ORGANIC
LETTERS
2011
Vol. 13, No. 3
540-542
Rh(III)-Catalyzed Oxidative Coupling of
Unactivated Alkenes via C-H Activation
Andy S. Tsai,† Mikae¨l Brasse,‡ Robert G. Bergman,*,§ and Jonathan A. Ellman*,†
Department of Chemistry, Yale UniVersity, New HaVen, Connecticut 06520, United
States, Department of Chemistry, UniVersity of California, Berkeley, California 94720,
United States, and DiVision of Chemical Sciences, Lawrence Berkeley National
Laboratory, Berkeley, California 94720, United States
rbergman@berkeley.edu; jonathan.ellman@yale.edu
Received November 30, 2010
ABSTRACT
Oxime directed aromatic C-H bond activation and oxidative coupling to alkenes is reported using a cationic Rh(III) catalyst. Significantly, the
method can be used to oxidatively couple unactivated, aliphatic alkenes.
Directed C-H bond activation and oxidative coupling with
alkenes provide an atom economical alternative to traditional
transformations such as the Heck reaction. Palladium,1
ruthenium,2 and rhodium3 have been reported to effect the
former transformation. However, nearly all oxidative cou-
plings have employed “activated” alkenes such as acrylates
and styrenes.1e,f Herein, we report a general method for the
oxidative coupling of aryl O-methyl oximes with unactivated
alkenes via C-H bond functionalization using a cationic
Rh(III) catalyst.
† Yale University.
‡ University of California.
§ Lawrence Berkeley National Laboratory.
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We began our exploration with attempts to oxidatively
couple 1-hexene with imine 1a. We initially employed
conditions reported by Miura for the oxidative coupling of
1-phenylpyrazole with acrylates using [Cp*RhCl2]2 as the
catalyst in the presence of Cu(OAc)2 as an oxidant and with
DMF as the solvent (Table 1, entry 1).3f Only trace amounts
of the coupled product were observed, and none of the
desired product was obtained with other solvents (entries 2
and 3). Prompted by reports that noted a positive effect of
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10.1021/ol102890k 2011 American Chemical Society
Published on Web 12/22/2010