S. Yekta et al. / Tetrahedron Letters 48 (2007) 8048–8051
8051
Table 3 (continued)
Entry
Ar1X
Ar2B(OH)2
Product
Conv. (%)
64
Yield (%)
F
F
F
F
3
50b
F
F
OMe
F
F
OMe
B(OH)2
Br
F
F
F
F
F
F
4
69
55
OMe
B(OH)2
F
F
OMe
OTf
a Reaction conditions: 5 mol % Pd(OAc)2/10 mol % ligand, 1 equiv Ar1Br, 1.5 equiv Ar2B(OH)2, 2 equiv K3PO4.
b GC yield (product was not separable from starting aryl bromide by flash chromatography).
Tetrahedron 1997, 53, 14437–14450; For bulky electron-
rich phosphine ligands see: (f) Grushin, V. V.; Alper, H.
Top. Organomet. Chem. 1999, 3, 193, and references
therein; (g) Littke, A. F.; Fu, G. C. Angew. Chem., Int. Ed.
2002, 41, 4176, and references therein.
In conclusion, we have shown that the steric and
electronic balance at the phosphorous centre of polyflu-
orinated phosphine ligands allows for room tempera-
ture palladium-catalyzed cross-coupling reaction of
aryl bromides and aryl boronic acids. These fluorinated
ligands are readily accessible and can be synthesized on
a gram scale. The versatility of the synthetic methodol-
ogy allows access to a series of ligands with different
substituents having a variety of substitution patterns.
2. Bayardon, J.; Cavazzini, M.; Maillard, D.; Pozzi, G.;
Quici, S.; Sinou, D. Tetrahedron: Asymmetry 2003, 14,
2215–2224.
3. For a review on fluorine chemistry see: Dolbier, W. R., Jr.
J. Fluorine Chem. 2005, 126, 157–163.
4. For examples see: (a) Silva, M. R.; Paixao, J. A.; Beja, A.
˜
M.; da Veiga, L. A. J. Fluorine Chem. 2007, 113, 7–12; (b)
Kundig, E. P.; Saudan, C. M.; Bernardinelli, G. Angew.
Chem., Int. Ed. 1999, 38, 1219–1223.
¨
Acknowledgements
5. Chen, Y.; Yekta, S.; Martyn, L. J. P.; Zheng, J.; Yudin,
A. K. Org. Lett. 2000, 2, 3433–3436.
6. Mohr, B.; Lynn, D. M.; Grubbs, R. H. Organometallics
1996, 15, 4317–4325.
We thank NSERC, CFI, ORDCF, and Amgen for
financial support. We also thank Dr. A. Lough for X-
ray structure analysis.
7. A 2:1 mixture of ligand/Pd(OAc)2 was prepared in CDCl3.
8. Phosphorous NMR shifts correspond to reported litera-
ture values: (a) Power, W. P. J. Am. Chem. Soc. 1995, 117,
1800–1806; (b) Grim, S. O.; Keiter, R. L. Inorg. Chim.
Acta 1970, 4, 56–60. Also, see experimental section.
9. Kiplinger, J. L.; Richmond, T. G.; Osterberg, C. E. Chem.
Rev. 1994, 94, 373–431.
10. Less than 10% conversion is achieved in the absence of any
ligand.
11. Hartwig, J. F.; Richards, S.; Baranano, D.; Paul, F. J. Am.
Chem. Soc. 1996, 118, 3626–3633.
References and notes
1. For selected references see: (a) De Meijere, A.; Diederich,
F. Metal-Catalyzed Cross-Coupling Reactions, 2nd ed.;
Wiley-VCH: Weinheim, 2004; (b) Grushin, V. V.; Alper,
H. Chem. Rev. 1994, 94, 1047–1062; (c) Zhang, C.;
Huang, J.; Trudell, M. L.; Nolan, S. P. J. Org. Chem.
1999, 64, 3804–3805; (d) Shen, W. Tetrahedron Lett. 1997,
38, 5575–5578; (e) Bumagin, N. A.; Bykov, V. V.