Abstract
| - Evidence is presented for a proposed mechanism of C−H activation of 3-methyl-3,4-dihydroquinazoline (1) by (PCy3)2RhCl. One intermediate (3), a coordination complex of 1 with (PCy3)2RhCl, wasidentified along the path to the Rh-N-heterocyclic carbene product of this reaction (2). Isotopic labelingand reaction-rate studies were used to demonstrate that C−H activation takes place intramolecularly onthe reaction coordinate between 3 and 2. Computational studies corroborate the proposed mechanismand suggest that the rate-limiting step is oxidative addition of the C−H bond to the metal center. Theconsequences of this mechanism for coupling reactions of N-heterocycles that occur via Rh-catalyzedC−H bond activation are discussed.
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