One-Pot Synthesis of Functionalized Carbazoles via a CAN-Catalyzed Multicomponent Process Comprising a C–H Activation Step

The
microwave-promoted three-component reaction between o-nitrochalcones, primary amines and β-dicarbonyl
compounds in the presence of Ce­(IV) ammonium nitrate constitutes the
first example of a multicomponent carbazole synthesis. This reaction
furnishes highly substituted and functionalized carbazole derivatives
via a double annulation process that generates two C–C and
two C–N bonds, with water as the only side product. Mechanistically,
this transformation has some unusual features that include an intramolecular
coupled hydrogenation-dehydrogenation process, the functionalization
of a C–H group by direct attack onto a nitrogen function and
a CAN-catalyzed reduction via hydride transfer from ethanol. The mechanisms
of these reactions were studied with the aid of computational techniques.