ORGANIC
LETTERS
2009
Vol. 11, No. 17
3974-3977
Rhodium-Catalyzed ortho-Benzoxylation
of sp2 C-H Bond
Zhishi Ye,† Wenhui Wang,† Fang Luo,† Shouhui Zhang,† and Jiang Cheng*,†,‡
College of Chemistry & Materials Engineering, Wenzhou UniVersity, Wenzhou 325027,
P. R. China, and State Key Laboratory of Coordination Chemistry, Nanjing UniVersity,
Nanjing 210093, P. R. China
Received July 14, 2009
ABSTRACT
A rhodium-catalyzed ortho-benzoxylation of the sp2 C-H bond by carboxylic acids is described. The procedure tolerates carbomethoxy,
formyl, bromo, chloro, and nitro groups, providing the benzoxylated products in moderate to good yields. Importantly, no external oxidant was
required for the transformation.
Selective functionalization of the C-H bond is a longstand-
ing goal in organic synthesis because it obviates the
prefunctionalization of substrates.1 Combinations of transition
metals and directing groups are useful strategies to facilitate
the cleavage of the C-H bond, affording valuable transfor-
mations of an sp2-hybridized C-H bond to C-C,2 C-X,3
and C-N bonds.4 Recently, much attention has been paid
to the development of regioselective C-O bond formation
via C-H cleavage. For example, Sanford, Crabtree, Wang,
and Stock demonstrated acetoxylation of an sp2 C-H bond
employing PhI(OAc)2,5 Oxone,6 K2S2O8,7 and other reagents8
as terminal oxidants. The Pd-catalyzed sp3 C-H bond
acetoxylation reactions9 were also developed by Yu, Corey,
and Sanford, respectively. However, most of the reports on
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5554. (c) Hennessy, E. J.; Buchwald, S. L. J. Am. Chem. Soc. 2003, 125,
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Chem. Soc. 2007, 129, 7742. (h) Do, H.-Q.; Khan, R. M. K.; Daugulis, O.
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† Wenzhou University.
‡ Nanjing University.
(1) For representative reviews on C-H functionalization, see: (a) Shilov,
A. E.; Shul’pin, G. B. Chem. ReV. 1997, 97, 2879, and references therein.
(b) Dyker, G. Angew. Chem., Int. Ed. 1999, 38, 1699. (c) Ritleng, V.; Sirlin,
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10.1021/ol901609t CCC: $40.75
Published on Web 08/11/2009
2009 American Chemical Society