Intramolecular C-H Activation of Heterocyclic Substrates

Martinez, Urriolabeitia, and coworkers have studied the regioselective C-H activation of (Z)-2-aryl-4-arylidene-5(4//)-oxazolones, 22, at Pd(OAc)2 in acidic media [27]. As seen in related studies on Af-methylbenzylimine [19], reactivity is enhanced by increased acidity and favors the arylidene position (i.e., C-H ) to give, unusually, a six-membered palladacycle, isolated as a dimer. B3LYP(MeC02H) calculations (X = Y=H) showed reduced barriers to C-H activation upon sequential protonation of the Pd active species and 

Free energies (at 413 K) for the enantio-determining C-H activation transition states leading to products ds-/trans-28 and 29 are indicated in kcalmoh [31a]. 

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