regarded as the least active sulfonate leaving group, which
has limited their application in coupling reactions.5,6 There-
fore, it is of great importance to develop general and efficient
methods for transition-metal-catalyzed couplings of unacti-
vated aryl mesylate substrates.
substrates, in the presence of palladium acetate as catalyst
(Table 1). Due to the relatively inert leaving group activity
Table 1. Initial Studies for Pd-Catalyzed Hiyama Coupling of
Among the organometallic reagents employed in cross-
coupling reactions, the palladium-catalyzed Hiyama coupling
of organosilicon compounds with organic electrophiles is an
attractive method for carbon-carbon bond formation,8,9 due
to their ease of handling, stability toward air/moisture, and/
or low toxicity compared to some of the other organometallic
reagents (Zn, Mg, Sn, etc.). Although couplings of aryl
halides with organosilicon compounds have been well
developed, to the best of our knowledge, aryl mesylates have
never been involved in the Hiyama coupling reactions.
Herein, we present the first example of palladium-catalyzed
Hiyama couplings of aryl mesylates.
4-tert-Butylphenyl Mesylate 1a with Trimethoxy(phenyl)silane
2a
Initial studies were performed by using 4-tert-butylphenyl
mesylate 1a and trimethoxy(phenyl)silane 2a as model
entry
ligand
XPhos
XPhos
XPhos
XPhos
XPhos
XPhos
XPhos
solvent
T (°C)
yielda (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
none
DMF
80
110
110
110
110
110
90
90
90
90
90
45
trace
12
nr
18
10
nr
92
38
trace
11
trace
15
(3) Kumada coupling: (a) Roy, A. H.; Hartwig, J. F. J. Am. Chem. Soc.
2003, 125, 8704. (b) Limmert, M. E.; Roy, A. H.; Hartwig, J. F. J. Org.
Chem. 2005, 70, 9364. (c) Ackermann, L.; Althammer, A. Org. Lett. 2006,
8, 3457. Iron-catalyzed coupling of alkyl Grignard reagents with ArOTs:
(d) Fu¨rstner, A.; Leitner, A.; Mendez, M.; Krause, H. J. Am. Chem. Soc.
2002, 124, 13856. Stille couplings: (e) Badone, D.; Cecchi, R.; Guzzi, U.
J. Org. Chem. 1992, 57, 6321. (f) Nagatsugi, F.; Uemura, K.; Nakashima,
S.; Minoru, M.; Sasaki, S. Tetrahedron Lett. 1995, 36, 421. (g) Schio, L.;
Chatreaux, F.; Klich, M Tetrahedron Lett. 2000, 41, 1543. Negishi-type
reaction of arenesulfonates: (h) Zhou, J.; Fu, G. C. J. Am. Chem. Soc. 2003,
125, 12527. (i) Wu, J.; Sun, X.; Zhang, L. Chem. Lett. 2005, 34, 796.
Hiyama coupling: (j) Zhang, L.; Wu, J. J. Am. Chem. Soc. 2008, 130, 12250.
Carbonylation reaction: (k) Munday, R. H.; Martinelli, J. R.; Buchwald,
S. L. J. Am. Chem. Soc. 2008, 130, 2754.
dioxane
DMSO
toluene
CH3CN
DCE
t-BuOH
t-BuOH
t-BuOH
t-BuOH
t-BuOH
t-BuOH
t-BuOH
XPhos
S-Phos
JohnPhos
CyJohnPhos
PCy3
DPPP
IPr•HCl
90
90
90
(4) For examples of amination, see: (a) Hamann, B. C.; Hartwig, J. F
J. Am. Chem. Soc. 1998, 120, 7369. For C-S bond formation (one substrate
example), see: (b) Ferna´ndez-Rodr´ıguez, M. A.; Shen, Q.; Hartwig, J. F.
J. Am. Chem. Soc. 2006, 128, 2180. For Buchwald-Hartwig amidation,
see: (c) Klapars, A.; Campos, K. R.; Chen, C.-y.; Volante, R. P Org. Lett.
2005, 7, 1185.
trace
a Isolated yield based on 4-tert-butylphenyl mesylate 1a.
(5) Nickel-catalyzed C-C bond couplings of aryl mesylates, see: (a)
Kobayashi, Y.; Mizojiri, R. Tetrahedron Lett. 1996, 37, 8531. (b) Ueda,
M.; Saitoh, A.; Oh-tani, S.; Miyuara, N. Tetrahedron 1998, 54, 13079. (c)
Percec, V.; Bae, J.-Y.; Zhao, M.; Hill, D. H. J. Org. Chem. 1995, 60, 176.
(d) Percec, V.; Bae, J.-Y.; Hill, D. H. J. Org. Chem. 1995, 60, 1060. (e)
Percec, V.; Bae, J.-Y.; Hill, D. H. J. Org. Chem. 1995, 60, 1066. (f) Percec,
V.; Bae, J.-Y.; Hill, D. H. J. Org. Chem. 1995, 60, 6895. (g) Ueda, M.;
Saitoh, A.; Oh-tani, S.; Miyuara, N. J. Org. Chem. 1997, 62, 8024. (h)
Percec, V.; Golding, G. M.; Smidrkal, J.; Weichold, O. J. Org. Chem. 2004,
69, 3447. For direct cross-coupling of 4-mesylcoumarins with aryl- or vinyl
halides, see: (i) Lei, J.-G.; Xu, M.-H.; Lin, G.-Q. Synlett 2004, 2364.
(6) Palladium-catalyzed amination of aryl mesylates: (a) So, C. M.; Zhou,
Z.; Lau, C. P.; Kwong, F. Y. Angew. Chem., Int. Ed. 2008, 47, 6402.
Palladium-catalyzed carbonylation of aryl mesylates: (b) Munday, R. H.;
Martinelli, J. R.; Buchwald, S. L. J. Am. Chem. Soc. 2008, 130, 2754.
(7) Trost, B. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 259.
of aryl mesylate, bulky electron-rich phosphines10,11 were
screened in this palladium-catalyzed Hiyama reaction. Grati-
fyingly, in the presence of XPhos (10 mol %) and TBAF
(2.0 equiv), this reaction proceeded smoothly in THF to
afford the corresponding product 3a in 45% yield (Table 1,
entry 1). Further investigation revealed that the solvent
combination of THF/t-BuOH was the best choice for solvent
screening, and the desired biaryl product 3a was generated
in 92% yield (Table 1, entry 8). Under these conditions, the
catalyst and substrates were soluble.1b Inferior results were
displayed when other ligands were employed in the reaction
(Table 1, entries 9-14).
(8) For a review of the Hiyama reaction, see: (a) Hiyama, T. In Metal-
Catalyzed Cross-Coupling Reactions; Diederich, F., Stang, P. J., Eds.;
Wiley-VCH: New York, 1998; Chapter 10. (b) Hiyama, T. J. Organomet.
Chem. 2002, 653, 58. (c) Denmark, S. E.; Baird, J. D. Chem.sEur. J. 2006,
12, 4954. (d) Strotman, N. A.; Sommer, S.; Fu, G. C. Angew. Chem., Int.
With this preliminary result in hand, the scope of these
Pd-catalyzed Hiyama coupling reactions of aryl mesylates
was investigated under the optimized conditions [Pd(OAc)2
Ed. 2007, 46, 3556
.
(9) For some recent developments in Hiyama cross-coupling chemistry,
see: (a) Denmark, S. E.; Sweis, R. F. Acc. Chem. Res. 2002, 35, 835. (b)
Itami, K.; Nokami, T.; Yoshida, J.-i. J. Am. Chem. Soc. 2001, 123, 5600,
and references therein. (c) Lee, J.-Y.; Fu, G. J. Am. Chem. Soc. 2003, 125,
5616. (d) Clarke, M. L. AdV. Synth. Catal. 2005, 347, 303. (e) Seganish,
W. M.; Handy, C. J.; DeShong, P. J. Org. Chem. 2005, 70, 8948. (f) Alacid,
E.; Na´jera, C. AdV. Synth. Catal. 2006, 348, 945. (g) Denmark, S. E.; Butler,
(10) (a) Martin, R.; Buchwald, S. L. Acc. Chem. Res. 2008, 41, DOI:
10.1021/ar800036s and references therein. (b) Anderson, K. W.; Ikawa,
T.; Tundel, R. E.; Buchwald, S. L. J. Am. Chem. Soc. 2006, 128, 10694.
(c) Huang, X.; erson, K. W.; Zim, D.; Jiang, L.; Klapars, A.; Buchwald,
S. L. J. Am. Chem. Soc. 2003, 125, 6653
.
´
C. R. Org. Lett. 2006, 8, 63. (h) Gordillo, A.; de Jesu´s, E.; Lo´pez-
(11) For a recent review on the development and application of bulky
electron-rich phosphines for palladium-catalyzed cross-coupling reaction
of aryl halides and sulfonates, see: Zapf, A.; Beller, M. Chem. Commun.
Mardomingo, C. Org. Lett. 2006, 8, 3517. (i) Napier, S.; Marcuccio, S. M.;
Tye, H.; Whittaker, M. Tetrahedron Lett. 2008, 49, 3939. (j) Napier, S.;
Marcuccio, S. M.; Tye, H.; Whittaker, M. Tetrahedron Lett. 2008, 49, 6314
.
2005, 431, and references cited therein.
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Org. Lett., Vol. 10, No. 21, 2008