Web Release Date: March 7,
Intermediacy of an N-Heterocyclic Carbene Complex in the Catalytic C-H Activation of a Substituted Benzimidazole
Center for New Directions in Synthesis, Department of Chemistry, University of California and Division of Chemical Sciences, Lawrence Berkeley National Laboratory, Berkeley, California 94720
Received October 22, 2001
Revised Manuscript Received January 4, 2002
Abstract:
An N-heterocyclic carbene complex was found to be the active catalyst in the Rh(I)-catalyzed intramolecular coupling of an alkenyl group to a C-H bond of a substituted benzimidazole. Kinetic studies demonstrated that the catalytic cyclization is zero-order in substrate and first-order in catalyst. Furthermore, DFT calculations with a model system suggest that the rate-limiting step involves insertion of the alkenyl double bond into the rhodium-carbene bond.
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