Synthesis of Indazole Scaffolds from Arynes and Suitable Coupling Partners - A Brief Review

Transition metal-free annulation/cascade reactions have been embraced as a powerful synthetic tool to access carbo/heterocyclic molecules. Among them, benzyne chemistry gained significant interest due to the formation of diverse functionalized arenes via unusual carboncarbon (C-C) or carbon-heteroatom (C-O, C-N, C-S) bond-formation under different reaction conditions. In this review, few dynamic methods have been documented to construct the synthetically and pharmaceutically valuable indazole scaffolds using benzyne precursor and various other coupling partners. In this mini-review, we have described the recent progress on metal-free cascade strategies, highlighting the contribution from several synthetic chemists, including our research work. Specific attention has been paid to offer the detailed mechanistic pathway to explain the developed methodologies.