A novel and efficient synthesis of pyrido[1,2-a]benzimidazoles through direct intramolecular aromatic C-H amination of N-aryl-2-aminopyridines has been developed. The reaction, cocatalyzed by Cu(OAc)(2) and Fe(NO(3))(3)·9H(2)O, is carried out in DMF under a dioxygen atmosphere. Diversified pyrido[1,2-a]benzimidazoles containing various substitution patterns are obtained in moderate to excellent yields by using this procedure. The results of mechanistic studies suggest that a Cu(III)-catalyzed electrophilic aromatic substitution (S(E)Ar) pathway is operating in this process. The unique role of iron(III) is believed to lie in its ability to facilitate formation of the more electrophilic Cu(III) species. In the absence of iron(III), a much less efficient and reversible Cu(II)-mediated S(E)Ar process takes place.

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A direct synthesis of carbaldehydes through intramolecular dehydrogenative aminooxygenation has been developed. The process uses a catalytic amount of copper(II) in DMF or DMA under oxygen and does not require additional oxidants (see scheme). Mechanistic studies suggest that the carbonyl oxygen atom of the aldehyde is derived from oxygen through a copper‐mediated oxygen activation process via a peroxy–copper(III) intermediate.