Angewandte
Chemie
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Pyridine and related azaarenes are interesting cores of
biologically active molecules and functional materials. We
have found a new method to install such azaarenes by taking
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[5] The pyridyl alcohol C(OH)(iPr)2CHMe(2-pyridyl) underwent a
similar cleavage of a carbon–carbon bond, but unfortunately we
only obtained vinylpyridine and other by-products.
À
advantage of chelation-assisted cleavage of a Csp3 Csp3 bond.
Experimental Section
Cesium carbonate (0.32g, 0.97 mmol) was placed in a 30-mL two-
necked reaction flask equipped with a Dimroth condenser. The
cesium carbonate was dried in vacuo by heating (with a hair dryer for
2min). The flask was then filled with argon by using the standard
Schlenk technique. Palladium trifluoroacetate (13.4 mg, 0.040 mmol),
tricyclohexylphosphine (0.5m in toluene, 0.16 mL, 0.080 mmol),
xylene (1.6 mL), pyridyl alcohol 1a (0.17 g, 0.81 mmol), and chloro-
benzene (2a, 0.11 g, 0.97 mmol) were added sequentially at room
temperature. The resulting mixture was then heated at reflux for 6 h.
After the mixture had cooled to room temperature, water (10 mL)
was added and the product extracted with ethyl acetate (3 10 mL).
The combined organic layer was dried over sodium sulfate, and
concentrated in vacuo. Purification by column chromatography on
silica gel (hexane:ethyl acetate 5:1) gave 2-benzylpyridine (3a, 0.12g,
0.71 mmol) in 88% yield.
À
[6] For examples of catalytic Csp3 Csp3 bond cleavage assisted by
coordination of a single oxygen atom, see a) T. Kondo, K. Kodoi,
E. Nishinaga, T. Okada, Y. Morisaki, Y. Watanabe, T. Mitsudo, J.
Am. Chem. Soc. 1998, 120, 5587 – 5588; b) P. Shukla, C. H. Cheng,
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Yorimitsu, K. Oshima, J. Am. Chem. Soc. 2006, 128, 2210 – 2211;
d) Y. Takada, S. Hayashi, K. Hirano, H. Yorimitsu, K. Oshima,
Org. Lett. 2006, 8, 2515 – 2517; e) A. Yanagisawa, T. Aoki, T. Arai,
Synlett 2006, 2071 – 2074.
[7] We prepared the palladium complex [PdBr(Ph)(PPh3)2] and
performed the stoichiometric reaction of the aryl palladium
complex with 1a in the presence of an equimolar (1.2equiv)
amount of cesium carbonate in refluxing xylene for 12h. The
reaction afforded 3a in 50% yield.
Received: November 1, 2006
Revised: December 25, 2006
Published online: March 2, 2007
[8] The X-ray structures of similar metal amides have been reported,
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[9] Alternatively, a b-carbon elimination process would produce 7,
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10790 – 10791; d) T. Nishimura, H. Araki, Y. Maeda, S. Uemura,
Org. Lett. 2003, 5, 2997 – 2999.
À
Keywords: azaarenes · C C activation · cross-coupling ·
homogeneous catalysis · palladium
.
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