8)].
This result indicates that the transmetallation proceeds
with inversion of the configuration.[15] To better understand
the transmetallation process, we carried out theoretical
calculations by using DFT method.[12] As shown in Figure 1,
the transmetallation occurs through weak Pd–Cu adducts (13
and 14) and via a transition-state TS14–15. The initial adduct 13
is moderately more stable than the sum of the starting
complexes and reluctant to undergo the transmetallation
before the phosphane dissociation to give 14. The trans-
metallation of the 1-phenylethyl group (abbreviated as R
below) takes place from 14 via TS14–15, in which the Pd–C (of
R) distance somewhat decreases, the Cu–C (of R) distance
moderately increases, and the geometry change occurs in the
alkyl group [Pd–C (of R) = 2.529 Š, Cu–C (of R) = 2.008 Š,
Pd–Cu = 4.202 Š, and the dihedral angle around the alkyl C =
1978; see Figure S14].[12] The evaluated Gibbs activation
energy is 28.0 kcalmolÀ1 relative to 13, and is not very large
for a thermal reaction.[16] This value matches well with the
idea that the transmetallation would be rate-determining and
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hydrosilanes by cooperative palladium/copper catalysis has
been developed, thus giving 1,1-diarylalkanes and trisubsti-
tuted alkenes in a highly regio- and stereoselective manner.
Mechanistic studies revealed that stereoinvertive transmetal-
lation including dissociation of one phosphane is likely rate-
determining and that PCyp3 and MeIPr selectively coordinate
to palladium and copper, respectively, in both catalytic and
stoichiometric reactions. This information is quite beneficial
for the new palladium/copper-catalyzed reactions. Further
studies on details of the reaction mechanism and the
development of an asymmetric variation are currently in
progress.
Figure 1. Geometry and Gibbs free energy changes in the transmetalla-
tion between 8a and (SIPr)CuR (R=1-phenylethyl).
Acknowledgments
the experimental result that the high temperature (1008C) is
needed [Eq. (8)]. Though the product 15 is less stable than 13,
it is likely that the subsequent reductive elimination easily
occurs in the case of a palladium complex. It is noted that this
activation energy is smaller than that of the stereoretentive
transmetallation, which agrees well with the experimental
result (see Figure S16). Finally, it is worth mentioning that the
crossover of the ligands PCyp3 and MeIPr coordinated to
palladium and copper, respectively, is unlikely under the
catalytic and stoichiometric reaction conditions [Equa-
tion (7); see Equation (S2)].
This research was supported by a Grant-in-Aid for Young
Scientists (B) (26810058) from MEXT and the CREST
program “Establishment of Molecular Technology towards
the Creation of New Functions” Area from JST.
Keywords: alkenes · alkynes · copper · cross-coupling ·
palladium
How to cite: Angew. Chem. Int. Ed. 2016, 55, 6275–6279
Angew. Chem. 2016, 128, 6383–6387
[1] a) N. Miyaura, Top. Curr. Chem. 2002, 219, 11; b) T. Hiyama, E.
Shirakawa, Top. Curr. Chem. 2002, 219, 61; c) K. Fugami, M.
Kosugi, Top. Curr. Chem. 2002, 219, 87; d) “Palladium-Catalyzed
Reactions Involving Reductive Elimination”: Handbook of
Organopalladium Chemistry for Organic Synthesis, Vol. 1 (Ed.:
E. Negishi), Wiley, New York, 2002, pp. 215 – 994; e) R. Jana,
T. P. Pathak, M. S. Sigman, Chem. Rev. 2011, 111, 1417; f) J.
Terao, N. Kambe, Acc. Chem. Res. 2008, 41, 1545; g) E. Negishi,
G. Wang, H. Rao, Z. Xu, J. Org. Chem. 2010, 75, 3151.
To extend the present strategy to alkenylation reactions,
we examined the reductive cross-coupling of the alkynes 16
with the aryl bromides 3 using a similar catalytic system
[Eq. (11)]. Whereas Maleczka and co-workers have already
[2] For reviews on hydrometallation, see: a) B. M. Trost, Z. T. Ball,
Synthesis 2005, 853; b) Modern Reduction Methods (Eds.: P. G.
Andersson, I. J. Munslow), Wiley-VCH, Weinheim, 2008.
[3] For reviews on reductive cross-coupling reactions of carbon–
carbon unsaturated compounds with carbonyls, see: a) E. P.
Jackson, H. A. Malik, G. J. Sormunen, R. D. Baxter, P. Liu, H.
Wang, A.-R. Shareef, J. Montgomery, Acc. Chem. Res. 2015, 48,
1736; b) E. Skucas, M.-Y. Ngai, V. Komanduri, M. J. Krische,
Acc. Chem. Res. 2007, 40, 1394; c) H.-Y. Jang, M. J. Krische, Acc.
Chem. Res. 2004, 37, 653.
[4] a) Y. Hatanaka, T. Hiyama, J. Am. Chem. Soc. 1990, 112, 7793;
b) D. Imao, B. W. Glasspoole, V. S. Laberge, C. M. Crudden, J.
Am. Chem. Soc. 2009, 131, 5024; c) B. W. Glasspoole, M. S.
Oderinde, B. D. Moore, A. Antoft-Finch, C. M. Crudden, Syn-
thesis 2013, 1759; d) M. A. Schade, A. Metzger, S. Hug, P.
Knochel, Chem. Commun. 2008, 3046; e) C. I. Someya, S. Inoue,
S. Krackl, E. Irran, S. Enthaler, Eur. J. Inorg. Chem. 2012, 1269.
[5] For selected references on biologically active 1,1-diarylalkanes,
see: a) K. Srinivas, N. Srinivasan, K. S. Reddy, M. Ramakrishna,
C. R. Reddy, M. Arunagiri, R. L. Kumari, S. Venkataraman,
V. T. Mathad, Org. Process Res. Dev. 2005, 9, 314; b) K. Vukics,
T. Fodor, J. Fischer, I. Fellegvµri, S. LØvai, Org. Process Res. Dev.
2002, 6, 82; c) M. Alami, S. Messaoudi, A. Hamze, O. Provot, J.-
D. Brion, J.-M. Liu, J. Bignon, J. Bakala, Patent WO/2009/147217
A1, Dec 10, 2009.
reported similar transformations using catalytically generated
alkenylstannanes to access disubstituted alkenes,[17] the pres-
ent reaction allows concise synthesis of trisubstituted
alkenes.[18] A good yield was observed in the case of
diphenylacetylene (16a), whereas
a modest yield was
observed in the case of 6-dodecyne (16b). When 1-phenyl-1-
butyne (16c) was employed, the reaction afforded a regioiso-
mer mixture of trisubstituted alkenes 17c and 17c’’ in 87%
total yield (17c/17c’ = 88:12). Terminal alkynes such as 1-
octyne and phenylacetylene were not viable substrates for
these reaction conditions.[19]
[6] For selected references on the hydroboration of styrenes, see:
a) T. Hayashi, Y. Matsumoto, Y. Ito, J. Am. Chem. Soc. 1989, 111,
3426; b) C. M. Crudden, Y. B. Hleba, A. C. Chen, J. Am. Chem.
In conclusion, the reductive cross-coupling of conjugated
arylalkenes or internal alkynes with aryl bromides and
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Chemie
Soc. 2004, 126, 9200; c) D. Noh, H. Chea, J. Ju, J. Yun, Angew.
Yamamoto, Bull. Chem. Soc. Jpn. 1981, 54, 1868; b) K. Tatsumi,
Chem. Int. Ed. 2009, 48, 6062; Angew. Chem. 2009, 121, 6178; for
selected references on the hydrosilylation of styrenes, see: d) T.
Hayashi, K. Tamao, Y. Katsuro, I. Nakae, M. Kumada, Tetrahe-
dron Lett. 1980, 21, 1871; e) K. Kitayama, Y. Uozumi, T.
Hayashi, J. Chem. Soc. Chem. Commun. 1995, 1533.
R. Hoffmann, A. Yamamoto, J. K. Stille, Bull. Chem. Soc. Jpn.
1981, 54, 1857.
[14] Selected references on syn addition of copper hydride across
conjugated arylalkenes: a) Ref. [10e]; b) D. Noh, S. K. Yoon, J.
Won, J. Y. Lee, J. Yun, Chem. Asian J. 2011, 6, 1967; c) J. Won, D.
Noh, J. Yun, Y. Lee, J. Phys. Chem. A 2010, 114, 12112.
[15] References on stereospecific cross-coupling of stereochemically
defined organometallics with inversion of the configuration:
a) J. W. Labadie, J. K. Stille, J. Am. Chem. Soc. 1983, 105, 6129;
b) ref. [4a]; c) K. W. Kells, J. M. Chong, J. Am. Chem. Soc. 2004,
126, 15666; d) T. Ohmura, T. Awano, M. Suginome, J. Am.
Chem. Soc. 2010, 132, 13191; e) D. L. Sandrock, L. Jean-GØrard,
C. Chen, S. D. Dreher, G. A. Molander, J. Am. Chem. Soc. 2010,
132, 17108; f) J. C. H. Lee, R. McDonald, D. G. Hall, Nat. Chem.
2011, 3, 894; g) L. Li, S. Zhao, A. Joshi-Pangu, M. Diane, M. R.
Biscoe, J. Am. Chem. Soc. 2014, 136, 14027; h) ref. [8h].
[16] TS14–15 was defined on the potential energy surface, as usual.
Though TS14–15 is slightly less stable than 14 in terms of potential
energy, TS14–15 is slightly more stable than 14 in terms of Gibbs
energy, because the potential energy is very flat for the
transmetallation (see Figure S15). It is concluded that the
transmetallation occurs with nearly no barrier after phosphane
dissociation.
[17] a) R. E. Maleczka, Jr., I. Terstiege, J. Org. Chem. 1998, 63, 9622;
b) R. E. Maleczka, Jr., W. P. Gallagher, I. Terstiege, J. Am.
Chem. Soc. 2000, 122, 384; c) W. P. Gallagher, I. Terstiege, R. E.
Maleczka, Jr., J. Am. Chem. Soc. 2001, 123, 3194; d) R. E.
Maleczka, Jr., W. P. Gallagher, Org. Lett. 2001, 3, 4173; e) W. P.
Gallagher, R. E. Maleczka, Jr., J. Org. Chem. 2005, 70, 841.
[18] The nickel-catalyzed reductive coupling of diphenylacetylene
with aryl bromides using HSiEt3 has been reported. However,
the reaction exclusively affords anti-addition products: D. W.
Robbins, J. F. Hartwig, Science 2011, 333, 1423.
[7] a) K. M. Gligorich, S. A. Cummings, M. S. Sigman, J. Am. Chem.
Soc. 2007, 129, 14193; b) Y. Iwai, K. M. Gligorich, M. S. Sigman,
Angew. Chem. Int. Ed. 2008, 47, 3219; Angew. Chem. 2008, 120,
3263; c) K. M. Gligorich, Y. Iwai, S. A. Cummings, M. S. Sigman,
Tetrahedron 2009, 65, 5074.
[8] For selected examples on cooperative palladium/copper catal-
ysis, see: a) K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron
Lett. 1975, 16, 4467; b) L. S. Liebeskind, R. W. Fengl, J. Org.
Chem. 1990, 55, 5359; c) J. Huang, J. Chan, Y. Chen, C. J. Borths,
K. D. Baucom, R. D. Larsen, M. M. Faul, J. Am. Chem. Soc.
2010, 132, 3674; d) F. Nahra, Y. MacØ, D. Lambin, O. Riant,
Angew. Chem. Int. Ed. 2013, 52, 3208; Angew. Chem. 2013, 125,
3290; e) S. Vercruysse, L. Cornelissen, F. Nahra, L. Collard, O.
Riant, Chem. Eur. J. 2014, 20, 1834; f) F. Nahra, Y. MacØ, A.
Boreux, F. Billard, O. Riant, Chem. Eur. J. 2014, 20, 10970;
g) K. B. Smith, K. M. Logan, W. You, M. K. Brown, Chem. Eur.
J. 2014, 20, 12032; h) K. M. Logan, K. B. Smith, M. K. Brown,
Angew. Chem. Int. Ed. 2015, 54, 5228; Angew. Chem. 2015, 127,
5317.
[9] Recently, we reported the arylboration of alkenes by coopera-
tive palladium/copper catalysis: a) K. Semba, Y. Nakao, J. Am.
Chem. Soc. 2014, 136, 7567; the arylboration of alkenes was
independently reported Brown and co-workers, see b) ref. [8g];
c) ref. [8h].
[10] For the hydrocupration of 3-hexyne, see: a) N. P. Mankad, D. S.
Laitar, J. P. Sadighi, Organometallics 2004, 23, 3369; the hydro-
cupration of styrenes has been proposed in the context of
hydroboration and hydroamination of styrene derivatives, see
b) Ref. [6c]; c) Y. Miki, K. Hirano, T. Satoh, M. Miura, Angew.
Chem. Int. Ed. 2013, 52, 10830; Angew. Chem. 2013, 125, 11030;
d) S. Zhu, N. Niljianskul, S. L. Buchwald, J. Am. Chem. Soc.
2013, 135, 15746; e) Y.-M. Wang, N. C. Bruno, . L. Placeres, S.
Zhu, S. L. Buchwald, J. Am. Chem. Soc. 2015, 137, 10524.
[11] For pioneering work on palladium-catalyzed cross-coupling
reactions with organocopper reagents, see a) ref. [8a]; b) N.
Jabri, A. Alexakis, J. F. Normant, Tetrahedron Lett. 1981, 22, 959.
[12] See the Supporting Information for details.
[19] The reaction of 1-octyne afforded the corresponding hydro-
arylated products in ca. 10% yield as estimated by GC and GC-
MS analyses. In the case of phenylacetylene, dehydrogenative
À
silylation of the C(sp) H bond proceeded, exclusively.
Received: December 28, 2015
Revised: February 20, 2016
Published online: April 15, 2016
[13] References on reductive elimination from three-coordinated
palladium species: a) F. Ozawa, T. Ito, Y. Nakamura, A.
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