Rhodium/N-heterocyclic carbene-catalyzed cross-couplings of aryl arenesulfonates with arylboronic acids

Article abstract of DOI:10.1002/adsc.200800414

The combination of rhodium(I) and N-hetercyclic carbenes (NHC) was found to be effective as a catalyst for cross-coupling reactions of aryl arenesulfonates with arylboronic acids, which gave rise to the desired biaryl compounds in good yields.

Full text of DOI:10.1002/adsc.200800414

FULL PAPERS
DOI: 10.1002/adsc.200800414
Rhodium/N-Heterocyclic Carbene-Catalyzed Cross-Couplings of
Aryl Arenesulfonates with Arylboronic Acids
Liang Zhanga and Jie Wua,b,*
a
Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433, Peopleꢀs Republic of China
Fax : (+86)-216-510-2412; e-mail: jie_wu@fudan.edu.cn
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of
b
Sciences, 354 Fenglin Road, Shanghai 200032, Peopleꢀs Republic of China
Received: July 4, 2008; Published online: September 26, 2008
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200800414.
Abstract: The combination of rhodium(I) and N-he- nesulfonates with arylboronic acids, which gave rise
tercyclic carbenes (NHC) was found to be effective to the desired biaryl compounds in good yields.
as a catalyst for cross-coupling reactions of aryl are-
Keywords: aryl arenesufonates; arylboronic acids;
cross-couplings; N-heterocyclic carbenes; rhodium
Introduction
unreactive compared with the corresponding aryl
halide and triflate counterparts.[6] For instance, several
The transition metal-catalyzed cross-coupling reaction examples have been reported of Suzuki–Miyaura[7] re-
is known to be a powerful tool for C C bond forma- actions by using palladium[6b] or nickel[6a] catalysts.
À
tion,[1] and this field is largely dominated by the use Prompted by the development of Rh-catalyzed cross-
of palladium or nickel complexes as catalysts. An elec- coupling reactions, we envisioned that an electron-
tron-deficient aryl-Pd(II) or aryl-Ni(II) intermediate is rich arylrhodium intermediate might be employed in
believed to be involved in the reaction process. How- cross-coupling reactions of aryl arenesulfonates.
ever, a rhodium catalyst might also undergo oxidative Herein, we report the first example utilizing rhodium
addition of electrophilic aromatic substrates via an as the catalyst in the cross-coupling reactions of aryl
electron-rich arylrhodium intermediate, as demon- arenesulfonates with boronic acids.
strated by the fact that the stoichiometric activation
of aryl chlorides on a phenylrhodium complex could
be realized.[2] The following report showed that aryl- Results and Discussion
boron compounds could be coupled efficiently with
various aryl bromides and electron-deficient aryl To verify the practicability of this projected route, a
chlorides in the presence of an appropriate rhodium- set of experiments was carried out using 4-methoxy-
based catalyst system.[3] Moreover, a rhodium catalyst phenyl tosylate 1a and 4-tolylboronic acid 2a as
has been employed in the cross-coupling of arylboron model substrates. This preliminary survey, carried out
reagents with acid anhydrides,[4] as well as in the cou- in the presence of [RhCl
ACHTREUNG
pling of arylzinc reagents with aryl iodides.[5]
Among the electrophiles employed in transition efficient catalytic system (Table 1). In an initial ex-
metal-catalyzed cross-coupling reactions, aryl arene- periment, only a trace amount of product was detect-
sulfonates, which could be easily accessible from ed when the reaction was performed in the presence
cheap, readily available phenols and arenesulfonyl of [RhCl(COD)]2 (2 mol%) and CsF in toluene
G
chloride, are emerging as important alternatives to (Table 1, entry 1). All the phosphine ligands investi-
aryl halides and triflates.[6] Moreover, they are less ex- gated gave the desired product in markedly poor
pensive, more stable and easier to handle than the yields (Table 1, entries 2–11). In view of the inferior
corresponding triflates. In recent years, cross-coupling oxidative addition capability of aryl arenesulfonates
reactions employing aryl arenesulfonates as electro- to a rhodium(I) intermediate, we conceived that a
philes have been realized although they are relatively strong s-donation from the supporting ligand might
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Liang Zhang and Jie Wu
Table 1. Screening of ligands for rhodium-catalyzed coupling reaction of aryl tosylates 1a with arylboronic acid 2a.[a]
FULL PAPERS
Entry
Ligand
Yield [%][b]
Entry
Ligand
Yield [%][b]
1
2
3
4
5
6
7
8
none
Ph3P
Cy3P
CyJohnPhos
JohnPhos
S-Phos
dppf
trace
trace
7
2
7
13
14
15
16
17
18
19
20
21
22
23
24
IMes·HCl
IMes·HBF4
SIMes·HCl
IPr·HCl
SIPr·HCl
IXy·HCl
SIXy·HCl
IEt·HCl
ITol·HCl
I-2-Tol·HCl
ItBu·HCl
ICy·HCl
42
49[d]
14[d]
trace[d]
11[d]
12
9
56[d]
27[d]
dppp
trace
trace
7[c]
trace[d]
trace[d]
trace[d]
31[d]
9
Xantphos
S-Phos
S-Phos
IMes·HCl
10
11
12
14[d]
81[d]
trace[d]
[a]
Reaction conditions: MeOC6H4OTs 1a (0.25 mmol), MeC6H4B(OH)2 2a (1.1 equiv.), CsF (4.0 equiv.), toluene (1 mL).
Isolated yield based on 1a.
8 mol% ligand.
[b]
[c]
[d]
[RhCl(COD)]2, ligand, CsF and toluene were stirred at room temperature for 30 min before the reactants were added.
G
enhance the electron density of the metal center. It
seemed that N-heterocyclic carbenes (NHC) should
be a good choice. Since their first introduction as li-
gands for catalysis by Herrmann in 1995, NHCs are
attracting increasing interest in transition metal-cata-
lyzed reactions,[8] due to their variable steric bulk and
ease of synthesis, as well as their excellent s-donor
power. Interestingly, although no reaction occurred in
the presence of a palladium catalyst and an NHC as
reported by Buchwald,[6b] the combination of Rh(I)
and NHC, in contrast to that with phosphines, was
proven to be the catalyst of choice in our investiga-
tion of the Suzuki–Miyaura coupling of aryl tosylates.
As shown in Table 1, in an effort to access a phos-
phine-free catalyst system, the air-stable, easily avail-
able imidazolium salts and imidazolinium salts were
examined as precursors of N-heterocyclic carbene li-
gands (Figure 1). To our delight, use of the catalyst
system arising from IMes·HCl resulted in a satisfacto-
ry isolated yield (81% yield, Table 1, entry 12). De-
protonation of the imidazolium salt at room tempera-
ture with CsF as a mild base was crucial for such an
efficiency (entry 13). Further screening of solvents
and bases revealed that CsF and toluene were the
best choices (data not shown in Table 1). Decreasing Figure 1. Ligands for screening.
the temperature retarded the reaction.
The scope of this reaction was then investigated
under optimized conditions, and the results are sum- sired product 3b in 75% yield (Table 2, entry 2). a- or
marized in Table 2. For all cases, aryl arenesulfonates b-naphthyl tosylate was also a suitable partner for this
1 reacted with arylboronic acids 2 leading to the cor- Rh-catalyzed reaction of 4-methylphenylboronic acid
responding products 3 in moderate to good yields. For 2a (Table 2, entries 7 and 8). Reaction of 4-trifluoro-
instance, reaction of 4-benzylphenyl tosylate 1b with methylphenyl tosylate proceeded well under the con-
4-methylphenylboronic acid 2a gave rise to the de- ditions to generate the coupling product 3m in 80%
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Rhodium/N-Heterocyclic Carbene-Catalyzed Cross-Couplings of Aryl Arenesulfonates
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Table 2. Rhodium/NHC-catalyzed coupling reactions of aryl tosylates 1 with arylboronic acids 2.[a]
Entry
Arenesulfonate
Arylboronic acid
Product
Yield [%][b]
1
2
3
4
5
6
1a
1b
1c
1d
1e
1f
2a
2a
2a
2a
2a
2a
3a
3b
3c
3d
3e
3f
81
75
55
60
43
80
7
1g
2a
3g
86
8
9
1h
1i
2a
2a
3h
3i
81
61
10
11
1j
2a
2a
3j
63
70
1k
3k
12
1l
2a
3l
70
13
14
15
1m
1a
2a
2b
2b
3m
3n
3o
80[c]
46
1b
65
16
1g
2b
3p
61
17
18
1h
1a
2b
2c
3q
3r
71
32
19
1a
2d
3s
52
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Liang Zhang and Jie Wu
FULL PAPERS
Table 2. (Continued)
Entry
Arenesulfonate
Arylboronic acid
Product
Yield [%][b]
60
20
1n
1o
2a
3a
3g
21
2a
2b
75
50
22
1o
3p
[a]
Reaction conditions: 2 mol% [RhCl(COD)]2, 4 mol% IMes·HCl, CsF (4.0 equiv.), toluene (1 mL), room temperature,
A
30 min; then aryl arenesulfonate 1 (0.25 mmol) and arylboronic acid 2 (1.1 equiv.) were added, 1208C, 10 h.
Isolated yield based on aryl arenesulfonate 1.
KOH used as base.
[b]
[c]
yield (Table 2, enrty 13). Other arylboronic acids Conclusions
were employed in the reactions of aryl tosylates and
similar results were observed (Table 2, entries 14–18). In conclusion, the combination of Rh(I) and NHC
Meanwhile, aryl benzenesulfonates were examined was found to be effective for cross-coupling reactions
for the Rh/NHC-catalyzed coupling reactions. 4-Me- of aryl arenesulfonates with arylboronic acids. The re-
thoxyphenyl benzenesulfonate 1n reacted with 4- sults not only demonstrate the efficiency of the rhodi-
methylphenylboronic acid 2a leading to the desired um catalyst in cross-coupling reactions of aryl arene-
product 3a in 60% yield (Table 2, entry 19). When a- sulfonates, but also provide an interesting comple-
naphthyl benzenesulfonate 1o was employed in the ment to the phosphine-based palladium or nickel cat-
reaction with 4-methylphenylboronic acid 2a or 4-me- alyst systems.
thoxyphenylboronic acid 2b, a 75% or 50% yield of
the corresponding product was obtained, respectively
(Table 2, entries 20 and 21). We also tested other bor-
Experimental Section
onic acids, such as 4-chlorophenylboronic acid or 4-ni-
trophenylboronic acid in the reaction with 4-methoxy-
phenyl tosylate 1a under the standard conditions.
However, the results were inferior and the yields
ranged form 20–30%.
General Procedure for the Suzuki–Miyaura Couplings
of Aryl Arenesulfonates
A mixture of [RhCl(COD)]2 (2.5 mg), IMes·HCl (3.4 mg)
G
In the reaction process, an RhCl
G
G
and CsF (152 mg) in 1 mL toluene was stirred for 30 min at
room temperature. Under a nitrogen flow, aryl arenesulfo-
nate 1 (0.25 mmol) and arylboronic acid 2 (1.1 equiv.) were
added. The Schlenk tube was put into a 1208C oil bath and
the mixture stirred for 10 h. After quenching with brine, the
reaction mixture was extracted with ethyl acetate. The or-
ganic layer was directly subjected to flash chromatography
on silica gel to yield the desired products 3.
Data of a selected example 4-(4-methylphenyl)anisole
(3a):[6a] 1H NMR(CDCl 3, 400 MHz): d=2.39 (s, 3H), 3.85
(s, 3H), 6.97 (d, J=8.7 Hz, 2H), 7.23 (d, J=8.2 Hz, 2H),
7.46 (d, J=8.2 Hz, 2H), 7.52 (d, J=8.7 Hz, 2H); 13C NMR
(100 MHz): d=159.0, 138.1, 136.5, 133.8, 129.5, 128.1, 126.7,
114.2, 55.4, 21.2; for further details, please see Supporting
Information.
plex generated in situ might be the active species. The
RhCl
N
N
literature and the structure was identified.[9] We also
synthesized this complex according to the reported
method and applied it in the reaction of tosylate 1a
with 4-methylphenylboronic acid 2a. The desired
product 3a was generated as expected although the
yield was lower (Scheme 1).
Supporting Information
Experimental procedure, characterization data, as well as
copies of the H and 13C NMRspectra of compound 3 are
available as Supporting Information.
1
Scheme 1.
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Rhodium/N-Heterocyclic Carbene-Catalyzed Cross-Couplings of Aryl Arenesulfonates
FULL PAPERS
hold, J. Org. Chem. 2004, 69, 3447–3452; g) J. M.
Baxter, D. Steinhuebel, M. Palucki, I. W. Davies, Org.
Lett. 2005, 7, 215–218; h) D. Steinhuebel, J. M. Baxter,
M. Palucki, I. W. Davies, J. Org. Chem. 2005, 70, 10124–
10127; i) M. R. Netherton, G. C. Fu, Angew. Chem. Int.
Ed. 2002, 41, 3910–3912; j) L. Zhang, T. Meng, J. Wu, J.
Org. Chem. 2007, 72, 9346–9349; k) A. H. Roy, J. F.
Hartwig, J. Am. Chem. Soc. 2003, 125, 8704–8705; l) A.
Fꢂrstner, A. Leitner, M. Mendez, H. Krause, J. Am.
Chem. Soc. 2002, 124, 13856–13863; m) J. Zhou, G. C.
Fu, J. Am. Chem. Soc. 2003, 125, 12527–12530.
Acknowledgements
Financial support from National Natural Science Foundation
of China (20772018), Shanghai Pujiang Program, and Pro-
gram for New Century Excellent Talents in University
(NCET-07–0208) is gratefully acknowledged.
References
[1] a) J. Tsuji, Palladium Reagents and Catalysts, 2nd edn.,
John Wiley & Sons, Chichester, 2004; b) A. de Meijere,
F. Diederich, Metal-Catalyzed Cross-Coupling Reactions,
2nd edn., John Wiley & Sons, Weinheim, 2004.
[2] V. V. Grushin, W. J. Marshall, J. Am. Chem. Soc. 2004,
126, 3068–3069.
[7] For reviews, see: a) N. Miyaura, Top. Curr. Chem. 2002,
219, 11–59; b) A. Suzuki, J. Organomet. Chem. 1999,
576, 147; c) D. A. Culkin, J. F. Hartwig, Acc. Chem. Res.
2003, 36, 234–245; d) J. Hassan, M. Sevigon, C. Gozzi,
E. Schulz, M. Lemaire, Chem. Rev. 2002, 102, 1359–
1470; e) S. Kotha, K. Lahiri, D. Kashinath, Tetrahedron
2002, 9633–9695.
[3] K. Ueura, T. Satoh, M. Miura, Org. Lett. 2005, 7, 2229–
2231.
[4] a) K. Oguma, M. Miura, M. Nomura, J. Organomet.
Chem. 2002, 648, 297–301; b) T. Sugihara, T. Satoh, M.
Miura, M. Nomura, Angew. Chem. Int. Ed. 2003, 42,
4672–4674; c) T. Sugihara, T. Satoh, M. Miura, M.
Nomura, Adv. Synth. Catal. 2004, 346, 1765–1772;
d) C. G. Frost, K. J. Wadsworth, Chem. Commun. 2001,
2316–2317; e) L. J. Goossen, J. Paetzold, Adv. Synth.
Catal. 2004, 346, 1665–1668; f) M. Yamane, K. Uera, K.
Narasaka, Chem. Lett. 2004, 424–425.
[5] K. M. Hossain, K. Takagi, Chem. Lett. 1999, 1241–1242.
[6] For selected examples, see: a) Z.-Y. Tang, Q.-S. Hu, J.
Am. Chem. Soc. 2004, 126, 3058–3059; b) H. N. Nguyen,
X. Huang, S. L. Buchwald, J. Am. Chem. Soc. 2003, 125,
11818–11819; c) V. Percec, J.-Y. Bae, D. H. Hill, J. Org.
Chem. 1995, 60, 1060–1065; d) D. Zim, V. R. Lando, J.
Dupont, A. L. Monteiro, Org. Lett. 2001, 3, 3049;
e) M. K. Lakshman, P. F. Thomson, M. A. Nuqui, J. H.
Hilmer, N. Sevova, B. Boggess, Org. Lett. 2002, 4, 1479–
1482; f) V. Percec, G. M. Golding, J. Smidrkal, O. Weic-
[8] For selected examples, see: a) F. Glorius, (Ed.), N-Heter-
ocyclic Carbenes in Transition Metal Catalysis, Springer,
Berlin, 2007; b) W. A. Herrmann, Angew. Chem. Int. Ed.
2002, 41, 1290–1309; c) O. Navarro, R. A. , III Kelly,
S. P. Nolan, J. Am. Chem. Soc. 2003, 125, 16194–16195;
d) G. A. Grasa, S. P. Nolan, Org. Lett. 2001, 3, 119–122;
e) M. R. Fructos, T. R. Belderrain, M. C. Nicasio, S. P.
Nolan, H. Kaur, M. M. Diaz-Requejo, P. J. Perez, J. Am.
Chem. Soc. 2004, 126, 10846–10847; f) C. Yang, H. M.
Lee, S. P. Nolan, Org. Lett. 2001, 3, 1511–1514; g) R.
Singh, M. S. Viciu, N. Kramareva, O. Navarro, S. P.
Nolan, Org. Lett. 2005, 7, 1829–1832; h) G. A. Grasa,
A. C. Hillier, S. P. Nolan, Org. Lett. 2001, 3, 1077–1080;
i) M. S. Viciu, R. F. Germaneau, O. Navarro-Fernandez,
E. D. Stevens, S. P. Nolan, Organometallics 2002, 21,
5470–5472.
[9] X, Yu, B. O. Patrick, B. R. James, Organometallics
2006, 25, 2359–2363.
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