Harnessing Cascade Suzuki‐Cyclization Reactions of Pyrazolo[3,4‐b]pyridine for the Synthesis of Tetracyclic Fused Heteroaromatics

Numerous procedures have been described for the functionalization of pyrazolo[3,4‐ b ]pyridine, mainly involving nucleophilic substitutions at the C‐4 position or esterifications/amidations at the C‐5 position. In this paper, we describe a robust, easy to implement protocol for the Suzuki cross‐coupling reaction of chloroarene 2 , followed by in‐situ lactonization to provide chromenopyrazolopyridines. The extension of the scope of the reaction to fused naphthyridinones is also reported. This strategy gave access to 10 original pyrazolopyridine‐containing tetracyclic compounds.