Thomas Vogler and Armido Studer
COMMUNICATIONS
standard Schlenk techniques. All solvents for filtration and References
flash chromatography were distilled before use. Ethanol
(Acros, 99%) was distilled from Na and was stored under an
argon atmosphere. 1,4-Dioxane (Acros, extra dry, water
<50 ppm), tert-butanol (Fluka, >99.7%) was used as re-
ceived was used without further purification.
[1] G. Bringmann, M. Breuning, S. Tasler, Synthesis 1999,
525–558, and references cited therein.
[2] a) J. Hassan, M. SØvignon, C. Gozzi, E. Schulz, M.
Lemaire, Chem. Rev. 2002, 102, 1359–1469; b) L. Pu,
Chem. Rev. 1998, 98, 2405–2494.
[3] A. Kraft, A. C. Grimsdale, A. B. Holmes, Angew.
Chem. Int. Ed. 1998, 37, 402–428.
[4] J. Roncali, Chem. Rev. 1992, 92, 711–738.
1H NMR (300 MHz) and 13C NMR (75 MHz) spectra
were recorded on a Bruker DPX 300 spectrometer. Chemi-
cal shifts d in ppm are referenced to the solvent residual
peak as an internal standard. TLC was carried out on Merck
silica gel 60 F254 plates; detection by UV or dipping into a
[5] For leading references see: a) M. J. Burns, I. J. S. Fair-
lamb, A. R. Kapdi, P. Sehnal, R. J. K. Taylor, Org. Lett.
2007, 9, 5397–5400; b) Y. Yamamoto, Synlett 2007,
1913–1916; c) C. Adamo, C. Amatore, I. Ciofini, A.
Jutand, H. Lakmini, J. Am. Chem. Soc. 2006, 128,
6829–6836; d) C. Zhou, R. C. Larock, J. Org. Chem.
2006, 71, 3184–3191; e) H. Yoshida, Y. Yamaryo, J. Oh-
shita, A. Kunai, Tetrahedron Lett. 2003, 44, 1541–1544;
f) D. J. Koza, E. Carita, Synthesis 2002, 2183–2186;
g) A. Lei, X. Zhang, Tetrahedron Lett. 2002, 43, 2525–
2528; h) M. Moreno-MaÇas, M. PØrez, R. Pleixats, J.
Org. Chem. 1996, 61, 2346–2351; i) Z. Z. Song, H. N. C.
Wong, J. Org. Chem. 1994, 59, 33–41.
[6] a) H. Sakurai, H. Tsunoyama, T. Tsukuda, J. Organo-
met. Chem. 2007, 692, 368–374; b) S. Carrettin, J.
Guzman, A. Corma, Angew. Chem. Int. Ed. 2005, 44,
2242–2245; c) C. Gonzµlez-Arellano, A. Corma, M. Ig-
lesias, F. Sµnchez, Chem. Commun. 2005, 1990–1992;
d) A. S. Demir, Ö. Reis, M. Emrullahoglu, J. Org.
Chem. 2003, 68, 10130–10134; e) J. R. Falck, S. Moha-
patra, M. Bondlela, S. K. Venkataraman, Tetrahedron
Lett. 2002, 43, 8149–8151; f) H. Mizuno, H. Sakurai, T.
Amaya, T. Hirao, Chem. Commun. 2006, 5042–5044.
[7] For Rh-catalyzed oxidative homocoupling of aryl- and
alkenylmercury compounds see: R. C. Larock, J. C.
Bernhardt, J. Org. Chem. 1977, 42, 1680–1684; for Rh-
catalyzed oxidative homocoupling of phenols see:
A. G. M. Barrett, T. Itoh, E. M. Wallace, Tetrahedron.
Lett. 1993, 34, 2233–2234.
solution of Ce(SO4)2·H2O (10 g), phosphormolybdic acid hy-
R
drate (25 g), concentrated H2SO4 (60 mL) and H2O (0.94 L)
or NaHCO3 (5.0 g), KMnO4 (1.5 g) and H2O (0.40 L) fol-
lowed by heating. Flash chromatography (FC) was carried
out on Merck or Fluka silica gel 60 (40–63 mm) with an
argon pressure of about 0.1–0.5 bar. GC spectra were ac-
quired on a Hewlett–Packard HP 6890 Series GC system
equipped with a HP 5 column (30 m0.32 mm, film thick-
ness 0.25 mm) by using hydrogen as carrier gas. IR spectra
were recorded on a Digilab FTS 4000 equipped with a
MKII Golden Gate Single Reflection ATR System. Melting
points were determined with a Stuart SMP10 and are uncor-
rected. GC-MS (EI) and HR-MS were performed on a
Waters-Micromass GC TOF.
General Procedure for the Rhodium-Catalyzed
Homocoupling
A solution of the corresponding boronic acid (1.00 mmol),
TEMPO (313 mg, 2.00 mmol) and tris(triphenylphosphine)-
A
and H2O (0.1 mL) was heated in a sealed tube at 1308C for
2 h. The reaction mixture was filtered through a plug of
silica gel (MTBE as eluent). The filtrate was concentrated
under vacuum, and the residue was purified by FC.
Rhodium-Catalyzed Homocoupling by using Oxygen
A flask containing a solution of phenylboronic acid (122 mg,
1.00 mmol) and tris(triphenylphosphine)rhodium(I) chloride
(28 mg, 30 mmol) in dioxane (1.0 mL) and H2O (0.1 mL) was
equipped with a balloon filled with O2. The reaction mixture
was stirred at 708C for 14 h and filtered through a plug of
silica gel (MTBE as eluent). The filtrate was concentrated
under vacuum, purification of the residue by FC (pentane/
MTBE=100:1) afforded biphenyl as a white solid; yield:
35 mg (0.23 mmol, 45%).
[8] Modern Rhodium-Catalyzed Organic Reactions, (Ed.:
P. A. Evans), Wiley-VCH, Weinheim, 2005.
[9] For example: a) M.-Y. Ngai, J.-R. Kong, M. J. Krische,
J. Org. Chem. 2007, 72, 1063–1072; b) S. Gatard, R.
C¸ elenligil-C¸ etin, C. Guo, B. M. Foxman, O. V. Ozerov,
J. Am. Chem. Soc. 2006, 128, 2808–2809; c) R. Shinta-
ni, T. Yamagami, T. Hayashi, Org. Lett. 2006, 8, 4799–
4801; d) X. Wang, B. S. Lane, D. Sames, J. Am. Chem.
Soc. 2005, 127, 4996–4997.
Supporting Information
ꢀ
[10] For examples in C H activation and arylation: a) M.
Montag, L. Schwartsburd, R. Cohen, G. Leitus, Y. Ben-
David, J. M. L. Martin, D. Milstein, Angew. Chem. Int.
Ed. 2007, 46, 1901–1904; b) S. Proch, R. Kempe,
Angew. Chem. Int. Ed. 2007, 46, 3135–3138; c) J. C.
Lewis, R. G. Bergman, J. A. Ellman, J. Am. Chem. Soc.
2007, 129, 5332–5333; d) S. Yanagisawa, T. Sudo, R.
Noyori, K. Itami, J. Am. Chem. Soc. 2006, 128, 11748–
11749; e) X. Wang, B. S. Lane, D. Sames, J. Am. Chem.
Soc. 2005, 127, 4996–4997; f) K. Ueura, T. Satoh, M.
Miura, Org. Lett. 2005, 7, 2229–2231; g) R. B. Bedford,
S. J. Coles, M. B. Hursthouse, M. E. Limmert, Angew.
Chem. Int. Ed. 2003, 42, 112–114; h) S. Oi, S.-i. Wata-
Further experimental procedures and compound characteri-
zation data are available as Supporting Information.
Acknowledgements
We thank Novartis Pharma AG (YoungInvestigator Award
to A.S.) and the Fonds der Chemischen Industrie for a sti-
pend (T.V.). Ciba Specialty Chemicals is acknowledged for
donation of chemicals (TEMPO, nitroxide 1).
1966
ꢁ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2008, 350, 1963 – 1967