A diphenyl ether derived bidentate secondary phosphine oxide as a preligand for nickel-catalyzed C-S cross-coupling reactions

Article abstract of DOI:10.1039/c5ob01874a

A new bidentate secondary phosphine oxide (SPO) was synthesized from diphenyl ether via ortho-lithiation, phosphorylation with PhP(Cl)NEt₂, and hydrolysis in an acidic medium. Nickel(0) species ligated with this new SPO was established as a mor

Full text of DOI:10.1039/c5ob01874a

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A diphenyl ether derived bidentate secondary
phosphine oxide as a preligand for nickel-
Cite this: DOI: 10.1039/c5ob01874a
catalyzed C–S cross-coupling reactions†
Received 9th September 2015,
Accepted 6th October 2015
Nadeesha P. N. Wellala and Hairong Guan*
DOI: 10.1039/c5ob01874a
www.rsc.org/obc
A new bidentate secondary phosphine oxide (SPO) was synthesized
from diphenyl ether via ortho-lithiation, phosphorylation with PhP
(Cl)NEt2, and hydrolysis in an acidic medium. Nickel(0) species
ligated with this new SPO was established as a more effective cata-
lyst than Ni(0)–Ph2P(O)H for the cross-coupling of aryl iodides
with aryl thiols.
Scheme 1 Tautomeric equilibria of SPOs and their P-bound
complexes.
Secondary phosphine oxides (SPOs) have become increasingly
important for transition-metal-catalyzed reactions.1 They are
often described as preligands because upon mixing with a
metal complex or salt, the tautomeric equilibria between SPOs
and phosphinous acids are usually shifted to the trivalent-
phosphorus compounds, resulting in the formation of
P-bound complexes (Scheme 1). In rare cases, however, SPOs
can coordinate to a metal via the oxygen lone pair without iso-
merization to the phosphinous acids.2 The attractiveness of
using SPOs for catalysis stems from the fact that they are gene-
rally air and moisture stable. For reactions under basic con-
ditions, the coordinated phosphinous acids can be
deprotonated, which may provide additional benefits,
especially for catalytic reactions requiring an electron-rich
metal center. The calculated Tolman’s electronic parameters
for O-anionic phosphinito ligands3 have suggested that these
ligands are more donating than many trialkylphosphines.4 In
the early 2000s, Li and co-workers first demonstrated the
success of SPOs such as (t-Bu)2P(O)H in promoting palladium-
or nickel-catalyzed C–C, C–N and C–S cross-coupling reac-
tions.5 Since then, many new SPOs have been developed as
preligands for cross-coupling reactions6 and other catalytic
processes.7–10
Scheme 2 Reactivity of nickel POCOP-pincer complexes in C–S cross-
coupling reactions.
mechanistic investigation focusing on catalyst 1 showed that,
under the catalytic conditions, the pincer scaffold was
degraded to Ph2POK, PPh3 and other phosphorus-containing
products. The true catalytically active species was proposed to
be an SPO-ligated Ni(0) complex based on the observation that
Ni(COD)2–Ph2P(O)H exhibited similar catalytic activity.
Ph2P(O)H, though effective, was shown to react with KOH at
80 °C to yield PPh3 and some unidentified species, which com-
promised its ability to promote the catalytic reactions.
To develop a more efficient catalytic system, we shifted our
attention to bidentate SPOs under the premise that chelating
ligands would be less likely to dissociate from metals to
provide the opportunity for a base to decompose the ligands.
It should be mentioned that two mono SPOs can coordinate to
the same metal, and with the loss of proton(s), can be tethered
together by hydrogen bonding (structure A in Fig. 1),5,6k,7a–e,12
or via electrostatic interactions with an alkali ion (structure
We became interested in SPOs several years ago when we
were exploring catalytic applications of nickel POCOP-pincer
complexes for C–S cross-coupling reactions (Scheme 2).11 Our
Department of Chemistry, University of Cincinnati, P.O. Box 210172, Cincinnati,
Ohio 45221-0172, USA. E-mail: hairong.guan@uc.edu; Fax: (+1)513-556-9239;
Tel: (+1)513-556-6377
†Electronic supplementary information (ESI) available: Experimental procedures
and spectroscopic characterization data (NMR and IR) in pdf format. See DOI:
10.1039/c5ob01874a
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spectrum. The IR spectrum of 3 revealed a characteristic band
at 2333 cm−1 for the P–H bond stretch.20 Separation of the two
diastereomers was not attempted, and the isomeric mixture
described above was used directly for the C–S cross-coupling
study.
Cross-coupling of iodobenzene (4) with 3-methyl-
benzenethiol (5) was selected for the optimization of the reac-
tion conditions (Table 1). In order to use the catalytic system
Ni(COD)2–Ph2P(O)H (1 : 2) as a benchmark, substrate concen-
trations, the amount of base (2 equiv. of KOH with respect to 5),
solvent (DMF) and temperature (80 °C) were initially kept the
same as those used in our previous study with the mono
SPO.11 A series of experiments with variable amounts of cata-
lyst (entries 1–4) showed that a catalyst loading as low as
0.5 mol% was sufficient for obtaining a nearly quantitative GC
yield of the sulfide 6a, in which case the cross-coupling reac-
tion was completed in 1 h (entry 3). By comparison, the reac-
tion catalyzed by Ni(COD)2–Ph2P(O)H needed 2 h and 1 mol%
catalyst. As expected, control experiments without using Ni
(COD)2 or 3 or both under otherwise the same conditions
showed a negligible amount of product formed, confirming
that both nickel and the ligand are required. At room tempera-
ture, almost no sulfide product was detected (entry 5). Unlike
the mono SPO system,11 weaker bases such as K3PO4 (entry 6)
and Na2CO3 (entry 7) could be used here in place of KOH
without affecting the GC yield of 6a. Interestingly, NaOH,
which was shown to be as effective as KOH in the mono SPO
system, was an inferior base for the new catalytic system,
giving a noticeably lower product yield (entry 8). Both catalytic
systems suffered low yields when Cs2CO3 (entry 9) or NaOMe
(entry 10) was used as the base, or when the reaction was
Fig. 1 Complexes bearing a pseudo bidentate SPO (A and B, charge-
localized forms) and SPOs with a covalent backbone.
B),4 thus mimicking a bidentate SPO ligand. For bidentate
ligands with a covalent backbone, we are aware of only one
study in which a ferrocene unit was used to link two SPOs
(ligand 2).13 Our design of new bidentate SPO ligands was
inspired by van Leeuwen’s DPEphos, which was prepared from
diphenyl ether14 and successfully employed in cross-coupling
reactions.15 Recently, we sought to prepare the analogous SPO
ligand 3, guided by the hypothesis that the large bite angle
and the central oxygen atom might be particularly beneficial
for the reductive elimination of ArSAr′.16
Synthesis of the targeted ligand 3 was accomplished in
three steps as illustrated in Scheme 3. Slow addition of PhP(Cl)
NEt2 to the lithiated diphenyl ether was necessary for obtain-
ing a good product yield. The final hydrolysis step had to be
carried out using a concentrated HCl solution.17 Other stan-
dard methods for preparing SPOs from RP(R′)NEt2 (e.g., hydro-
lysis on silica gel13 or with Amberlyst-15®,18 or conversion to
RP(R′)H using LiAlH4 or LiBEt3H19 followed by air oxidation)
proved to be unsuccessful here. Analytically pure 3 was
obtained from recrystallization of the crude product in ethyl
acetate at −5 °C, which resulted in 46% overall isolated yield
starting from diphenyl ether. The 31P{1H} NMR spectrum of 3
in CDCl3 showed two singlets at 13.75 and 13.87 ppm with an
integration ratio of 28 : 72. This is due to fact that there are
two (meso and racemic) diastereomers of 3. The presence of a
diastereomeric mixture was further confirmed by 1H NMR
spectroscopy, which gave the same ratio for the PH and aro-
Table 1 Optimization of the catalytic conditionsa
1
matic resonances. The one-bond coupling constant JP–H was
measured to be 503 Hz from the proton-coupled 31P NMR
Temp.
(°C)
Time
(h)
GC yieldb
(%)
Entry
x
Solvent Base
1
2
3
4
5
6
7
8
5
1
80
80
80
0.5
1
1
24
24
1
1
1
1
1
1
1
1
1
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
THF
KOH
KOH
KOH
KOH
>99
>99
99
0.5
0.25 80
59
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
23
80
80
80
80
80
80
80
80
80
KOH
Trace
>99
98
87
10
6
6
Trace
95c
45c,d
K3PO4
Na2CO3
NaOH
Cs2CO3
NaOMe
KOH
9
10
11
12
13
14
Toluene KOH
DMF
DMF
KOH
KOH
a Reaction conditions: 1.1 mmol of 4, 1.0 mmol of 5, 2.0 mmol of base
(except entries 13 and 14), Ni(COD)2-3 (variable), and 1.0 mmol n-
decane (GC internal standard) in 6 mL of solvent. b Average of three
runs. c 1.1 equiv. of KOH was used. d 3 was replaced by DPEphos.
Scheme 3 A synthetic route to 3.
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carried out in THF (entry 11) or toluene (entry 12). Although fully converted. Because of the foul odor, even a trace amount
using a large excess of KOH may not be a concern for the syn- of unreacted thiol could make the work-up process unpleasant.
thesis, the amount could be reduced from 2 to 1.1 equiv. with However, in the case of 4-iodobenzonitrile (entry 6), an exact
limited impact on the yield (entry 13). Under such catalytic 1 : 1 mixture of aryl iodide and aryl thiol was used because
conditions, replacing 3 by DPEphos afforded 6a in only 45% separating the leftover 4-iodobenzonitrile from 6d proved to be
yield (entry 14), suggesting that the SPO moiety is critical to challenging. Sterically crowded substrates (entries 8, 9 and 11)
the success of the reaction.
required a higher catalyst loading (1 or 5 mol%) to achieve syn-
The substrate scope of the new catalytic system was sub- thetically useful yields, and so did electron-rich thiols such as
sequently examined using the optimized conditions (0.5 mol% the one in entry 10. Despite rigorous exclusion of oxygen from
catalyst in DMF, 1.1 equiv. of KOH, 80 °C, 1 h). As shown in the reagents and solvent, disulfides (ArS–SAr) were observed as
Table 2, the bidentate SPO-ligated nickel catalyst was effective the byproducts along with 6f–i. In the event that separating the
for the C–S coupling of aryl iodides, but not aryl bromides disulfide from the desired sulfide became problematic (entries
(entry 2) and chlorides (entry 3). Functional groups such as 8 and 9), NaBH4 was added to the crude product prior to puri-
OMe, CF3, CN and pyridyl groups (entries 4–7) were tolerated fication by column chromatography (see ESI† for details). The
under the reaction conditions. In general, a slight excess of borohydride could effectively remove the disulfides; however,
aryl iodide was employed to ensure that all the thiols were it also eroded the sulfide yields.
Table 2 Nickel-catalyzed thiolation of aryl halidesa
Entry
Aryl halide
Aryl thiol
Product
Yieldb (%)
1
2
3
4
(X = l)
(X = Br)
(X = Cl)
86
33c
2c
89
5
6
90
86d
7
8
94
58e
9
37 (85)e, f
10
11
91e
77g
a Reaction conditions: 1.1 mmol of aryl halide, 1.0 mmol of aryl thiol, 1.1 mmol KOH and Ni(COD)2-3 (0.5 mol%) in 6 mL of DMF at 80 °C.
b Isolated yield unless otherwise mentioned. c GC yield determined using 1.0 mmol of n-decane as an internal standard. d 1.0 mmol of aryl iodide
was used. e 1 mol% catalyst loading. f NMR yield (in parenthesis) determined using 0.33 mmol of mesitylene as the internal standard. g 5 mol%
catalyst loading.
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It is noted that only a handful of studies have included mation of a pair of diastereomeric P-bound complexes. IR
alkyl thiosalicylates as substrates for cross-coupling reac- spectrum of 10 further confirmed the absence of P–H bonds.
tions.21 In DMSO-d6,22 methyl thiosalicylate was shown to The same reaction carried out in THF was slightly faster (com-
react with KOH to afford methyl aryl sulfides 7 and 8 (5 : 1) as pleted within 2 h), producing a 59 : 41 mixture of isomers. In
a result of intra- and intermolecular nucleophilic attack of the contrast, the reaction conducted in toluene was substantially
methyl group by the thiolate (eqn (1)). Therefore, it was not too slower, requiring more than 3 days to complete the substi-
surprising that with a low catalyst loading, methyl aryl sulfide tution process. At the 3 h mark, about 40% of 3 was consumed
8 was the main isolated product (entries 1 and 2, Table 3).23 and the ratio for the resultant two P-bound complexes was cal-
However, when the catalyst loading was increased to 5 mol%, culated to be 63 : 37. These results suggest that the rate for the
the cross-coupling reaction became more competitive than the complexation of 3 with nickel and the product ratio of the reac-
uncatalyzed reactions depicted in eqn (1), providing diaryl tion are solvent dependent. Increasing the temperature could
sulfide 6i as the major product (entry 3).
potentially accelerate the ligand substitution process; however,
Ni(COD)2 is known to degrade rapidly above the ambient
temperature.26 For this reason, all the catalytic reactions
described in this work employ Ni(COD)2 and 3 that are pre-
mixed at room temperature for 3 h.
ð1Þ
Yuan, Bolm and co-workers have demonstrated that it is
possible to create a superbasic medium with KOH dissolved in
DMSO, allowing the C–S bond formation between aryl halides
and thiophenol to take place without using any metal cata-
lyst.24 Such a process operates at a more elevated temperature
of 130 °C, and for a para-substituted aryl halide, often pro-
duces a mixture of regioisomers presumably via a benzyne
intermediate. In our system, the cross-coupling reaction is
clearly a nickel-catalyzed process, supported by the following
two pieces of evidence: first, only one regioisomer was
observed for the coupling of a para-substituted aryl iodide
(entries 4–6, Table 2); and second, the control experiment in
the absence of Ni(COD)2 did not yield an appreciable amount
of cross-coupling product.
We propose that in the present study, 3 first displaces one
of the COD ligands from Ni(COD)2, forming complex 10 as
illustrated in eqn (2).25 Isolation and full characterization of
this particular nickel complex are ongoing in our laboratory.
Monitoring the reaction in DMF by 31P{1H} NMR spectroscopy
indicated that at room temperature, the ligand substitution
process was completed within 3 h (see ESI†). As the resonances
of 3 started to diminish, two new resonances emerged at 88.64
and 90.98 ppm (with a 55 : 45 ratio), possibly due to the for-
ð2Þ
In the presence of KOH, the phosphinous acid moieties of
10 are likely to be deprotonated, resulting in an O-anionic bis
(phosphinite) Ni(0) complex 11 (eqn (3)), which may or may
not have the central oxygen atom coordinated to the nickel. A
similar palladium complex [κP-{(t-Bu)2PO}2Pd(0)]2− has been
proposed by Li and co-workers for cross-coupling reactions
catalyzed by a palladium complex ligated with (t-Bu)2P(O)H
(two SPOs per palladium).5b How such a species affect the sub-
sequent steps of the catalytic process (see ESI† for a plausible
mechanism) will be the focus of our future study.
ð3Þ
Conclusions
Table 3 Reaction of methyl thiosalicylate with iodobenzene
In conclusion, we have synthesized a new bidentate secondary
phosphine oxide 3, only the second of the kind bearing a
covalent backbone. The 1 : 1 mixture of Ni(COD)2 and 3 is a
very effective catalyst for C–S coupling of aryl iodides with aryl
thiols, including those with an OMe, CF3, CN, pyridyl or ester
group. Sterically crowded aryl iodides and aryl thiols are viable
substrates, although higher catalytic loadings are required.
Compared to our previously reported catalyst prepared from
Ni(COD)2 and Ph2P(O)H,11 the new catalytic system shows
improvement, as measured by catalytic loading, reaction time
and the amount of base used. It also compares favorably
(in terms of catalyst loading and temperature) with other
nickel-based catalytic systems for C–S bond formation reactions.27
Temp.
(°C)
Isolated yields
for 6i/8/9 (%)
Entry
x
1
2
3
0.5
0.5
5
80
120
80
3/22/9
1/25/0
77/3/0
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Our preliminary mechanistic study suggests that 3 binds to
nickel via its phosphinous acid based tautomer. More detailed
mechanistic investigations of the proposed catalytic species
are currently in progress.
C.-M. Weng and F.-E. Hong, Organometallics, 2011, 30,
1139–1147; (k) Y.-C. Chang, W.-C. Chang, C.-Y. Hu and
F.-E. Hong, Organometallics, 2014, 33, 3523–3534; (l) F. Hu,
B. N. Kumpati and X. Lei, Tetrahedron Lett., 2014, 55, 7215–
7218.
7 SPOs used for catalytic cycloaddition reactions:
(a) J. Bigeault, L. Giordano and G. Buono, Angew. Chem.,
Int. Ed., 2005, 44, 4753–4757; (b) J. Bigeault, L. Giordano,
I. de Riggi, Y. Gimbert and G. Buono, Org. Lett., 2007, 9,
3567–3570; (c) J. Bigeault, I. de Riggi, Y. Gimbert,
L. Giordano and G. Buono, Synlett, 2008, 1071–1075;
(d) D. Gatineau, D. Moraleda, J.-V. Naubron, T. Bürgi,
L. Giordano and G. Buono, Tetrahedron: Asymmetry, 2009,
20, 1912–1917; (e) T. Achard, A. Lepronier, Y. Gimbert,
H. Clavier, L. Giordano, A. Tenaglia and G. Buono, Angew.
Chem., Int. Ed., 2011, 50, 3552–3556; (f) F. Schröder,
C. Tugny, E. Salanouve, H. Clavier, L. Giodano,
D. Moraleda, Y. Gimbert, V. Mouriès-Mansuy, J.-P. Goddard
and L. Fensterbank, Organometallics, 2014, 33, 4051–4056.
8 SPOs used for catalytic hydration of nitriles:
(a) S. M. M. Knapp, T. J. Sherbow, R. B. Yelle, J. J. Juliette
and D. R. Tyler, Organometallics, 2013, 32, 3744–3752;
(b) E. Tomás-Mendivil, F. J. Suárez, J. Díez and V. Cadierno,
Chem. Commun., 2014, 50, 9661–9664.
Acknowledgements
We thank the U.S. National Science Foundation (CHE-0952083
and CHE-1464734) and the Alfred P. Sloan Foundation for
support of this research.
Notes and references
1 (a) N. V. Dubrovina and A. Börner, Angew. Chem., Int. Ed.,
2004, 43, 5883–5886; (b) L. Ackermann, Synthesis, 2006,
1557–1571; (c) L. Ackermann, R. Born, J. H. Spatz,
A. Althammer and C. J. Gschrei, Pure Appl. Chem., 2006, 78,
209–214; (d) L. Ackermann, Synlett, 2007, 507–526;
(e) T. Nemoto and Y. Hamada, Chem. Rec., 2007, 7, 150–
158; (f) L. Ackermann, Isr. J. Chem., 2010, 50, 652–663;
(g) T. Nemoto and Y. Hamada, Tetrahedron, 2011, 67, 667–
687; (h) T. M. Shaikh, C.-M. Weng and F.-E. Hong, Coord.
Chem. Rev., 2012, 256, 771–803.
9 SPOs used for catalytic hydrocarbamoylation of alkenes:
P. A. Donets and N. Cramer, J. Am. Chem. Soc., 2013, 135,
11772–11775.
2 (a) P. N. Kapoor, R. Saraswati and I. J. McMahon, Inorg.
Chim. Acta, 1985, 110, 63–68; (b) F. A. Cotton, P. A. Kibala
and C. S. Miertschin, Inorg. Chem., 1991, 30, 548–553; 10 SPO-decorated nanoparticles for catalytic hydrogenation
(c) D. Magiera, A. Szmigielska, K. M. Pietrusiewicz and
H. Duddeck, Chirality, 2004, 16, 57–64; (d) S. Teo, Z. Weng
and T. S. A. Hor, Organometallics, 2008, 27, 4188–4192;
(e) L. V. Graux, M. Giorgi, G. Buono and H. Clavier, Organo-
metallics, 2015, 34, 1864–1871.
3 P. Sutra and A. Igau, Coord. Chem. Rev., 2015, DOI: 10.1016/
j.ccr.2015.07.002, article in press.
4 D. Martin, D. Moraleda, T. Achard, L. Giordano and
G. Buono, Chem. – Eur. J., 2011, 17, 12729–12740.
5 (a) G. Y. Li, Angew. Chem., Int. Ed., 2001, 40, 1513–1516;
reactions: (a) E. Rafter, T. Gutmann, F. Löw,
G. Buntkowsky, K. Philippot, B. Chaudret and P. W. N.
M. van Leeuwen, Catal. Sci. Technol., 2013, 3, 595–599;
(b) I. Cano, A. M. Chapman, A. Urakawa and P. W. N.
M. van Leeuwen, J. Am. Chem. Soc., 2014, 136, 2520–2528;
(c) I. Cano, M. A. Huertos, A. M. Chapman, G. Buntkowsky,
T. Gutmann, P. B. Groszewicz and P. W. N. M. van
Leeuwen, J. Am. Chem. Soc., 2015, 137, 7718–7727.
11 J. Zhang, C. M. Medley, J. A. Krause and H. Guan, Organo-
metallics, 2010, 29, 6393–6401.
(b) G. Y. Li, G. Zheng and A. F. Noonan, J. Org. Chem., 2001, 12 (a) K. R. Dixon and A. D. Rattray, Can. J. Chem., 1971, 49,
66, 8677–8681; (c) G. Y. Li, J. Org. Chem., 2002, 67, 3643–
3650; (d) G. Y. Li, J. Organomet. Chem., 2002, 653, 63–68;
(e) D. X. Yang, S. L. Colletti, K. Wu, M. Song, G. Y. Li and
H. C. Shen, Org. Lett., 2009, 11, 381–384.
3997–4004; (b) I. W. Robertson and T. A. Stephenson, Inorg.
Chim. Acta, 1980, 45, L215–L216; (c) E. Y. Y. Chan,
Q.-F. Zhang, Y.-K. Sau, S. M. F. Lo, H. H. Y. Sung,
I. D. Williams, R. K. Haynes and W.-H. Leung, Inorg. Chem.,
2004, 43, 4921–4926; (d) I. Pryjomska, H. Bartosz-Bechowski,
Z. Ciunik, A. M. Trzeciak and J. J. Ziółkowski, Dalton Trans.,
2006, 213–220; (e) R. Thota, D. Lesage, Y. Gimbert,
L. Giordano, S. Humbel, A. Milet, G. Buono and J.-C. Tabet,
Organometallics, 2009, 28, 2735–2743; (f) A. Christiansen,
D. Selent, A. Spannenberg, W. Baumann, R. Franke and
A. Börner, Organometallics, 2010, 29, 3139–3145;
(g) T. Achard, L. Giordano, A. Tenaglia, Y. Gimbert and
G. Buono, Organometallics, 2010, 29, 3936–3950;
(h) N. Allefeld, J. Bader, B. Neumann, H.-G. Stammler,
N. Ignat’ev and B. Hoge, Inorg. Chem., 2015, 54, 7945–7952.
6 (a) C. Wolf and R. Lerebours, J. Org. Chem., 2003, 68, 7077–
7084; (b) L. Ackermann and R. Born, Angew. Chem., Int. Ed.,
2005, 44, 2444–2447; (c) L. Ackermann, Org. Lett., 2005, 7,
3123–3125; (d) L. Ackermann, A. Althammer and R. Born,
Angew. Chem., Int. Ed., 2006, 45, 2619–2622;
(e) L. Ackermann and A. Althammer, Org. Lett., 2006, 8,
3457–3460; (f) C.-H. Wei, C.-E. Wu, Y.-L. Huang,
R. G. Kultyshev and F.-E. Hong, Chem. – Eur. J., 2007, 13,
1583–1593; (g) L. Ackermann and M. Mulzer, Org. Lett.,
2008, 10, 5043–5045; (h) L. Ackermann, A. R. Kapdi and
C. Schulzke, Org. Lett., 2010, 12, 2298–2301;
(i) L. Ackermann, S. Barfüsser, C. Kornhaass and 13 L.-Y. Jung, S.-H. Tsai and F.-E. Hong, Organometallics, 2009,
A. R. Kapdi, Org. Lett., 2011, 13, 3082–3085; ( j) D.-F. Hu,
28, 6044–6053.
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14 M. Kranenburg, Y. E. M. van der Burgt, P. C. J. Kamer, 22 Based on GC-MS analysis, the outcome for the reaction
P. W. N. M. van Leeuwen, K. Goubitz and J. Fraanje,
Organometallics, 1995, 14, 3081–3089.
15 (a) J. P. Sadighi, M. C. Harris and S. L. Buchwald,
conducted in DMF was similar to that carried out in
DMSO. The NMR experiment was performed in DMSO-
d6 because it is more affordable than DMF-d7.
Tetrahedron Lett., 1998, 39, 5327–5330; (b) B. C. Hamann 23 Because the crude product was not neutralized, compound
and J. F. Hartwig, J. Am. Chem. Soc., 1998, 120, 3694–3703. 7 was likely to be left on the column.
16 P. W. N. M. van Leeuwen, P. C. J. Kamer, J. N. H. Reek and 24 Y. Yuan, I. Thomé, S. H. Kim, D. Chen, A. Beyer,
P. Dierkes, Chem. Rev., 2000, 100, 2741–2769.
17 M. Narsireddy and Y. Yamamoto, J. Org. Chem., 2008, 73,
9698–9709.
J. Bonnamour, E. Zuidema, S. Chang and C. Bolm, Adv.
Synth. Catal., 2010, 352, 2892–2898.
25 At this stage, we cannot rule out the possibility of forming
a species with 3 bridging two nickel atoms.
18 (a) G. Baba, J.-F. Pilard, K. Tantaoui, A.-C. Gaumont and
J.-M. Denis, Tetrahedron Lett., 1995, 36, 4421–4424; 26 P. A. Wender and T. E. Smith, Bis(1,5-cyclooctadiene)nickel
(b) J.-F. Pilard, G. Baba, A.-C. Gaumont and J.-M. Denis,
Synlett, 1995, 1168–1170.
19 M. T. Honaker, J. M. Hovland and R. N. Salvatore,
Curr. Org. Synth., 2007, 4, 31–45.
20 A. Christiansen, C. Li, M. Garland, D. Selent, R. Ludwig,
A. Spannenberg, W. Baumann, R. Franke and A. Börner,
Eur. J. Org. Chem., 2010, 2733–2741.
21 (a) F. Y. Kwong and S. L. Buchwald, Org. Lett., 2002, 4,
3517–3520; (b) N. Jarkas, J. McConathy, R. J. Voll and
M. M. Goodman, J. Med. Chem., 2005, 48, 4254–4265;
(c) C. Mispelaere-Canivet, J.-F. Spindler, S. Perrio and
P. Beslin, Tetrahedron, 2005, 61, 5253–5259; (d) X. Du,
H. Liu and D.-M. Du, Tetrahedron: Asymmetry, 2010, 21,
241–246; (e) M. S. Kabir, M. Lorenz, M. L. Van Linn,
O. A. Namjoshi, S. Ara and J. M. Cook, J. Org. Chem., 2010,
75, 3626–3643; (f) P. Zheng, B. P. Lieberman, K. Ploessl,
L. Lemoine, S. Miller and H. F. Kung, Bioorg. Med. Chem.
Lett., 2013, 23, 869–872.
(0), in Encyclopedia of Reagents for Organic Synthesis, ed.
L. A. Paquette, D. Crich, P. L. Fuchs and G. A. Molander,
Wiley, Chichester, UK, 2nd edn, 2009, vol. 2, pp. 906–912.
27 (a) H. J. Cristau, B. Chabaud, A. Chêne and H. Christol,
Synthesis, 1981, 892–894; (b) K. Takagi, Chem. Lett., 1987,
2221–2224; (c) V. Percec, J.-Y. Bae and D. H. Hill, J. Org.
Chem., 1995, 60, 6895–6903; (d) C. Millois and P. Diaz, Org.
Lett., 2000, 2, 1705–1708; (e) N. Taniguchi, J. Org. Chem.,
2004, 69, 6904–6906; (f) V. Gómez-Benítez, O. Baldovino-
Pantaleón, C. Herrera-Álvarez, R. A. Toscano and
D. Morales-Morales, Tetrahedron Lett., 2006, 47, 5059–5062;
(g) Y. Zhang, K. C. Ngeow and J. Y. Ying, Org. Lett., 2007, 9,
3495–3498; (h) S. Jammi, P. Barua, L. Rout, P. Saha and
T. Punniyamurthy, Tetrahedron Lett., 2008, 49, 1484–1487;
(i) G. T. Venkanna, H. D. Arman and Z. J. Tonzetich, ACS
Catal., 2014, 4, 2941–2950; ( j) R. Singh, B. K. Allam,
N. Singh, K. Kumari, S. K. Singh and K. N. Singh, Adv.
Synth. Catal., 2015, 357, 1181–1186.
Org. Biomol. Chem.
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