Organometallics
ARTICLE
23.6 (s, iPr), 27.2 (s, iPr), 28.7 (s, CHiPr), 46.3 (s, N(CH2CH3)), 53.3
(s, CH2), 124.0 (s, CH aromatic), 129.2 (s, CH aromatic), 135.1 (s, C
aromatic), 148.3 (s, C aromatic), 185.9 (s, C carbene). Anal. Calcd for
C33H53Cl2N3Pd: C, 59.23; H, 7.98; N, 6.28. Found: C, 58.88; H, 8.14;
N, 6.29.
(2) Selected examples: (a) Miyaura, N.; Yamada, K.; Suzuki, A.
Tetrrahedron Lett. 1979, 36, 3437–3439. (b) Kosugi, M.; Sasazawa, K.;
Shimizu, Y.; Migita, T. Chem. Lett. 1977, 301–302. (c) Milstein, D.;
Stille, J. K. J. Am. Chem. Soc. 1978, 100, 3636–3638. (d) Stephen, R. D.;
Castro, C. E. J. Org. Chem. 1963, 28, 3313–3315. (e) Dieck, H. A.; Heck,
R. F. J. Organomet. Chem. 1975, 93, 259–263. (f) Sonogashira, K.; Tohda,
Y.; Hagihara, N. Tetrahedrom Lett. 1975, 4467–4470. (g) Chodkiewicz, W.;
Cadiot, P. Compt. Rend. Hebd. Seances Acad. Sci. 1955, 214, 1055–1057.
(h) Negishi, E. Aspects Mech. Organomet. Chem. 1978, 285–317.
(3) Selected examples: (a) Littke, A. F.; Fu, G. C. Angew. Chem., Int.
Ed. 1998, 37, 3387–3388. (b) Old, D. W.; Wolfe, J. P.; Buchwald, S. L.
J. Am. Chem. Soc. 1998, 120, 9722–9723. (c) Oh-e, T.; Miyaura, N.;
Suzuki, A. J. Org. Chem. 1993, 58, 2201–2208. (d) Littke, A. F.; Dai, C.;
Fu, G. C. J. Am. Chem. Soc. 2000, 122, 4020–4028. (e) Grasa, G. A.;
Viciu, M. S.; Huang, J.; Zhang, C.; Trudell, M. L.; Nolan, S. P.
Organometallics 2002, 21, 2866–2873. (f) Brenstrum, T.; Gerristma,
D. A.; Adjabeng, G. M.; Frampton, C. S.; Britten, J.; Robertson, A. J.;
McNulty, J.; Capretta, A. J. Org. Chem. 2004, 69, 7635–7639. (g) Takagi,
J.; Takahashi, T. I.; Miyaura, N. J. Am. Chem. Soc. 2002, 124, 8001–8006.
(4) Viciu, M. S.; Germeneau, R. F.; Navarro-Fernandez, O.; Stevens,
E. D.; Nolan, S. P. Organometallics 2002, 21, 5470–5472.
General Procedure for the SuzukiÀMiyaura Reaction. In a
glovebox, complex (1 mol %), base (0.6 mmol), and phenylboronic acid
(0.55 mmol) were added in turn to a vial equipped with a magnetic bar
and sealed with a screw cap fitted with a septum. Outside the glovebox,
technical grade solvent (1 mL) was injected into the vial, and the mixture
stirred on a stirring plate at room temperature. Aryl chloride (0.5 mmol, if
liquid) was then injected (or previously charged in the glovebox if solid).
The reaction was monitored by gas chromatography. When finished, the
solvent was evaporated under vacuum and the product isolated by flash
chromatography. The amount of product shown is the average of two runs.
General Procedure for the BuchwaldÀHartwig Reaction.
In a glovebox, complex (1 mol %), base (1.1 mmol), and 1,2-dimethox-
yethane (DME) (1 mL) were added in turn to a vial equipped with a
magnetic bar and sealed with a screw cap fitted with a septum. Outside
the glovebox, the amine (1.1 mmol) and the aryl halide (1 mmol) were
injected in turn through the septum. If one of the two starting materials
was a solid, it was added to the vial inside the glovebox, and DME and the
second starting material were added outside the glovebox under nitro-
gen. The reaction mixture was then stirred at 50 °C unless otherwise
indicated. When the reaction reached completion, or no further con-
version could be observed by gas chromatography, water was added to
the reaction mixture, the organic layer was extracted with ethyl acetate
and dried over magnesium sulfate, and the solvent was evaporated under
vacuum. When necessary, the product was purified by flash chromatog-
raphy on silica gel. The reported yields are the average of at least two runs.
(5) For an illustrative example, see: Lebel, H.; Janes, M. K.; Charette,
A. B.; Nolan, S. P. J. Am. Chem. Soc. 2004, 126, 5046–5047.
(6) For instance: (a) Organ, M. G.; Avola, S.; Dubovyk, I.; Hadei, N.;
Kantchev, E. A. B.; O’Brien, C. J; Valente, C. Chem. Eur. J. 2006,
12, 4749–4755. (b) Marion, N.; Navarro, O.; Mei, J.; Stevens, E. D.;
Scott, N. M.; Nolan, S. P. J. Am. Chem. Soc. 2006, 128, 4101–4111.
(c) Viciu, M. S.; Navarro, O.; Germaneau, R. F.; Kelly, R. A., III; Sommer,
W.; Marion, N.; Stevens, E. D.; Cavallo, L.; Nolan, S. P. Organometallics
2004, 23, 1629–1635. (d) Fraunhoffer, K. J.; White, M. C. J. Am. Chem. Soc.
2007, 129, 7274–7276. (e) Fors, B. P.; Watson, D. A.; Biscoe, M. R.;
Buchwald, S. L. J. Am. Chem. Soc. 2008, 130, 13552–13554.
(7) (a) Chass, G. A.; O’Brien, C. J.; Hadei, N.; Kantchev, E. A. B.;
Mu, W.-H.; Fang, D.-C.; Hopkinson, A. C.; Csizmadia, I. G.; Organ,
M. G. Chem. Eur. J. 2009, 15, 4281–4288. (b) Valente, C.; Belovich,
M. E.; Hadei, N.; Organ, M. G. Eur. J. Org. Chem. 2010, 4343–4354.
(c) Organ, M. G.; Chass, G. A.; Fang, D.-C.; Hopkinson, A. C.; Valente,
C. Synthesis 2008, 2776–2797. (d) Nasielski, J.; Hadei, N.; Achonduh,
G.; Kantchev, E. A. B.; O’Brien, C. J.; Lough, A.; Organ, M. G. Chem. Eur.
J. 2010, 16, 10844–10853. (e) Valente, C.; Baglione, S.; Candito, D.;
O’Brien, C. J.; Organ, M. G. Chem. Commun. 2008, 735–737. (f) Hadei,
N.; Valente, C.; O’Brien, C. J.; Organ, M. G. Angew. Chem., Int. Ed. 2011,
50, 3896–3899.
(8) Diebolt, O.; Jurꢀcik, V.; Correa da Costa, R.; Braunstein, P.;
Cavallo, L.; Nolan, S. P.; Slawin, A. M. Z.; Cazin, C. S. J. Organometallics
2010, 29, 1443–1450.
(9) NHC ligands have been shown to be flexible enough to modulate
their bulkiness in response to the steric requirements of the other ligands
surrounding the metal center (ref 8).
’ ASSOCIATED CONTENT
S
Supporting Information. Characterization and crystal-
b
lographic information files (CIF) of complexes 1b, 3a, and 3b
and characterization of coupling products. This material is
’ AUTHOR INFORMATION
Corresponding Author
‡To whom inquiries regarding the crystal structures of 1b and 3b
should be addressed.
*E-mail: oscarnf@hawaii.edu.
’ ACKNOWLEDGMENT
(10) Only IPr-bearing complexes were tested for the SuzukiÀ
Miyaura reaction since it has been shown that IPr-bearing complexes
generally perform better in this cross-coupling reaction than SIPr-
bearing complexes. On the other hand, SIPr-bearing complexes are
known to generally provide the best results for BuchwaldÀHartwig
amination reactions. For an example, see ref 6b.
(11) The use of complexes 2 for the coupling of this specific sub-
strate is reported only at high temperature and low catalyst loading
(ref 8). Under similar reaction conditions to those in Table 2, all complexes
2 in Figure 1, with the exception of 2aPr, afforded yields of >95% for the
coupling of p-Cl-toluene and phenylboronic acid in 4 h. In comparison, this
coupling is performed less than half that time using 3a (Table 3, entry 1).
(12) An additional proof of a stronger PdÀN bond is that 3a can be
converted to 1a in quantitative yield in a DCM solution with an excess of
3-Cl-pyridine, at room temperature and in less than 1 h. Attempts to
achieve the opposite conversion were partially successful and only at
higher temperature (55% conversion of 1a into 3a in refluxing TEA after
48 h).
O.N. gratefully acknowledges the National Science Founda-
tion for funding (CHE-0924324). M.L.T. acknowledges the
NWDA and the EPSRC for financial support. The authors also
thank Dr. Lee M. Daniels (Rigaku Americas Corp.) for assistance
solving the crystal structure of 3a, and Prof. Craig M. Jensen for
helpful discussions.
’ REFERENCES
(1) (a) Tsuji, J. Palladium Reagents and Catalysis, 2nd ed.; Wiley:
West Sussex, England, 2004. (b) de Meijere, A., Diederich, F., Ed. Metal-
Catalyzed Cross-Coupling Reactions, 2nd ed.; Wiley-VCH: Weinheim,
Germany, 2004. (c) Negishi, E., Ed. Handbook of Organopalladium
Chemistry for Organic Synthesis; Wiley-Interscience: New York, 2002.
(d) Navarro, O.; Nolan, S. P. C-C Bond Formation by Cross-Coupling.
In Comprehensive Organometallic Chemistry III; Crabtree, R. H., Mingos,
M. P., Eds.; Elsevier: New York, 2007; Vol. 11, Chapter 1.
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dx.doi.org/10.1021/om200699p |Organometallics 2011, 30, 5052–5056