Communications
with this substrate rarely translates into similiar levels of activity
radiation, l = 0.71073 , m = 0.577 mmÀ1
, Siemens Platform
or generality with even slightly more hindered or functionalized
substrates. For recent examples of cross-couplings employing
phenyl boronic acid see: a) A. Zapf, R. Jackstell, F. Rataboul, T.
Riermeier, A. Monsees, C. Fuhrmann, N. Shaikh, U. Dingerdis-
sen, M. Beller, Chem. Commun. 2004, 1, 38; b) N. Leadbeater,
M. Marco, Angew. Chem. 2003, 115, 1445; Angew. Chem. Int. Ed.
2003, 42, 1407; c) R. B. Bedford, C. S. J. Cazin, S. J. Coles, T.
Gelbrich, P. N. Horton, M. B. Hursthouse, M. E. Light, Organo-
metallics 2003, 22, 987; d) J. P. Stambuli, R. Kuwano, J. F.
Hartwig, Angew. Chem. 2002, 114, 940; Angew. Chem. Int. Ed.
2002, 41, 4746; e) A. Zapf, A. Ehrentraut, M. Beller, Angew.
Chem. 2000, 112, 4315; Angew. Chem. Int. Ed. 2000, 39, 4153.
[3] a) S. Kaye, J. M. Fox, F. A. Hicks, S. L. Buchwald, Adv. Synth.
Catal. 2001, 343, 789; b) H. Tomori, J. M. Fox, S. L. Buchwald, J.
Org. Chem. 2000, 65, 5334.
three-circle diffractometer equipped with a CCD detector,
7703 measured and 5293 independent reflections, Rint = 0.0200,
4858 reflections with I > 2s(I). Data processed using the
program SAINTsupplied by Siemens Industrial Automation,
Inc., structure determination by direct methods (SHELXTL
V6.10, G. M. Sheldrick, University of Göttingen, and Siemens
Industrial Automation, Inc.), structure refined on F2 by full-
matrix least-squares methods, absorption correction applied
with SADABS. All non-hydrogen atoms were refined aniso-
tropically. All hydrogen atoms were located in the electron
density map and refined isotropically. The refinement of 435
parameters using 5293 reflections and 0 restraints gave R1 =
0.0286, wR2 = 0.0676 (I > 2s(I) data), goodness of fit on F2 =
1.052, D1max/min = 0.509/À0.338 eÀ3. CCDC-227390 contains the
supplementary crystallographic data for this paper. These data
retrieving.html (or from the Cambridge Crystallographic Data
Centre, 12, Union Road, Cambridge CB21EZ, UK; fax: (+
44)1223-336-033; or deposit@ccdc.cam.ac.uk).
[4] E. R. Strieter, D. G. Blackmond, S. L. Buchwald, J. Am. Chem.
Soc. 2003, 125, 13978.
[5] For a review see: A. D. Ryabov, Chem. Rev. 1990, 90, 403.
[6] a) J. Yin, M. P. Rainka, X.-X. Zhang, S. L. Buchwald, J. Am.
Chem. Soc. 2002, 124, 1162; b) S. M. Reid, R. C. Boyle, J. T.
Mague, M. J. Fink, J. Am. Chem. Soc. 2003, 125, 7816; c) T. E.
Barder, X.-X. Zhang, S. L. Buchwald, unpublished results.
[7] a) J. P. Wolfe, R. A. Singer, B. H. Yang, S. L. Buchwald, J. Am.
Chem. Soc. 1999, 121, 9550; b) R. B. Bedford, S. L. Hazelwood,
M. E. Limmert, Chem. Commun. 2002, 2610. The presence of
underligated Pd complexes may promote the formation of Pd
black. For a recent study on the deactivation processes of
homogeneous Pd catalysts see: M. Tromp, J. R. A. Sietsma, J. A.
van Bokhoven, G. P. F. van Strijdonck, R. J. van Haaren, A. M. J.
van der Eerden, P. W. N. M. van Leeuwen, D. C. Koningsberger,
Chem. Commun. 2003, 128.
[14] a) P. Kocovsky, S. Vyskocil, I. Cisarova, J. Sejbal, I. Tislerova, M.
Smrcina, G. C. Lloyd-Jones, S. C. Stephen, C. P. Butts, M.
Murray, V. Langer, J. Am. Chem. Soc. 1999, 121, 7714; b) T.
Hayashi, H. Iwamura, M. Naito, Y. Matsumoto, Y. Uozumi, M.
Miki, K. Yanagi, J. Am. Chem. Soc. 1994, 116; 775; c) P. Dotta,
P. G. A. Kumar, P. S. Pregosin, A. Albinati, S. Rizzato, Organo-
metallics 2003, 22, 5345.
[15] T. E. Barder, S. L. Buchwald, unpublished results.
À
[16] Enhanced activity in C N bond-forming processes with a related
ligand have been attributed to the formation of a PdII palladate
species.[14a] While we cannot unequivocally rule this out, the fact
that higher levels of catalytic activity for analogous C–N
couplings have been observed for catalysts derived from 2-
dicyclohexylphosphanyl-2’,4’,6’-triisopropylbiphenyl than for 1
(E. R. Strieter, S. L. Buchwald, unpublished results) cast doubt
on this explanation of the high level of catalytic activity
manifested with 1.
[8] For a review on Pd-catalyzed couplings of aryl chlorides see:
A. F. Littke, G. C. Fu, Angew. Chem. 2002, 114, 4350; Angew.
Chem. Int. Ed. 2002, 41, 4176.
[9] a) A. F. Littke, C. Dai, G. C. Fu, J. Am. Chem. Soc. 2000, 122,
4020; b) S.-Y. Liu, M. J. Choi, G. C. Fu, Chem. Commun. 2001,
2408; c) G. Altenhoff, R. Goddard, C. W. Lehmann, F. Glorius,
Angew. Chem. 2003, 115, 3818; Angew. Chem. Int. Ed. 2003, 42,
3690; d) O. Navarro, R. A. Kelly III, S. P. Nolan, J. Am. Chem.
Soc. 2003, 125, 16194; e) The best previous results for this
reaction are described in ref. [2c], although no yield of isolated
product is reported.
[10] The half-life was determined by GC analysis.
[11] While exceedingly high turnover numbers have been realized for
the coupling of phenyl boronic acid with 4-bromoacetophenone,
this is a particularly trivial process and does not extend to the
efficient coupling of unactivated and ortho-substituted sub-
strates at low catalyst levels. We have previously shown this
reaction to proceed even in the absence of added ligand and
recommend that it not be used as a benchmark to test new
catalysts, see ref. [7a].
[12] For
a recent report describing the cross-coupling of aryl
chlorides with alkyl boronic acids, see: N. Kataoka, Q. Shelby,
J. P. Stambuli, J. F. Hartwig, J. Org. Chem. 2002, 67, 5553. For a
report describing the coupling of an alkyl boronic acid with an
alkyl bromide, see: J. H. Kirchhoff, M. R. Netherton, I. D. Hills,
G. C. Fu, J. Am. Chem. Soc. 2002, 124, 13662.
[13] Crystals suitable for X-ray diffraction were obtained by stirring a
solution of [Pd2(dba)3] and 1 in benzene for 5 d, concentrating
the resulting mixture, and inducing crystallization by slow
evaporation from hexane (in a glovebox). Crystal data for 5:
C41H49O3PPd, crystals from hexane, Mr = 727.17, 0.20 0.18
3
¯
0.14 mm , triclinic, space group P1 (No. 2), a = 11.4552(15),
b = 11.6697(15), c = 15.5298(19) , a = 94.058(2), b = 96.084(2),
g = 114.705(2)8, V= 1860.1(4) 3, Z = 2, 1calcd = 1.298 gcmÀ3, T=
193(2) K, F(000) = 760, 2qmax = 46.588, monochromated MoKa
1876
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2004, 43, 1871 –1876