When 1-naphthol and 1-naphthyl bromide were used for the
reaction, the corresponding naphthyl ether was obtained in
45% yield (Table 2, entry 10). The coupling reaction of
4-bromobenzonitrile with phenol has also been performed
with lower catalyst loadings (Scheme 2).
E. Gomez-Bengoa, Chem. Commun., 1998, 2091; (f) J.-F. Marcoux,
S. Doye and S. L. Buchwald, J. Am. Chem. Soc., 1997, 119, 10539.
3 For Fe-catalyzed diaryl ether synthesis see: (a) O. Bistri, A. Correa
and C. Bolm, Angew. Chem., Int. Ed., 2008, 47, 586; for metal free
diaryl ether synthesis see: (b) F. Li, Q. Wang, Z. Ding and G. Tao,
Org. Lett., 2003, 5, 2169; (c) Z. Liu and R. C. Larock, J. Org. Chem.,
2006, 71, 3198; general review: (d) S. V. Ley and A. W. Thomas,
Angew. Chem., Int. Ed., 2003, 42, 5400; (e) I. P. Beletskaya and
A. V. Cheprakov, Coord. Chem. Rev., 2004, 248, 2337.
4 (a) A. Aranyos, D. W. Old, A. Kiyomori, J. P. Wolfe, J. P. Sadighi
and S. L. Buchwald, J. Am. Chem. Soc., 1999, 121, 4369;
(b) K. E. Torraca, S.-I. Kuwabe and S. L. Buchwald, J. Am. Chem.
Soc., 2000, 122, 12907; (c) C. A. Parrish and S. L. Buchwald,
J. Org. Chem., 2001, 66, 2498; (d) K. E. Torraca, X. Huang,
C. A. Parrish and S. L. Buchwald, J. Am. Chem. Soc., 2001, 123,
10770; (e) S.-I. Kuwabe, K. E Torraca and S. L. Buchwald, J. Am.
Chem. Soc., 2001, 123, 12202; (f) M. Palucki, J. P. Wolfe and
S. L. Buchwald, J. Am. Chem. Soc., 1996, 118, 10333;
(g) M. Palucki, J. P. Wolfe and S. L. Buchwald, J. Am. Chem.
Soc., 1997, 119, 3395; (h) R. A. Widenhoefer, H. A. Zhong and
S. L. Buchwald, J. Am. Chem. Soc., 1997, 119, 6787;
(i) R. A. Widenhoefer and S. L. Buchwald, J. Am. Chem. Soc.,
1998, 120, 6504.
5 (a) Q. Shelby, N. Kataoka, G. Mann and J. F. Hartwig, J. Am.
Chem. Soc., 2000, 122, 10718; (b) G. Mann, C. Incarvito,
A. L. Rheigold and J. F. Hartwig, J. Am. Chem. Soc., 1999, 121,
3224; (c) N. Kataoka, Q. Shelby, J. P. Stambuli and J. F. Hartwig,
J. Org. Chem., 2002, 67, 5553; (d) G. Mann and J. F. Hartwig,
J. Am. Chem. Soc., 1996, 118, 13109; (e) G. Mann and
J. F. Hartwig, Tetrahedron Lett., 1997, 38, 8005.
6 (a) S. Harkal, K. Kumar, D. Michalik, A. Zapf, R. Jackstell,
F. Rataboul, T. H. Riemeier, A. Monsees and M. Beller,
Tetrahedron Lett., 2005, 46, 3237; (b) N. Schwarz, A. Pews-Davtyan,
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Here, the diaryl ether is observed in 55% and 85% yield in
toluene at 100 1C and in p-xylene at 130 1C, respectively in the
presence of 0.1 mol% of Pd(OAc)2 and 0.3 mol% ligand. This
demonstrates the potential usefulness of the parent catalyst
system for larger scale applications in the pharmaceutical and
agrochemical industries.
Finally, several aryl chlorides were also coupled with
phenol, 2-cresol, and 1-naphthol. As shown in Table 3 the
novel protocol is applicable for most aryl chlorides. Again,
reactions of aryl chlorides with electron-withdrawing groups
such as nitrile, aldehyde, ketone, and ester groups afforded the
corresponding diaryl ether in good to very good yields
(Table 3, entries 1–3, 6–9, 11; 81–99%). In addition, the
coupling of 2- and 4-chloroanisole with phenol gave
the corresponding diaryl ethers in 42–65% yield (Table 3,
entries 5, 13). Moreover, the reactions of 2-chlorobenzaldehyde
with phenol and 2-methylphenol proceeded smoothly towards
the formyl-substituted diaryl ether (Table 3, entries 4, 10).
In summary, we have demonstrated a novel and general
Pd-catalyzed C–O coupling protocol which is applicable for
various aryl bromides and chlorides with phenols, cresols, and
naphthols in high yields.
¨
7 (a) M. Akkoc, N. Gurbuz, E. Cetinkaya and I. Ozdemir, Synlett,
¨
¨
This work was supported by NSFC (Natural Science
Foundation of China) (grant No. 20802008) and the foundation
from State Key Laboratory of Materials-Oriented Chemical
Engineering, Nanjing University of Technology.
2008, 1781; (b) J.-P. Finet, A. Y. Fedorov, S. Combes and
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ꢀc
This journal is The Royal Society of Chemistry 2009
7332 | Chem. Commun., 2009, 7330–7332