Fused Heteroaromatic Rings via Metal-Mediated/Catalyzed Intramolecular C–H Activation: A Comprehensive Review

The present review highlights the most important recent contributions toward the synthesis of functionalized fused heteroaromatic rings via intramolecular C–H activation mediated or catalyzed by transition metals. This type of reaction constitutes a versatile strategy to obtain a great variety of fused heterocyclic systems through the formation of carbon–carbon (C–C) and C–heteroatom bonds from direct coupling between two adjacent C–H bonds or C–H/H–X bonds. The revision is focused on the synthesis of fused heterocycles through two chemical processes: (1) metal-catalyzed intramolecular oxidative C–H activation, and (2) intramolecular C–H activation mediated by metallic Lewis acids.